Is Ride-sharing Good for Environment?

We estimate the causal effect of ride-hailing entry on transport-related air pollution in U.S. cities, using granular satellite-based NO? concentration data in the staggered difference-in-differences research design. Our empirical strategy accounts for treatment effect heterogeneity both within and across cities, coupled with two additional strategies to strengthen identification: using geography-based instruments and exploiting a sharp, unanticipated change in ride-hailing activity in Austin due to its rule change. We find robust evidence that ride-hailing tends to improve air quality in highly dense cities, but has no significant impact in cities with low and medium density. We also find evidence that the NO? reduction in highly dense cities is associated with a decrease in private car use and an increase in public transit use. Taken together, our findings suggest that the environmental effect of ride-hailing depends on the complementarity between ride-hailing and public transit: While ride-hailing may increase congestion by inducing deadheading or displacing of mass transit for parts of daily trips, it may still decrease overall air pollution if a combined use of ride-hailing with other transit displaces private car use more than such adverse behavior.