Free buses: Citywide zero fare is associated with increased use of public transit.

Increasing reach and use of public transit holds the potential to improve population health by supporting active transportation and enhancing access to local resources. Emerging citywide zero-fare transit programs offer a policy-based approach to improving use of existing systems by eliminating economic barriers. The rapid rise of these programs in the U.S. warrants more research on their impacts. This study leverages a natural experiment in Kansas City, MO-the first major U.S. city to adopt an extended, citywide zero-fare bus program-to estimate the impact of zero-fare policy on bus ridership. Leveraging over seven years of temporally aligned data from multiple U.S. cities, a robust series of analyses including controlled interrupted time series along with matched and synthetic control methods allowed for the estimation of effects at both the city level and individual route level. Comparisons were made between Kansas City and nine similar cities without zero-fare policy, then replicated across three additional positive controls (cities that also implemented citywide zero-fare during the study period). Results indicate a strong and sustained increase in ridership attributable to the zero-fare policy. After accounting for pandemic-related disruptions, post-policy ridership in zero-fare cities was approximately 22% higher than in cities without such policies, relative to pre-policy baselines. Similar effects were observed across nearly 30 routes, even after adjusting for neighborhood characteristics, with elevated ridership persisting during the nearly four-year follow-up period. Findings support citywide zero-fare as an effective strategy for increasing public transit ridership at scale. Future work is needed to assess downstream economic and health implications of these changes.