It looks like Google will be posting monthly reports of their self-driving cars from now on. Looks very interesting. See: http://www.google.com/selfdrivingcar/reports/
A Google Lexus model AV was traveling northbound on El Camino Real in autonomous mode when another vehicle traveling westbound on View Street failed to come to a stop at the stop sign at the intersection of El Camino and View Street. The other vehicle rolled through the stop sign and struck the right rear quarter panel and right rear wheel of the Google AV. Prior to the collision, the Google AV’s autonomous technology began applying the brakes in response to its detection of the other vehicle’s speed and trajectory. Just before the collision, the driver of the Google AV disengaged autonomous mode and took manual control of the vehicle in response to the application of the brakes by the Google AV’s autonomous technology.
It looks like the Google Vehicle (GV) was traveling on El Camino (I'm assuming it had no stop sign), the computer saw the vehicle approaching (what should have been a stop) and hit the brakes. The driver took over (right before the collision) to stop the brakes from being applied and the car hit the rear of the GV. With out the computer controlling the speed, I wonder if the GV would have cleared the intersection already?
Then again, depending when each event happened, maybe if the driver didn't take over, the GV wouldn't have been hit? Hard to tell.