Rating the Environmental Impacts of Motor Vehicles: The Green Guide to Cars and Trucks Methodology, 1998 Edition

Research Report T981


John DeCicco and Martin Thomas


Consumer education and other market-oriented approaches to environmental protection require understandable and coherent information on the environmental performance of the products in question. Such information can influence buyer decisions and might thereby provide feedback to manufacturers' technology and product planning activities. Although light duty vehicles have long been a focus of federal and state environmental policies, existing information on the environmental performance of vehicles is rather fragmented. Various programs tend to focus on one or a few aspects of the issue, such as tailpipe emissions, fuel economy, electric or other alternative fuel capability, and technology type. The heightened interest in market-oriented approaches, as well as the rising importance of higher fuel economy as a way to address greenhouse gas emissions, motivates the development of a more integrated approach to motor vehicle environmental information.

An environmental rating methodology for light duty vehicles was developed based on principles of life-cycle assessment and environmental economics. The method was designed to be applicable given the limitations of data available by make and model in the U.S. market. The approach combines the impacts of traditionally regulated (criteria) pollutants with those of greenhouse gas emissions, covering both the vehicle life cycle and the fuel cycle, using a mass-based characterization of vehicle manufacturing impacts. This methodology was applied in a consumer-oriented publication, the Green Guide to Cars and Trucks, published in March 1998. This report covers the data issues, key assumptions, and analysis methods used to develop these vehicle ratings. It then summarizes the application of the methodology to the 1998 model year, highlighting results for major classes and technology types. Finally, it identifies research needs for updating and refining the methodology.