An analysis on long term emission benefits of a government vehicle fleet replacement plan in northern illinois

There have been a number of studies of the effectiveness of vehicle scrappage programs, which offer incentives to accelerated scrappage of older vehicles often thought to be high emitters. These programs are voluntary and aimed at replacement of household vehicles. In contrast, there is a gap in knowledge related to the emissions benefits of government fleet replacement (retirement) programs. In this study, the efficacy of a fleet replacement program for a local government agency in Northern Illinois, the Forest Preserve of DuPage County (FPDC), is examined using a probabilistic vehicle survival model that accounts for time-varying covariates such as vehicle age and gasoline price. The vehicle lifetime operating emissions are calculated based on the estimated vehicle survival probabilities from the survival model and compared with those derived using the EPA default fleet used in MOBILE6 and the fleet represented by the Oak Ridge National Laboratory (ORNL) survival curve. The results suggest that while there may be short term emission benefits of the FPDC fleet replacement plan, the long-term emission benefits are highly sensitive to economic factors (e.g., future gasoline price) and exhibit a decreasing trend. This indicates that an adaptive multi-stage replacement strategy as opposed to a fixed one is preferable to achieve optimal cost effectiveness.

Debbie A. NiemeierEmail:

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Dr. Jie Lin (Jane)   is an assistant professor in Department of Civil and Materials Engineering and a researcher with the Institute for Environmental Science and Policy at University of Illinois at Chicago. Her current research is focused on transportation sustainability through holistic modeling of energy consumption and emissions associated with private, freight, and public transportation activities. Dr. Cynthia Chen   is an assistant professor in the civil engineering department at City College of New York. Her research expertise and interests cover travel behavior analysis, land use and transportation, transportation safety, and environmental analysis. Dr. Deb Niemeier   is a professor at UC Davis and her current research focus is on the nexus between transportation, land use and climate change, particularly how land use and transportation decisions affect energy consumption and contribute to climate change. She is considered an expert on transportation-air quality modeling and policy and sustainability.