Description

This technical working paper presents the finalized mathematical formulation and modeling framework for vehicle tire wear and consumption within the Highway Development and Management (HDM-4) model, produced under the International Study of Highway Development and Management Tools (ISOHDM). The document details how physical forces acting on tires—including rolling resistance, aerodynamic drag, gravitational resistance on steep vertical gradients, and lateral cornering forces—translate into mechanical tread wear and carcass deterioration over continuous operational cycles. Key pavement surface characteristics such as International Roughness Index (IRI), microtexture, and surface macrotexture depth are integrated with vehicle operating conditions, axle loads, tire inflation pressures, and wheel alignment parameters to estimate overall tire wear rates across distinct vehicle classes, including passenger cars, light commercial vehicles, buses, and heavy articulated multi-axle freight trucks. Furthermore, the report distinguishes between radial and bias-ply tire technologies, establishing empirical calibration coefficients derived from extensive field trials across diverse climatic regions. Economic implications are comprehensively evaluated, translating physical tread volume loss into monetary unit costs associated with tire replacement, retreading cycles, and carcass maintenance. The output of this tire consumption model serves as a core module of HDM-4 Vehicle Operating Costs (VOC), enabling highway agencies, transport planners, and infrastructure engineers to conduct rigorous economic evaluations of pavement maintenance strategies, surface dressing policies, and long-term capital investments by accurately forecasting user cost savings resulting from smoother and better-maintained road networks worldwide. Overall, the report emphasizes rigorous empirical validation, standardized data acquisition protocols, and modular integration into the broader Highway Development and Management analytical engine.