Express Drive, the car rental service created by General Motors and Lyft, is launching in three US cities today: Baltimore, Boston, and Washington, DC, according to Recode. The short-term rental program, which first launched in Chicago in March, is designed for people who want to drive for the ride-hail service but lack the wheels to do so.

Express Drive is not your typical car rental program: the more trips drivers complete for Lyft, the less they pay in rental fees. And those who finish 65 trips or more per week will pay for nothing but gas.

First Chicago, now Baltimore, Boston, and DC

GM says Express Drive will be operated under its Maven car-sharing service, which it launched in Ann Arbor, Michigan last January. Maven will pay for the upkeep and maintenance of the rental cars involved in Express Drive, while GM works with Lyft to determine which insurance to use to cover the drivers.

The program is the first joint program by GM and Lyft since the two companies announced their plan to join forces to develop a fleet of on-demand, driverless cars. GM invested $500 million in Lyft as part of the deal, which provided the ride-hail service a much needed boost in its ongoing battle with Uber.