Planning, evaluating, selecting, and financing highway investments require an understanding of fundamental empirical relationships between the physical and service characteristics of roadways and the associated user costs. Integral to estimating highway needs are accurate measures of the economic costs associated with vehicle maintenance, tires, depreciation, oil, fuel consumption, accidents, emissions, and travel time--each expressed as a function of highway conditions. Further, there is a need to assess the fundamental empirical relationships between highway characteristics (e.g., roughness, alignment, service level) and user costs (e.g., vehicle operation and maintenance, travel time, safety, emissions). New measures are needed for the value of time and operating and safety costs as they relate to congestion and productivity, and there is a need to determine the sensitivity of user costs to external changes.

The objectives of this research were (1) to examine the validity of the data, concepts, assumptions, components, and methods currently used to determine highway user costs; (2) to identify methodological improvements that are possible through theoretical or empirical research; and (3) to propose action plans to undertake the identified research opportunities.

The research reviewed the validity and accuracy of current methods used to estimate highway user costs, considering the critical elements of each component, the realism of assumptions, the rigor of the concepts, the accuracy of the data for the current and future vehicle fleet, and the relative contribution of each component to overall highway user costs. The sensitivity of individual cost estimates, input data, and specification of the empirical relationships was systematically evaluated. Opportunities for improvements in the highway user cost-estimating procedures by using additional components, establishing more accurate and rigorous fundamental relationships, defining more realistic assumptions, and utilizing better data sources were identified. A strategic plan that prioritizes the candidate research opportunities in terms of the general magnitude of cost, length and difficulty of the research effort, and the likelihood that the methodological improvement can have significant decision-making impact was developed.

Status: The research is complete and the contractor's final report is available.

Product Availability: The contractor's final report is available on request from the NCHRP.