Tesla's long awaited Cybercab finally hit the streets of Austin yesterday, and the debut was something of a dud.

For a product Elon Musk has positioned as central to Tesla's future, the rollout was remarkably subdued. There was no major public livestream with appearance by Musk or traditional press presence, relatively little new information and just 45 Cybercabs registered in Texas as of Thursday. After years of hype surrounding Tesla's robotaxi ambitions, the event still felt more like a limited demonstration than the beginning of a transportation revolution.

Now federal regulators have thrown a wet blanket over even that modest celebration.

The National Highway Traffic Safety Administration has opened a review of the Cybercab to determine whether its unusual design complies with federal safety rules, according to the Wall Street Journal.  The two seat vehicle has no steering wheel, pedals or conventional mirrors, putting it outside many of the assumptions baked into decades old automotive regulations.