Federal regulars are pressing Tesla on whether its steering wheel-free Cybercab may have a way for humans to drive it after all.

The National Highway Traffic Safety Administration asked Tesla in an order published Tuesday whether the vehicle has the ability to be driven with traditional controls and, if so, whether that is why Tesla believes the Cybercab is compliant with federal safety standards.

"State whether temporarily installed human driver controls or other equipment for use by a human driver were a part of Tesla's basis for certifying compliance," NHTSA said in the order.

Cybercab is a two-seater robotaxi without pedals, mirrors or a steering wheel. Tesla began offering paid rides this month for customers in the vehicle as part of its fleet of robotaxis operating in Austin, Texas. Tesla said its design meets all applicable rules for vehicles operating on public roads.

An automaker has never sold a car without a steering wheel or pedals. Tesla has said it plans to eventually sell the Cybercab to the public.

The unique design of the Cybercab potentially puts it in conflict with safety standards, according to NHTSA, which launched an investigation into the vehicle earlier this month. In the order, NHTSA asked Tesla to confirm if it can "temporarily" install manual driving controls to operate the Cybercab, and if that's why it determined the vehicle is in compliance.

Tesla sees the Cybercab as a linchpin to its effort to transition from making traditional electric vehicles to fully autonomous cars. Tesla Chief Executive Elon Musk has said he wants the company to dominate the autonomous vehicle arena with its Full Self-Driving software, which underpins Cybercab's operations. The company's ride-hailing service is racing against rivals like Alphabet's Waymo and Amazon.com's Zoox to develop driverless taxi services.

NHTSA is in the process of overhauling safety standards to accommodate driverless vehicles, but those changes aren't yet in place. If NHTSA determines the Cybercab isn't compliant with federal safety standards, the agency could order a recall to address any issues. Refusing such an order could expose Tesla to fines.

In the run-up to the Cybercab's public launch, the company showed off prototypes at public events that had visible steering wheels attached to the car, people familiar with the events say. Tesla has said that some Cybercabs can be equipped with steering wheels, in documents posted on its website about the vehicle.

Tesla didn't respond to a request for comment. A spokesman for the agency declined to comment.

In a guide for first responders, Tesla said the Cybercab "typically" isn't equipped with a steering wheel, but that some versions might have one.

"To facilitate testing and validation of safety systems, a number of Cybercabs are equipped with hardware for manual operation, such as a steering wheel and pedals for acceleration and braking," Tesla said in the guide.

Tesla has considered novel ways before to design a driverless vehicle to federal safety standards. The company previously weighed the possibility of making a fully autonomous car with a steering wheel and pedals that could be stowed when they're not in use.

Experts say that Tesla could engineer a detachable steering wheel kit because the Cybercab was designed with a steer and brake "by wire" system, which uses an all-electronic design instead of mechanical components.

Paul Snyder, who is chair of the College for Creative Studies' transportation design program, said a temporary driver kit would require a "unique or heavily modified instrument panel on the driver side," Snyder said.

"A lot depends on if they planned for it when it was originally engineered," he said.