Enhanced Models for Vehicle Fuel Consumption for Life Cycle Assessment of Pavements

Abstract

A life cycle assessment (LCA) of pavements provides a comprehensive approach to evaluate the potential environmental impacts associated with all stages of a pavement’s life: material production, pavement design, construction, use phase, maintenance/preservation, and end of life. The use phase stage is influenced by the pavement’s structural and material properties as well as its surface characteristics. Pavement surface characteristics such as roughness can influence the vehicle operating costs (VOCs). This paper presents specific examples of the newly developed FHWA fuel economy models using full vehicle dynamic simulations while taking into consideration vehicle speed profiles, roadway properties (e.g., grade, curvature, roughness), and vehicle types. Physics-based full vehicle simulation models were implemented to estimate vehicle fuel economy over a range of synthetically optimized (SO) driving cycles. The SO driving cycles were determined based on a collected sample of Strategic Highway Research Program 2 (SHRP 2) Naturalistic Driving Study (NDS) and American Transportation Research Institute (ATRI) time series data. Thirty different vehicle types were considered and comprised six different vehicle categories: small light duty vehicles (SLDVs), large light duty vehicles (LLDVs), two-axle trucks, busses, single-unit truck, and combination trucks. Different engine types were also considered such as gasoline, diesel, hybrid-electric, ethanol (E85), and liquefied natural gas (LNG). Reduction in fuel economy due to roadway curvature (RFEC) prediction models along with pavement condition adjustment factors (PCAFs) for a range of pavement roughness conditions in terms of International Roughness Index (IRI) were also developed for the various modeled vehicles.