Toaster-shaped taxis that don't have a driver or a steering wheel have started rolling across San Francisco and charging for rides in Las Vegas.

The all-electric cars are the first robotaxis offering rides on the roads without standard driver features like a dashboard and pedals. They can drive in either direction and hold up to four passengers who sit facing each other. Windows stretch across much of the sides. The vehicles are called Zoox and they come from a new entrant in robotaxis: Amazon.com.

Amazon is betting it can become a major player in the growing robotaxi market, which Goldman Sachs expects to grow to nearly $19 billion in sales by 2030, from $376 million last year.

It is a risky move. Alphabet's Waymo, the early leader with roughly 4,000 vehicles operating in various cities, and Tesla provide stiff competition. Tesla has started volume production of the Cybercab, which lacks a steering wheel and pedals but the company hasn't gotten the same regulatory approval as Zoox to begin offering rides to the public.

Also, Zoox took on the tough task of building its cars from the ground up.

Zoox Chief Executive Aicha Evans says making its own vehicles allowed the company to more quickly fine-tune the design in response to rider feedback. "It takes a lot of imagination, belief, resilience and tenacity to do this when you're going against conventional wisdom," Evans said.

Regulators are approaching these new rides cautiously. The National Highway Transportation Safety Administration last month allowed Zoox to charge for rides in up to 5,000 vehicles within the next two years. Yet it barred Zoox taxis on roads with heavy rain, snow, large quantities of leaves or a speed limit of more than 45 miles an hour.

The cars must also provide riders a message, either posted within the vehicle or on the Zoox app, that directs them to a link where they can submit a complaint to NHTSA.

The company's fleet today counts about 100 vehicles. Zoox assembles them at a plant in Hayward, Calif., that spans 31/2 football fields and has the capacity to produce as many as 10,000 robotaxis a year. Zoox rides cost roughly the same as the comfort option of other ride-share services, a spokeswoman said. Riders expressed trepidation. Med Trimdal, a retired electrical engineer in Las Vegas who tried a Zoox taxi in June, said he found the lack of a driver disconcerting. After a few minutes, he said, he felt at ease. "It was exciting to witness something that seemed like science fiction."

Zoox was founded in 2014 on the idea of making the first purpose-built robotaxi. Amazon bought Zoox in 2020 for $1.2 billion.

Two years later, in 2022, Zoox self-certified its cars as compliant with NHTSA's Federal Motor Vehicle Safety Standards. The step would have eliminated barriers to Zoox's deployment, but the agency objected. In addition to not having manual controls such as brake pedals that are involved in safety tests, the cars didn't use the right type of glass or side reflectors, NHTSA said.

"There's stuff that they could have and should have done that had nothing to do with not having a driver that they failed to do," said Phil Koopman, an emeritus engineering professor at Carnegie Mellon University who specializes in autonomous vehicles.

Last year, NHTSA granted Zoox an exemption from the safety standards and allowed the company to offer free demonstration rides. Zoox taxis have logged more than three million driverless miles on public roads and carried nearly one million riders.

A NHTSA spokeswoman said the agency is modernizing its standards "to remove mandates that assume the presence of human drivers, such as manual brake pedals, transmission shifters, and windshield wipers and defrosters, while maintaining all relevant safety performance requirements."

The agency is also developing performance standards for autonomous vehicles, she said.

Alex Roy, an autonomous-vehicle expert and partner at New Industry Venture Capital, sees building a custom vehicle as the most difficult path to robotaxi deployment because of the time and money required for software development, manufacturing and safety testing.

"This vehicle decision is the ultimate risk factor," he said. "The stars have to align in every dimension of the business for that to become viable."

Waymo also developed a prototype of a robotaxi without a steering wheel, though the company never intended to mass produce the vehicle. Waymo retired the design in 2017 and moved forward with retrofitting existing cars with sensors that enable humanless driving.

Zoox is planning to expand. It is testing its robotaxi in Austin, Texas, and Miami, where it plans to start service soon. Lora and Dillon Harp, who live in Trenton, Mo., rode in Zoox twice in Las Vegas in May. Next time they face a choice between another ride-share service and Zoox, the couple said they would choose Zoox, especially if it could get them to their destination faster.

"I like that it's private, that there's not anybody else in the vehicle," said Lora Harp, 38, who works as a travel agent.