Pavement Management


Better Roads Magazine, September 1992, Interview of Dennis Polhill by Ruth W. Stidger, Editor-in-Chief

Is your PMS sophisticated enough?

The ability to predict future pavement conditions is what separates a leading-edge technology pavement management system from a database. Not only should such a system predict future conditions; it should also be able to tell you the impact of variously timed actions (such as specific maintenance steps). With these capabilities, PMS can help establish a more rational maintenance and rehabilitation policy — providing the most cost-effective solutions over the lifetime of the pavement.

Databases and aggregate index programs are system elements, says Pavement Management Systems’ Dennis Polhill, P.E. And, Polhill, previously a public works manager, believes that many of today’s systems rely on weak or incomplete technical approaches.

“Public policy makers should realize that PM is a fledgling technology without the benefit of standards, common definitions, and technologies, or a leadership entity that will oversee and facilitate its evolution,” Polhill says. “This lack of technical leadership causes compromises.”

“One of the benefits of a standardized aggregate index such as PCI [in the PAVER system] is to aid standardized, centralized control from top government. Thus, the FAA, military, and some state and federal highway agencies can use a common indicator to trade off need in one agency with another to allocate funding for the greatest benefit.

“However,” Polhill says, “not all PCIs are the same. The awkwardness and expense of using PCI as suggested by the Corps of Engineers has been met with dozens of creative approaches to minimize its difficulty.

“The result is that various PCIs represent different combinations of data, yielding the obvious compromise in the central authorities’ ability to compare these indexes.”

PMS’ evolution
What level is the pavement management system you use? At the low end of the evolutionary scale are non-computerized methods focusing primarily on individual judgment. Politics often play an important role in repair and rehab decisions at this level.

Cycles are a part of the low level of sophistication. The approach assumes that cyclic variables such as traffic loads, materials, and climate affect pavement performance in a constant way. But, with many such variables to consider — one often affecting another
— the situation becomes too complex for the simple databases used at this level of sophistication.

Public policy financial options are equally simple — a 10% overlay rate over a 10-yr. period, for instance.

The database organizes collected data, but cannot account for quality of data or major changes in road use that render historical data inaccurate.

Ranking is the next logical step, Polhill says. To easily and quickly communicate about the masses of data, it is converted into various indexes. These allow simple ranking, moving the technology a further step.

An expert system is of medium sophistication, too. It converts PM data to a needs list using a simple decision tree. In other words, if condition A exists, treatment X is applied. Cost extensions are possible.

Expert systems and the resulting needs lists present new problems. The needs are often impossible to fund. At the next higher level of PM sophistication, software measures the cost benefits of each possible action. This allows agencies to spend money where it will be most effectively used.

Today’s leading-edge level of PM sophistication focuses on performance prediction. ‘Although many companies claim their system has this capability, few do,” Polhill says.

The missing consideration and benefit/cost and cost-effectiveness analysis is the time dimension. Because every pavement structure has a different performance curve, two pavements with the same index and calling for the same treatment may produce different benefits in time. One on a steep downward performance curve may quickly fail and need more expensive treatment than a road with a flat performance curve.

A leading-edge PMS uses reliable models and manipulates and maintains increasing volume of highly technical data to help form the most effective policy. The system links with various tools such as linear programming, decision theory, regression analysis, and dynamic programming to optimize the decisions made.

by
Willard Price
PhD School of Business and Public Administration
University of the Pacific

and
Dennis Polhill
MPW Pavement Management Systems Denver

Presented at
the 1990 Regional IX Conference of the American Society for Public Administration Honolulu, Hawaii
October 8, 1990

For submission to
the Journal Public Productivity and Management Review
October 1991

Abstract:
The objective of this research is to examine methods for public works maintenance investment decisions. Beyond initial capital choices using benefit-cost analysis, this paper explores performance measures to observe the physical condition and performance levels over the life of infrastructure systems. Given adequate information, alternative investment policies or maintenance strategies (prevention, rehabilitation and reconstruction) can be compared using performance levels and costs.

A general approach is presented for examining infrastructure systems and maintenance investment choices, with an example drawn from pavements. A discussion of the analytical process of maintenance management systems is provided in terms of required information, decision rules and optimization models Since public works managers are inundated by consultants with computer packages purporting to assist with infrastructure policy making, this article provides managers with a basis for criticizing maintenance management packages and their role in investment decisions.

Infrastructure Maintenance Investment: Beyond the Benefit-Cost Analysis
Today the word infrastructure is the popular usage for what has been known for most of our history as public works. While these two terms can be used interchangeably, conceptually a distinction will be drawn between infrastructure as the physical
platforms used to serve our communities and public works as the public agencies which own and deliver services at all three levels of governments. Infrastructure systems are normally owned by public agencies, often operated as public enterprises with
some degree of independence from parent governments. A portion of these systems are owned and/or operated privately, some water and transit agencies and almost all electrical distribution even though power systems are also provided by federal or local
government enterprises.

Examples of these physical infrastructure systems include:

  • Highways, streets, sidewalks, lighting and curbs and gutters
  • Water resource systems, water supply and sewage treatment
  • Flood control systems, storm drains, channels and dams
  • Solid waste systems, collection and disposal resources
  • Transport systems, airports, seaports, mass transit, and tunnels
  • Public buildings, grounds and parks
  • Equipment, vehicles, pumps, treatment facilities
  • Electrical, natural gas and telecommunication networks

These are systems that are widely available to the general public, although similar systems are developed by the military and many private industries on their own property and at their production plants and facilities. the focus here are those public works wholly owned by governments and planned, delivered and financed through public institutions.

Public works has historical connotations of public investment for the wrong reasons, that is “pork barrel” rewards by elected representatives to local constituents, for political tradeoffs among legislative members or as employment patronage. Such negative images of public works have clearly been overblown and have overshadowed the massive contribution that public works investment has provided for urban, regional and national growth, for the public health, safety and convenience.

The goal of this research is to focus on the management tasks of professional engineers and managers who deliver desirable and necessary public works platforms for commerce and public activity. The maintenance investment levels these managers recommend, not for the traditional capital decisions on new facilities, but for continuing repair, rehabilitation or reconstruction, are the policy decisions in question. These ought to be reviewed as economic investments decisions as is any infrastructure expenditure in the private sector.

Public works facilities have grown significantly during the last 40 years, with investment financed by local/state government debt, by federal/state grants to local agencies and by economic growth and general taxation of urban and suburban communities. This growth was strong during the period of 1950-1975, with almost all governments having the fiscal capacity to finance the infrastructure developments and adequately cope with maintenance burdens. Investment was justified by cheap debt, legal debt capacity, federal largesse and the ability of local/regional governments to realize increased property/sales tax revenue, sufficient to pay for debt retirement, the local share of capital costs and a lifetime of maintenance costs.

Now we are faced with a new reality, the results of drastic shifts in the environment of government. Economic stress caused by an oil crisis, massive inflation, unfathomable tax increases and a political reversal that found a welcome audience for a decreased role of the public sector in the lives of citizens. The impact on public works was a dual threat created by an aging infrastructure, some originally built 100 years ago, and a maintenance budget neglect stimulated by financial scarcity and deliberate cutbacks in the expenditures of governments in the 1970s and 1980s.(1)

Deferred maintenance is politically and physically acceptable because an immediate effect is not felt: Yet this neglect is insidious. As these facilities age they physically decay and provide less capacity and service to users and slowly but surely the public is faced with an increased risk of failure, delay, accident and injury. The stress of competing priorities has left public works agencies with “hypofunding” at exactly the wrong time in their life cycle.

Traditional Public Works Investment Decisions
While public works investment decisions are the choices of government leadership based on the recommendations of public works managers, political preferences as well as concepts of economics have impacted investment. Since the 1930s, investment decisions for new public works facilities have sought to base budgeting decisions on the technique of benefit-cost analysis. Considered by engineers, managers and legislators alike to be an appropriate method for comparing projects, benefit-cost has the neutral objective of maximizing the net payoff of benefits and costs that can be measured in dollars.

It is an intoxicating method, for the initial understanding of the analysis easily convinces one the investment decision that chooses the highest present value of the net cash flow is surely the most rational act for public decision making. Given the acceptability of the benefit-cost logic, the method has been mandated by some federal statutes for federal program projects as well as categorical/project grants to state/local governments. Of course, analysis of a flood control or transportation project does not always insure projects across all public works functions are compared or insist certain areas/regions be neglected if their benefit-cost ratios were low or less than one. Obviously, imbalances between highways and flood control development would not be practicable solely on the basis of the highest benefit-cost projects for all infrastructure, let alone other public programs. Government is not simply maximizing total wealth as a private enterprise would do, but instead it is required to Provide a set of infrastructure necessary for community life
whether or not the best investment return is realized. But given limited resources, the goal of economic rationality may become more desirable for public investment.

In spite of the inference above, it is not the intention of this paper to challenge the use of benefit-cost analysis in infrastructure capital development. None-the-less, there are
both strengths as well as potential in such economic analysis.(2)

Arguments that justify benefit-cost:

  1. Utility of benefits and costs are compared as dollars
  2. Time value of money is expressed by present values
  3. Discount rate is chosen as the best opportunity rate for alternative use of the resources
  4. Net present value calculations can compare projects and determine whether projects should be funded at all

In sum, the analysis can take the capriciousness out of decisions.

Dangers that decrease the value of benefit-cost, even create risk with its use:

  1. Benefits must be reduced to dollars, neglecting some utility that cannot be measured easily with dollars
  2. Benefit calculations are often implied and can be exaggerated
  3. Possible alternative actions are easily neglected
  4. Discount rates affect results of the analysis, slower rates can help justify investments

In sum, the analysis can be misused to support predetermined preferences.

Another issue in capital decisions is how maintenance costs and choices are included in the analysis of public works projects? Commonly an estimated cost for maintenance is included in the benefit-cost calculations over the life of the project. There is some doubt as to whether a serious understanding of maintenance burdens over the life of the facility is developed at the time the capital decision was made. More likely a simple estimate is developed with little thought of alternative maintenance strategies or alternative designs that affect maintenance requirements and costs over time.

In benefit-cost analysis, cost estimates are thought to be more accurate and honest than benefit data. Benefit measurements may well be implied or imputed and contain data which is often subjective and uncertain. For maintenance costs, inaccuracy and uncertainty may creep into the analysis because a serious exploration of the maintenance management task has not been attempted at the early stage of new facility development.

In spite of new infrastructure construction in may parts of the nation, for the most part of public works task is shifting from capital development to maintenance of a decaying infrastructure where planned useful lives of many facilities are being exceeded. As systems decay, capacities are decreased and failures become more frequent. The result is a public not able to finance the necessary rehabilitation to protect their interests and decrease their risks.

Infrastructure Management Today
A thoughtful essay prepared by Royce Hanson entitled “The Next Generation in the Management of Public Works” challenges us to recognize a generation of public works management where the “management of the capital stock will be more important than
adding to it.” He admonishes public works managers:

“Engineers and public works directors think of themselves as builders, not maintainers and managers. They live capital-intensive fantasy lives. Replacing the ‘edifice complex’ with a passion for management will require major changes in the education and acculturation of those who lead public works organization and those who educate them.”(3)

A premise of this research is that the task of maintenance management has not been well developed in the field of public works management. Hanson explains the maintenance immaturity as follows:

“Maintenance has fared poorly in public management for several reasons. There are no well-defined standards …it is hard to measure the impact of preventive and regular maintenance programs-construction has a strong constituency… maintenance has weak public support. The effects of poor maintenance are insidious but slow to become obvious… maintenance is usually supported from general operating revenues and must compete with other higher visibility services… it is, therefore, an easy budget item to cut or constrain …since the effects …are unlikely to show for several years.”(4)

Given this challenge, the purpose here is to comprehend the maintenance management task facing public works managers, to address the methods of analysis used by those at the cutting edge of maintenance technology and to prepare managers for the consultants trying to assist agencies with the management needs for more sophistication in infrastructure maintenance decisions.

Public Works managers have significant choices as they commit resources to maintenance of existing facilities. Several maintenance strategies are available and the management task is to determine which strategy should be applied with what frequency throughout the life of infrastructure systems. A simple set of alternative interventions is listed below, from routine and repetitive preventive maintenance to major and infrequent reconstruction:

  1. Preventive maintenance and inspection of facilities: cleaning, clearing, protecting
  2. Periodic repair of weaknesses or failures: patching, filling, correcting
  3. Rehabilitate or to refurbish: overlay, reline, or reapply
  4. Reconstruct part or all of the system: remove and reconstruct or replace

Managers normally rely on their past practices and intuition with these systems to decide which maintenance strategies are appropriate for each budget cycle. They are faced with political pressure to select particular segments of the infrastructure network for immediate attention, while they have a professional obligation to uniformly and fairly serve user needs. In either event they may not choose an optimal allocation of resources in economic terms or by any other performance standard. A simple economic analysis may not consider the actual utility of system performance to the jurisdiction, because such performance measures can go beyond dollar benefits to more elaborate measures of capacity/convenience, safety/injuries and strength/failure risk which are not easily measured in dollars.

If works managers seek a more sophisticated method, then a “maintenance management system” which includes a technical evaluation of infrastructure performance history, a prediction of system performance under different maintenance strategies and costs can allow a more optimal allocation of maintenance dollars. This does not mean managers’ intuitive should not enter the investment decisions. The collective experience, knowledge and judgment of public works maintenance manager can be captured via “expert systems” and used as input to investment decisions. The ultimate decision ought to be made after seeing the evidence of a maintenance management which can integrate an expert system into the analysis.

The following description captures the momentum of academics, consultants and practitioners who are already engaged in maintenance management systems.

Maintenance Management Systems(MMS)
Public works will need a maintenance management perspective to meld with a capital investment plan. Non-growth communities as well as those cities with aging infrastructure are increasingly obligated maintenance and rehabilitation. Royce Hanson suggests the opportunity for public works managers:

“Faced with less money to replace facilities, managers have begun to perfect their maintenance regimes …with the availability of analysis units, computers and other advanced technology, managers are moving from 2nd generation preventive maintenance programs, based on regular cycles of inspection to condition-based systems that can target maintenance efforts more precisely to areas of greatest need. A number of jurisdictions are also developing guidelines based on analysis of levels of risk to set work priorities and to improve on targeted systems”(5)

A comprehensive MMS allows questions to be fully and analytically examined. What is the best combination of alternative maintenance strategies? Does increased preventive maintenance decrease the frequency of periodic repair? Will more frequent rehabilitation extend the life of the facility and lower the life time cost to the owner? Are minimum performance standards being met regarding capacity, safety and structural integrity? What is the expenditure required each year to obtain the minimum life cycle cost for the desired system performance?

Given accurate initial costs, coupled with life cycle maintenance expenses, public works managers can provide rational recommendations for needed infrastructure investment.

Yet design choices also affect maintenance decisions. Decisions in the design process may reduce the overall maintenance cost or may suggest different maintenance
interventions than expected or traditionally performed by public works managers. It may be better to increase capital costs to save in the long term, defensible only with more elaborate analysis.

MMS goes beyond minimizing cost to include measurement of infrastructure system performance expected with maintenance intervention. Over the last decade an approach to maintenance management has evolved that replaces simple dollar measures of infrastructure benefits. A comprehensive measure of condition and performance can be chosen and observed over time. Engineering studies will predict performance decay rates under usage and maintenance choices. Analysis can then compare maintenance polices to maximize performance for a minimum cost or a predetermined budget.

The following procedure details a generic method for conducting a MMS. It can be applied to any infrastructure system, be it roadways, embankments/levees, channels, pipes,
buildings or equipment. A specific discussion of pavements will be introduced later since roadways have received the most frequent application of MMS methods to date.

A General Maintenance Management Procedure

  1. Assuming the physical system is in place, gather relevant information on its layout and characteristics. Also identify maintenance assumptions in design regarding expected life and planned usage.
  2. Define service parameters for any infrastructure system. Multiple variables can be chosen and integrated into a comprehensive effectiveness measure. Selected parameters may include capacity, comfort, safety and structural integrity. These variables should represent the utility of performance as preferred by the owner jurisdiction, influenced by professional standards. These performance measurers may evolve over time and may include more complex engineering analysis. Generally, an integrated performance measure will be a simple multiple attribute model as shown:

    PERFORMANCE INDEX = WiXi

    Where Xi are parameters for quality of the service and Wi are weightings or coefficients chosen by the agency in concert with engineering analysis.

  3. Observe the current condition of the system in terms of the performance parameters. Ideally a history is available to help predict future performance with a particular maintenance strategy for the actual system under its unique environmental and usage conditions.
  4. If an agency’s own performance history is not available because they have not kept necessary records or have not tested their systems with alternative maintenance configurations, they must rely upon research studies which have tested comparable systems under similar environmental situations and demands.(6) Then engineering analysis allows a prediction of performance with different maintenance choices. A conceptual model for expected performance decay and maintenance interventions with minimum standards is demonstrated below:(7)
  5. Given the performance variables and the predicted performance of maintenance programs, it is possible to make choices as to maintenance investments in the short term and long term. The method of selecting projects or areas of your network for interventions can range from a simple ranking procedure to a complex optimization technique. A representation of this analytical continuum follows:
    a) List all projects needed to achieve minimum acceptable performance levels and select by least cost or a heuristic criterion
    b) Rank projects by total performance achieved over time (area under performance curve) and accept all those within the budget
    c) Rank cost effectiveness or total performance area divided by cost for all projects and select within budget limits
    d) Select optimal combination of projects based on performance area and costs, using a mathematical model
  6. Implement the desired investment policy over several years through a work scheduling and control system. Establish an information system to record data on the resources expended on maintenance projects (actual costs of equipment, labor and materials), including productivity data. Conduct surveys on facility condition to verify predicted performance. This validation step also provides information to revise the methodology in subsequent years.

Measurement of Present Serviceability

Applying Maintenance Management to Pavements
Pavements are a common usage of MMS because they exist everywhere, in highways, bridges, streets, airports/seaports and parking lots. Pavements represent a large portion of public works investment than any other pubic facility. Pavements provide direct, immediate economic benefit to the concern unity, thus they receive the fist and most attention.

It is relatively easily to observe and feel the physical conditions of pavements and the public may demand quick fixes to the potholes, cracks and rough surfaces. Many research and professional organizations have done much on pavement maintenance strategies but this research has received minimal development and application. Public works mangers need to learn how to put these ideas and research results into practice.(8)

To begin a pavement management system(PMS) the search for performance measure is the initial step. The research have established a very similar integrated performance measure or present serviceability index(PSI).(9) This approach integrates several parameters into an overall performance measure. For instance:

PSI = f(riding comfort, skid resistance, structural strength, visual condition)

Riding quality or comfort had correlate well with PSI according to AASHO highway research.(10)

 

Major Types of Pavement Outputs

These individual parameters can be weighted according to the choice of agency. To some managers the strength parameter is more important to their decision making.

