More than 50% of ride-sharing trips taken by surveyed drivers in California replaced more sustainable forms of transportation — such as walking, biking, carpooling and public transit — or resulted in new vehicle miles, according to a study by the University of California, Davis Institute of Transportation Studies.

The study was conducted to support the development of the Clean Miles Standard, a state rule set by the California Air Resources Board to reduce greenhouse gas emissions from ride-sharing services.

Published in Transportation Research Record: Journal of the Transportation Research BoardThe study analyzed data collected between November 2018 and November 2019 from ridesharers in three metropolitan areas—the San Francisco Bay Area, San Diego, and Los Angeles and Orange counties. The dataset consisted of 7,333 rideshare trips from 2,458 respondents.

About 47% of trips replaced trips made by public transit, carpooling, walking, or biking. Another 5.8% of trips were “induced trips,” meaning the person would not have taken the trip if Uber or Lyft were not available. This suggests that ride-hailing often tends to replace most sustainable transportation modes and results in additional car miles driven.

Share issues

The study also found that respondents who did not own a car or who identified as a racial minority were least likely to cancel a ride when no ride service was available, suggesting that their Uber or Lyft ride was a necessary rather than voluntary ride, although the authors say this finding needs further research.

“Hopefully the results of this study can be used to increase the sustainability of ride-hailing and also address potential equity issues that are evident,” said lead author James Giller, a doctoral student at UC Davis’ Institute of Transportation Studies.

At their best, ride-sharing services can provide people with mobility options they would not have had otherwise. And if the vehicle is electric and the ride is shared, they can ideally save emissions and reduce traffic. But if such services are not used sustainably, they can also increase traffic, reduce the use of public transport – a low-cost and sustainable mode of transport for many income groups – and increase social inequalities.

Recommendations for sustainable ride-hailing

To improve sustainability, the study recommends that ridesharing trips – especially those provided by shared or pooled services – be better integrated with public transit in low-demand areas so that they complement, rather than replace, those services.

“There is certainly a place for ride-hailing and opportunities to improve its sustainability,” Giller said. “It’s about making sure it’s used as efficiently as possible by increasing vehicle utilization; by making sure those trips connect people to transit stations for longer trips; that they’re done in efficient, clean cars; and that we can reduce as much as possible the inefficiencies associated with finding and picking up passengers.”

Co-authors of the study include lead author Giovanni Circella of the UC Davis Institute of Transportation Studies and Mischa Young of the Université de l’Ontario français in Canada.

“This study will help agencies understand the role of ridesharing as a complement and substitute for other modes of transportation,” Circella said.

“The study is unique primarily because of the wealth of data used. Although the data was collected before the pandemic and therefore may reflect different market conditions, the research helps establish an important benchmark that will help policymakers improve the sustainability of passenger transit as part of efforts to decarbonize transportation in California and beyond.”