A computer image of its prototype was released in May of last year, and in December the Self-Driving Project unveiled the first real prototype.
On Wednesday the Google Self-Driving Car Project announced the launch of 'paint the town,' an art experiment which invited artists to submit art to be painted on the cars, in return for which the selected artists received a ride in the self-driving cars.
The new prototype cars join Google's self-driving adapted Lexus RX450h SUV crossovers, which were used to test the new technology before it was fitted to the completely original prototype earlier this year.
Last month, the head of Google's self-driving car program, Chris Urmson, wrote in a blog post that after over six years and 1.7 million miles of self- driving, the Lexus fleet was involved in just 11 minor accidents, with no injuries and light damage to the vehicle, adding that "not once was the self-driving car the cause of the accident."
The busier streets of California present a new challenge to the car, which before now was mainly tested in simpler conditions on the open highway. In Mountain View, the cars will have to contend with pedestrians, cyclists, traffic revisions, railroad tracks and the poor driving of other, human road users.
Google is not the only technology company developing a self-driving car; earlier this month Chinese search technology giant Baidu, which has its own mapping service, announced progress in its collaboration with BMW to produce a self-driving car. The project, which the partners first announced in September last year, plans the first release in China of the autonomous vehicle before the end of 2015.