Users overwhelmingly choose ride hail services over transit to save time even when their destinations are served by transit, according to a study of Chicago area commuters.

Shorter wait times, closer stops, and a more efficient service could boost transit’s potential, according to researchers at the University of Michigan, but developing policies requires more robust data.

The study investigated other factors that could impact riders’ choices, such as pollution, traffic, and collision risk. Researchers found that charging users for these social harms would only slightly increase the value people have to place on their time to still choose ride hails over transit, bumping the value from $34 per hour, close to the city’s average hourly wage, to $37.

“If you were to tax riders based on how much harm they cause, it’s not clear they would behave any differently,” Parth Vaishnav, one of the researchers from the School for Environment and Sustainability at the University of Michigan, said.

Read more about the study here.