The leader of the technology giant's driverless car project wrote in a blog post that test vehicles are becoming far more adept at city driving.
They can already comfortably handle motorways, he said, but city driving presents a virtual obstacle course of pedestrians, cyclists and blind corners.
Google says the cars can now negotiate thousands of urban situations that would have stumped them a year or two ago.
To navigate and avoid crashes, Google's fleet of retrofitted Lexus SUVs relies on sensors such as lasers and radar. A driver is ready to take over if needed.
Google has said it wants to get the technology to the public by 2017.