Google's self-driving cars are designed to break the speed limit under certain conditions, according to the lead software engineer Dmitri Dolgov.
Speaking to newswire Reuters, the engineer said the vehicles are programmed to go up to 10mph faster when other cars are also speeding, citing research that it is the safer option under the circumstances.
"Thousands and thousands of people are killed in car accidents every year," he said. "This could change that."
Another prototype that runs on electricity is limited to 25mph, seats two people and lacks a steering wheel and pedals for accelerating and braking.
The cars are due to be on British roads as of January next year having been tested extensively over more than 700,000 miles, and UK road regulations are to be reviewed to take account of the new transport.