The rise of ride-sharing services has reduced US public-transportation usage and worsened traffic jams in US cities. Ride-sharing giants Uber and Lyft began operating in the United States in 2010 and 2012, respectively, and promote this form of travel as a sustainable way to increase urban mobility. To quantify the services’ effects, Jinhua Zhao at the Massachusetts Institute of Technology in Cambridge and his colleagues analysed transport data from across the country. The authors found that ride-sharing services had almost no effect on private car ownership but reduced public-transport ridership by almost 9%. Traffic jams also became longer and slightly more intense in cities where car-sharing services were available. Well-organized ride-sharing does hold potential to improve mobility, the researchers note. But the road to sustainable urban transport will be even rockier because of the COVID-19 pandemic, which put an end to pooled car-sharing services.