Drivers for ride-hailing services Uber and Lyft treat African Americans and women differently from white men, according to new research released Monday.

The study found three notable trends: In Seattle, Black people waited longer for Uber and Lyft drivers to accept their ride requests, and Black riders waited up to 35% longer to be picked up by their UberX drivers. In Boston, Uber drivers cancelled on men with “African American sounding” names more than twice as often as on other men. Meanwhile, both ride-hailing companies took women in Boston for longer and more expensive rides than men.

The paper comes at time when other so-called sharing economy companies are being called on the carpet over accusations of discrimination on their platforms. Airbnb, which has faced strong criticism from African American users, recently published an extensive report outlining its plan to reduce user bias.

Conducted over more than two years, the study included nearly 1,500 rides. In the Seattle test, a group of four Black and four White research assistants (equally divided by gender) ordered cars over a six-week period. The Boston testers’ appearances “allowed them to plausibly travel as a passenger of either race,” though they requested rides under two different names, one “White sounding” and the other “distinctively Black.”

The paper suggests a number of possible countermeasures to address the problems identified by the study, including avoiding the use of passengers names and imposing stricter penalties on drivers who cancel a ride. To address the issues related to female riders, the academics suggest upfront pricing, a service Uber is rolling out in New York City.

Zoepf notes that there are easy answers for ride-hailing companies, which must decide whether they want to focus on eliminating biased drivers or on implementing policies that ensure all their customers get the best service, regardless of drivers’ behavior.”