MOUNTAIN VIEW, California — Google said it has adjusted its self-driving software following a February 14 crash in which one of its autonomous 2012 Lexus RX 450h SUVs collided with a bus in Mountain View, California.
The RX 450h was in autonomous mode at the time of the crash and was traveling at less than 2 mph, according to the accident report filed with the California Department of Motor Vehicles.
There were no injuries.
While there has been no official determination of fault in the crash, the incident is raising concerns about how self-driving vehicles will cope with some driving situations.
Google characterized the crash as a "misunderstanding" in an advance copy of its February monthly report for self-driving cars provided to Edmunds. The report said the self-driving Lexus "ran into a tricky set of circumstances."
The Google SUV had moved into the right side of the lane at a traffic light to make a right turn but was blocked by sandbags, the report said.
"After waiting for some other vehicles to pass, our vehicle, still in autonomous mode, began angling back toward the center of the lane at around 2 mph — and made contact with the side of a passing bus traveling at 15 mph," the report said. "Our car had detected the approaching bus, but predicted that it would yield to us because we were ahead of it.
"Our test driver, who had been watching the bus in the mirror, also expected the bus to slow or stop. And we can imagine the bus driver assumed we were going to stay put.
Unfortunately, all these assumptions led us to the same spot in the lane at the same time. This type of misunderstanding happens between human drivers on the road every day."
Google added: "In this case, we clearly bear some responsibility because if our car hadn't moved, there wouldn't have been a collision."
The tech giant said it reviewed the crash in its simulator and made refinements to the self-driving software.
"From now on, our cars will more deeply understand that buses (and other large vehicles) are less likely to yield to us than other types of vehicles and we hope to handle situations like this more gracefully in the future," it said.
The nonprofit Consumer Watchdog group said the crash was "further proof that Google's self-driving robot cars cannot reliably cope with everyday ordinary driving situations" and called for a police investigation and the release of technical data and video associated with the crash.
Edmunds says: Self-driving vehicles are still in the experimental stage, as this latest incident illustrates.