Google showed reporters its tiny, bubble-shaped self-driving prototype vehicle on 29 September. Google's pet project of driverless cars started in 2009 with an intention to revolutionise the car industry.

Google and other automotive manufacturers and suppliers have said the technology to build self-driving cars should be ready by 2020. Project director Chris Urmson said the company was taking things steadily.

"This kind of technology – cars that drive themselves – is a different type of product than most of what Google does. It requires us to think a little differently about how we bring it to market and make sure we're very thoughtful about the bar we set before we let it out for people to use," he said.

Mainstream carmakers General Motors and Volkswagen and newcomer Tesla are also pushing down the road to automation. Urmson said the new technology in the auto industry was exciting.

"We're really focusing on this broader goal of mobility for everyone, vehicles that can drive all these places. We think that's really the big opportunity to help people. It's really exciting to see what's happening in the automotive industry, the technology that's flowing in. There's a lot of opportunity for different solutions and we think this one's exciting," he said.

Google executives have said the company does not want to build its own self-driving cars, but would prefer to find a development and production partner.