It said that a "few" of the prototypes will be tested after clocking almost one million autonomous miles on its private test tracks. The fleet self-drive around 10,000 miles per week, it revealed.
"Safety drivers" will sit as passengers in the cars, with a removable steering wheel, brake and accelerator pedals.
Google began testing a fleet of self-driving Lexus RX450h SUVs with its proprietary driverless software in 2012. So far, the cars have a good record for safety, with only 11 accidents during testing - none of which were caused by the driverless car but by other (human) drivers on the road.
Now its self-driving project will test a combination of its software with its purpose built vehicle which was unveiled in its early stages last year.
Chris Urmson, the director of the self-driving project said: "We're looking forward to learning how the community perceives and interacts with the vehicles, and to uncovering challenges that are unique to a fully self-driving vehicle - for example, where it should stop if it can't stop at its exact destination due to construction or congestion. In the coming years, we'd like to run small pilot programs with our prototypes to learn what people would like to do with vehicles like this."
While manufacturers like Google are free to test driverless cars in the state of California, certain states have blocked any use of the technology in cars on public roads.
However, within the UK there is no legislation blocking testing - putting it at a distinct advantage in the international driverless car race.