California Air Resources Board

Zero-emission vehicles (ZEVs) are key to reducing transportation-related emissions needed to meet California's air quality and climate goals. While California has aggressive goals for ZEV adoption, their true impacts can only be understood though real-world, on-road data collection. This research project examined the driving and refueling behaviors of households that drive battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs) and fuel cell electric vehicles (FCEVs) in order to improve projections of greenhouse gas and criteria air pollutant emissions and to inform refueling infrastructure planning efforts. This study (and its predecessor) collected information from households that drive ZEVs between 2015 and 2020 by surveying over 13,000 California ZEV buyers and logging approximately one year of real-world data for all vehicles in more than 400 households that drive one or more ZEVs.

Results indicate that longer electric range BEV and PHEV models (i.e., those with comparatively larger batteries that can travel farther on a single charge) drove a larger share of their total vehicle miles traveled (VMT) as electric vehicle miles traveled (eVMT) both at the vehicle and household level. Short-range BEVs were unlikely to be used for long road trips or long freeway speed trips. BEVs and PHEVs are driven a similar number of total miles as conventional vehicles, not more (due to rebound) or less (due to range anxiety) as some have suggested. For PHEVs with short all-electric ranges, the fraction of eVMT to VMT or utility factor is lower than expected due to observed charging behavior, daily VMT distribution, annual VMT, and effective charge depleting range. In contrast, PHEVs with long all-electric ranges had a higher utility factor as expected. PHEVs with a mid-sized battery logged more cold-starts compared to low and high all-electric range PHEVs.

Results from this study provide insights on first and second generation ZEVs by exploring the impacts of battery range, household fleet composition, driving behavior, and charging/refueling behavior.  The findings from this study will help inform CARB's Advanced Clean Cars program, improve emission inventories, and support ZEV infrastructure planning efforts.

Speaker Biographies

Gil Tal

Director for the Plug-in Hybrid & Electric Vehicle (PH&EV) Research Center at the University of California, Davis (UCD). He is also a member of the faculty at the Transportation Technology and Policy Graduate Group and the Energy Graduate Group at UCD. Dr. Tal is a leading expert on electric vehicle travel behavior, as well as understanding the role that incentives and infrastructure play in the electric vehicle market worldwide. Dr. Tal has published more than a hundred articles, peer-reviewed conference proceedings, reports and books and works with policy makers and decision makers from government and industry in the US, China, and Europe. He holds a Ph.D. in Transportation Technology and Policy from UCD and a M.A. in geography and environmental policy and planning from the Hebrew University in Jerusalem.

Debapriya Chakraborty

Postdoctoral researcher at the PH&EV Research Center at UCD. Her research focuses on the impact of policies to encourage electric vehicle adoption and the role of market-based strategies in maximizing their environmental benefits. Dr. Chakraborty holds a Ph.D. in Economics from the University of California, Irvine with a specialization in transportation and environmental economics.

Vaishnavi Karanam

Ph.D. student in Transportation Technology and Policy at the PH&EV Research Center at UCD with a background in computer science. Her research focuses on forecasting and optimizing electric vehicle driving and charging behavior using machine learning models.