Air Pollution, Greenhouse Gas, and Traffic Externality Benefits and Costs of Shifting Private Vehicle Travel to Ridesourcing Services.

On-demand ridesourcing services from transportation network companies (TNCs), such as Uber and Lyft, have reshaped urban travel and changed externality costs from vehicle emissions, congestion, crashes, and noise. To quantify these changes, we simulate replacing private vehicle travel with TNCs in six U.S. cities. On average, we find a 50-60% decline in air pollutant emission externalities from NOx, PM2.5, and VOCs due to avoided "cold starts" and relatively newer, lower-emitting TNC vehicles. However, increased vehicle travel from deadheading creates a ∼20% increase in fuel consumption and associated greenhouse gas emissions and a ∼60% increase in external costs from congestion, crashes, and noise. Overall, shifting private travel to TNCs increases external costs by 30-35% (adding 32-37 ¢ of external costs per trip, on average). This change in externalities increases threefold when TNCs displace transit or active transport, drops by 16-17% when TNC vehicles are zero-emission electric, and potentially results in reduced externalities when TNC rides are pooled.

The impact of Uber and Lyft on vehicle ownership, fuel economy, and transit across U.S. cities.

We estimate the effects of transportation network companies (TNCs) Uber and Lyft on vehicle ownership, fleet average fuel economy, and transit use in U.S. urban areas using a set of difference-in-difference propensity score-weighted regression models that exploit staggered market entry across the U.S. from 2011 to 2017. We find evidence that TNC entry into urban areas causes an average 0.7% increase in vehicle registrations with significant heterogeneity in these effects across urban areas: TNC entry produces larger vehicle ownership increases in urban areas with higher initial ownership (car-dependent cities) and in urban areas with lower population growth (where TNC-induced vehicle adoption outpaces population growth). We also find no statistically significant average effect of TNC entry on fuel economy or transit use but find evidence of heterogeneity in these effects across urban areas, including larger transit ridership reductions after TNC entry in areas with higher income and more childless households.