Should cars that drive themselves have steering wheels? That question is causing Tesla some issues as the National Highway Traffic Safety Administration continues to investigate Tesla's Cybercab.

The low-cost two-seat purpose-built robo-taxi doesn't have pedals or a steering wheel. It's part of Tesla's plan to grow and dominate the fledgling robo-taxi industry. Tesla introduced a handful of Cybercabs into its robo-taxi fleet earlier this month.

Before the introduction, Tesla self-certified that Cybercab was compliant with all Federal Motor Vehicle Safety Standards. After the introduction, NHTSA opened an investigation "to examine the process and technical data on which Tesla relied when certifying the Cybercab and related issues." In short, NHTSA wants to ensure Cybercab is safe and that Tesla is following rules.

On Tuesday, NHTSA sent a letter to Tesla as part the existing investigation. It's asking for information about Tesla's self-certification. NHTSA is looking for a response by the end of the month.

One of the odd questions in the letter: "Confirm whether the subject vehicles are capable of being driven by a human driver using temporarily attached human driver controls." Maybe Cybercab can have a steering wheel after all.

Tesla didn't respond to a request for comment about the letter.

At NHTSA, investigations precede recalls. The latter are the outcome of investigations. Tesla's self-driving technology has been investigated in the past. NHTSA has "recalled" Tesla vehicles, requiring modifications. Those Tesla vehicles, of course, didn't leave the road. They were modified as requested to improve overall safety.

What the outcome of the NHTSA investigation will be is difficult to say. Robo-taxis, however, are here to stay. Alphabet's Waymo is expanding. And those robo-taxis will continue to generate surprise and questions. Amazon.com's Zoox doesn't have steering wheels.

The outcome is important to investors because they have pinned much of Tesla's trillion-dollar valuation on AI applications such as robo-taxis. In short, investors believe it's better to have a fleet of robo-taxis generating revenue every day than simply selling a car once.

Tesla's robo-taxi business isn't generating significant sales and profits yet. Time will tell if it will.

The letter isn't doing much to Tesla stock. Shares were up 0.1% in premarket trading Wednesday at $357, while S&P 500 and Dow Jones Industrial Average futures were up 0.2% and 0.1%, respectively.

Tesla stock was about $350 just after it launched a robo-taxi service in June 2025. Shares were just over $350 after Cybercab's introduction earlier in September.