On the bases of engineering research pavement serviceability can be related to technical design measurements. Without presenting the precision mathematical expression, the following function has been developed empirically:(11)

PSI = f(pavement structure, regional climate factor, soil support value, number of design axle loads)

Agencies must find the commitment to observe the chosen parameters over the usage history of their pavements. While this is a task they ought to be able to conduct themselves, most will need to be trained. Some smaller communities may continually need assistance.(12)

Predicting performance of a pavement under environmental conditions and usage is essential, yet by far the most technically demanding part of PMS. It is beyond this paper to capture the engineering research and analysis involved in establishing the relationship with pavement overlays, patching, seal coating or reconstruction and the expected performance over time after maintenance actions. This is a critical part of this method and will depend on an engineering analysis and past research results. Significant research has been conducted and agencies, together with consultants in PMS, will need to rely on the work of the Army Corps of Engineering and the American Association of State Highway and Transportation Officials.(13)

To help comprehend the analysis involved in pavement management investment choices, a simplified example from the book by Haas and Hudson is presented.(14) Performance curves and cost calculations are shown on the figures which follow. The example proposes 3 alternative rehabilitation strategies, essentially using different pavement overlay thickness. The performance profiles in the first figure displays the rates of performance decay expected, which would be based on surveys and research information.

Analysis of Pavement Management Investment Choices

Summary of Cost Calculations for Three Sample Alternative Pavement Rehabilitation Strategies

In this example the utility of serviceability has been converted to reduced costs to users. These benefits or cost savings are different for the 3 alternative strategies. This approach requires the agency or their consultant to convert improvements to reduced costs. But the credibility of this conversion remains questionable and further work must be done to develop adequate information to convince managers and political leadership. All agency and user costs are then discounted to present values, very much like a benefit-cost approach. While the figures demonstrate the cost analysis, the risk of faulty calculations of user costs remains.A preferred approach because of the weakness of benefit or cost savings calculation would not assign dollar values to pavement performance but would maximize the level of PSI over the life of the facility, choosing the strategy with the largest area under the PSI curve.(15)

In this case, the objective would be the maximum performance for the minimum cost over some period of time. This could be achieved analytically by ranked comparison of the performance-cost ratios for a finite number of alternative maintenance treatments within a given budget: A more elaborate approach could use an optimization model like linear programming to provide the maximum performance for a mix of projects within a budget constraint or another version of a LP model would minimize total cost over time, constrained by required minimum serviceability levels across part of all of the network.

Choices for conducting a PMS and its required engineering studies and management analyses are the responsibility of the public works manager. Before making a budget recommendation, each manager ought to comprehend methods, data requirements, performance variables, research inputs and determine the staff and computer resources needed to complete the process.

Critical Questions for Maintenance System Managers
From the perspective of the public works manager, several questions and related policy issues are addressed. The following arguments are ordered according to the generic MM procedure introduced before.

  1. How is the agency’s infrastructure system performance being measured? Let it be a conscious choice of the management and not simply an acceptance of an engineering text or computer program. Of course, for any performance measures chosen, it must be possible to relate maintenance strategies and to decay of the system serviceability over time.
  2. Historical records of infrastructure systems provide a necessary start toward understanding MMS and achieving an analysis which is rational. Given the technical sophistication and an era of privatization, most will need to hire a consultant to survey systems, train staff and conduct analysis. While taking advantage of the consultant’s experience, can public works agencies develop the internal skills to gather information, comprehend the approach and the analysis and build the computer data bases needed?
  3. Since the most difficult part of the process in the determination of performance decay rates for systems under different maintenance applications, most agencies will need to rely on research of others and use consultants to develop these relationships. Managers can become technical critics at this stage, using their engineering and administrative staff to insure understanding and prevent domination by technicians and consultants.
  4. Decisions about the economic or analytical methods used to finally choose a set of maintenance projects is the burden of public works managers. In reality, many agencies will choose a simple ranking of projects by cost, possibly with some heuristic rule for selecting projects within the budget constraint. A simple approach results for a variety of reasons. First simplicity readily allows political input: second, managers may not understand the methods: third, data availability may limited analysis and, finally, the cost of elaborate analysis is often unacceptable? Managers need to recognize their obligation to choose the method used to select projects when they enter into an agreement with a consultant.
  5. Project cost control is always desirable for budget responsibility, but a valuable payoff of a comprehensive cost accounting record goes beyond fiduciary control. Such data is essential to provide information to validate MMS decisions. Were the costs predicted in design or in the maintenance decision stage accurate? This same control system can include observation of infrastructure facility serviceability, also critical to validation of the MMS methodology.

An Inundation of Consultants
At every turn, public works managers have opportunities to acquire a consultant’s service to assist them with a MMS, for almost every infrastructure system they manage. The APWA package called PAVER can be an alternative to consultants. (16) During the preparation of this article, MMS consultants contacted were quite hesitant to share information about their methods and computer packages. They do consider the information proprietary and welcome the purchase of services to get access to their computer program.

An argument for open sharing of computer packages is not being made. Since most public works organizations could not accomplish maintenance management without consultant assistance, the availability of consultant services and their price will affect usage. Since wider use is encouraged, some means need to be developed to distribute the potential of MMS to the broader public works community at a reasonable cost. Hopefully, this manuscript will contribute to that end.

Nonetheless, there are some issues to be raised as practitioners are considering consultant packages. Managers who consider consultant services are acquiring both a method of determining maintenance investment, as well as a computer package for handling data, conducting analysis and producing reports.

To begin, any computer package ought to be judged by at least these criteria:

  1. What hardware storage capacity and processing speed is needed?
  2. How does the program interface or network with existing information systems and formats in your organization?
  3. Is the program user friendly, does it contain menus for clear options and ease of execution?
  4. Is the personnel training required kept to a minimum, are manuals available?
  5. Is technical assistance readily available and at what cost?
  6. Does the program accomplish the needed tasks you had predetermined?

As important as these initial questions, there are further issues managers face with MMS:

  1. onsidering the balance between the agency’s own efforts and those of the consultant, can the agency minimize costs with certain tasks completed by agency staff? Field testing, data collection and even report generation may be done in house, serving to increase the knowledge of the agency and reduce costs.
  2. Can the agency adapt the program to fit special needs and existing information systems? It is acceptable if the agency’s present project, work schedule and cost accounting record systems must be recreated in the format of the consultants’ computer package?
  3. Are there options used for comparing performance and costs when selecting maintenance strategies and work projects? This critical part of maintenance investment recommendations is often not considered seriously by public works managers.

It is not expected that all agencies and computer packages will achieve sophisticated methods of analysis. While there may be little additional payoff compared to less sophisticated methods, even a small marginal benefit can save millions of dollars over the life of these expensive capital projects. Also the cost rises when computer packages are more complex and demand better hardware capacity, speed and processing. Many users of computer services are not ready to comprehend high sophistication in analysis, so there is a tendency by managers and consultants alike to choose a method that is understandable by all actors in the policy making process. The goal of optimality in maintenance investment decision making remains an issue to be recognized by managers as they embark on a MMS.

In general, a consultant can do it all for you. For most agencies, asking the above questions will cause them to take actions to save consulting dollars and enhance their ability to
eventually more of the work themselves.

Conclusion and Opportunities
MMS provides a focus on infrastructure and public works management at the right time and brings the right solution to a national problem. With aging facilities and maintenance neglect, public managers have the opportunity to address the political lethargy. If they develop management systems, gather data, conduct analyses, they can offer public works investment recommendations that convincingly argue for getting beyond the infrastructure crisis.

No other path seems possible: that is, in absence of the management methods presented here, no progress on infrastructure seems likely and the public will continue to be placed at increasing risk when using our public works. More use of private consultants will likely result in acceleration of change and technological innovation in public works.

MMS have been installed by many communities in this nation whose managers have been willing to pursue an innovative approach. The large number of consultants could not survive if many public works managers were not taking the leap. How these managers are actually using MMS should be the focus of substantial research by all academics concerned with infrastructure as well as APWA, the professional association of public works managers. Civil engineering and public management disciplines ought to join together to raise the national consciousness about infrastructure condition and the methods and criteria used to make these public policy decisions.(17)

No doubt there will not be sufficient funds forthcoming to bring infrastructure conditions up to ideal standards any time some. Therefore, it is even more critical that the best decision models are available to the policy process to seek the maximum performance for limited dollars and to create the most convincing case in this national political neglect.

There has been much written to suggest new institutional, financial and managerial innovations to address the infrastructure issue. This presentation offers an approach, an innovation for many public works organizations, that can improve public policy making without demanding significant additional workers or management resources. No new administrative units, no structural change in government or new legislation is proposed. Rather the message is simply concerned with the managerial method of making budget recommendations for public works maintenance expenditures.

None-the-less, this approach to maintenance management may surface the need for increased budget dollars to achieve the minimum standard of infrastructure performance, let alone to achieve the optimal long term performance-cost. In addition, this analysis of total life cycle costs will suggest the need to reconsider design standards and assumptions. It will focus managers and policy makers on the main policy issues and make the need for infrastructure investment more manageable. Whether or not increased funding is received in the short term to begin to overcome weak performance, all this research asks is that the condition of infrastructure and the consequences of investment be made clear and open to public debate.

Bibliography

  1. Pat Choate-and Susan Walter, America in Ruins, Council of Planning Agencies, 1981
  2. See the critique of benefit-cost in “The Economics of Planning and Managing Public Investments”, Ch.4, Vaughn and Pollard, Rebuilding America, Vol. 1, 1984
  3. Royce Hanson, The Next Generation in the Management of Public Works, National Academy of Public Administration, Washington DC, November 4, 1987, p. 40
  4. Ibid, p. 21
  5. Ibid, p. 26
  6. AASHO (AASHTO)
  7. Ralph Haas and W. Ronald Hudson, Pavement Management Systems, Krieger, 1978, p. 264
  8. TRB, NSF, FHWA, NCHRP, State DOTS and APWA . . . .(PAVER)
  9. Ibid: and Pavement Management Guide, Roads and Transportation Association of Canada, 1977
  10. AASHO tests at UI
  11. Hass, p. 76 R. Yoder and Witsak, Principles of Pavement Design, John Wiley, NY, 2nd edition, p. 508
  12. Haas and Hudson, p. 51
  13. AASHO Road Test etc.
  14. Ibid, pp. 223-226
  15. Pavement Management Guide, p. 3.14
  16. Contact the American Public Works Association’s Research Foundation, Chicago, for information on PAVER
  17. A network of public works management academics have been formed, including faculty from eleven graduate programs in Public Works management recognized by the American Public Works Association. One author, Willard Price, chairs the network. See Graduate Education in Public Works Management: Comparing Recognized Programs, addressing the Maturation of the Field, a report to the American Public Works Association, Graduate Education Committee, September 1990, by Willard Price.

PUBLIC WORKS MAGAZINE, October 1987

Pavement Management System Data: Relevance and Cost
DENNIS POLHILL, P.E.

Mr. Polhill is vice president with Pavement Management Systems, Denver, Colorado

DATA are critical to a pavement management system, and there are three categories of field performance measures that are important. In order of significance for network level pavement management they are: roughness, structural and visual distress data. A fourth category — safety or skid resistance data — is considered on occasion.

Roughness is the parameter of most interest to road users because it costs a user much more money in operating costs to drive on rough roads than on smooth ones. Any acceleration or force imparted to the riders of a vehicle are contributing factors to the driver’s perception of road roughness. To define a pavement roughness function completely, some evaluation of the roughness of the entire surface area of the pavement is required. For most purposes this roughness can be divided into three components of pavement alignment: transverse, longitudinal, and horizontal variations of alignment. Anyone or combination of these variables can make a road appear rough.

The wavelength of the roughness is also important. Vehicle suspension systems and speeds determine which wavelengths are important. Obviously, an aircraft taking off at 200 mph will feel a different roughness than a truck at 55 mph, an automobile at 25 mph, or a bicycle. Consequently, vehicle speeds and types should be considered in assessment of roughness.

Structure is the parameter of greatest importance to the pavement management engineer. A pavement’s performance will deteriorate more quickly because of poor strength than from any other design parameter. An important component of structure is traffic loadings, which are typically considered part of the structural component. A strong pavement with light traffic loads will perform longer than a weak pavement with heavy traffic loads.

Structure is a key variable in how pavements perform. The length and shape of pavement performance curves are significantly affected by pavement strength. Strength information is essential for accurate performance prediction.

Last But Not Least

Visual distress data is the third most important category of data to include in a pavement management system. Distresses are the symptoms of poor performance. Visual distress data are a fruit salad; a combination of many different and unrelated distresses such as raveling, bleeding, cracking, and distortion. Visual distress rating systems in use today vary with regard to the number of distresses used. Some use as few as 2 distresses and others use over 35.

Visual distresses are the result of a combination of variables acting on a pavement. Raveling, bleeding, transverse cracking, and longitudinal cracking are each caused by different sets of variables. Thus, the components of a visual distress index are largely unrelated.

Because visual distresses are caused by unrelated factors, their rates of change are not related. Visual distress data collected over a period of time tend to have significant scatter when plotted on a graph. It is very difficult to draw a curve through visual distress data. The statistical correlation of curves of different visual distresses is typically quite low. Additionally, the weighting factors used to combine distress into an index are important. By changing weighting factors, the shape of a visual distress curve can change dramatically.

Other factors of interest in considering pavement management data are the cost of data collection and the shelf-life of data. Table 1 illustrates the relative costs of various types of data and the annual cost to maintain a current database.

Table 1 – Pavement Management Data Costs

Importance

Shelf Life

Initial Survey Cost

Cost per year of Useful Value

Roughness

1

2-3 years

Low

Low

Structure

2

3-7 years

High

Moderate

Visual Distress

3

1-3 years

Moderate to High

High

Table 1 represents broad ranges. Obviously, there are many variables that affect actual costs. Some cost variables relate to thoroughness or amount of detail data collected, type of equipment used, numbers of tests, and depth of data analysis.

Many agencies that enter into pavement management do so without thoroughly considering the implications of their initial decisions. A visually based system trades off prediction model precision and long term data collection costs in favor of lower initial database setup costs.

The wisdom of visual-only based systems is certainly debated. However, visual-only systems have value. This is particularly true with agencies that have no existing pavement management system.

Pavement management holds enormous potential savings for agencies. The most serious error an agency can make is not to have a pavement management system. Even a poor pavement management system will save more than the cost of its set up and operation.

MAY 1987 Better Roads

EDITORIAL VIEWPOINT
By Ruth W. Stidger, Editor-in-Chief

Better technical leadership is needed in public works. This fact repeatedly comes to the forefront of almost any after-session conversation at meetings where highway department officials gather.

“I was 26 years old and just two years out of college when the Director of Public Works first asked me to look at a street and tell him how to fix it,” one engineer told me recently.

“Having no college training in pavement design or in rehabilitation, I was surprised that my recommendation to overlay was accepted and implemented without question. The following spring, I was even more surprised to find my project in pieces. It was totaled!”

How did this mistake happen? How could the more senior public works manager let it happen? Wasn’t the $60,000 per mile that was spent too much money to throw away on a project that was doomed to failure, because it had been designed by an engineer without the needed technical expertise?

The people in the United States own four million miles of roads. About $10 billion is spent per year maintaining these roads. Too much of that is spent in just such a fashion as the project described.

“The judgment of a more experienced staff person may be used sometimes,” the engineer told me, “but arbitrary judgment is the norm. If you ask where the experienced person gained the knowledge to make these judgments, it comes from the school of hard knocks. And the tuition is $60,000 per mile.”

What could put a stop to waste of this sort? The answer is evolution of new scientific methodologies that systematically lead us to the correct solution more often. Private companies are developing such technical leadership for our highways. Their technology is called pavement management.

Now, it is time for governmental leadership. A pavement management system can tie together all of the aspects of managing the bridges and roads within each geographical area, ensuring that hard-won funding is used to build and maintain our transportation system as effectively as possible. For only a small portion of the total budget, states, counties, and cities can put the methods to work — determining what methods of repair are best, when they are needed for greatest effect, and how to spend that $60,000 per mile to rebuild a road that will last for five years, rather than five months.

Articles about pavement management have appeared often in Better Roads, and more will appear in the months ahead. If you want specific, detailed information, write us, and we will try to obtain it for you. You are needed — to be the leaders in accepting this new technology — and in using it.

PUBLIC WORKS MAGAZINE, April 1987

Benefits of Network Level Pavement Management

DENNIS POLHILL, P.E.

Mr. Polhill is vice president of Pavement Management Systems, Denver, Colorado.

Pavement management has become a familiar concept among public works managers, and each year more public agencies develop a structured program. It is important that technical issues be discussed among public works professionals so that a common understanding of such systems can be developed. To adopt a system without a clear understanding of the possible options can result in expenditures that are not as cost-effective as desired.

The benefits of pavement management can be substantial. At the design or project level the benefits of using the latest and best information available fall into two categories:  

·        Immediate savings in construction cost by not building over-designed facilities.

·        Long term cost savings in the form of reduced future maintenance costs by preventing “under-designed” structures.

Assigning a dollar figure to future maintenance costs is difficult because some service is provided up until the time of premature failure and repair. A further complication is the inflation of construction costs and the discounting of dollars to present value. However, investing in information acquisition on which to base a design can easily be recouped in construction and maintenance savings. Even relatively small cities have reported savings ranging from $20,000 to $250,000; and in several cases the return on the investment has been more than 5,000 percent.

Rehabilitation and Timing

At the design level the focus is on determining the most appropriate rehabilitation. At the network level the focus is on timing. Many communities and agencies have implemented network level pavement management systems. But the questions to be asked include: Are these systems worthwhile? Do they generate savings? Are the savings significant?

At the network level agencies are interested in a reasonably accurate method of predicting pavement performance. A reliable and useful prediction model will determine both the best timing as well as the funding level required for rehabilitation. It is not practical from a cost standpoint to collect all the data needed for detailed engineering design of the rehabilitation for an entire network. Network level pavement management is a management tool while design level pavement management is an engineering tool.

To determine the benefits of a network system it is necessary to know future funding levels and to have a knowledge of how the funds will be expended. This forms a baseline for future comparisons.

Both politically motivated public works management and simplistic pavement management systems that operate without the benefit of structural strength data tend to establish priorities on a “worst-first” basis. Under this approach, however, the needs can quickly outstrip available funding. As the road surfaces become more and more deteriorated the rehabilitation options become fewer and the associated costs higher. The required funding level can grow exponentially. Often the streets deteriorate to a point where the governing agency makes a massive funding effort to correct the problems. Unfortunately because of the crisis atmosphere generated by the hasty attempts to catch up with the deterioration, the funding is often not used cost-effectively. But because the “worst-first” mentality prevails, the solution is short lived.

Substantial Savings

Changing this philosophy requires the use of modern pavement management techniques that accurately evaluate the benefits of different options. Municipalities that have benefited from such a program include Ottawa-Carleton, Ontario, a 14 percent reduction in its street budget; Thermopolis, Wyoming, 16 percent reduction in street budget; and Hartland, Wisconsin, a 24 percent budget reduction. Waterloo, Ontario saved 107 times the cost of the system in four years. Figure 1 illustrates conceptually the impact on the backlog of needs after implementing a management system.

