He describes an incident in which a human-driven car (can you imagine: In a few years we may have to indicate that a car is human-driven more often than not) slammed into the back of Google’s self-driving Lexus.

Google’s car, explains Urmson, stopped (together with two human-driven cars in front) at a green light to avoid being stuck at the middle of an intersection due to heavy traffic ahead — just like a human would.

However, the human-driven car behind just kept going, hitting the Google car at 17 mph. The human in it did not hit the brakes at all, probably due to distraction. You can see the incident in Google’s video, below.