Description

This comprehensive working paper provides the master framework for modeling Road User Effects (RUE) within the Highway Development and Management (HDM-4) system. Road user effects represent the dominant economic component in highway investment appraisals, encompassing vehicle operating costs (VOC), travel time costs, crash costs, and environmental effects. The report details the physical and economic sub-models responsible for estimating fuel consumption, lubricating oil consumption, tire wear, vehicle repair and maintenance parts, maintenance labor hours, vehicle depreciation, capital interest costs, passenger travel time values, and cargo holding costs. Each sub-model is defined as a function of road characteristics (roughness, geometry, surface type, pavement structural strength), vehicle characteristics (mass, engine power, drag coefficient, payload), and driver behavior under varying traffic flow conditions. The document synthesizes decades of international empirical research—including World Bank studies in Brazil, Kenya, India, and the Caribbean—to establish unified mechanistic equations suitable for global application. Implementation protocols, default parameter sets, and calibration procedures are provided to ensure that highway agencies can tailor the RUE relationships to local economic conditions, currency values, vehicle fleet profiles, and transport cost structures. Overall, the report emphasizes rigorous empirical validation, standardized data acquisition protocols, and modular integration into the broader Highway Development and Management analytical engine. By combining physical principles with statistical calibration across international trial sites, this working paper provides a robust theoretical and practical baseline for highway authorities to evaluate long-term infrastructure policy options, allocate maintenance budgets efficiently, and maximize economic returns across regional and national road networks.