Tesla launched its Cybercab taxi service in Austin, Texas, on September 3. But hours later, the US National Highway Traffic Safety Administration (NHTSA) opened a formal investigation into how the company certified the vehicle for public roads.

The agency launched Audit Query AQ26002 on September 4. Covering an estimated 1,000 Cybercab, the investigation focuses on how Tesla certified the Cybercab and whether the company properly determined which safety standards apply to its design.

The Cybercab has no steering wheel, brakes, gas pedals, or rearview and side mirrors. Under the Trump administration, the NHTSA is reevaluating its existing rules requiring vehicles to have brake controls and rearview mirrors if they are “designed never to be operated by a human.” But those rules are currently in place, and the agency wants to know why Tesla believes certain standards don’t apply to its driverless taxis.

“NHTSA fully supports the safe development and deployment of automated vehicles,” agency administrator Jonathan Morrison said in a statement. “But as the federal regulator, we need to ensure that all of our laws are followed.”

Tesla shares fell about 6% after the probe became public. But if the past is any guide, Tesla might prevail. A similar incident happened with Amazon’s Zoox in 2022, when the brand’s self-certification led to an NHTSA audit before limited commercial operations received approval in July 2026. Now, up to 2,500 Zoox vehicles are permitted to operate this year.