PUBLIC WORKS MAGAZINE, January 1987
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.