Description

This research report published by Waka Kotahi NZ Transport Agency details the modern integration of vehicle operating cost (VOC) models with environmental emissions modeling frameworks for transport evaluation in New Zealand. As national policies emphasize carbon reduction and environmental sustainability alongside economic efficiency, traditional VOC appraisal tools must be updated to dynamically model fuel consumption, greenhouse gas (GHG) emissions (CO2, CH4, N2O), and airborne pollutants (PM2.5, NOx) across modern vehicle fleets. The study updates traditional HDM-4 vehicle operating cost algorithms to reflect New Zealand's evolving fleet profile, including hybrid, plug-in hybrid, and battery electric vehicles (EVs). It establishes integrated mathematical models that calculate energy consumption and emissions as functions of road geometry, gradient, surface roughness (IRI), speed variance, and congestion levels. Field validation using real-world driving data confirms that smoother road surfaces and optimized gradients yield measurable reductions in energy use and carbon output across both internal combustion and electric powertrains. The integrated model is incorporated into New Zealand's Monetised Benefits and Costs Manual (MBCM), providing transport planners with a unified analytical tool to evaluate the economic and environmental trade-offs of roading investments, pavement maintenance policies, and decarbonization strategies.