Dennis Polhill

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.

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.

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.