Expenditure of funds is based on cost/benefit calculations for each rehabilitation strategy employed. Establishing priorities based on assessment of the incremental cost/benefit calculations produces the maximum use of available funds and makes candidate projects compete with each other for priority. The projects that yield the greatest rate of return are chosen. The technique of setting priorities by minimizing costs and maximizing benefits is called optimization. (Cutting off the bottom of the “worst-first” list is not optimization.)

Examining the street funding power curve shown in Figure 2 illustrates the following:

·        The y-ordinate represents the total needs backlog at any point in time.

·        Many highway agencies have a backlog of needs that grows exponentially.

·        Funding the backlog of needs is very difficult if not impossible.

·        If currently available funds are used more efficiently, the future needs backlog can he reduced.

On Figure 2, I is the point in time when the management system was put in place and S represents the point where the backlog of needs stops growing. To some observers during the time frame between I and S it may appear that pavement management is not working. The y-ordinate value represented by the difference of Y2 and Y1 is the benefit of the pavement management program. Close to point I the benefit is small, but as the two curves diverge the benefit becomes substantial. The point N represents the time where there is no backlog. When this is reached the governing agency can make some major policy decisions: Should budgets be reduced? Should the street quality standard be increased? Should funds be redirected to other municipal service areas?

Justifying Funding

Governing bodies usually feel more comfortable in providing increased funding for streets after a pavement management program is in place since the expenditures can be readily justified. In Figure 3 two funding levels are shown — a high funding level marked as curve 1 and a lower funding level noted as curve 2. Many management systems work in different ways and may have different levels of efficiency.

Sometimes it is necessary to phase the implementation of a pavement management system. Phasing can be either vertical or horizontal. Vertical phasing is the implementation of a system over part of the network. Horizontal phasing is the implementation of a partial system over an entire network. In Figure 3, curve 2 may represent the first phase in a horizontal or vertical plan while curve 1 may represent a system that is not phased.

The commitment of top management can also affect the success of the management system. While it is sometimes important to deviate from a specified plan of action, it should be realized that the variables introduced from the deviation will require certain trade-offs, which may have some long term effects. Thus in Figure 3, curve 2 may represent a greater degree of “tinkering” with the system than is represented by curve 1.

Many public works managers must work with programs that are underfunded. A proper pavement management system may help some agencies reduce yearly budgets, but will not help those whose expenditures are already inadequate. If the funding level is too low or the backlog of work too large even the most efficient use of funds may not be enough to overcome a growing backlog of needs.

The benefits of pavement management systems can be substantial; savings can be many times the initial investment for engineering data. A good pavement management system will provide benefits that increase with time. These benefits become greater as the needs backlog curves diverge from one another.  nullnullnull

PUBLIC WORKS MAGAZINE, January 1987

Evaluating a Pavement Management System

DENNIS POLHILL, P.E.

Mr. Polhill is Vice President, Pavement Management Systems, Denver, Colorado.

It’s benefits once debated, pavement maintenance has now been accepted as an essential element of public works. The public works profession can now turn its attention to the implementation of pavement management, or managing the management system. This not only involves the selection of a first-time system, but also the improvement, refinement, or rejection of a presently used system.

Numerous questions surround pavement management systems:

  • How much should be spent on pavement management?

  • What features are most important?

  • What part of pavement management should be installed first?

  • What options exist to minimize costs?

  • What are the set-up costs?

  • What are the long term operational costs?

  • What in-house resources are required to operate the system?

  • Can the system be set up with in-house resources?

  • Must a consultant be used?

  • With what level of precision can future conditions be estimated?

  • Of what advantage is some particular piece of equipment?

  • How much data is enough?

  • Are structural tests necessary? How many?

  • Can a visual-based system operate?

  • What is traded off when sample units are used?

  • How do I write a request for proposals?

  • What is a viable selection criteria?

  • What about computer hardware and software?

  • What should the new management system tell me?

  • What are the advantages of “canned” or off-the-shelf programs?

  • How much customization is appropriate?

  • What should this management system tell me about the new “miracle” products in the paving industry?

If you are a pavement manager looking for your first system, these questions may overwhelm you and prevent you from taking action. It has been said that truth lies in simplicity; an understood system is a “simple” system. If one implements this simple system, a structure for gaining knowledge about the effects of using the system will have been established. Do not be embarrassed by selecting a simple system. The entire public works profession is learning about these systems. The sooner a city implements a system, the sooner it will become more knowledgeable and the sooner it will realize the opportunity to capture the cost savings. The advice here is: Take action, select a system, and keep it simple.

Cost or Exactness?

In managing the management system, one concept that can help clarify our thought process is the trade off between cost and exactness. This trade off is a nemesis to managers. It follows them around and attaches itself to virtually every decision rnanagers are asked to make. A simple cost-exactness graph can be applied for comparison of total pavement management systems or for comparison of individual components such as deflection testing, visual ratings, data analysis, etc.

For example, there are dozens of visual rating systems available from various sources. Each has its own set of advantages and disadvantages. As a manager, you must select a system for implementation by your organization. First, you must know what data is most important to you. If it is wheel patch cracking, the measure of exactness might be a percent of accuracy that the visual system can maintain. Plot the cost versus exactness for each system on a simple graph. A range of accuracy and costs may be available from the same source. These sources will plot as lines or points on the graph (Figure 1). Now you must know the percent of accuracy you desire. Then choose the system that best fits your cost and accuracy needs.

The same graph can be applied to structural data (Figure 2). Nondestructive testing, usually in the form of deflection testing, has become popular because of the amount of data that is produced at a relatively low cost. However, the cost-exactness trade-off decisions do not go away. Pavements tend to be very non-homogeneous. Thus, more deflection tests are necessary to increase exactness. The manager must know what the data will be used for and what degree of exactness is required to make a decision from the graph.

Pavement management has come a long way and its benefits are now widely acknowledged. Public works professionals are now focusing on finding the answers to questions arising from managing the pavement management system. This will be an evolutionary process that will produce better and more sophisticated methods.

image

Many large metropolitan areas have initiated pavement management systems during the last several years, as scarce resources and rapidly deteriorating roadways have necessitated cautious and efficient expenditures of tax dollars. Such management helps to prevent accelerated street deterioration through an active preventive maintenance program. Not only is the life span of streets increased, but fewer dollars are spent for repair and construction.

But how does a small city find the dollars to finance a testing program that will provide this kind of management system? Small city street maintenance budgets usually are not adequate for handling necessary rehabilitation, let alone an active preventive maintenance program.

Hartland, Wisconsin, a town of 6,500 people, with a paved street system of 24 miles, decided to look the problem squarely in the eye and initiate a long-range pavement management plan. Even though the cost of the testing and analysis program could have funded 1.5 miles of repair, the Town Council engaged the services of Pavement Management Systems of Denver to establish a 10-year maintenance and rehabilitation plan.

Town Administrator Robert Schaumleffel, who spearheaded the move to the maintenance plan, cites experience in Thermopolis, Wyoming, where that city is saving 5100,000 a year in immediate benefits – 16 percent of the total street budget. He says timely, cost-effective rejuvenation and resurfacing programs were implemented in Thermopolis before rapid deterioration began, thus extending pavement life for a fraction of the cost experienced previously.

“Most cities wait in order to save dollars,” Schaumleffel says. “We feel that the increase in cost for waiting two or three years beyond that critical point in the deterioration curve is something more like 10 times rather than the popularly quoted fivefold increase. The reports allowed Thermopolis to establish those critical points in a pavement’s life cycle, thus saving thousands of dollars over just a three-year period.”

Hartland expects to realize similar results, Schaumleffel says. Accurate testing, coupled with a reliable prediction model for determining pavement deterioration rates, will give the city the ability to establish a timely and effective maintenance and rehabilitation program. In addition, the budget projections generated will allow the city to allocate expenses wisely and plan for long-range financial needs. Although the Town Council had to reallocate scarce dollars for a service ~ whose benefits would only be realized as the program develops, long-range savings are expected to more than replenish that relatively small investment.

Broomfield has redesigned its standards and specifications to include performance specifications before new streets are accepted. Here’s why – and how it works.

by Gene Putman, P.E. and Dennis Polhill, P.E.

Broomfield is a city of 24,945 people located midway between Denver and Boulder. Because of its location, it has grown from a community of 7,000 in 1970. Broomfield ,is affected by the numerous urgent issues typical of boom cities.

The city accepts approximately eight miles of new streets from various developers each year. The soil is primarily clay. typical of front range cities, and is a poor foundation for all types of structures. With limited staff resources to monitor street construction, city engineer Gene Putnam proposed a modification to the city standards and specifications.

Reviewing standards

In 1982 and 1983, the city’s engineering department began a thorough review of the existing city standards and specifications. This review determined which requirements worked properly and where problems in the field suggested a need for changes to the Standards and Specifications. The review and rewrite of the Standards took 24 months to complete, including working with other city departments and reviewing the standards and specifications of other cities in the Denver metro area.

Broomfield’s streets were not performing as required by design. The city’s original pavement section in residential areas was two inches of asphalt and six inches of base. This was changed to three inches of asphalt on eight inches of base as a minimum standard.

The city standards were also changed to require that, during the construction of a residential street, the entire pavement section must be installed with the exception of the final one-inch of asphalt. This final inch would remain oft until the construction of the majority of homes in that area is completed. The reason for the requirement is that, during the construction period, the construction traffic (concrete trucks, material haulers, cranes. etc.) is heavier than normal residential traffic would be. It is unreasonable to require the street design to accommodate this heavier loading, since it exists only at the beginning of construction and not during the normal life of the street.

Before the last inch of asphalt is applied, a new city specification requires that testing be performed to check the adequacy of the existing pavement and what additional asphalt overlay is required to bring the street into conformance.

Deflection testing

The new specification requires the use of non-destructive deflection testing to evaluate the adequacy of pavements. The evaluation is performed by the developer at the time that acceptance is requested. The city requires that the evaluation use a 10-year design life and that the deflections be analyzed by a registered professional engineer with demonstrated experience in the pavement evaluation field. The design life criteria requires that minimal maintenance will be required over the 10-year life.

The application of deflection technology is fairly new. In simple terms, the pavement gets weaker each time it deflects. The pavement deflects each time a load passes over it. The rate at which cracking, distortion, and other irregularities appear is dependent upon the pavement strength. The amount of pavement strength can be measured by measuring how much the pavement deflects under a known load and load application procedure.

Specification accepted

The new standard was adopted September 1984, with some apprehension on the part of both city council and developers. The apprehension increased when the first development evaluated showed serious deficiencies. The apprehension ceased, however, when another development proved acceptable. The standard is now solidly endorsed by all parties – council, developers, city management, and city engineering.

Without the performance specification. Broomfield would have accepted the streets in the first acceptance request and would have been burdened with excessive maintenance costs and a poor service level until capital expenditures could have been budgeted for major rehabilitation. Because the deficiencies were identified prior to pavement failure, the developer was able to make repairs to the roadway before applying the final lift of asphalt.

At first the development community was concerned about the extra cost. However, the credibility level of the more conscientious developers has increased, and even the developers are happy with the new standard. Now they can sell homes with a virtual guarantee that the street will be in good condition for a period of time. Home buyers also have the assurance that disputes over street maintenance responsibility between the city and the developer are not likely to occur.

Other communities in front range Colorado have followed Broomfield’s lead. Several communities have conducted performance evaluations on an individual project basis. Littleton and Arapahoe County have adopted the Broomfield specification for all street acceptances.

For a copy of the Broomfield performance specification, contact Gene Putman at 303-469-3301, or Dennis Polhill, Pavement Management Systems, Inc., at 303-232-2207.

Deflection Analysis and Case Illustrations of Thin Asphalt Pavements for Overlay Design

April 9, 1984

Frank Meyer, PhD, P.Eng.
PMS Group, Cambridge, Ontario

Ralph Haas, PhD, P.Eng.,
Professor & Chairman, Dept. of Civil Engineering
University of Waterloo

 

Dennis Polhill, MSCE, MPW, P.E.
PMS Group, Denver, Colorado

 

Paper Prepared for
Presentation to
The Annual Meeting of
The Association of Asphalt Paving Technologists
Scottsdale, Arizona
April 9-11, 1984

ABSTRACT

Lack of structural adequacy is often a major reason for the rapid deterioration of a thin asphalt pavement. Deflection testing and analysis provides a sound basis for assessing the degree of such structural inadequacy and for designing overlays of sufficient thickness to strengthen the pavement.

This paper describes the basic role of overlay design as a project level activity within pavement management, defines the factors involved in deflection testing, describes how deflection data can be analyzed and used in overlay thickness design, and provides a specific case illustration.

Deflection testing involves three basic considerations: (1) type of equipment, (2) the testing program itself and (3) analysis and use of the data for overlay design. The paper identifies the most common pieces of equipment used in North America, and some of their features. As well, a suggested test program for different classes of highway or streets is given.

The analysis of deflection data for use in overlay design depends on the design method to be used. This can range from an empirical approach where overlay thicknesses are to be sufficient to reduce the surface deflection to a maximum tolerable value, which itself is a function of the traffic level, to the theoretical or mechanistic where material properties and elastic layer models are used. While the latter approach is desirable, it has some problems with thin asphalt pavements; consequently, the empirical approach is currently more applicable in this case.

An example is provided in the paper which uses empirical procedures but which is equally applicable to a mechanistic procedure in terms of results. The example illustrates how a designer can use computer graphics and analysis in an efficient way to capture the deflection variation along a section of road, and between lanes, in an efficient way so that a final, practical and balanced overlay design can be determined.

INTRODUCTION

The United States and Canada have a large mileage of thin asphalt pavements. These pavements can deteriorate fairly rapidly and require rehabilitation after relatively short service lives.

Rehabilitation, including overlaying, may be required for one or more of the following reasons:

1. Inadequate structural capacity for current or expected future traffic loading

2. Unacceptable level of service in terms of Present Service ability Index (PSI) or Riding Comfort Index (RCI)

3. Unacceptable level of surface distress

4. Unacceptable level of safety

5. Unacceptable costs to the road user

6. Unacceptable maintenance costs.

In the case of thin asphalt pavements, lack of structural adequacy is usually a major reason, which itself is responsible for accelerated loss of serviceability, surface distress, etc.

Several methods exist for assessing structural adequacy, both destructive (i.e. coring) and non destructive in nature. The latter usually is carried out by deflection testing, with several devices commonly used in North America. Consequently, deflection testing and analysis represents a sound basis for overlay design, especially in the case of thin asphalt pavements.

But the way in which deflection data can be and is used for overlay design varies widely, ranging from the relatively simple and empirical to the theoretical where back calculation of material properties is used with layered elastic models. The latter, often termed a “mechanistic approach” is attractive in that it allows new materials, varying load limits and configurations, varying materials properties, etc. to be explicitly recognized. However, it can also have limitations, as subsequently discussed.

Scope and Objectives of the Paper

This paper is concerned with the use of deflection testing and analysis to design overlays for thin asphalt pavements. More specifically, the objectives are as follows:

1. To identify the role of overlay design in pavement management

2. To define and describe the factors involved in deflection testing

3. To describe how deflection data can be analyzed and used in overlay thickness design, and

4. To present specific examples of the foregoing.

OVERLAY DESIGN AND PAVEMENT MANAGEMENT

Much has been written on pavement management, and there are two books available (1,2) plus many published papers. It is generally accepted that pavement management is actually carried out at two distinct but interrelated levels. One is the network level, where the end result is priority programs of rehabilitation, maintenance and new pavement construction for the various years of the program period. The other is the project level, where the end result includes detailed designs for the projects that come “on stream” from the network program, plus construction and periodic maintenance. Figure 1 illustrates these two basic levels of pavement management.
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Overlay design of course is a project level activity. It requires more detailed testing, including deflection, than the network level. For example, a network level field inventory may involve very limited deflection testing, if at all [There is a lack of agreement in the pavement engineering field as to whether deflection surveys are needed at the network level. For example, Arizona and New York do not use them; Utah and Idaho use them. While good arguments can be made for either situation, the authors of this paper support the use of deflection surveys at the network level because they feel the “quality” of the information gained far outweighs other, indirect measures of structural adequacy (such as layer thicknesses), and because of its value in identifying needs and developing rehabilitation strategies.], while deflection testing for a project level overlay design may be carried out at 50 m or closer intervals. Karan, et al (3) have shown that an approximate overlay design of uniform thickness for an entire section length is sufficient at the network level, and that subsequent detailed testing and design at the project level, when it has come on stream (i.e., it’s designated year in the program has arrived), can “fine tune” the design to result in padding and level up where needed along the section length, varying thicknesses, detailed quantities, etc. that are required for the actual contract.

The following sections in this paper assume that the first network level of pavement management has been carried out, that a project has been programmed, and that the next step is detailed testing, analysis and design.

DEFLECTION TESTING

Of the non-destructive methods available for measuring pavement response to load and hence evaluating structural adequacy, deflection testing is by far the most popular. Deflection as a structural measure has many advantages. It is relatively simple, generally proportional to load and a good indicator of how the pavement will perform. However, deflection measurements also have some limitations, including wide variations with season and temperature which must somehow be represented for design purposes, the fact that maximum deflection under load may not adequately capture the structural characteristics of the pavement and that deflection is sometimes not well related to fatigue and permanent deformation damage.

If deflection testing is to be used, the following questions must be answered:

l. What type of equipment is most suitable?

2. How should a testing program be set up (i.e., factors to consider, one lane or both lanes, spacing of measurements, etc.)?

3. How can the data be analyzed and used for overlay design?

The first two questions are addressed in the following paragraphs, while the third question is addressed in the next section.

Regarding equipment, the most commonly used types in North America are the Benkelman Beam, Dynaflect, Road Rater and Falling Weight Deflectometer. The various features and attributes of these pieces of equipment were extensively considered in two FHWA work-shops on pavement management in Phoenix and Charlotte in 1980. Table 1 provides a summary listing (4). It is not the purpose of this paper to try and define which is best on an absolute basis, because each has advantages and disadvantages which vary in importance with the individual user. The Dynaflect is used for illustrative purposes in this paper, primarily because of its widespread use and experience with it. However, the principles employed and type of results subsequently shown should be similar for any of these four pieces of equipment.

The operation and theories associated with the devices listed in Table 1 are described in detail in many publications, including Ref. (5,6).

TABLE 1 – STRUCTURAL EVALUATION EQUIPMENT

After Ref. (4)

 

INVENTORY

               
 

OR DESIGN

Cap.

COST OF

MAN-

 

RELI-

REPRODUC-

PRODUCT-

AUTO-

EQUIPMENT TYPE

(I OR D)

Cost

OPERATION

POWER

SAFETY

ABILITY

IVITY

IVITY

MATED

                   
Benkelman Beam

I/D

Low.

High

2 – 6

 

Good

Fair

Medium

No

Dynaflect

I/D

Low.

Med.

 1 – 6

 

Good

Good

Med/Hi

Avail.

Road Rater

I/D

Med.

Med.

 1 – 6

 

Good

Good

Med/Hi

Avail.

Falling Weight Deflectometer

D

Med.

Med.

2 – 6

 

Good

Good

Med/Hi

Avail.

                   
Cox Meter

D

?

 

 1 – 6

 

Fair

Good

Hi+

Avail.



California

Deflectometer

D

High

 

 2 – 6

 

Satisf.

