Does a region need its own zero emission vehicle mandate, or can it free-ride off another? Modelling British Columbia and California

Policymakers are investigating how to transition to zero emission vehicles (ZEVs) to achieve long-term GHG targets. ZEV adoption is limited by regional and global barriers, where reductions in global barriers spill over between regions. I use an energy-economy model to investigate whether a smaller North American region (British Columbia) needs its own strong ZEV policy or can instead free-ride off spillovers from policy in other jurisdictions (California and other ZEV States) to achieve their GHG target. I find that 50% of new vehicles sold in 2040 and over 90% in 2050 need to be ZEVs, and that these adoption levels likely cannot be achieved through free-riding. Rather, regions likely need their own strong ZEV policy alongside other vehicle and fuel policies, even under optimistic assumptions about technological progress. Moreover, regions with strong ZEV policy may lower GHG abatement costs 11-48% by convincing other jurisdictions to follow with similar policy.