Google has taken "some responsibility" after one of its self-driving cars struck a public bus in a minor crash earlier this month.

The Mountain View, California-based internet search leader and tech firm said on Monday that it updated its software after the crash to avoid future incidents.

In a February 23 report filed with California regulators, Google said the crash happened in Mountain View on February 14 when a self-driving Lexus RX450h tried to get around some sandbags in a wide lane.

Google said the car was travelling at less than 3km/h per hour, while the bus was moving at about 24km/h per hour.

The car and 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 centre of the lane, it struck the side of the bus, damaging a front fender, front wheel and a driver-side sensor. No one was injured.

"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," Google said.

The company also 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".

Google has previously said that its autonomous vehicles have never been at fault in any crashes.