The crash may be the first case of one of its autonomous cars hitting another vehicle and the fault of the self-driving car. The Mountain View, California-based Internet search leader said it made changes to its software after the crash to avoid future incidents.
In a Feb. 23 report filed with California regulators, Google said the crash took place in Mountain View on Feb. 14 when a self-driving Lexus RX450h sought to get around some sandbags in a wide lane.
Google says it bears 'some responsibility' after self-driving car hits bus
Google's self-driving Lexus car drives along street during a demonstration at Google campus on Wednesday, May 13, 2015, in Mountain View, Calif. (AP Photo/Tony Avelar)
In this May 13, 2015 photo, Google's new self-driving prototype car is presented during a demonstration at the Google campus in Mountain View, Calif. The car, which needs no gas pedal or steering wheel, will make its debut on public roads this summer. (AP Photo/Tony Avelar)
People exit Daimler's Freightliner Inspiration self-driving truck after a demonstration Wednesday, May 6, 2015, in Las Vegas. Although much attention has been paid to autonomous vehicles being developed by Google and traditional car companies, Daimler believes that automated tractor-trailers will be rolling along highways before self-driving cars are cruising around the suburbs. (AP Photo/John Locher)
In this photo taken Wednesday, May 14, 2014, a camera is shown inside a Google self-driving car on exhibit at the Computer History Museum in Mountain View, Calif. Four years ago, the Google team developing cars which can drive themselves became convinced that, sooner than later, the technology would be ready for the masses. There was just one problem: Driverless cars almost certainly were illegal.(AP Photo/Eric Risberg)
Some of the computer equipment that is used for autonomous operation is seen in a storage area in this Cadillac SRX that was modified by Carnegie Mellon University as it is parked in a lot in Cranberry, Pa., Butler County, on Wednesday, Sept. 4, 2013. U.S. Rep. Bill Shuster, and Barry Schoch, secretary of the Pennsylvania Department of Transportation, then rode in the self-driven car that went along local roads and highways operated by a computer that used inputs from radars, laser rangefinders, and infrared cameras as it made a 33-mile trip to the Pittsburgh International Airport. A Carnegie Mellon engineer was in the driver's seat as a safety precaution. (AP Photo/Keith Srakocic)
Graphic shows some details on the FreightlinerÃ¢â¬â¢s first autopilot driverless truck; 2c x 3 inches; 96.3 mm x 76 mm;
This handout photo provided by the US Secret Service appears to be a Parrot BeBop drone, seen in Lafayette Park across from the White House in Washington, Thursday, May 14, 2015. The U.S. Secret Service apprehended a man who was flying the small drone Thursday afternoon in a park outside the White House. (US Secret Service via AP)
File - In this Oct. 15, 2014, file photo, a drone called the RMAX, a remotely piloted helicopter, sprays water over grapevines during a demonstration of it's aerial application capabilities at the University of California, Davis' Oakville Station test vineyard in Oakville, Calif. The drone large enough to carry tanks of fertilizers and pesticides has won rare approval from federal authorities to spray crops in the United States, officials said Tuesday, May 5, 2015. (AP Photo/Rich Pedroncelli, File)
FILE - In this June 6, 2013 file photo, University of North Dakota aviation student Logan Lass lifts a lightweight drone used in training at the school's unmanned aircraft program in Grand Forks, N.D. Construction is schedule to begin in May 2015 for the nationâs first unmanned aircraft business park, called Grand Sky, to be located at nearby Grand Forks Air Force Base. It will have access to talent at the base, the UND aerospace school and a nearby technical school. The 1.2 million-square-foot park will have space for hangars, offices, shops, laboratories and data centers. (AP Photo/Dave Kolpack, File)
In this photo taken Thursday, March 19, 2015, a six-bladed drone casts a shadow on a heavily looted 5,000-year-old cemetery, known as Fifa, in southern Jordan. At the sprawling Bronze Age site, archaeologists have developed a unique way of peering into the murky world of antiquities looting: With aerial photographs taken by the drone, researchers are mapping exactly where and roughly when new tombs were robbed. (AP Photo/Sam McNeil)
Romeo Durscher, director of education for drone-maker DJI, flies one of his company's products Tuesday, March 10, 2015, in Davenport , Calif. Top drone-makers, along with investors, regulators and inventors, are gathering in one of the most popular regions for outdoor activity in the U.S., Californiaâs Central Coast, to show off their devices, hear about new uses for airborne robots, and hit the waves and trails at the Drones Data X Conference in Santa Cruz, Calif., from May 1 to 3, 2015. (AP Photo/Marcio Jose Sanchez)
