June 22 (UPI) -- Tesla will begin its launch of robotic taxis in Austin, Texas, on Sunday afternoon, Elon Musk announced. "The @Tesla_AI robotaxi launch begins in Austin this afternoon with customers paying a $4.20 flat fee!" Musk said in a post on social media.

The company debuted its autonomous ride-hailing service Sunday. The limited program is invite-only and uses around 20 cars—signs that Tesla has a long way to go to catch up to its robotaxi rivals.

The vehicles will have safety monitors and may not operate in bad weather, making them more restricted than the fully autonomous vehicles promised by Elon Musk.