Tesla has started testing robotaxis with passengers in Austin, Texas, CEO Elon Musk said on Sunday, with customers paying a flat fee of $4.20, as the electric vehicle maker looks to roll out the much-anticipated service and gain a foothold in the self-driving technology race.

Texas enacts legislation requiring a permit to operate self-driving vehicles just before Tesla's planned launch of a robotaxi trial.

In ramping up robotaxi service, Tesla is hoping to slingshot past Waymo, another autonomous car service that operates in Phoenix, San Francisco, Los Angeles and Austin, according to its website. Last week, Waymo applied for a permit to test its vehicles in New York City.