 

Medium

?

LaCroix Deflectograph  

High

 

2 – 6

 

Satisf.

 

Medium

Yes

WES Vibrator  

High

 

3 – 6

 

Fair

Good

Medium

No

FHWA “Thumper”

Research

High +

 

3 – 6

 

Fair

Good

High

?

Plate Bearing  

High

 

3 – 6

 

Satisf.

 

Low

No

Field CBR                  
Laboratory Tests                  

Test Program and Procedures

The development of test programs and procedures for deflection testing is usually influenced by the following factors: (1) testing budget available, (2) type or class of highway or street – i.e., free way, arterial, collector or local, (3) variation of subgrade and drainage conditions along the section length (4) number of lanes, (5) volume of traffic, (6) length of the section itself.

For thin asphalt pavements these factors can assume particular importance and it may be necessary to do some “tailoring” of the testing program to the particular conditions at hand. However, for thin asphalt pavements and average conditions, the program shown in Figure 2 may be used as a guideline. It is based on a background of experience with many thousands of miles of both rural and urban pavements.

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The costs will of course vary somewhat with the interval spacings shown in Figure 2. Larger intervals could cut the costs somewhat, but the decrease would be marginal and the quality of information loss could be substantial.

DEFLECTION ANALYSIS AND THICKNESS DESIGN

Deflection test results can either be used almost directly, with a minimum of analysis, in designing overlay thicknesses, or they can be used to “back calculate” material properties using mechanistic analyses. A considerable number of such mechanistic analysis methods exist, some of which are listed in Table 2, along with references. The use of mechanistic procedures for overlay design has been described in many publications and is incorporated, with a considerable number of variations, in the overlay design procedures of various agencies. Epps and Hicks have provided a good summary of typical approaches and methods (31). While the advantages of such mechanistic procedures are many, as previously pointed out, and while improvements in technology will undoubtedly lead to their use on a more widespread and effective basis in the future, they currently have some major limitations with thin pavements. The results (i.e., material properties, stresses and strains, deflections) are often quite unrealistic and the reasons probably include some of the boundary condition assumptions used in the layer theories.

The empirical deflection based procedures thus find more widespread application in the case of thin asphalt pavements and are used in the following paragraphs and sections. Again, however, the types of results shown could be the same for empirically or mechanistically based design procedures.

The empirical, deflection based approaches are typified by The Asphalt Institute’s procedure in their 1969 MS-17 Manual (32), The Roads and Transportation of Canada’s (RTAC) procedure (1), and the British TRRL method (33). They all are based on providing sufficient overlay thickness to reduce the surface deflection to some standard or maximum tolerable value, which is a function of the number of equivalent single axle loads to be carried.

TABLE 2 – TYPICAL METHODS – FROM DEFLECTION TO MATERIAL PROPERTIES

METHOD COMMENTS REFERENCES
SWIFT 2 layer system, elastic 7
VASWANI equivalent 2 layer system 8,9,10
ODEMARK equivalent 2 layer system 11,12
WISEMAN 2 layer system 13,14
ULLIDTZ 3 layers, equivalent system 15,16
IRWIN – (MODCOMP, NELAPAV) 8 layers, non-linear elastic model (stress-dependent) 17,18,19,
THOMPSON – ILLI-PAVE stress-dependent finite-element 20
BUSH – CHEVDEF 4 layers, layered elastic model 21,22,23
DYNATEST – ISSEM4        – ELMOD 4 layers –elastic moduli3 layers – limited stress-dependent equivalent system 24
SHELL – BISAR 99 layers, layered elastic 25,26
PENN. STATE elastic layer, 4 layers 27,28
MAJIDZADEH-MOD4 4 layers, elastic layer 29,30

KENTUCKY

   

Maximum Tolerable Deflection

The maximum tolerable deflection (MTD) is a function of traffic and various relationships have been developed by a number of agencies. Figure 3 provides some comparisons between various agencies in North America, England and Australia.
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Correlation to Benkelman Beam

Since the empirical, deflection based procedures were developed with Benkelman Beam deflections, correlations must be established if, for example, Dynaflect is used. Figure 3 provides example correlations for several agencies. These can vary widely, depending on sub-grade soil type, pavement type, and climatic conditions.

It is desirable that an agency establish a correlation for its own particular area.

Also, there is usually considerable-scatter in the data whenever such correlations are attempted. This is quite understandable because the Dynaflect and Benkelman Beam are quite different in configuration, and what and how they measure (i.e., dynamic vs static). But the scatter often results in engineers believing one or the other device is deficient (which is not the case, for the aforementioned reasons) or that the correlation is useless. The latter is also not valid because the errors involved in estimating Benkelman Beam deflection from Dynaflect deflection are not inconsistent with other errors and variations in the overlay design and construction process (i.e., variation in deflection along the section length, errors in predicting traffic, and variations in constructed thickness).. Moreover, these errors should be random and thus have the effect of negating each other.

Overlay Thickness

When the Benkelman Beam deflection has been directly measured to be overlayed, (usually referred to as the design estimated from Dynaflect measurements (using the type in Fig. 4), then the overlay thickness required to reduce the surface deflection to the MTD value (which has been determined from a Fig. 3 type relationship) can be determined from the type of design curve shown in Figure 5. The overlay thickness is in inches of equivalent gravel and has to be converted to asphalt concrete. For example, if the Benkelman Beam deflection on the section were 125×10-3 in., and if the MTD were 0.070 in., overlay thickness required (Fig. 5) would be about 5.6 in. Further, if the equivalency were 2:1 for asphalt would be 5.6 : 2 = 2.8 in. on the section deflection) or of correlation existing then the of equivalent gravel. concrete to gravel, then the actual thickness = 2 3/4 in. of asphalt concrete.
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Adjustment to Design Deflection Values

Two major adjustments are usually required to design deflection values:

1. Conversion of the (measured) design deflection to a peak spring value (because the design charts are based on this)

2. Temperature corrections.

Extensive studies in Canada (1) and elsewhere have shown that the ratio of fall to spring deflection values usually range between about 1.6 to 1.8. Thus, if a set of deflection measurements are made in the summer or fall, they should be multiplied by about 1.7 to convert them to peak spring values. However, this should be used with considerable caution because it certainly varies with region or climatic zone. For example, in Texas or Arizona, these ratios might be closer to 1.0.

Temperature correction graphs have been published by the Asphalt Institute (32) and RTAC (1).

CASE ILLUSTRATION

An actual example of a partially automated overlay design for a thin asphalt pavement can illustrate the approach and procedures out-lined in the foregoing sections.

It involves 2.825 km (1.75 miles) of two-lane rural road with an AADT of 5,000, commercial traffic volume of 5% and estimated growth rate of 7.5% per year. The average daily number of equivalent single axle loads in the design lane (DTN) for the design period of 10 years has been calculated as 226, with an accumulated total of 680,000 for the 10 years. Summary data for the project is shown in Table 3.

TABLE #3

SUMMARY INFORMATION FOR THE OVERLAY DESIGN PROJECT

       
NUMBER OF TESTS

57

AADT (BOTH DIRECITONS)

5000

MAN OF S-1

0.90

GROWTH FACTOR  

1.53

STANDARD DEVIATION OF S-1

0.38

AADT IN DESIGN YEAR

3826

DESIGN DEFLECTION

2.41

COMMERCIAL TRAFFIC CONTENT

191.3

ANALYSIS PERIOD (YEARS)

10

ESAL EQUIVALENCY FACTOR

1.00

SEASONAL ADJUSTMENT

1.80

DTN

226.4

NUMBER OF LANES

2

TOTAL-DESIGN PERIOD ESAL

679082

COMMERCIAL TRAFFIC (%)

5

MTD (MILS)

1.45

GROWTH RATE (%)

7.5

   

For the traffic levels shown, a maximum tolerable deflection value of 1.45 miles is determined, using the Ontario criteria in Figure 3. This means that the actual deflection or design deflection must be reduced to this value by sufficient overlay thickness.

The field work consisted of the following: (1) deflection testing every 50 m (150 ft), (2) cores to determine existing layer types and thicknesses and (3) a surface condition survey.

Figure 6 provides a plan view of the roadway plus a variety of other information. The coded boxes on this plan view give estimates of the subgrade’s ability to support the loads. Also on this plan view are the core/bore locations. Above and below the plan view are the calculated overlay thickness recommendations and deflection profiles for each lane; the solid horizontal line on each of these plots is the MTD (adjusted by the seasonal adjustment factor) and the measured deflection profiles then appear along the length of the plot for each station. Whenever the deflection profile is above the adjusted MTD line, an overlay is required to provide some strength and reduce the deflection to the acceptable value. The number written above the rectangular box at each station represents the calculated overlay thickness in millimetres of asphalt necessary to reduce the deflection. For example, at station 0+300 in the eastbound lane 160 mm (6 in.) of AC is required to reduce the deflection from 2.2 mil to the acceptable MTD. The top and bottom sketches provide the Dynaflect deflection bowls which can be used to identify the source of the problem if overlays are needed. Obviously the recommended overlay thicknesses for each lane will have to be translated to practical values for the entire roadway width and for actual construction. This will subsequently be illustrated.

An examination of the core/bore data for the project indicated about 50-55 mm (2-2 1/2 inches) of asphalt concrete for varying thickness of granular 225-600 mm (9 to 26 inches) for the existing pavement. It also indicated a SW-SM subgrade, using the unified soil classification.

The surface distress report, Table 4, shows raveling throughout and various amounts of cracking. The ride was considered good throughout.

TABLE #4

RESULTS OF SURFACE CONDITION SURVEY

CLIENT: XXXXXXXXXXXXXXXXXXX
PROJECT: DETAILED SURFACE DISTRESS REPORT
DATE: JUNE 1983
SECTION: 0001
LANE: EAST BOUND LANE #1
LOCATION: TAYLOR BOULEVARD FROM MONA DRIVE TO GARDINERS ROAD

STATION

STAT SDI

PAVEMENT TYPE

RIP/ SHOV

RAV/ STRK

FLUS H/BL

DIST ORTN

EX C ROWN

EDGE CRK

ALLI GATR

POT HOLE

MAP CRAK

LONG CRK

TRAN CRK

RUT TING

STAT SDI

00+000

9.2

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

10.0

9.2

00+050

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+100

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+150

9.4

OLD AC

10,0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+200

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+250

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+300

8.8

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

4.0

10.0

10.0

8.8

00+350

8.8

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

4.0

10.0

10.0

8.8

00+400

9.2

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

10.0

9.2

00+450

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+500

8.6

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

2.6

10.0

8.6

00+550

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+600

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+650

9.0

OLD AC

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

5.6

10.0

9.0

00+700

7.8

OLD AC

10.0

10.0

10.0

10.0

10.0

4.0

5.1

10.0

10.0

10.0

10.0

10.0

7.8

00+750

8.8

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

4.0

10.0

8.8

00+800

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+850

8.8

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

4.0

10.0

8.8

00+900

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

00+950

9.0

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

7.6

10.0

9.0

01+000

9.2

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

10.0

9.2

01+050

9.2

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

10.0

9.2

01+100

9.2

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

10.0

9.2

01+150

9.2

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

10.0

9.2

01+200

9.0

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

7.6

10.0

9.0

01+250

8.2

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

5.1

10.0

10.0

10.0

7.6

10.0

8.2

01+300

9.2

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

7.6

10.0

9.2

01+350

8.0

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

3.4

10.0

10.0

10.0

10.0

10.0

8.0

01+400

9.4

OLD AC

10.0

3.3

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

9.4

Consideration of a11 this information suggests the road is in reasonable good shape, but without some strengthening in the not too distant future, it will deteriorate quite rapidly under those high traffic volumes.

The deflection profiles for each lane are basically duplicates in that they are low at locations where the cores identified bedrock (#’s 2 and 4) and high on the silty sand subgrade (#’s 1 and 3).

The profiles for the 2 lanes also peak at the same locations and drop off together, further substantiating the effect of the bedrock.

The rehabilitation recommendation that comes from the assessment of this data is a combination of an overlay and padding where appropriate. The road has not deteriorated (distress wise) to warrant removal of any large amounts of cracked areas before padding; normally this should be considered in all cases of badly distressed pavements before padding/overlay. Furthermore, there are no constraints (curb, gutter) to warrant milling before overlay; this strategy may prove valuable if these constraints exist or if the road was showing significant distress but had sufficient strength and the intent was to retard reflection cracking. Table 5 illustrates this recommendation, with consideration for uniform thickness across the road and for reasonable lengths. Routine maintenance should be applied on all portions not receiving an overlay. The overlay work should be carried out within the next two years; otherwise the surface distress and deflection data might be invalid.

The case illustration of the foregoing paragraphs involves two key points:

1. Automation of the deflection information in terms of computer graphics plotting, and calculation of overlay thicknesses corresponding to the deflection, as in Figure 6 relieves the designer from a lot of drudgery and allows him/her to actually do more in-depth analysis and creative interpretation as illustrated in Table 5. In other words, all of the front end work can be automated and then the designer can look at a Figure 6 type plot, plus the surface distress report of Table 5 and other information, and quickly arrive at a final overlay recommendation for the entire road width.

2. Deflection can vary quite markedly along the road length, and between lanes, as shown by the deflection profiles of Figure 6. This suggests that it is better to capture such variation by using the type of overlay design approach shown in Figure 6 and Table 5, as compared to using a more complex method but with only average data for a section. In fact, with the type of balanced final design of Table 5, which involves practical variations of thickness along the section length, it is probable that there would actually be savings in material quantities. Moreover, because of the varying thicknesses, the deflection profile on the overlayed pavement should be much more uniform.

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TABLE #4

FINAL REHABILITATION RECOMMENDATIONS FOR

TAYLOR BOULEVARD

(from Mona Drive to Gardiners Road)

STATION (meters) RECOMMENDATION*
0+000 – 0+225 No overlay
0+225 – 0+400 100 mm of padding + 50 mm overlay
0+400 – 0+550 50 mm overlay
0+550 – 0+750 50 mm of padding + 50 mm overlay
0+750 – 1+250 No overlay
1+250 – 1+800 50 mm overlay
1+800 – 1+950 100 mm of padding + 50 mm overlay
1+950 – 2+150 50 mm overlay
2+150 – 2+300 50 mm of padding + 50 mm overlay
2+300 – 2+825 No overlay

(*) Any severely alligatored portions on a localized basis should be dug out and replaced prior to padding or overlay and severe cracks (longitudinal and transverse) should be filled prior to padding or overlay.

CONCLUSIONS

Thin asphalt pavements may require overlays for several reasons but inadequate structural capacity is usually a major one. Deflection testing and analysis provides a sound basis for determining the thickness of overlay required.

However, the way in which such deflection test results can be used ranges from the empirical, where sufficient overlay thickness is provided to reduce the surface deflection to some maximum tolerable value, to the theoretical or mechanistic where materials properties and elastic layer models-are used. The latter is certainly a desirable approach but the current state of technology makes its applicability to thin asphalt pavements somewhat limited. Consequently, the empirical method is, for the time being, still more appropriate for thin asphalt pavements.

Whatever method is used, though, it is highly desirable that the layer variations in deflection along a section length and between lanes be adequately reflected in the overlay design. A convenient way of doing this is to automate the process to the point where the designer can look at ideal thickness variations along the section for each lane, plus other information on surface distress, etc., and arrive at a balanced, practical overlay design.

REFERENCES

1. Roads and Transportation Association of Canada, “Pavement Management Guide”, 1977.

2. Haas, Ralph and W. Ronald Hudson, “Pavement Management Systems”, Krieger Publishing Co., 1978.

3. Karan, M.A., Ralph Haas, D.A. Kobi and A. Cheetham, “Implementation and Verification Examples of Successful Pavement Management”, Proc., Int. Conf. on Structural Design of Asphalt Pavements, Univ. of Michigan, 1982.

4. Phang, W.A. and Ralph Haas, “Draft Report on National Workshops on Pavement Management Resource Requirements Task Group”, Prepared for TBB and FHWA, December, 1980.

5. Eaglesen, B., Heisey, S., Hudson, W.R., Meyer, A.H. and Stokoe, K., “Comparison of the Falling Weight Deflectometer and the Dynaflect for Pavement Evalution”, RR 256-1, Center for Transp. Research, University of Texas at Austin, November 1982.

6. Bush III, A.J., “Non-Destructive Testing In Light Aircraft Pavements – Phase I, “U.S. Army Waterways Experimental Station, Vicksburg, Mississippi, August 1979.

7. Swift, “A Graphical Technique for Determining the Elastic Moduli of a Two-Layered Structure from Measured Surface Deflection”, HRB Record 431, 1973.

8. Vaswani, N.K., 1971. Method for Separately Evaluating Structural Performance of Subgrades and Overlaying Flexible Pavements, Record 362, Highway Res. Bd., pp. 48-62.

9. Vaswani, N.K., 1974. Estimating Moduli of Pavement Materials from Field Deflection Measurements, Report VHTRC 75-R20, Virginia Highway and Transp. Res. Council, Charlottesville, VA. 29 pp.

10. Vaswani, N.K., 1977. Determining Moduli of Materials from Deflections, Trans. Engrg. Jour., ASCE, 103 (TE1): 125-141.

11. Wiseman, G., 1973. Flexible Pavement Evaluation Using Hertz Theory, Transp. Engrg. Jour. ASCE, 99(TE 3): pp. 449-466.

12. Wideman, G., et al. 1977. Simple Elastic Models for Pavement Evaluation Using Measured Surface Deflection Bowls, Proceedings, 4th International Conf. on the Structural Design of Asphalt Pavements, Ann Arbor, MI.

13. U1lidtz, P., 1973. The Use of Dynamic Plate Loading Tests in Design of Overlays, Report 22, Technical University of Denmark, Copenhagen, 26 pp.

14. Ullidtz, P., 1977. Overlay and Stage by Stage Design, Proceedings, 4th Inter-national Conf. on the Structural Design of Asphalt Pavements. Ann Arbor, MI. pp. 722-735.

15. Irwin, L.H., “Equipment and Methods for Deflection-Based Structural Evaluation of Pavements”. Proceedings – Forest Service Geotechnical Workshop – Ames, Iowa, 1979.

16. Irwin, L.H., and Johnson, T.C., “Frost-Affected Resilient Moduli Evaluated With the Aid of Nondestructive Measured Pavement Surface Deflections”. Paper presented to TRB-A2T56 Workshop on “Nondestructive Evaluation of Airfield Pavements”, August 1981.

17. Hoffman, M.S., Thompson, M.R., “Mechanistic Interpretation of Nondestructive Pavement Testing Deflection, FHWA/IL/UI-190, June 1981.

18. Hoffman, M.S., Thompson, M.R., “Nondestructive Testing of Flexible Pavement Field Testing Program Summary”, FHWA/IL/UI-188, June 1981.

19. Thompson, M.R., “ILLI-PAVE Procedure for Determining In-situ Properties from NDT Deflection Data”. Paper presented to TRB-A2T56 Workshop on Nondestructive Evaluation of Airfield Pavements, August 1981.

