Beyond the Early Era of EVs: Evidence from the Staggered Rollout of the HOV Lane Network in California

Eric Avis, Jing Li, and Katalin Springel

November 2025

Local policies like high-occupancy vehicle (HOV) lane exemptions play an important role in encouraging electric vehicle (EV) adoption, a key component of climate programs. Using tract-level vehicle registrations and detailed data on HOV lane openings from 2012 to 2024, we study the causal effect of HOV policies on EV adoption in California. We find that HOV exemptions significantly increased EV uptake, with effects that were stronger in later years as EV technology and markets advanced. The impact is also greater in more congested areas with longer commutes and concentrated in higher-income tracts, highlighting both the effectiveness and distributional implications of HOV incentives.

Keywords: electric vehicles, transportation policy, environmental subsidy, HOV lane access

JEL codes: H23, Q58, R48