The level of funding by various highway agencies is inadequate to keep roads at the current condition if current maintenance and rehabilitation policies are continued. Through a preventive maintenance program, pavements can be maintained in a cost-effective manner leading to a better pavement quality at lower total costs. Preventive maintenance is a program strategy that can arrest light deterioration, retard progressive failures, and reduce the need for routine maintenance activities. The objective of such a program strategy is to extend the functional life of the pavement by applying treatments before the pavement deteriorates to a condition that requires a corrective treatment, such as a structural overlay. An effective strategy would feature a combination of different treatments, such as periodic crack treatment followed by chip sealing. A number of highway agencies have used preventive maintenance strategies for both low and high volume roads and found them to be successful. Preventive maintenance treatments for flexible pavements include fog seal, chip seal, slurry seal, micro-surfacing, crack treatment, and thin hot-mix dense, open and gap graded overlays. The selection of a preventive maintenance treatment should be based on the condition of the existing pavement, traffic volume, and environmental conditions. Other factors include experience, budget constraints, and political reality.

From 1979 through 1982 the Federal Highway Administration contracted with the Texas Research and Development Foundation to update vehicle operating cost tables. In this research five components of vehicle operating cost were studied, including fuel consumption, maintenance and repair, oil consumption, tire consumption, and depreciation. The approach used in this research was to identify the consumption involved for each of these parameters and then to price these components to obtain vehicle operating costs. This approach allows future updating of the vehicle operating cost tables from simply knowing the changes in prices. This is highly desirable since component consumption changes much less frequently than the unit prices. The results of this research present a new set of table relating vehicle operating costs to the serviceability index of pavements and the geometric design features of the roads. The component consumption tables were established for constant speed and speed change cycle operations.

Much has been done in recent years to relate various roughness statistics to rider comfort in terms of a serviceability index (developed by Carey and Irick). Much less has been done on correct evaluation of a true profile in terms of summary statistics for field comparison of vehicle operating costs and user comfort. Important work in this area has been done by Gillespie and Sayers at the University of Michigan, and additional work has been done by Hudson, Williamson, and McKenzie at the University of Texas. Work has also been done in Brazil by Queiroz and others. At least two statistics have been offered for summarizing roughness information: (a) the average rectified velocity, by Gillespie and Sayers, and (b) the root-mean-square vertical acceleration, by Hudson et al. The purpose of this paper is to examine and compare these statistics with particular emphasis on their potential effects on rider comfort and their use as standard calibration statistics for response-type road roughness meters. A complete parameter study is reported comparing these two statistics. The results of the study will be helpful in selecting useful analytical techniques for routine applications.