Uber has launched a "handful" of self-driving cars in San Francisco.
The Volvo luxury SUVs have a number of in-built sensors in order to steer, accelerate, brake and change lanes.
The pilot programme began in Pittsburgh in September, and is now expanding.
Testing out the cars will allow the company to identify any glitches, before rolling the idea out further.
Trips in the self-driving cars cost that same as ordinary cars, but users can opt out of using the self-drive service.
However, California law requires a test permit for self-driving prototype vehicles, something that Uber does not have.
Uber lawyers argue that because there is a human backup, they do not require a permit.
Uber says its cars are ready to tackle the city, however the company admits the technology is not good enough to use without a human backup for tricky situations.