An anonymous reader quotes a report from Engadget: Google's self-driving cars are not only getting smarter by the day, but they're also getting a little bit more polite. According to the project's latest monthly report, the self-driving car team has recently been teaching the car's AI when and how to honk the horn and give the human drivers on the road a helpful heads up. In order to train its honking algorithm, the team tested a variety of honk-worthy situations, like a car backing out of a blind driveway or a car headed the wrong way down a one-way street. At first, the car would play a little honk sound inside the vehicle so engineers could record whether there was a legitimate need for a honk and provide teaching feedback. Once they felt the AI was ready, they let it blare its horn to the world. The report goes on to say Google has "sound-designed the self-driving car's 'hum' so pedestrians and cyclists around the car can hear it coming." The sound increases when the car speeds up, and decreases when the car slows down.