Low speed collision. The car saw the bus, and assumed the bus would yield. The bus did not yield. Google drew correct conclusion: Never Expect Buses or Trucks to Yield.
"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."
This is one of the most interesting google car accidents so far, because it doesn't involve someone or something else hitting a google car. However, the headline "slams into" is very misleading. It was a _very_ low speed crash with no injuries, even tho the driver of the bus wasn't wearing his seatbelt (this, honestly, is why ordinary passenger vehicles must always yield to buses and trucks -- they are so big, that they just get very relaxed about things that could be quite bad for us. Physics!).