Look mum - no hands

Google co-founder Sergey Brin with a self-driving Prius (and right) on the day California law was changed to allow 'autonomous vehicles'. Photo / Eric Risberg

Self-driving car hits the road with a little help from Google.

That little old lady from Pasadena needs to watch out: self-driving cars will be allowed to cruise California's roads.

Governor Jerry Brown this week signed a law, written with the help of Google, to permit testing of "autonomous vehicles" as long as there's a fully licensed human in the driver's seat to take over if needed.

"Today we are looking at science fiction become tomorrow's reality," Brown said at a signing ceremony at Google headquarters in Mountain View, California.

Google has modified a Toyota Prius to drive itself using video cameras, radar sensors, a laser rangefinder and detailed maps. It includes a failsafe mechanism that lets the driver take control by grabbing the steering wheel or hitting the brakes - like the override on a cruise control.

While major carmakers are working on self-driving prototypes and rolling out features such as parking assistance, lane-departure warning systems and adaptive cruise control, Google's car has inspired the law change in Nevada last year and now in California.

"Anybody who gets into a car and finds the car driving itself is going to be skittish at first," said Brown, who took a test ride.

"But they will get over it."

The law directs the state's Department of Motor Vehicles to develop regulations governing the licensing, testing and operation of self-drive vehicles.