20. Bush, J.J., “Pavement Evaluation Using Deflection Basin Measurements to Characterize an Elastic Layer System”. Paper presented to TRB-A2T56 Workshop on Nondestructive Evaluation of Airfield Pavements, August 1981.

21. Shahin, M.Y., Sharma, J., Smith, R.E., Stubstad, R.N., “Nondestructive Testing of Airfield Pavement – The Dynplot/ERES Method”. Paper presented to TRB-A2T56 Workshop on the Nondestructive Evaluation of Airfield Pavements, August 1981.

22. Larsen, H.J., Stubstad, R.N., “Use of Nondestructive Testing in Flexible Pavement Rehabilitation Design”. Proceedings Vol. 1, Bearing Capacity of Roads and Airfields, Norweigan Institute of Technology, Trandheim, Norway, 1982.

23. Ullidtz, P., “Overlay and Stage-by-Stage Design”. Proceedings Fourth Inter-national Conference on the Structural Design of Asphalt Pavements, Ann Arbor Michigan, 1977.

24. Koole, R.C., and Visser, W., “Aircraft Pavements, Evaluation and Overlay Design”. Proceedings, Volume 2 Bearing Capacity of Roads and Airfields, Norweigan Institute of Technology, Trandheim, Norway, 1982.

25. Wong, M.C., “Pavement Layer Modules Evaluation From Deflection Basin”. Pro-ceedings Volume 2 – Bearing Capacity of Roads and Airfields, Norweigan Institute of Technology, Trandheim, Norway, 1982.

26. Kilareski, W.P. and Bassan, A.A., “Evaluation of In-situ Moduli and Pavement Life from Deflection Basins”. Proceedings, Fifth International Conference on the Structural Design of Asphalt Pavements, Delft University, Netherlands, 1982.

27. Transportation Research Record 666, “Pavement Surface Properties, Evaluations, and Shoulders”, TRB, 1978.

28. Majidzadeh, K., Ilves, G., McComb, R., “Overlay Design of Flexible Pavements Using Dynaflect”. Proceedings Volume Z Bearing Capacity of Roads and Airfields, Norweigan Institute of Technology, Norway, 1982.

29. Sharpe, G.W., Southgate, H.F. and Deen, R.C., “Pavement Evaluation Using Dynamic Deflections”, TRB Research Record 700, 1979.

30. Southgate, H.F., Sharpe, G.W., Deen, R.C., and Havens, J.H., “Structural Capacity of In-Place Asphaltic Concrete Pavements from Dynamic Deflections”. Volume l, Fifth International Conf. on Structural Design of Asphalt Pavement Delft University, Netherlands, 1982.

31. Epps, Jon A. and R.G. Hicks, “Moderators Summary of Session V on Rehabilitation of Pavements”, Proc., Vol. II, Fifth Int. Conf. on the Structural Design of Asphalt Pavements, Univ. of Michigan, 1982.

32. Asphalt Institute MS-17 – Asphalt Overlap and Pavement Rehabilitation College Park, Maryland, 1969.

33. Lister, N.W., C.K. Kennedy and B.W. Berne, “The TRRL Method for Planning and Design of Structural Maintenance”, Proc., Vol. I, Fifth Int. Conf. on the Structural Design of Asphalt Pavements, Univ. of Michigan, 1982.

By Dennis Polhill

Mr. Polhill is a civil engineer, served in city government for 10 years, and is currently president of Pavement Management Systems. Inc.

Three trillion dollars is needed to restore the nation’s infrastructure. ‘Infrastructure’ is all of the physical public works facilities which support the way of life, standard of living and economic vitality which the U.S. has come to enjoy.

During the past several years, the rate of investment in public works has declined by 4 percent per year. From 1965 to 1977, federal, state and local infrastructure expenditures decreased by a total of 44 percent. During the same time, construction costs rose at twice the rate of the Consumer Price Index to the point that two-thirds of the local governments in the U.S. now are unable to afford the facilities necessary to accommodate growth.

Best estimates of the nationwide cost of bringing our infrastructure up to standard are in the $3 trillion range.

Although the infrastructure challenge is national in scope, solutions to the problem will have to be found at the local level, in individual cities. In this connection, every city should develop an action plan which includes:

  1. An inventory to determine the present condition of facilities and rank needs on the basis of objective criteria.
  2. A financing plan under which sufficient resources will be provided to address identified needs.
  3. An implementation plan which ensures that resources are utilized efficiently.

The most significant investment of cities is in their streets. Streets are more valuable, contribute more direct benefit to economic efficiency, and have a higher cost of replacement than most other facilities. Citizens are also more aware of the condition of streets than of other public works. Research has shown that the performance qualities of streets decline as the pavement ages, as illustrated in Figure One. Differing pavement structures, soil and environmental conditions, traffic loads and maintenance practices affect the shape of the curve in the illustration. Conceptually, however, the curve is always the same: the older the pavement becomes, the more rapidly it deteriorates and the more it costs to repair.

Figure 1

The process of inventorying and evaluating pavement systems is complicated because several factors are important, including strength, roughness, surface distress, skid resistance and rutting. Cities obviously are interested in maximum service as measured by all of these factors, but under economic restraints as they exist today cost is an overriding concern.

Scientific methods are now available for inventorying and making pavement decisions that can result in enormous cost savings.

To illustrate the cost significance of various street rehabilitation alternatives, take the typical overlay decision, which involves a myriad of considerations affecting cost and performance: (1) how thick should the overlay be?; (2) when should it be placed?; (3) when will the next overlay be required?; (4) what materials should be used?; (5) what alternatives to overlay are available and viable (recycle, fabrics, etc.)?

Concerning the thickness decision, too-thin overlay will fail prematurely, while too-thick overlay will cost more money than is necessary. Asphalt concrete costs about $40 per ton in-place, which is about $63,000 per two-lane mile for a 2″ thickness. If a 1 3/4″ thickness would serve as well, $8,000 per mile could be saved.

On the other hand, if a 2″ thickness would extend the serviceable life of the roadway by eight years and a 2 1/4″ thickness would extend its life by 16 years, trying to save the 1/4″ (or $8,000) would cost the city $55,000 in eight years, plus an accelerated reconstruction schedule to restore the crown and curb height.

Decisions concerning the best treatment for a specific street must, of course, take into account the needs o( the entire street network. In other words, optimum treatment “X” may result in 10 units of benefit for each dollar expended on Elm Street, but what about Main Street, where the optimum treatment may yield 12 units of benefit for the same expenditure of dollars?

Figure Two shows how maintenance costs increase over time, as the serviceability level of the street moves closer and closer to a minimum acceptable level. The end result is that a lower level of service is maintained at a higher cost than if rehabilitation was programmed at an optimum time.

Figure 2

This phenomenon has been verified by several studies, one of which was conducted by the Utah Department of Transportation. As shown in Figure Three, the Department found that the most cost-effective strategy for maintaining urban streets and the one which sustained the highest serviceability level involved timely rehabilitation activities performed during a comparatively short time frame: The most costly approach shown as “Strategy C” in Figure One was one under which rehabilitation was delayed until public pressure forced action to upgrade serviceability to minimum acceptable levels.

Figure 3

In summary, it is apparent that the extent of deterioration of streets and other public works is enormous – and growing -due to past policies of deferring needed maintenance. The problem can, however, be solved if local governments will inventory their needs and then adopt plans to finance those needs.

With specific respect to streets, research has demonstrated the correlation between varying maintenance levels and pavement serviceability. Proper management of maintenance activities can produce high levels of serviceability at minimum cost.

Reprinted from the January, 1983 issue of Colorado Magazine.

Published in Colorado Engineering

by Dennis Polhill, P.E.

Pavement Management is the process of making decisions about pavements. It is a daily activity of agencies responsible for pavements. In the con text in which “pavement management” is used today, it infers utilizing more information in order to make those decisions better.

In pavement management, decisions are considered to be made at two levels: the project level and the network level. A total pavement management system includes both project level analysis, network level analysis, and an information exchange back and forth between the two levels.

PROJECT LEVEL

Project level analysis is the process of looking intensely at a particular pavement for the purpose of optimizing the rehabilitation of that pavement. Project level analysis is considered an engineering application.

Project level analysis may include consideration of several pavement parameters such as ride quality, skid resistance, rutting, structural capacity. The single parameter considered most is structural capacity. The definition of project level analysis is clarified through the following examples. .

PROJECT LEVEL

ANALYSIS APPLICATIONS
Overlay Design

To make the best overlay decision, questions of thickness, type, timing and alternates must be considered. A “too-thin” overlay will result in premature failure and loss of some of the benefit (extension of serviceability) of the over-lay. A “too-thick”‘ overlay results in the expenditure of too much money now and in loosing the option to put those dollars into another needy project. A quarter of an inch difference in ~A.C. overlay thickness equates to about S8,000 per mile. In Edgewater, Colo. this type of analysis saved an overlay project 519,500

Reconstruction Design

If grades are to remain the same during a reconstruction project, considerations similar to an overlay design are in order. “Can the existing structure con-tribute to or be used in the new structure?”‘ In Frostburg, Maryland, this question was raised. By acquiring proper information the design engineer was able to determine which sections required rebuild and which sections could be rehabilitated. The estimated savings to the project was over 5200,000

Street Widening

If grades are to remain the same during a widening project. considerations similar to the reconstruction design are in order. ‘”Can the existing structure contribute to or be used in the new structure?” or “What needs to be done to the existing pavement to make it serviceable as the center two lanes of the project?”‘ This question was raised during a project in Aurora. Colo. In the final analysis, il was determined that the existing 2 lane roadway would be structurally sufficient with a minor overlay and isolated locations of additional structural padding or patching. The savings on this project was over S400,000.

Street Acceptance

The same type of analysis can be due on a new street. The obvious application is for acceptance of newly constructed streets. The process merely requires that the street must demonstrate its ability to perform through a process of performance evaluation. Some method of nondestructive testing and professional engineering analysis must be used. This approach will give owners the assurance they need that the facilities they accept will perform,

Assessment of Impacts

Assessment of impacts includes a variety of possible applications of project level pavement management information. How do you determine the amount of permit fees to be charged for an overweight load moving through your jurisdiction? How does the change of a bus route effect a particular street? How do you determine what the load limits should be on your roads? What is the consequence of a major change in traffic volume or traffic configuration? What is the effect of a new development that results in an increase in traffic loading both during and after construction? How much rehabilitation should reasonably be charged to the development and when should the work be scheduled? Timely rehabilitation resulting from assessment of conditions such as these can protect against premature failure of pavement facilities. Project level analysis gives the capability of addressing these questions.

NETWORK LEVEL

Network level analysis is the process of looking at an entire system (or net-work) of pavements. This is done to answer network-wide questions, such as which projects should be considered for rehabilitation. Network level analysis is a management application of pavement management. Some typical network level questions are:

  • What is the current level of service?
  • What will happen to the level of service over the next few years?
  • How will a budget change affect service level?
  • What streets should receive priority?
  • What would be the impact of a change in traffic characteristics?
  • What maintenance activities give maximum benefit?

Rehabilitation Costs

By referring to Figure 1, it can be seen that rehabilitation costs increase by over 4 to 5 times if rehabilitation is deferred only 12% of. a pavement’s design life.. For typical pavements, 12% amounts to about 2 years. Thus, deferring rehabilitation is very expensive. Good management dictates that rehabilitation occur at a tune so as to derive the greatest benefit (extension of serviceability) possible. Viewing this problem on a network level is very complex since every different pavement structure has a different performance curve and is at a different point in its service life.

Figure 1

An important point can be concluded here. Unless a jurisdiction has all the money it needs for rehabilitation, it is almost certainly a mistake to program rehabilitation on a “worst-first” basis. Maximum benefit cannot be derived from the limited public funds available if an agency binds itself to a “worst-first” programming philosophy.

Maintenance Costs and Serviceability Maintenance costs increase as serviceability declines. The increasing commitment to maintenance tends to extend serviceability but at a higher cost and lower service level than if timely rehabilitation was performed. This fact has been verified by several studies. The most widely known was done by the Utah Department of Transportation, which was referenced in NCHRP Report #58 (see Figures 2 and 3). For all categories of roadway the least cost strategy was “‘A”‘, where the highest service level was sustained. The highest was strategy “”D’~ at which rehabilitation was deferred until such point that substantial increases in maintenance activity was required in response to public pressure to sustain serviceability at a minimum acceptable level. Strategy “D'” was UDOT”s current mode of operation.

 Figure 2:

Figure 3

Figure 3:

Figure 6

Network Example

The best documented case of the successful implementation of a network level pavement management system is the Regional Municipality of Ottawa-Carleton, Canada, whose Transportation Director is Michael J.E. Shelfin, P.E. In 1980, Ottawa-Carleton’s road budget was 14% less in actual dollars and 43% less in inflated dollars than it was in 1977. At the same time average service level had improved. Shelfin gives credit for this accomplishment to the progressiveness of his council.

Dennis Polhill is a Registered Professional Engineer in seven states, Colorado, Utah, Pennsylvania, Maryland, Wyoming, New Mexico and Arizona and is a Registered Professional Land Surveyor in Maryland and Pennsylvania. He has been involved with pavement management for more than 12 years.

Currently a consulting engineer and manager of the Denver regional office for Pavement Management Systems, lnc., Polhill previously was city engineer for the city of Lakewood, Colo. As an engineer with Lakewood, and prior to that cities in Maryland and Illinois, Polhill has been responsible for construction of new street and drainage projects as well as for maintenance of existing streets.

He is a member of the American Consulting Engineers Council, American Public Works Association American Society of Civil Engineers, Institute of Transportation Engineers, National Society of Professional Engineers and the Transportation Research Board.

Prepared for Presentation to
29th Annual Highway Engineering Conference,
Las Cruces, New Mexico, March 24 and 25, 1983

By Ralph Haas, PhD., P.Eng.,
Chief Executive Officer,
The PMS Group, Paris, Ontario, Denver and Calgary,
and, Professor of Civil Engineering, University of Waterloo

 

and
Dennis Polhill, NIS, MPWA, P.E.,
President, PMS (Colorado), Inc.,
Denver, Colorado

SUMMARY

We have billions of dollars invested in our roads and streets. This investment has to be preserved through timely and cost-effective maintenance and rehabilitation. However, we are faced with fiscal restraint. Good pavement management provides a means for obtaining maximum value for the limited funds available.

This paper describes the major elements of pavement management for both the network and project levels. The network level starts with good inventory data and should produce priority programs of capital and maintenance work. The project level is concerned with detailed design and construction.

Three basic classes of pavement management users: elected representatives, administrators and technical people are considered in the paper, as well as their particular requirements.

Several other issues or questions are addressed, including the relationship between pavement management and road needs studies, the private sector role in pavement management, the effect of size of agency, the benefits to be expected from pavement management and the costs.

The paper suggests that the essential ingredient for successful pavement management implementation is a staged approach, including a pre-implementation planning stage and useable “products” available from each stage. These should be modular and stand-alone.

The role of consultants is explored, including advantages and disadvantages. An evaluation procedure is provided, and some of the problems faced by consultants are outllined.

Finally, some suggestions are made as to how to get started in pavement management.

INTRODUCTION

Conditions of restraint spur the need for good management. Limited available dollars have to be spent wisely. Nowhere is this more important than in transportation. The investment is large and it must be preserved.

The paved road network represents a particularly large portion of the total transport investment. In New Mexico alone this portion amounts to several billion dollars.

To preserve this investment, cities, counties and the State require at least several hundred million dollars each year for rehabilitation and maintenance. That is aside from the sums required to catch up on a backlog of needs.

Pavement management can certainly help in effectively spending even the limited available dollars for rehabilitation and maintenance. The question for most people is what does this term pavement management mean, how can it help us and what does it cost?

It is the purpose of this paper to answer that question, to explore the potential role of consultants, and to offer some suggestions to those who want to get started in pavement management.

PAVEMENT MANAGEMENT

Basic Objective and The Major Questions

The objective of pavement management has already been implied: preserve the investment and make the best possible use of limited available dollars. Nobody would disagree with that, but they would want to know how the objective is actually accomplished; in other words:

  1. What are the key elements of pavement management?
  2. What sort of answers should it provide for the elected, administrative and technical levels of a local authority or the State?
  3. What is the role of the private sector: contractors, suppliers, consultants?
  4. What are the benefits to be expected, and the costs?
  5. How do we get started, what’s the first step?

Key Elements of Pavement Management

Pavement management is a process for carrying out in a co-ordinated, systematic way a11 those activities that go into providing pavements (1 to 3). It can be viewed in terms of two basic working levels: (a) network and (b) project. Figure 1 lists the major activities occurring at both levels.

Figure 1

Network level management has as its primary purpose the develop-ment of a priority program and schedule of work, within overall budget constraints. Project level work thus comes “on stream” at the

appropriate time in the schedule. Since the network level of management is usually based on more approximate data and analyses, considerable “fine tuning” may be required when it comes to detailed project design and construction or section maintenance.

The ‘Users’ of Pavement Management and Their Requirements

The actual “users” of pavement management, whether the network or project levels are concerned, whether the State or a local authority is involved, can conveniently be classified as follows:

  1. Elected representatives
  2. Administrators
  3. Technical people.

Each type of user has certain requirements from a pavement management system and these are summarized in Figure 2. Obviously there is some overlap but what Figure 2 shows is that pavement management is not just done by administrators. In order to function successfully it has [o rely on people ranging from the technician who plans and carries out a testing program to the elected representative who approves or modifies a budget request.

Figure 2

Relationship Between Pavement Management and Road Needs Studies

The purpose of a road needs study is to arrive at inventory or appraisal of the total road system and provide a basis for planning and development policy. It should also provide a comprehensive assessment of road and bridge needs, the priority rankings attached to them and the costs of meeting those needs in various time periods; i.e., now, L to 5 years and 6 to 10 years.

The question is how does pavement management fit m with the Road Needs Studies? First, it should be pointed out that the studies are not a management tool, per se. They provide an inventory, a first cut estimate of needs, and, perhaps most important, the basis for financial planning. The next step is to actually spend those dollars in the most cost-effective way, starting with a determination of “real needs”.

In other words, for the pavement portion, a pavement management system can take over where the road needs study leaves off (i.e., it can “fine tune” the needs study results. As well, the objectively based data collected for pavement management purposes at the network level (i. , roughness, surface condition, geometrics, deflection, etc.) can be used directly to update the road needs studies. Thus, a pavement management system can and should be entirely complementary to the road needs study, and to higher level highway and transportation management in general.

STAGED IMPLEMENTATION

There are several essential ingredients to having a successful pavement management system (PMS) and one of the most important is staging. This step by step approach, if it is done as part of an overall, long term plan, has the following advantages: (a) it provides a modular system with useable, stand-alone products at the end of each stage, (b) the PMS can start to be used fairly quickly, (c) it can be accommodated to resources, (d) it recognizes the “learning curve” and time required for acceptance by an organization.

The major considerations in staged implementation are described in the following paragraphs.

Stages and Produces

Figure 3 shows the major stages which can be used in implementing a PMS. Also listed are the key products.

Figure 3

A pre-implementation planning stage is shown in Figure 3 as the beginning of the process. This can be most valuable in facilitating the actual implementation and is further discussed in the next section.

