Lyft has acquired Halo Cars, a small startup that lets ride-hailing drivers earn money via ad displays mounted atop their cars. Lyft confirmed the deal but declined to share any details.

Why it matters: Ride-hailing companies are increasingly eyeing additional ways to generate revenue, and Lyft rival Uber has been quietly testing a partnership with New York-based Cargo that gives it a cut of the advertising revenue, as I previously reported.

In fact, Cargo recently shut down its signature snack box business to focus on its nascent cartop ad displays.

Halo Cars is still small, operating in a couple U.S. cities, so Lyft appears to be largely focused on acquiring the team, which is likely joining its media division. It had raised a small pre-seed round, according to Forbes.

Go deeper: Uber is entering the ads business