Fare-Free Bus Service and CO2 Reductions: Evidence from a Natural Experiment

TL;DR

This study evaluates the impact of fare-free bus service in Alexandria on transit usage and CO2 emissions, finding modest increases in bus use and significant reductions in carbon emissions with cost-effective benefits.

Contribution

It provides empirical evidence on the environmental and behavioral effects of fare-free public transit through a natural experiment in Alexandria.

Findings

Up to 6% increase in bus usage among residents.

CO2 emissions reduced by approximately 0.3 to 0.5 tons annually.

No significant impact on ground-level ozone or road crashes.

Abstract

We devise a difference-in-difference study design to assess the impact of fare-free bus service in Alexandria, located in the Washington, DC metro area. Our surveys show modest to no effect, with at most 6% more residents in Alexandria increasing their bus usage compared to control locations. We find no effect on ground-level ozone or road crashes, suggesting little to no impact on road traffic. One-third of respondents in control locations indicated they would use buses more frequently if fare-free service were available in their areas. Based on the respondent-reported reductions in car miles, the program led to a reduction of 0.294 to 0.494 tons of CO2 per year, or 5% to 9% of the average annual emissions from a US car, at a cost of $70-$120 per ton of CO2. We predict a CO2 reduction of 0.454 tons per year, equivalent to 8% of the average US car's annual emissions if the fare-free bus covered all of the study areas.