Google teaching its self-driving cars to honk politely

"Our self-driving software is designed to recognize when honking may help alert other drivers to our presence," the report says, "for example, when a driver begins swerving into our lane or backing out of a blind driveway.  During testing, we taught our vehicles to distinguish between potentially tricky situations and false positives, ie the difference between a car facing the wrong way during a three-point turn, and one that's about to drive down the wrong side of the road.  At first, we only played the horn inside the vehicle so we wouldn't confuse others on the road with a wayward beep.  Each time our cars sound the horn, our test drivers take note whether the beep was appropriate, and this feedback helps our engineering team refine our software further.

"As our honking algorithms improved, we've begun broadcasting our car horn to the world.  We've even taught our vehicles to use different types of honks depending on the situation.  If another vehicle is slowly reversing towards us, we might sound two short, quieter pips as a friendly heads up to let the driver know we're behind.  However, if there's a situation that requires more urgency, we'll use one loud sustained honk."

The comments finish by insisting, "our goal is to teach our cars to honk like a patient, seasoned driver.  As we become more experienced honkers, we hope our cars will also be able to predict how other drivers respond to a beep in different situations."

The report also says that, since the project started in 2009, its cars have now driven 1,120,512 autonomous miles, and are now averaging a further 10-15,000 per week.