This study developed a framework to identify the range of possible travel effects, both positive and negative, of users of ride-hailing on greenhouse gas emissions (GHG) and vehicle miles traveled (VMT). This included the effects of ride-hailing on auto ownership, trip generation, destination choice, mode choice, network vehicle travel, and land use.
The study synthesized available literature as of Fall 2017 using this framework. The literature review focused on a small body of research, mostly conducted in 2016 and 2017, that provided some initial evidence on the impacts of these services. The research included population representative survey data, targeted ride-hailing user survey data, modeling studies and measured ride-hailing driver and passenger activity data.
- Auto ownership: 9 percent to 10 percent of respondents in two surveys stated that they gave up a vehicle after joining ridesharing. One of these studies included a representative sample of the population in seven major U.S. cities, and another targeted ride-hailing users in downtown San Francisco.
- Trip generation: Available research indicated that an increase in auto ride-hailing trips by people who cannot drive due to physical and cognitive limitations, no driver's license, no private vehicle, and alcohol consumption contributed to new vehicle trips. The availability of ride-hailing produced 8 percent to 22 percent more new vehicle trips. These results were from surveys of a representative sample of U.S. cities (22 percent), a representative sample of Millennial and Generation Xers in California (8 percent), and ride-hailing users in San Francisco (8 percent) and Denver (12 percent).
- Mode choice: The research as of the fall of 2017 suggested that the substitution effect is stronger than the complementary effect. In four surveys, 16 percent to 33 percent of respondents indicated that they would have taken transit if ride-hailing was not available. These results were from surveys of a representative sample of U.S. cities (17 percent), a representative sample of Millennial and Generation Xers in California (16 percent), and ride-hailing users in San Francisco (33 percent) and Denver (22 percent). These studies showed reductions in carpooling, walking, and bike travel, and one study suggested that ride-hailing may also reduce carsharing.
- Network Vehicle Travel without Passengers: Based on three studies using ride-hailing driver activity data and two modeling studies, empty vehicle travel was estimated to range from about 10 percent to 20 percent in high density downtown urban areas where the supply of ride-hailing vehicles was relatively high, and about 45 percent to 60 percent in lower density suburban areas where the supply of ride-hailing vehicles was relatively low.
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