The first three stages of Figure 3 occur at the network level while the next three occur mainly at the project level

A description of the six stages of Figure 3 , and actual examples of the products,is beyond the scope of this paper. However, there are some good references which illustrate these in some detail. For example, Idaho (4) and Alberta (5) have very well developed Stage 1 systems. These include performance prediction models so that future needs can be estimated. Both agencies are in the process of developing and implementing Stage 2. Alberta has plans [o develop the remaining four stages listed in Figure 3, while Idaho already has implemented Stage 4 as part of their pavement management system (4).

There are good examples of working priority programming systems for rehabilitation, Stage 2, in Ref. (6, 7) while Ref. (8) contains an example of a Stage 3 maintenance programming system.

There are many examples of good structural design and life cycle costing systems for new pavements (3), Stage 5, which have already been developed. However, there are far less examples of how they have been integrated or modified to fit into an overall PMS.

The operational deficiency and improvement analysis system, Stage 6, which relates to safety, capacity, geometrics, etc. is usually treated at the broader highway level. Explicit integration with a PMS represents a major challenge which to date has not apparently been accomplished by any agencies.

There is some flexibility in carrying out the stages of Figure 3, with the exception of Stage 1 which is the foundation for all other stages. Stage ? would normally be nest; after that, the sequence can vary, but it is essential that it be properly planned.

Pre-Implementation Planning

Pre-implementation planning (Stage “0” of Figure 3) can result in a much easier, efficient implementation, and enhance the acceptability of the PMS. Its purpose is to let the client knew exactly what their

PMS will do, how it will operate, what answers it will provide, what resources will be required, etc. Then, when they agree, or after any desired modifications are made, the actual implementation can proceed. The pre-implementation procedure has been very successfully used for both State and city level PMS projects by the authors of this paper and their colleagues.

It essentially consists of the following:

  1. Detailed planning (identification and articulation of the – client’s goals and objectives, finalization of the work plan, detailed project schedule),
  2. Evaluation of the client’s existing conditions, resources . and procedures (characteristics of the road network and existing data, organizational structure, physical resources including equipment, human resources, facilities including computer hardware and software,operating procedures, documentation system, maintenance facilities, equipment and operations, etc.)
  3. Functional design of the staged PMS (required stages and components, examples of products, staffing and resource requirements, cost estimates, etc.)
  4. Recommendations and approval to proceed (report, presentations to senior officials of results of 1. to 3. above, modifications if necessary, final acceptance).

The pre-implementation stage should take no longer than two or three months and would normally range in cost from about $10,000 to $30,000 depending on the type of client, nature of the job, etc. It is desirable that such pre-implementation be carried out by a group with comprehensive knowledge and experience in the pavement management field. The results should be “stand alone” in that they can be used for the actual implementation by the client’s own people (i.e., in-house), or by another consultant.

Size of Agency and the Usefulness of Pavement Management

Good pavement management is certainly applicable and indeed necessary at the State level. In fact, even Canada’s smallest Province, PEI, implemented one of the mast comprehensive systems in North America several years ago for its network of highways (6). This network is comparable in size to the average District in a State Highway Department.

Cities and counties of various sizes, ranging from only a hundred or less miles of roads and streets to over a thousand, have either made excellent use of a well developed and smoothly functioning pavement management system (7, 9) or are currently implementing a PMS, such as Pima County and the City of Phoenix in Arizona.

Thus, the size of agency should not be a deterrent to the useful-ness or applicability of pavement management. The scale may differ but the principles are the same from the State level through to small cities or counties.

Benefits to be Expected, and Costs

The benefits to any agency should generally include better chances of making the correct decisions, better use of available funds, improved coordination and use of technology and better communication (2). For senior management, these benefits can be more specifically identified to include the following:

  1. A comprehensive, comparative assessment of the current status of the network.
  2. Objectively based answers to:
    (a) What level of funding is required to keep the current status, or
    (b) The implications of greater or lesser budgets.
  3. Being able to justify capital and maintenance program recommendations to the elected council, or legislature.
  4. Having the assurance that the recommended program represents the best use of available dollars.

There are also benefits for elected representatives and they can include the following:

  1. The program of pavement maintenance and rehabilitation is defensible;
  2. It represents the best expenditure of the tax funds; and,
  3. It may in fact put less pressure on them to make arbitrary program modifications.

Turning to costs, and using a county example, they might expect to pay between about $50 to $150 per lane-mile per year for a Stage 1 to 3 type of PMS, depending on size of network involved, whether its a first time or update run, the field tests required, traffic conditions, types of reports and recommendations desired, etc. For example, if an 800 lane-mile network at $50 per lane-mile were involved, the annual cost would be $40,000. This would represent an annual management fee” on the investment of about ~, to 17, (assuming a value of $80,000 to $320,000 per lane-mile).

The project level of pavement management of course costs more because this is where the normal engineering fees for detailed testing, design, quantity estimates, contract preparation and supervision, quality control, etc. are incurred.

The Private Sector Role in Pavement Management

The main users of pavement management are of course the State and the cities and counties. But the private sector (i.e., contractors, suppliers and consultants) also has a role.

Any contractor or supplier should not suffer when the client spends dollars in a cost-effective way. In fact they should benefit could mean less work and materials; as well, scheduled program of work provides stability suppliers know what’s ahead and can themselves plan accordingly.

Consultants can play a direct role in that they can provide testing, engineering and computing services. In fact, if they have sufficient experience and expertise, [heir services can be particularly valuable and more cost-effective than doing the work in-house.

However, particular caution should also be exercised. Since the tremendous popularity of pavement management all across North America in the last few years, a lot of “instant experts” have come forward. Pavement management is not easy, it requires a lot of technical knowledge, resources,facilities, at,., and it doesn’t consist of nice, easy-to-use black boxes or off-the-shelf methods. It has to be tailored to each individual client’s situation and requirements. Consequently, while good use can certainly be made of consultants, their credentials and because wasting dollars a carefully planned and in that contractors and experience in pavement engineering and technology should be carefully assessed. The following section further addresses the role of consultants.

ROLE OF CONSULTANTS

The obvious questions for any agency contemplating the use of consultants for PMS implementation would include the following: why hire a consultant; what are the potential advantages and disadvantages; who should we consider and how should we evaluate them; how do we prepare clear terms of reference; how do we ensure control and getting what we want and need?

The reasons for hiring a consultant (i.e., the potential advantages), can include the following:

  1. Obtaining specialized expertise, and outside experience, in PMS development and implementation,
  2. Obtaining outside objectivity,
  3. Getting the implementation done if insufficient internal resources exist (i.e., equipment, software, people, etc.) or accelerating it,
  4. Lower overall cost.

Potential disadvantages can also exist, such as the possibility of getting a less qualified consultant than possible, less control on the work, etc.

Turning to the question of who should be considered and how- should they be evaluated, the first part can easily be done by asking other agencies, professional organizations, etc., who they know of in this field. It may be informal but is simple and effective. Evaluation is a bit more difficult, and can be done in two parts: (a) screening by asking for a statement of qualifications, or screening by actually carrying out an evaluation, and then (b) asking for a sole-source proposal, or evaluating proposals from qualified consultants (which assumes that terms of reference or request for proposals, RFP, have preceded). A convenient procedure for actually carrying out a consultant evaluation is given in Table 1. If this is used, and backup information or examples are obtained from the consultant for the various questions, then the most qualified one(s) can be identified fairly quickly.

TABLE 1

Yes No ?

 

CONSULTANT EVALUATION PROCEDURE

A. PAVEMENT MANAGEMENT

1. Is their PMS fundamentally sound, and practical?

2. Does their interest and expertise cover both network and project levels?

3. Will their PMS really assist us, administra-tively and operationally?

4. Are their programs and procedures such that we will know at all times what is going on, through regular consultation?

5. Is there provision far client input during implementation, and support afterwards?

6. Is the PMS sequential and modular to allow for maintenance, future updates and client operation?

7. Can the PMS be tailored to a client’s specific needs?

8. Can and will the firm do a pilot implementation on a portion of the client’s network?

B. EXPERTISE AND PERSONNEL

1. Do they have sufficient years of experience in pavement evaluation, design and management?

2. Is pavement management their primary business?

3. Do they have known and respected senior professionals with sufficient experience and training?

4. Have their people contributed in a meaningful way to professional and technical organizations?

5. Have their people been recognized by awards, citations, etc., in the pavement management field?

C. FIELD AND OFFICE EQUIPMENT

1. Is their PMS based on objective field data?

2. Do they have sufficient equipment to evaluate a11 pavement performance parameters?

3. Do they have sufficient computer equipment and staff to handle field data?

4. Does their computer hardware and software capabilities allow for flexibility in data treatment?

5. Have they shown initiative in developing equipment, software packages, new techniques, etc.

D. SOFTWARE AND DATA ANALYSIS

1. Can they do performance prediction modelling, tailored to region and agency; are the procedures sound?

2. Do they work with objective data, such as roughness, surface distress, deflection, skid, geometrics, etc.?

3. Can they take into account such factors as subjective u opinion, alternative rehabilitation strategies, budget variations, user costs, etc.?

4. Does their priority analysis produce a truly optimized program of work and can it allow for testing of different budget levels?

5. Can the analysis results be provided in graphic. and tabular formats tailored to the needs of different users?

6. Will they provide user manuals for specific programs?

7. Will they install a data bank and ancillary software on the client’s computer?

E. COST AND TIME FRAME

1. Does their priority analysis take into account deferral of work and timing alternatives?

2. Do they have the staff and in-house facilities to implement a complete PMS within one year?

3. Can their system be “tailored” to our needs and operated by our people after training?

4. What are the costs of the specific products and services they can provide, and what would it cost us to run the PMS in terms of people, hardware, software, etc.?

F. TRACK RECORD

1. Can they provide evidence of growth and financial stability?

2. How many proven pavement management systems have they actually implemented?

3. Do they have experience with systems of different size and complexity?

4. Do they have a PMS which is technically up

to the leading agencies and state of technology in the field?

5. Can they document and describe the steps in any work done for the client?

6. Can they provide testimonials from clients as to their work on various pavement management projects?

     

Clear terms of reference or RFP’s are essential to consultants

if they are to prepare a good proposal. This requires careful thought on the part of the client as to what they want, what they can provide in terms of resources and what money they have available. A good way to proceed is by stages, where, after screening of consultants,a pre-implementation RFP is firstly put out. This respesents a modest expenditure and allows for a “go” or “no go” decision at the end of the stage.

Similarly, control can be exercised on the project by incorporating decision points after each stage and by having a steering committee to meet regularly with the consultant.

Some Irritants from the Consultant’s Viewpoint

Among the most common irritants or problems consultants face are the following:

  1. When-the client says “we can do it cheaper”. On a total accounting basis this is rarely if ever the-case. Consultants face stiff competition and they have to run an efficient operation to survive. As well, people who make the above statement usually forget any cost items that don’t come directly out of their budgets, but which nevertheless have to be paid for by the taxpayer.
  2. Asking for proposals from a large set of consultants. This is wasteful and inefficient. It is not uncommon to see 10 or 15 proposals on a fairly small job. Consultants have to recover the costs of preparing these proposals from somewhere if they are to stay in business, and it is reflected in their prices. Why not do a screening and then invite the 3, 4 or 5 most qualified consultants to submit proposals?
  3. Asking consultants for interviews with no consideration of costs, size of job, etc. Not too long ago, a city asked four firms to come for 15 minute interviews, after their proposals had been reviewed. The size of job was $30,000. Because they a11 had to come from some distance, the actual cost to each in terms of travel and time was about $2,000. Thus, the total interview costs alone to the consultants, aside from the costs of preparing the proposals, was $8,000, which is ridiculous when compared to the size of the job.
  4. Asking consultants for a proposal, but not giving out a contract. There are few consultants who have not been “burned” in this way, where the prospective client either did not have the money approved to start with, or never did have any intention of hiring the consultant.
  5. Assuming that the consultant can do extras for nothing. Some clients are very prone to ask for all kinds of extras and do not appreciate that there is a very fine line between profit and loss on almost all jobs. A 10% profit is, for example, quite common, which means that a $10,000 profit on a $100,000 nroject can very quickly “evaporate” if the client asks for free extras, or if there is any kind of overrun.

GETTING STARTED IN PAVEMENT MANAGEMENT

“How do we get started” is the first question from those making a decision to get into pavement management. While a comprehensive set of implementation guidelines is available (2, 3), the key to getting started is a pre-implementation stage (see Figure 3) if at all possible, including a plan of field inventory measurements. Good inventory data is the foundation for good pavement management., This would apply to either doing the work in-house, hiring a consultant, or some combination of both.

The inventory can include measurements for and evaluation of (a) structural adequacy, (b) ride quality, (c) surface condition and (d) skid resistance. It should also include data on: (e) geometrics and layer thicknesses, (f) rehabilitation and maintenance costs, and (g) traffic.

The inventory data provides a means for assessing the current status of the network, and identifying current needs, in Stage 1 (Figure 3). It also provides a basis for predicting when currently adequate sections will reach an “action level” in the future. This requires the development of a performance prediction method.

But what about setting up the inventory plan? How much of the network should be covered and with what measurements and frequency? What equipment and manpower are required, and/or should outside help be sought? How is the data to be handled? [Shat are the costs: Specific answers to these questions depend upon the available resources and management needs of each particular agency; thus the importance of the pre-implementation stage. Considerable experience has been accumulated which points out that the inventory can be staged and tailored [o the agency. Anyone getting started in pavement management would be wise to look at the experience of others and to examine the feasibility of bringing in outside expertise and/or help.

Let’s consider the questions of equipment and manpower require-ments, and costs, a bit further. A large highway department might buy much of its own deflection, roughness, skid, computer and other equipment, and be able to hire people to work mainly on pavement management. Conversely, a city or county might purchase all the required services. While size of organization certainly has an influence, what’s really important is the unit cost of doing the work and management use of the inventory data.

In summary, a pre-implementation stage with a good inventory scheme is the key to getting started. But it is not sufficient by itself. It should 6e part of a carefully developed and staged overall implementation plan, with “stand-alone” and useable products at the end of each stage.

REFERENCES

  1. Haas, Ralph and Don Kohl, “Pavement Management: Why It’s Important and How to Accomplish It”, Paper Presented to APWA Kansas City, Missouri, Sept., 1980 .
  2. Roads and Transportation Association of Canada, “Pavement Management Guide”, RTAC, Ottawa, 1977
  3. Haas, Ralph and W. Ronald Hudson, “Pavement Management Systems”, McGraw-Hill, 1978
  4. Karen, M.A., K. Longenecker, A. Stanley and Ralph Haas, “Implementation of Idaho’s Pavement Management System”, Paper Presented to Transp. Res. Bd., Washington, D.C., Jan., 1983
  5. Karen, M.A., T.J. Christison, A. Cheetham and G. Berdahl, “Development and Implementation of Alberta’s Pavement Information and Needs System (PINS)”, Paper Presented to Transp. Res. Bd., !,’ash., D.C., Jan., 1983
  6. Karen, M.A., Ralph Haas, and Thomas Walker, “Illustration Pavement Management, from Data Inventory to Priority Analysis”, IRS, Res. Record 814., 1981
  7. Karen, M.A., Ralph Haas, D.A. Kobi and A. Cheetham, “Implementa-tion and Verification Examples of Successful Pavement Manage-ment”, Proc., Int. Conf. on Structural Design of Asphalt Pavements, Univ. of Mich., 1982
  8. Haas, Ralph and Alan Cheetham, “Combined Priority Programming of Maintenance and Rehabilitation for Pavement Networks”, IRB, Res. Record 846, 1982
  9. Smeaton, W. Kirk, G.A. Thompson, Clare Bauman and M.A. Karen, “The Payoff in Long-Term Management of the Investment in Paved Road Networks”, Paper presented to RTAC, Halifax, Sept., 1982

This was published in the Municipal Management, a Journal, Spring 1983, Vol. 5 No. 4.

By Dennis Polhill, P.E.

Dennis Polhill is president of Pavement Management Systems, Inc., a company that evaluates existing pavement structures and makes recommendations for maintenance and rehabilitation. He is a civil engineer and was a city engineer for ten years.

How can a city or town decide the best way to use what money it has available for repairing its infrastructure?

Three trillion dollars is needed to restore the United States’ infrastructure.

The infrastructure is all of the physical public works facilities which support the way of life, standard of living, and economic vitality which the U.S. has come to enjoy.

Investment in public works has declined at a rate of 4 percent per year. From 1965 to 1977 investment in public infrastructure declined 44 percent. Construction costs have inflated at twice the rate of consumer prices. Two thirds of the local governments in the U.S. cannot accommodate growth.

In a recent address, Representative Don Clawson of California suggested that “the pork-barrel mentality” of cutting capital projects in times of budget crunch is jeopardizing the economic vitality of the nation. Economic growth requires both an active public works and a strong transportation system.

The steady deterioration of the U.S. infrastructure is receiving increasing attention. Within the last year, leading news magazines have featured the problem; books have been written about it; TV documentaries have been aired about it; Congress has proposed legislation; and professional organizations have appointed study committees and issued position statements.

Best estimates of the infrastructure repair bill set the cost at $3 trillion. Some of the estimates that contribute to the $3 trillion figure are:

  • $1,800 billion for roads and streets
  • $33 billion for interstate highways (repairs only)
  • $700 billion for non-urban highways
  • $48 billion for bridges
  • $110 billion for water systems in 750 major urban areas
  • $40 billion for mass transit
  • $31 billion for wastewater treatment
  • $15 billion for prisons and jails
  • $600 billion for city streets

John Wiedeman, president of the American Society of Civil Engineers, says “Virtually every part of the country has its own horror story. The full extent of the challenge of decaying public works is not yet known.”

  • Poor roads cost the private sector $30 billion per year (Gasoline consumption increases 56 percent; tire costs increase 150 percent).
  • Numerous lives are lost each year in accidents caused or aggravated by poor road conditions.
  • In 1980, New York City paid $20,000,000 in liability claims for negligent maintenance.
  • In 1980, $3,500,000,000 was paid by states in liability claims for negligent maintenance.
  • 250,000 bridges (46 percent) are structurally deficient.
  • 130 dams in highly populated areas are in danger of imminent collapse.
  • 9,000 dams in highly populated areas are unsafe.
  • 8,000 miles of interstate highway must be rehabilitated.
  • 2,000 miles of interstate highway are wearing out each year.

Horror stories

Although these cost figures and horror stories are nationwide in scope, the concepts apply to every state, to every county, and to every city and town in the United States. Every governmental agency must develop an action plan which includes:

1) Inventory to determine the present condition of facilities and rank needs on the basis of objective criteria.

2) Financing to have sufficient resources to address the identified needs.

3) Implementation to ensure that financing is utilized efficiently and that resources committed to inventory efforts are not wasted.

Robert H. Gooden, director of public works for Rockville, Maryland, and chairman of the APWA Committee on Revenue Shonfall, states, “Only proper maintenance and operation of facilities will assure that the planned service life will be realized. While with adequate care facilities can serve well beyond their service life, at some point almost every public facility will require replacement…”

The most significant investment owned by cities and counties is their pavement facility. It is more valuable, contributes more direct benefit to economic efficiency, and has a higher cost of replacement than sewer systems, water systems, public buildings, and treatment plants. Citizens are also more aware of the condition of pavements than of other infrastructure needs.

