A Google self-driving car sideswiped a bus last month, the first blemish on the otherwise spotless driving record of the company's vehicles.
Google's 53 vehicles have driven more than 2.25 million km autonomously and been in 17 crashes, but never been at fault before. The crash took place at 3:20pm on February 14 local time, about 5km from Google's headquarters in Mountain View, California.
Google's car was attempting to make a right-hand turn on red, and moved to the right side of a wide lane on El Camino Real to pass traffic stopped at the light. But as Google's car neared the intersection of Castro Street, its path was blocked by sandbags around a storm drain, according to a report Google filed with the California DMV.
Google's car tried to go around the sandbags by cutting into the line of vehicles on the left side of the lane. Instead, it struck a metal piece connecting the two halves of an accordion-style bus, according to a Valley Transportation Authority spokeswoman. Google said its car was going less than 3km/h and the bus was moving at 25km/h. Both parties said there were no injuries and described the crash as minor.
The 15 passengers on the bus were transferred to another bus following the accident.
Google characterised the crash as a misunderstanding and a learning experience, saying its cars will learn that large vehicles are less likely to yield than other types of vehicles.
"We hope to handle situations like this more gracefully in the future," Google said in a monthly report.
"We clearly bear some responsibility, because if our car hadn't moved there wouldn't have been a collision."
The accident highlights the imperfections of the current self-driving technology, which is widely seen as a promising solution to the thousands of lives lost each year on roadways.
While many in the tech and auto industry have circled 2020 as a roll-out date for self-driving vehicles, others have warned that it will likely take longer.
Google's self-driving cars have two employees present, and they are trained to intervene to prevent crashes. Earlier this year, Google revealed that 13 times over a 14-month span, its drivers had to intervene to prevent crashes.
In the February 14 crash, Google said its test driver thought the bus would slow or stop so the Google car could go ahead of it.