According to a report released by Google (PDF) this month, the company's self-driving cars were involved in two human-error accidents in the month of June. In addition, Google's funny little prototype self-driving bubble cars hit the streets of Mountain View for the first time. The company says that so far, the two prototypes logging hours on public streets have not been involved in any accidents.

Google received some pressure from an advocacy group called Consumer Watchdog as well as the Associated Press in May, notably after the AP reported that there had been at least three collisions involving Google's self-driving cars in the previous six months. More detail could not be obtained because of the DMV's privacy rules surrounding accident reports, but Google vowed it would release a monthly report detailing any accidents involving the company's self driving cars from then on.

The most recent report says that Google self-driving cars have only been involved in 14 accidents since they began roaming the streets in 2009. Ars covered the 13th accident earlier this month, when a Lexus outfitted with Google's autonomous vehicle sensors was rear-ended by another, human-operated car. Both cars were going less than 1 mph.

The 14th accident was a bit more involved. Google writes that on June 18:

A Google Lexus model autonomous vehicle (“Google AV”) was traveling northbound on California St. in Mountain View in autonomous mode and was stopped at a red light in the straight-only lane at the intersection of California St. and Bryant St. The lane to the left of the Google AV was a left-turn-only lane. The vehicle waiting immediately behind the Google AV in the straight-only lane began to move forward when the green arrow left turn signal appeared (despite the signal for the straight-only lane remaining red) and collided with the rear bumper of the Google AV. The Google AV had been stopped for about 11 seconds at the time of impact. The other vehicle was traveling about 5 mph at the time of impact. There were no injuries reported at the scene by either party. The Google AV sustained minor damage (scrapes) to its rear bumper. The other vehicle sustained minor damage (scrapes) to its front bumper.

One incident that does not appear in Google's report is an incident claimed by a Delphi executive in mid-June. Delphi later corrected its statement to say there was no close call at all, but at first the company said that a Google autonomous vehicle suddenly “cut off” the Delphi autonomous vehicle. Both companies stated to the press that no collision happened, and both cars operated as they were programmed to.

Finally, the June report notes that Google put two of its 25 licensed prototype bubble vehicles on the public road. The cars always contain human operators during testing, but they come with a removable steering wheel. For now, their speed is capped at 25 mph. Although there's little information about how the early tests have gone, neither of those two prototypes were involved in any accidents, Google reported.