Dennis Polhill

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.

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:

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.