Abstract The popularity of Uber and Lyft and advances in autonomous vehicle technology have spurred public interest in the potential of shared ride services to reduce traffic congestion, vehicle emissions and space devoted to parking. However, research has shown that long waiting times, circuitous routes and privacy concerns might lead most patrons to choose exclusive-ride services over shared services (ride-hail or autonomous), thus increasing rather than decreasing vehicle mileage. This paper uses Uber and Lyft experience from 2014 to 2020 to examine the effectiveness of shared (or “pooled”) services in reducing vehicle miles traveled (VMT) in four cities with large concentrations of ride-hail trips and suburban areas of California. Taking into account three key inputs -- pooling rates, modal shifts and deadhead miles – results show that pre-pandemic levels of pooling led to at least a doubling of VMT when comparing ride-hail trips with patrons’ previous mode, with increases of 97% in Chicago, 114% in New York City, 118% in San Francisco, 157% in Boston and 118% in California suburbs. These large VMT increases are driven by the addition of dead-head miles before each pick-up and the absence of offsetting VMT reductions among travelers who switch to ride-hail from public transportation, biking and walking. VMT increases are only modestly mitigated by the use of ride-hail for “first mile/last mile” trips to connect to public transportation or by reduced cruising for parking by drivers in their personal vehicles. In sum, ride-hail adds to vehicle mileage for trips associated with ride-hail even taking into account pooling. This pattern is likely to endure in a world of autonomous vehicles given that auto users tend to switch to solo services due to considerations of travel time, reliability, comfort and privacy, while pooled options mainly draw patrons from sustainable modes like public transportation. The implication for public policy is that in dense urban areas, it remains important for policy-makers to prioritize space-efficient modes of public transportation, walking and biking. At the same time, ride-hail can clearly be valuable to meet specific needs such as providing paratransit services to people with disabilities, providing first and last mile connections to transit services and connecting late-night workers to jobs. These results will be important as cities emerge from the coronavirus pandemic and navigate a path to economic recovery, social equity, and environmental sustainability.

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Highlights • Ride-hail leads to doubling or more of vehicle mileage in 4 major U.S. cities and a suburban environment. • Increases are due to ride-hail patrons shifting from public transit and other sustainable modes, and from added deadhead miles. • Changes in travel behavior underscore core distinction between shared and non-shared urban travel markets. • Autonomous vehicles are unlikely to change resistance of auto users to shared services.