Google has revealed that its driverless cars have crashed 11 times, but said that all the collisions were caused by other drivers.

On Monday, Chris Urmson, Google's lead for its driverless car project, said that the accidents were all 'minor', meaning light damage and no injuries. Urmson wrote that the self-driving car was not the cause of the accident even once.

Google has revealed the crashes after Associated Press came to know that the company had notified California's Department of Motor Vehicles (DMV) that its driverless cars were involved in three crashes since September, the month in which it was required to report accidents as part of the permits for tests on public roads.

On Monday, consumer advocacy group Consumer Watchdog called on the DMV to make all future incidents public. At present, the reports are confidential.

John Simpson, director of the watchdog said, "Unbelievably, Google is planning to offer its robot cars without a steering wheel, brake pedal, or accelerator so there would be no way for a person to take control in an emergency. That plan underscores the need for public to know full details of all accidents".

Further, the company wants the reports to be made public when drivers are forced to take control of a car in driverless mode.

According to AP, the DMV had received four driverless car accident reports since September. The fourth accident involved a vehicle being trialed by Delphi.

Urmson said that Google has over 20 cars on California's roads. They have driven 1.7 million miles between them, one million of which have been in driverless mode.

During that time, its cars have been hit from behind seven times at lights and on the freeway. They've also been "side-swiped a couple of times" and hit by a car rolling through a stop sign, according to Urmson. He also highlighted that its car had avoided hitting a cyclist near its headquarters in Mountain View.