Research has shown that performance of pavement declines as the pavement ages, as illustrated in Figure One. Differing pavement structures, traffic loads, soil and environmental conditions, and maintenance practices affect the shape of this curve. Conceptually, however, the curve is always the same; the older the pavement gets, the more rapidly it deteriorates and the more it costs to repair.

Figure 1

The process of inventorying and evaluating pavement systems is complicated because several pavement parameters are important: strength, roughness, surface distress, skid resistance, and rutting. Governmental agencies are interested in maximum service as measured by all of these parameters but, under economic restraints as they exist today, cost is an overriding concern.

Scientific methods are now available for inventorying and making pavement decisions that can result in enormous cost savings.

Overlay decisions

To illustrate the cost significance of these decisions, take the typical overlay decision. The decision “to overlay” involves a myriad of decisions which affect cost and performance:

  • How thick should the overlay be?
  • When should it be placed?
  • When will the next overlay be required?
  • What material(s) should be used?
  • What alternates to overlay are available and viable (recycle, fabrics, etc.)?

Concerning the thickness decision, too-thin overlay will fail prematurely and too-thick overlay will cost more money than is necessary (and restrict a community’s ability to deal with another need). Asphalt concrete costs about $40 per ton in-place, which is about $63,000 per two-lane mile for a two-inch thickness. If a 1 3/4 inch thickness can serve as well, a city can save $8,000 per mile.

Similarly, if two inches extends service by eight years and 2 1/4 inches would extend service by 16 years, trying to save the one-fourth inch (or $8,000) costs your city $55,000 in eight years, plus an accelerated reconstruction schedule to restore crown and curb height.

If the judgments of your engineer are 90 percent accurate, he is costing your agency about $10,000 per mile. Generally, judgment decisions are no better than 50 percent accurate. Agencies which do not use systematic and scientific methods of managing pavements are costing their taxpayers a lot of money.

The decision concerning the best treatment for a specific street must, of course, be tempered by the needs of the entire street network. In other words, treatment “D” may give 10 units of benefit for each dollar expended on Colorado Street; but what about Main Street? The optimum treatment on Main Street may yield twelve units of benefit for the same expenditure of dollars. The process of making individual projects compete with each other to receive priority for rehabilitation is called network level optimization.

Complex process
This process is complex. Optimum priorities may change from year to year because of different performance curves. In other words, Main Street may yield more benefit one year but Colorado Street may yield more benefit another year. To do network level optimization, all possible combinations for each year of a programming period must be computed and compared. These calculations require computerization. A management system with this level of sophistication has the capability of testing several policy-level “what if” questions.

Figure Two shows how maintenance costs increase with time as the service level gets closer and closer to a minimum acceptable level. The end result is that a lower level of service is maintained at a higher cost than if rehabilitation was programmed at an optimum time.

Figure 2

This fact has been verified by several studies. One such study was done by the Utah Department of Transportation, which was referenced in NCHRP Report #58 (see Figure Three). For all categories of roadway, the least costly strategy was “A,” where the highest service level was sustained. The most costly was strategy “D” at which rehabilitation was deferred until substantial increases in maintenance activity were required in response to public pressure to sustain serviceability at a minimum acceptable level. Strategy “D” was UDOTs current mode of operation.

Figure 3

Annual Cost Summary

By using a system of network optimization, Ottawa, Canada, on the other hand, was able to reduce its road budget by 14 percent in actual dollars, which equates to 43 percent in inflated dollars while at the same time improving service levels.

Summary

  • Pavement needs are enormous and growing due to past policies of deferring needed maintenance.
  • The number of specific examples of infrastructure failure is increasing.
  • Public works infrastructure must be inventoried, funded, and implemented.
  • Pavements are our largest infrastructure investment.
  • Research has produced performance curves for pavements.
  • Scientific management of pavements can result in substantial cost savings.

This article is reprinted from Colorado Municipalities/January-February, 1983 with permission.

How can a city or town decide the best way to use what money it has available for repairing its infrastructure?

By Dennis Polhill, P.E

Dennis Polhill is president of Pavement Management Systems, Inc., a company that evaluates existing pavement structures and makes recommendations for maintenance and rehabilitation. He is a civil engineer and was formerly a city engineer for 10 years.

Three trillion dollars is needed to restore the United States’ infrastructure.

The infrastructure is all of the physical . public works facilities which support the way of life, standard of living, and economic vitality which the U.S. has come to enjoy.

Investment in public works has declined at a rate of 4 percent per year. From 1965 to 1977 investment in public infrastructure declined 44 percent. Construction costs have inflated at twice the rate of consumer prices. Two thirds of the local governments in the U.S. cannot accommodate growth.

In a recent address, Representative Don Clawson of California suggested that “the pork-barrel mentality” of cutting capital projects in times of budget crunch is jeopardizing the economic vitality of the nation. Economic growth requires both an active public works and a strong transportation system.

The steady deterioration of the U.S. infrastructure is receiving increasing attention. Within the last year, leading news magazines have featured the problem; books have been written about it; TV documentaries have been aired about it; Congress has proposed legislation; and professional organizations have appointed study committees and issued position statements.

Best estimates of the infrastructure repair bill set the cost at $3 trillion. Some of the estimates that contribute to the $3 trillion figure are:

  • $1,800 billion for roads and streets
  • $33 billion for interstate highways (repairs only)
  • $700 billion for non-urban highways
  • $48 billion for bridges
  • $110 billion for water systems in 750 major urban areas
  • $40 billion for mass transit $31 billion for wastewater treatment
  • $15 billion for prisons and jails $600 billion for city streets

John Wiedeman, president of the American Society of Civil Engineers, says “Virtually every part of the country has its own horror story. The full extent of the challenge of decaying public works is not yet known:”

  • Poor roads cost the private sector $30 billion per year(Gasoline consumption increases 56 percent; tire costs increase 150 percent).
  • Numerous lives are lost each year in accidents caused or aggravated by poor road conditions.
  • In 1980, New York City paid $20,000,000 in liability claims for negligent maintenance.
  • In 1980, $3,500,000,000 was paid by states in liability claims for negligent maintenance.
  • 250,000 bridges (46 percent) are structurally deficient.
  • 130 dams in highly populated areas are in danger of imminent collapse.
  • 9,000 dams in highly populated areas are unsafe.
  • 8,000 miles of interstate highway must be rehabilitated.
  • 2,000 miles of interstate highway are wearing out each year.

Horror stories
Although these cost figures and horror stories are nationwide in scope, the concepts apply to every state, to every county, and to every city and town in the United States. Every governmental agency must develop an action plan which includes:

  1. Inventory to determine the present condition of facilities and rank needs on the basis of objective criteria.
  2. Financing to have sufficient resources to address the identified needs.
  3. Implementation to ensure that financing is utilized efficiently and that resources committed to inventory efforts are not wasted.

Robert H. Gooden, director of. public works for Rockville, Maryland, and chairman of the APWA Committee on Revenue Shortfall, states, “Only proper maintenance and operation of facilities will assure that the planned service life will be realized. While with adequate care facilities can serve well beyond their service life, at some point almost every public facility will require replacement…”

The most significant investment owned by cities and counties is their pavement facility. It is more valuable, contributes more direct benefit to economic efficiency, and has a higher cost of replacement than sewer systems, water systems, public buildings, and treatment plants. Citizens are also more aware of the condition of pavements than of other infrastructure needs.

Research has shown that performance of pavement declines as the pavement ages, as illustrated in Figure One. Differing pavement structures, traffic loads, soil and environmental conditions, and maintenance practices affect the shape of this curve. Conceptually, however, the curve is always the same; the older the pavement gets, the more rapidly it deteriorates and the more it costs to repair.

Figure 1

The process of inventorying and evaluating pavement systems is complicated because several pavement parameters are important: strength, roughness, surface distress, skid resistance, and rutting. Governmental agencies are interested in maximum service as measured by all of these parameters but, under economic restraints as they exist today, cost is an overriding concern.

Scientific methods are now available for inventorying and making pavement decisions that can result in enormous cost savings.

Overlay decisions

To illustrate the cost significance of these decisions, take the typical overlay decision. The decision “to overlay” involves a myriad of decisions which affect cost and performance:

  • How thick should the overlay be?
  • When should it be placed? When will the next overlay be required?
  • What material(s) should be used?
  • What alternates to overlay are available and viable (recycle, fabrics, etc.)?

Concerning the thickness decision, too-thin overlay will fail prematurely and too-thick overlay will cost more money than is necessary (and restrict a community’s ability to deal with another need). Asphalt concrete costs about $40 per ton in-place, which is about $63,000 per two-lane mile for a two-inch thickness. If a 1 3/4 inch thickness can serve as well, a city can save $8,000 per mile.

Similarly, if two inches extends service by eight years and 2 1/4 inches would extend service by 16 years, trying to save the one-fourth inch (or $8,000) costs your city $55,000 in eight years, plus an accelerated reconstruction schedule to restore crown and curb height.

If the judgments of your engineer are 90 percent accurate, he is costing your agency about $10,000 per mile. Generally, judgment decisions are no better than 50 percent accurate. Agencies which do not use systematic and scientific methods of managing pavements are costing their taxpayers a lot of money.

The decision concerning the best treatment for a specific street must, of course, be tempered by the needs of the entire street network In other words, treatment “D” may give 10 units of benefit for each dollar expended on Colorado Street; but what about Main Street? The optimum treatment on Main Street may yield twelve units of benefit for the same expenditure of dollars. The process of making individual projects compete with each other to receive priority for rehabilitation is called network level optimization.

Complex process

This process is complex. Optimum priorities may change from year to year because of different performance curves. In other words, Main Street may yield more benefit one year but Colorado Street may yield more benefit another year. To do network level optimization, all possible combinations for each year of a programming period must be computed and compared. These calculations require computerization. A management system with this level of sophistication has the capability of testing several policy-level “what if” questions.

Figure Two shows how maintenance costs increase with time as the service level gets closer and closer to a minimum acceptable level. The end result is that a lower level of service is maintained at a higher cost than if rehabilitation was programmed at an optimum time.

Figure 2

This fact has been verified 5y several studies. One such study was done by the Utah Department of Transportation, which was referenced in NCHRP Report #58 (see Figure Three). For all categories of roadway, the least costly strategy was “A,” where the highest service level was sustained. The most costly was strategy “D” at which rehabilitation was deferred until substantial increases in maintenance activity were required in response to public pressure to sustain serviceability at a minimum acceptable level. Strategy “D” was UDOTs current mode of operation.

Figure 3

Annual Cost Summary

By using a system of network optimization, Ottawa, Canada, on the other hand, was able to reduce its road budget by 14 percent in actual dollars, which equates to 43 percent in inflated dollars while at the same time improving service levels.

Summary

Pavement needs are enormous and growing due to past policies of deferring needed maintenance.

To delay addressing this issue is to make the problem larger. The number of specific examples of infrastructure failure is increasing.

Public works infrastructure must be inventoried, funded, and implemented.

Pavements are our largest infrastructure investment. Research has produced performance curves for pavements. Scientific management of pavements can result in substantial cost savings.

PROCEEDINGS of the Twentieth Paving and Transportation Conference

Sponsored by:

Department of Civil Engineering
The University of New Mexico
Albuquerque, New Mexico

By Dennis Polhill
President
Pavement Management Systems, Inc.
Lakewood, Colorado

Pavement Management is the process of making decisions about pavements. It is a daily activity of agencies responsible for pavements. In the context in which “pavement management” is used today, it infers utilizing more information in order to make those decisions better.

In pavement management, decisions are considered to be made at two levels: the project level and the network level. A total pavement management system includes both project level analysis, network level analysis and an information exchange back and forth between the two levels.

PROJECT LEVEL

Project level analysis is the process of looking intensely at a particular pavement for the purpose of optimizing the rehabilitation strategy being considered for that pavement. Project level analysis is considered

an engineering application of pavement management information.

Project level analysis may include consideration of several pavement parameters such as ride quality, skid resistance, rutting, structural capacity. The single parameter considered most is structural capacity. The best way to clarify the definition of project level analysis is through example applications.

PROJECT LEVEL ANALYSIS APPLICATIONS

Overlay Design

To make the best overlay decision, questions of thickness, type, timing and alternates must be considered. A “too-thin” overlay will result in premature failure and loss of some of the benefit (extension of serviceability) of the overlay. A “too-thick” overlay results in the expenditure of too much money now and in the loss of the option to put those dollars into another needy project. In Denver, a quarter of an inch of A. C. overlay equates to about $8,000 per mile. In Edgewater, Colorado, this type of analysis saved an overlay project $19,500.

Reconstruction Design

If grades are to remain the same during a reconstruction project, considerations similar to an overlay design are in order. “Can the existing structure contribute to or be used in the new structure?” In Frostburg, Maryland, this question was raised. By acquiring proper information the design engineer was able to determine which sections required rebuild and which sections could be rehabilitated. The estimated savings to the project was over $200,000.

Street Widening

If grades are to remain the same during a widening project, considerations similar to the reconstruction design are in order. “Can the existing structure contribute to or be used in the new structure?” or “What

needs to be done to the existing pavement to make it serviceable as the center two lanes of the project?” This question was raised during a project in Aurora, Colorado. In the final analysis, it was determined that the existing 2-lane roadway would be structurally sufficient with a minor overlay and isolated locations of additional structural padding or patching. The theoretical savings on this project was over $400,000.

Street Acceptance

The same type of analysis can be done on a new street. The obvious application is for acceptance of streets built by developers. Everyone has seen or heard of cases where as soon as a street is accepted by the municipality, it fails. The process merely requires that the street must demonstrate its ability to perform for a period of time as specified by the municipality. Some method of nondestructive testing and professional engineering analysis must be used. This approach will give cities the assurance they need that the facilities they accept will perform.

Assessment of Impacts

Assessment of impacts includes a variety of possible applications of project level pavement management information.. How do you determine the amount of permit fees to be charged for an overweight load moving through your jurisdiction? How does the change of a bus route effect a particular street? How do you determine what the load limits should be on your roads? What is the consequence of a major change in traffic volume or traffic con-figuration? A new development goes in that results in an increase in traffic loading both during and after construction. How much rehabilitation should reasonably be charged to the development and when should the work be scheduled? Timely rehabilitation resulting from assessment of conditions such as these can protect against premature failure of.pavement facilities. Project level analysis gives the capability of addressing these issues.

NETWORK LEVEL

Network level analysis is the process of looking at an entire system . (or network) of pavements. This is done to answer network-wide questions, such as which projects should be considered for rehabilitation. Network level analysis is considered a management application .of pavement management information. Some network level questions are:

  • What is the current level of service?
  • What will happen to the level of service over the next few years if the budget is set at “$????”?
  • What streets should receive priority consideration for maintenance of rehabilitation?
  • What would be the impact of a change in traffic characteristics?
  • What maintenance activity is required to get maximum benefit out of monies expended?

Rehabilitation Costs

By referring to Figure 1, it can be seen that rehabilitation costs increase by over 4 to 5 times if rehabilitation is deferred only 12% of a pavement’s design life. For typical pavements, 12% amounts to about 2 years. In view of this fact, deferred rehabilitation is very expensive. Good management dictates that rehabilitation occur at a time so as to derive the greatest benefit (or extension of serviceability) possible. The problem becomes very complex since each different pavement structure has a different point in their service lives.

Figure 1

An important point can be concluded here. Unless a jurisdiction has all the money it needs for rehabilitation, it is almost certainly a mis-take to program rehabilitation on a “worse-first” basis. Maximum benefit cannot be derived from the limited public funds available if an agency binds itself to a “worst-first” programming philosophy.

Maintenance Costs and Serviceability

Maintenance costs increase as serviceability declines. The increasing commitment to maintenance tends to extend serviceability but at a higher cost and lower service level than if rehabilitation was performed. This fact has been verified by several studies. The most widely known is research done by the Utah Department of Transportation, which was referenced in NCHRP Report #58 (see Figures 2 and 3). For all categories of roadway the least cost strategy was “A”, where the highest service level was sustained. The highest cost was strategy “D”. at which rehabilitation was deferred until such point that substantial increases in maintenance activity was required in response to public pressure to sustain service-ability-at a minimum acceptable level. Strategy “D” was UDOT’s current mode of operation.

Figure 2:

Figure 3

 

Figure 3:

Figure 6

Network Example

The best documented case of the successful implementation of a network level pavement management system is the Regional Municipality of Ottawa-Carleton, Canada, whose Transportation Director-is Michael J. E. Sheflin,

P. E. In 1980, Ottawa-Carleton’s road budget was 14% less in actual dollars and 43% less in inflated dollars than it was in 1977. At the same time average service level was improved. Shefiin gives credit for this accomplishment to the progressiveness of his council.

REFERENCES

1) Haas, R.C.G., and Hudson, W.R., “Pavement Management Systems”, McGraw-Hill, 1978.

2) Tessier, G.R., and Haas, R.C.G., “Pavement Management Guide”, Road and Transportation Association of Canada, 1977.

3) Chong, G.J., “Pavement Maintenance Guidelines”, Ontario Ministry of Transportation and Communications, 1980.

4) Chong, G.J., Phang, W.A., and Wrong, G.A., “Manual for Condition Rating of Rigid Pavements”, Ontario Ministry of Transportation and Communications, 1975.

5) Chong, G.J., Phang, W.A., and Wrong, G.A., “Manual for Condition Rating of Flexible Pavements”, Ontario Ministry of Transportation and Communications, 1975.

6) Eaton, R.A., and Joubert, R.H., “Pothole .Primer”, Special Report 81-21, U.S. Army Corps of Engineers, 1981.

7) Kobi, D., “ARAN, An Integrated and Automated Road Inventory Tool”, American Public Works Association, 1981.

8) Karan, M:A., “Municipal Pavement Management System”, University of Waterloo, 1977.

9) Sheflin, M.J.E., “Your Choice: Bad Roads At High Cost Or Good Roads At Low Cost”, Oklahoma State University, 1980.

10) Haas, R.C.G.,. “Combining the Priority Programing of Pavement Maintenance and Rehabilitation”, Transportation Research Board, 1982.

11) Yoder, E.J., and Witczak, M.W., “Principles of Pavement Design”, John Wiley and Sons, Inc., 1975.

12) AASHO, “AASHO Interim Guide for Design of ,Pavement Structures – 1972”.

13) Sheflin, M.J.E., “Good’ Roads _DO Cost Less”, Rural and Urban Roads, October, 1980.

14) NCHRP #5.8, “Consequences of Deferred Maintenance”, Transportation Research Board, 1979.

DENNIS POLHILL, P.E.
Pavement Management Systems
8725 W. 14th Avenue. Suite 208
Lakewood, Colorado
(303) 232-2207

Pavement management is the process of making decisions about pavements. It is a daily activity of agencies responsible for pavements. In the context in which “pavement management” is used today, it infers utilizing more information in order to make those decisions better.

