If you order up an UberX in the Bay Area, your car may show up sans driver. The ride-hailing app just debuted autonomous vehicles to supplement its fleet of human drivers in San Francisco, according to The Verge.

The company began testing autonomous vehicles in Pittsburgh in September, and tech-obsessed Silicon Valley seems like an obvious choice for a bigger trial. Uber says that San Francisco’s varied terrain, traffic, greater density of cyclists, and weather will provide a new layer of challenges that can help the company improve its vehicle technology. The San Francisco pilot will feature Volvo XC90s, compared to the Ford Fusions deployed in Pittsburgh.

You won’t necessarily get an autonomous car every time you order. Sometimes, a human driver may be closer. Even if you do, there will still be a human minder to take the wheel if something goes wrong. Still, if you prefer not to get in a car driven by a robot, you can also opt out in the app and end up with a person instead.

However, there are some roadblocks. According to The Verge, the pilot may run afoul of California’s strict driving laws, which require companies to obtain permits to let autonomous cars run wild on city streets. Uber doesn’t yet have those permits. But the company thinks those rules don't apply to its cars. Of the state requirement, the company's statement says, "We have looked at this issue carefully and we don’t believe we do [need testing permits]." Uber goes on to explain:

"First, we are not planning to operate any differently than in Pittsburgh, where our pilot has been running successfully for several months. Second, the rules apply to cars that can drive without someone controlling or monitoring them. For us, it’s still early days and our cars are not yet ready to drive without a person monitoring them."

Whether the California DMV will be persuaded is a different matter.

[h/t The Verge]