An autonomous vehicle owned by Cruise, the autonomous car startup that was acquired by GM last year, struck a motorcyclist on San Francisco streets earlier this year. According to a filing with the California DMV, the motorcyclist was able to walk away from the crash but reported shoulder pain and was taken to the hospital to receive medical care. Cruise says that police at the scene determined the motorcyclist was at fault for the collision.

The Cruise vehicle was traveling in the middle lane of a three-lane, one-way street in San Francisco's Lower Haight neighborhood. It spotted a gap in traffic in the left lane and began changing lanes—but then the gap started to close as the vehicle ahead slowed down. So the Cruise car shifted back into the center lane.

Normally, that would be an unremarkable chain of events on San Francisco's busy streets. Unfortunately, Cruise says, "a motorcycle that had just lane-split between two vehicles in the center and right lanes moved into the center lane." The motorcycle "glanced the side of the Cruise AV, wobbled, and fell over."

Cruise says its car was traveling at 12 miles per hour, while the motorcycle was going 17 miles per hour.

"We test our self-driving cars in challenging and unpredictable environments precisely because, by doing so, we will get better, safer AV technology on the roads sooner," Cruise said in an email statement. "In this case, the motorcyclist merged into our lane before it was safe to do so."

This is far from the first collision involving a Cruise vehicle on San Francisco streets. The company reported 14 collisions to California authorities between September and November of this year—a reflection of the company's active testing on San Francisco streets. Many of these involved another car rear-ending the Cruise vehicle.

Cruise CEO Kyle Vogt has touted Cruise's decision to test on San Francisco streets, arguing that the company's software will learn the fastest if it's operating in challenging urban driving environments.

"Our vehicles encounter challenging (and often absurd) situations up to 46 times more often than other places self-driving cars are tested," Vogt wrote.

He provided statistics in October showing that San Francisco vehicles encounter tricky situations like "pass using opposing lane" and "construction navigation" 20 to 40 times more often in San Francisco than in the Phoenix suburbs where Waymo and Uber are doing a lot of their testing.

Unfortunately, while California collects statistics on every autonomous vehicle accident and posts the details to its website, we don't have comparable information from the extensive testing that is happening in Arizona.