By almost any definition, technology has penetrated the U.S. light-duty vehicle fleet significantly in conjunction with the increased stringency of fuel economy and GHG emissions regulations. The physical presence of advanced technology components provides one indication of the efforts taken to reduce emissions, but that alone does not provide a complete measure of the benefits of a particular technology application. Differences in the design of components, the materials used, the presence of other technologies, and the calibration of controls can impact the performance of technologies in any particular implementation. The effectiveness of a technology for reducing emissions will also be influenced by the extent to which the technologies are applied towards changes in vehicle operating characteristics such as improved acceleration, or customer features that may offset mass reduction from the use of lightweight materials.
This paper begins with an examination of trends in the penetration of key advanced technologies into the U.S. light-duty vehicle fleet. We then investigate the overall influence of these technologies and vehicle changes on tailpipe CO2 emissions using metrics for powertrain efficiency and tractive energy metrics. Finally, we introduce a methodology for representing existing technology implementations across the full fleet of non-electrified vehicles using EPA’s Advanced Light-duty Powertrain and Hybrid Analysis (ALPHA) full vehicle simulation model and library of benchmarked powertrain component models. Using such an approach, a compliance analysis can be conducted for a future vehicle fleet where the emissions reductions and associated costs are applied incrementally to the existing set of baseline fleet of vehicles, while giving appropriate consideration to how a particular vehicle’s technology implementation influences the potential for further emissions reductions.