In pavement management, decisions are considered to be made at two levels: the project level and the network level. A total pavement management system includes both project level analysis, network level analysis, and an information exchange back and forth between the two levels.

Project level analysis is the process of looking intensely at a particular pavement for the purpose of optimizing the rehabilitation strategy being considered for that pavement. Project level analysis is considered an engineering application of pavement management information.

Project level analysis may include consideration of several pavement parameters, such as ride quality, skid resistance, rutting, and structural capacity. The single parameter considered most is structural capacity.

Network level analysis is the process of looking at an entire system (or network) of’ pavements. This is done to answer network-wide questions, such as which projects should be considered for rehabilitation. Network level analysis is considered a management application of pavement management information. Some network level questions are:

  • What is the current level of service?
  • What will happen to the level of service over the next few years if the budget is set now?
  • What streets should receive priority consideration for maintenance or rehabilitation?
  • What would be the impact of a change in traffic characteristics?
  • What maintenance activity is required to get maximum benefit out of monies expended?

Any of the same pavement parameters measured in project level analysis may be measured for network level analysis: ride quality, skid resistance, rutting, and structural capacity. Those most typically used are ride quality (which is more commonly termed road roughness), surface distress, and structural adequacy. Pavement Management Systems has established network level pavement management systems based on each of these three parameters individually, but usually uses a measure of serviceability termed pavement quality index (PQI), which uses all three. Roughness, surface distress, and structural adequacy are measured, converted to indices, weighted, and added to get PQI.

Serviceability
The serviceability concept was initiated during the AASHO Road Test in 1958. The serviceability concept was an effort to put. the perception of the consumer into proper consideration. That is, when a consumer rates a road he does it with a substantially different outlook than an engineer. The consumer evaluates only roughness. Panels of people were used by AASHO to rate several test sections as they were subjected to loading. The ratings were termed present serviceability rating (PSR). PSR was converted to present serviceability index through curve fitting in order to reduce evaluation costs, write a performance equation, and encourage the development of equipment which would produce the same data as the panel.

Of course, a jurisdiction can establish any type of criteria or level of service which it desires. For example, skid resistance could be identified as the long parameter which, when it decreases to a certain level, would trigger the need for work. Few jurisdictions today have the funds to follow this as a strategy. Most cities and counties are struggling to have sufficient funds to meet immediate maintenance requirements. Capital programs and rehabilitation programs have been gutted due to inflation and budget cuts. In view of the economic factors in play today, most jurisdictions are concerned only with maintaining the maximum structural integrity for the minimum amount of money. That means either fixing or preventing potholes. The situation at the local level is desperate.

One pavement parameter which is symptomatic of structure is surface distress. Several standardized methods of performing surface distress surveys have been developed. The most common are: Asphalt Institute, Texas Transportation Institute, Army Corps of Engineers, and Province of Ontario. Surface distress surveys are popular among cities and counties because they are relatively simple to perform. They can be performed by in-house engineering staff or by local consultants. The information can be used to estimate “now” needs and has limited applications when summarized properly for engineering, maintenance, and management.

By referring to Figure 1, it can be seen that rehabilitation costs increase by over 4 to 5 times if rehabilitation is deferred only 12 percent of a pavement’s design life. For typical pavements, 12 percent amounts to about two years. In view of this fact, deferred rehabilitation is very expensive. Good management dictates that rehabilitation occur at a time so as to derive the greatest benefit (or extension of serviceability) possible. The problem becomes very complex since each different pavement structure has a different performance curve and on similar structures with similar curves different pavements will be at a different point in their service lives.

Figure 1

An important point can be concluded here. Unless a jurisdiction has all the money it needs for rehabilitation, it is almost certainly a mistake to program rehabilitation on a “worst-first” basis. Maximum benefit cannot be derived from the limited public funds available if an agency binds itself to a “worst-first” programming philosophy.

Within the field of pavement management the terms of maintenance and rehabilitation are distinguished from each other.

Maintenance is defined as those routine activities necessary to sustain the integrity of the pavement structure. Maintenance activities include: crack sealing, chip sealing, and pothole patching. They do not add significantly to the pavement structure and do not extend serviceability. Maintenance activities preserve serviceability.

Rehabilitation is defined as those activities which restore the pavement structure in whole or in part to original condition. Rehabilitation activities would include: overlaying, recycling, padding, and structural patching. Reconstruction is generally considered to be such a major undertaking that it is classified outside of rehabilitation in a third (capital project) category.

Maintenance costs increase as serviceability declines. This fact has been verified by several studies. The most widely known is research done by the Utah Department of Transportation (UDOT) which was referenced in NCHRP Report #58 (see Figure 2 and Table 1). For all categories of roadway the least cost strategy was “A,” where the highest service level was sustained. The highest cost was strategy “D” at which rehabilitation was deferred until such point that substantial increases in maintenance activity were required in response to public pressure to sustain serviceability at a minimum acceptable level. Strategy “D” had been UDOT’s mode of operation.

Table 1 - Annual Cost Summary, Utah DOT (1977)

 

Figure 2. Graphical representation of the four rehabilitation strategies

One of the best documented cases of’ successful implementation of a network level pavement management system is the Regional Municipality of Ottawa-Carleton, Canada, whose Transportation Director is Michael J. E. Sheflin, P.E. In 1980, Ottawa-Carleton’s road budget was 14 percent less in actual dollars and 43 percent less in inflated dollars than it was in 1977. At the same time, average service level was improved. Sheflin gives credit for this accomplishment to the progressiveness of his council.

NATIONAL ROAD AND STREET MAINTENANCE
The Third Annual
Road and Street Maintenance Conference
April 20 and 21,1982 Fort Worth, Texas

Sponsored by

U.S. Department of Transportation Federal Highway Administration
Center for Local Government Technology

Oklahoma State University
Texas Transportation Institute
Texas A&M University System

THE CENTER FOR LOCAL GOVERNMENT TECHNOLOGY
A University Extension Program of the
Division of Engineering, Technology and Architecture

PAVEMENT MANAGEMENT
Dennis Polhill, P.E.
Pavement Management Systems (Colorado), Inc.
118 Yank Way, Suite 101
Lakewood, Colorado 80228

INTRODUCTION

  • 37% of the interstate highway system has been rated to be in fair or poor condition.
  • 53% of the country’s paved roads need immediate attention.
  • Repair costs were figured at $225,000,000,000 in 1981.
  • Automobiles use 56% more fuel traveling over rough and worn surfaces.
  • 16.4 billion gallons of gasoline are wasted annually.
  • Rough roads increase vehicle maintenance by 100%. Rough roads increase tire wear by 150%.
  • Accidents attributable to obsolete roads cost $8.55 billion in 1979.
  • In 12 years from 1967 to 1979 the construction cost index increased at nearly twice the rate of the consumer price index. J `
  • In 1979 the State of Colorado decided to assess $92,000,000 to road uses in the form of accidents.
  • In 1980 the State of Massachusetts decided to assess $3.6 billion to road users in 1985.
  • In 1975 the State of Pennsylvania decided to assess $11 billion to road users iri 1979.
  • In 1980 the regional municipality of Ottawa-Carleton, Canada saved road users $10,000,000.

Political considerations often tend to force priorities which do not yield the best possible benefit from the limited public funds available. Most elected officials are committed to making the best decisions on behalf of their constituents. Therefore, we, public managers, must be armed with an adequate amount of proper information when presenting Policy and budget issues to our elected officials.

PAVEMENT MANAGEMENT
Pavement Management is the process of making decsions about pavements. It is a daily activity of agencies ‘esponsibfe for pavements. In the context in which “pave ment management” is used today, it infers utilizing more information in order to make those decisions better.

In pavement, decisions are considered to be made at t*O levels the project level and the network level.

Project Level
Project level analysis is the process of looking intensely at a particular pavement for the purpose of optimizing the rehabilitation strategy being considered for that pavement. Project level analysis is considered an engineering application of pavement management information.

Network Level
Network level analysis is the process of looking at an entire system (or network) of pavements. This is done to answer network-wide questions, such as which projects should be considered for rehabilitation. Network level analysis is considered a management application of pavement management information.

Interaction of Levels
A total pavement management system included both project level analysis, network level analysis and an information exchange back and forth between the two levels.

PROJECT LEVEL ANALYSIS APPLICATIONS
Project level analysis may include consideration of several pavement parameters such as ride quality, skid resistance, rutting, structural capacity. The single parameter considered most is structural capacity. The best way to clarify the definition of project level analysis is through example applications.

Overlay Design
To make the best overlay decision, questions of thickness, type, timing and alternates must be considered. A “too-thin” overlay will result in premature failure and loss of some of the benefit (extension of serviceability) of the overlay. A “too-thick” overlay results in the expenditure of too much money now and in the loss of the option to put those dollars into another needy project. In Denver, a quarter of an inch of A.C. overlay equates to about $8,000 per mile. In Edgewater, Colorado, this type of analysis saved an overlay project $19,500 (see Appendix “A”).

Reconstruction Design
If grades are to remain the same during a reconstruction project, considerations simtlarto an overlay design are in order. “Can the existing structure contribute to or be used in the new structure?” In Frostburg, Maryland, this question was raised (see Appendix “B”). By acquiring proper information the design engineer was able to determine which sections required rebuild and which sections could be rehabilitated. The estimated savings to the project was over $200,000.

Street Widening
If grades are to remain the same during a widening project, considerations similar to the reconstruction design are in order. “Can the existing structure contribute to or be used in the new structure?” or “what needs to be done to the existing pavement to make it serviceable as the center two lanes of the project?” This question was raised during a project in Aurora, Colorado. In the final analysis it was determined that the existing 2 lane roadway would be structurally sufficient with a minor overlay and isolated locations of additional structural padding or patching. The theoretical savings on the project was over $400,000, but the actual design has not progressed enough to calculate a savings based on actual costs and other changes to the project.

Street Acceptance
The same type of analysis can be done on a new street. The obvious application is for acceptance of streets built by developers. We have all seen or heard of cases where as soon as a street is accepted by the mdriicipality, it fails. A draft specification for street acceptance is shown in Appendix “C”. The process merely requires that the street must demonstrate its ability to perform for a period of time as specified by the municipality. Some method of non-destructive testing and professional engineering analysis must be used. This approach will give cities the assurance they need that the facilities they accept will perform up to some minimum.

Assessment of Impacts
Assessment of impacts includes a variety of possible applications of project level pavement management information. How do you determine the amount of permit fees to be charged for an overweight load moving through your jurisdiction? How does the change of a bus route effect a particular street? How do you determine what the load limits should be on your roads? What is the consequence of a major change in traffic volume or traffic configuration? A new development goes in that results in an increase in traffic loading both during and after construction. How much rehabilitation should reasonably be charged to the development and when should the work be scheduled. Timely rehabilitation resulting from assessment of conditions such as these can protect against premature failure of pavement facilities. Project level analysis gives the capability of addressing these issues.

NETWORK LEVEL PROGRAMING
Network level analysis is the process of looking at an entire system (or network) of pavements to answer network-wide questions. Some typical network level questions are:

  • What is the current level of service?
  • What will happen to the level of service over the next few years if the budget is set at “X”?
  • What streets should receive priority consideration for maintenance or rehabilitation?
  • What would be the impact of a change in traffic characteristics?
  • What maintenance activity is required to get maximum benefit out of monies expanded?

Any of the same pavement parameters measured in project level analysis may be measured for network level analysis: ride quality, skid resistance, rutting, structural ca pacity. Those most typically used are ride quality (which is more commonly termed road roughness), surface distress and structural adequacy. PMS has established network level pavement management systems based on each of these three parameters individually but usually uses a measure of serviceability termed pavement quality index (POI) which uses all three. Roughness, surface distress and structural adequacy are measured, converted to indices (RCI, SDI, SAI respectively), weighted and added to get PQ1.

Serviceability
The serviceability concept was initiated during the AASHO Road Test in 1958. The serviceability concept was an effort to put the perception of the consumer into proper consideration. That is, when a consumer rates a road he does it with a substantially different outlook than an engineer. The consumer evaluates only roughness. Panels of people were used by AASHO to rate several test sections as they were subjected to loading. The ratings were termed present serviceability rating (PSR). PSR was converted to an index (present serviceability index, PSI) through curve fitting in order to reduce evaluation costs, write a performance equation and encourage the development of equipment which would produce the same data as the panel. Figure 1 shows a typical plot of PSI versus time. The equation for this curve is:

Pavement Management Formula

Figure 1

Network Programing Criteria
Of course, a jurisdiction can establish any type of criteria or level of service which it desires. For example, skid resistance could be identified as the lone parameter which when it decreases to a certain level would trigger the need for work. Few jurisdictions today have the funds to follow that as a strategy. Most cities and counties are struggling to have sufficient funds to meet immediate maintenance requirements. Capital programs and rehabilitation programs have been gutted due to inflation and budget cuts. In view of the economic factors in play today most jurisdictions are concerned only with maintaining the maximum structural integrity for the minimum amount of money. That means either fixing or preventing potholes. The situation at the local level is desperate.

Surface Distress Surveys
One pavement parameter which is symptomatic of structure is surface distress. Several standardized methods of performing surface distress surveys have been developed. The most common are: Asphalt Institute, Texas Transportation Institute, Army Corps of Engineers and Province of Ontairo. Surface distress surveys are popular arnong cities and counties because they are relatively simple to perform. They can be performed by in-house engineering staff or by local consultants. The information can be used to estimate “now” needs and has limited applications when summarized properly for engineering, maintenance and management.

Rehabilitation Costs
Let’s look at the performance curve again in terms of rehabilitation costs (see Figure 2). It can quickly be seen that rehabilitation costs increase by over 4 times if rehabili tation is deferred only 12% of a pavement’s design life. For typical pavements, 12% amounts to only about 2 years. In view of this fact, deferred rehabilitation is very expensive. Good management dictates that rehabilitationi occur at a time so as to derive the greatest benefit (or extension of serviceability) possible. The problem becomes very complex since each different pavement structure has a different performance curve and on similar structures with similar curves different pavements will be at a different point in their service lives.

 Figure 2

An important point can be concluded here. Unless a jurisdiction has all the money for rehabilitation, it is almost certainly a mistake to program rehabilitation on a”vorse first” basis. Maximum benefit cannot be derived from the limited public funds available if an agency binds itself to a “worst-first” programing philosophy.

Maintenance and Rehabilitation
Within the field of pavement management the terms of maintenance and rehabilitation are distinguished Irom each other.

Maintenance
Maintenance is defined as those routine activities necessary to sustain the integrity of the structure. Maintenance activities include: crack sealing, chip sealing and pothole patching.

Rehabilitation
Rehabilitation is defined as activities which restore the structure in whole or in part to the condition which it was in originally. Rehabilitation activities would include: overlay ing, recycling, padding and structural patching. Reconstruction is generally considered to be such a major undertaking that it is classified outside of rehabilitation in a third (capital project) category.

Maintenance and Serviceability
Serviceability is affected if proper maintenance is not performed. Figure 3 is a graph of serviceability versus time with two serviceability curves: with maintenance and with out maintenance. The normal serviceability curve assumes that maintenance will be performed. If maintenance is not performed the structure of the pavement will gradually be affected adversely.

Figure 3

Maintenance Costs and Serviceability
Maintenance costs increase as serviceability declines. Figure 4 illustrates this. This graph shows that as serviceability increases in its rate of decline, maintenance costs increase. The increasing commitment to maintenance tends to extend serviceability but at a higher cost and lower service level than if rehabilitation was performed. This face has been verified by several studies. The most widely known is research done by the Utah Department of Transportation, which was referenced in NCHRP Report #58 (see Figures 5 and 6). For all categories of roadway the least cost strategy was “A”, where the highest service level was sustained. The highest cost was strategy “D” at which rehabilitation was deferred until such point that substantial increases in maintenance activity was required
in response to public pressure to sustain serviceability at a minimum acceptable level. Strategy “D” was their current’, mode of operation.

Figure 4

Figure 5

Figure 6

Network Example
One of the best documented cases of the successful implementation of a network level pavement management system is the Regional Municipality of Ottawa-Carleton, Canada. The transportation director is Michael J.E. Sheflin, P.E., who spoke at this conference last year. In 1980 Ottawa-Carleton’s road budget was 14% less in actual dollars and 43% less in inflated dollars than it was in 1977. At the same time average service level was improved. Sheflin gives credit for this accomplishment to the progressiveness of his council.

SUMMARY
The U.S. is a great country with unlimited potential. However, the element of human nature which makes us take our life style for granted is once again upon us. Just as it was in 1941 when the U.S. was surprised at Pearl Harbor. Just as it was in 1957 when Russia launched the first satelite into orbit. So it is today with our transportation system. The majority of mileage in our highway system is approaching 75% of its original design life in age. The rate of deterioration is increasing rapidly. We as a nation must pool our knowledge and resources to prevent the catastrophe that will result with the deterioration of our highway system. We are all managers of road systems. Your management role carries with it the burden of leadership. How knowledgeable are you of this problem? How significant is this problem within your own jurisdiction?
This is not a problem which any of us can solve alone. Its solution will require the accumulation of more knowledge than currently exists about pavements and the commitment of the proper level of resources at all levels of government.

REFERENCES
1. Hass, R.C.G., and Hudson, W.R., “Pavement Management Systems”, McGraw-Hill, 1978.
2. Tessier G.R., and Haas, R.C.G., “Pavement Management Guide”, Road and Transportation Association of Canada, 1977.
3. Chong, G.J., “Pavement Maintenance Guidelines”, Ontario Ministry of Transportation and Communications, 1980.
4. Chong, G.J., Phang, W.A., and Wrong, G.A., “Manual for Condition Rating of Rigid Pavements”, Ontario Ministry of Transportation and Communications, 1977.
5. Chong, G.J., Pahng, W.A., and Wrong, G.A., “Manual for Condition Rating of Rigid Pavements”, Ontario Ministry of Transportation and Communications, 1977.
6. Eaton, R.A., and Joubert, R.H., “Pothole Primer”, Special Report 81-21; U.S. Army Corps of Engineers, 1981.
7. Kobi, D., “ARAN, An Integrated And Automated Road Inventory Tool”, American Public Works Association, . 1981.
8. Karan, M.A., “Municial Pavement Management System”, University of Waterloo, 1977.
9. Sheflin, M.J.E., “Your Choice: Bad Roads At High Cost Or Good Roads At Low Cost”, Oklahoma State University, 1980.
10. Haas,. R.C.G., “Combining the Priority Programing of Pavement Maintenance and Rehabilitation”, Transportation Research Board, 1982.
11. Yoder, E.J., and Witczak, M.W., “Principles of Pavement Design”, John Wiley and Sons, Inc., 1975.
12. AASHO, “AASHO Interim Guide for Design of Pavement Structures -1972”.
13. Sheflin, M.J.E., “Good Roads Do Cost Less”, Rural and Urban Roads, October, 1980.
14. NCHRP #58 “Consequences of Deferred Maintenance”, Transportation Research Board, 1979.
15. The Road Information Program, ‘The Extent of Road and Bridge Deterioration on Colorado’s Interstate System”, 1981.
16. The Road Information Program, “The Effect of Obsolete Road Design and Engineering on Driving Safety in Colorado”, 1980.