A Disaggregated Approach for the Computation of Network-Level Highway User Costs

Highway asset management (HAM) is comprised of constituent management systems for physical highway assets such as pavements and bridges as well as for enhanced highway operations through improved safety, mobility, and air quality. Effective HAM involves establishment of system goals that maximize utility to the highway agency as well as the highway user for all such management systems. As such, it is important to determine values for highway user costs and benefits for a given highway network in order to monitor the extent to which goals are being achieved and also to determine the tradeoff relationships that may exist between various aspects of highway user costs. Also, it is often desired to establish tradeoff relationships between the improvement of highway operational characteristics on one hand and physical asset conditions on the other. The components of highway user costs considered include those related to vehicle operation, travel time, roadway collisions, and highway vehicle emissions. The aim of this paper is to develop statistical models for estimating network-level highway user costs using basic data on network physical and operational characteristics. Various user cost components were determined using established user cost relationships and past data on the Indiana state highway network. It was found that the average network travel speed and roadway surface condition are significant variables that affect highway user costs. With the developed network-level user cost models, it is possible to evaluate impacts of system level decisions and ultimately to ascertain the extent to which a system level decision may influence attainment of HAM goals.