This handout photo provided by the US Secret Service shows the drone that crashed onto the White House grounds in Washington, Monday, Jan. 26, 2015. A small drone flying low to the ground crashed onto the White House grounds before dawn Monday, triggering a major emergency response and raising fresh questions about security at the presidential mansion. A man later came forward to say he was responsible and didn't mean to fly it over the complex. The man contacted the Secret Service after reports of the crash spread in the media, a U.S. official said. The man told the agency that he had been flying the drone recreationally. The man is a Washington resident and is cooperating with investigators. (AP Photo/US Secret Service)
In this Thursday, Sept. 26, 2013, photo, Decatur Self Storage's array of solar cells are installed on the flat roof of the building as they capture solar energy and convert it to electrical energy for the storage facility, in in Decatur, Ga. Owner Mike Easterwood also returns excess electricity to the Georgia Power Company electrical grid in exchange for a reduced monthly power rate. (AP Photo/David Tulis)
KNUTSFORD, ENGLAND - OCTOBER 13: A youth poses as he rides a hoverboard, which are also known as self-balancing scooters and balance boards, on October 13, 2015 in Knutsford, England. The British Crown Prosecution Service have declared that the devices are illegal as they are are too unsafe to ride on the road, and too dangerous to ride on the pavement. (Photo by Christopher Furlong/Getty Images)
In this Oct. 30, 2014 photo, Arx Pax engineer Garrett Foshay stands over a Hendo Hoverboard in Los Gatos, Calif. Skateboarding is going airborne this fall with the launch of the first real commercially marketed hoverboard which uses magnetics to float about an inch off the ground. (AP Photo/Jeff Chiu)
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Google said in the filing the autonomous vehicle was traveling at less than 2 miles per hour, while the bus was moving at about 15 miles per hour.
The vehicle and the test driver "believed the bus would slow or allow the Google (autonomous vehicle) to continue," it said.
But three seconds later, as the Google car in autonomous mode re-entered the center of the lane, it struck the side of the bus, causing damage to the left front fender, front wheel and a driver side sensor. No one was injured in the car or on the bus.
Google said in a statement on Monday that "we clearly bear some responsibility, because if our car hadn't moved, there wouldn't have been a collision. That said, our test driver believed the bus was going to slow or stop to allow us to merge into the traffic, and that there would be sufficient space to do that."
The Santa Clara Valley Transportation Authority will investigate the circumstances of the accident, Stacey Hendler Ross, spokeswoman for the Santa Clara Valley Transportation Authority, said on Monday.
She said the Google car caused minor damage to the bus, striking the "pivoting joint," or flexible area in the middle of the articulated bus. After the crash, 15 passengers on the bus were transferred to another bus.
An investigation to determine liability is pending, she said.
John M. Simpson, privacy project director for advocacy group Consumer Watchdog, said the crash "is more proof that robot car technology is not ready for auto pilot."
A spokesman for the California Department of Motor Vehicles said on Monday it will speak to Google to gather additional information, but added "the DMV is not responsible for determining fault."
Google said it has reviewed this incident "and thousands of variations on it in our simulator in detail and made refinements to our 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."
There has been no official determination of fault in the crash. Google has previously said that its autonomous vehicles have never been at fault in any crashes.
The Mountain View Police Department said no police report was filed in the incident.
A spokesman for the U.S. National Highway Traffic Safety Administration declined to comment.
The crash comes as Google has been making the case that it should be able to test vehicles without steering wheels and other controls.
In December, Google criticized California for proposing regulations that would require autonomous cars to have a steering wheel, throttle and brake pedals when operating on public roads. A licensed driver would need to be ready to take over if something went wrong.
Google said in November that in six years of its self-driving project, it has been involved in 17 minor accidents during more than two million miles of autonomous and manual driving combined.
"Not once was the self-driving car the cause of the accident," Google said at the time. (Reporting by David Shepardson, additional reporting by Bernie Woodall; editing by Chris Reese, G Crosse)