Internet search company Google said Tuesday its self-driving cars were involved in 11 accidents since testing of its fleet of 20 driverless cars had begun six years ago. In a post on technology news website Medium Backchannel, the program's director, Chris Urmson, said "not once was the self-driving car the cause of the accident," and added that no one was injured in the accidents.

"If you spend enough time on the road, accidents will happen whether you're in a car or a self-driving car," Urmson wrote.

Google's autonomous cars have been rear-ended seven times, mainly at traffic lights, and side-swiped, with a majority of the accidents being on city streets rather than on freeways.

"We'll continue to drive thousands of miles so we can all better understand the all-too common incidents that cause many of us to dislike day-to-day driving  -  and we'll continue to work hard on developing a self-driving car that can shoulder this burden for us," Urmson wrote

Safer than conventional cars?

Google's self-drive vehicles are equipped with cameras, radar and laser sensors, which provide a far more detailed understanding of their surroundings than that of humans. Thereore, the cars can react more quickly, and they are programmed to adjust if they sense a crash coming - by moving a few feet, tightening seat belts, honking the horn or flashing lights at a distracted driver.

"Even when our software and sensors can detect a sticky situation and take action earlier and faster than an alert human driver, sometimes we won't be able to overcome the realities of speed and distance," Google's Urmson wrote. "Sometimes we'll get hit just waiting for a light to change."

Google's 11 accidents happened during 1.7 million miles of driving, working out to 0.6 percent per 100,000 miles (160,000 kilometers). The national rate for reported "property-damage-only crashes" in the United States is about 0.3 per 100,000 miles driven, according to the National Highway Traffic Safety administration. But as Google noted, as many as 5 million minor accidents are not reported to authorities each year.

Major alliances

Google's autonomous prototype cars are currently being built in Detroit by engineering and specialty manufacturing company Roush.

In January, Google announced it had begun discussions with most of the world's top automakers to speed up efforts to bring self-driving cars to market by 2020. They include Japan's Toyota, US auto giants General Motors and Ford, as well as Germany's Daimler and Volkswagen.

"For us to jump in and say that we can do this better, that's arrogant," Urmson said at the time.

In addition, Google is developing and refining self-driving systems and components with such auto parts suppliers as Continental, Bosch, ZF and LG Electronics. Google's prototype cars use microprocessors made by Nvidia, a Silicon Valley chipmaker that also supplies Daimler and other automakers.

Google will begin deploying a test fleet of fully functioning prototypes of its pod-like self-driving car shortly, which no longer needs a steering wheel, brakes or a gas pedal. While each of the Google's current prototypes have a "test driver" on board, the new cars have no provision for human intervention in steering or braking.

uhe/ng (AP, Reuters, dpa)