Google wants to teach its self-driving cars to honk politely

Google's self-driving cars just learned a new trick: how to honk - and how to do it politely.

Google's Self-Driving Car Project May report outlines the work it's done to teach its cars how and when to honk. Testing was initially performed inside the vehicle so as not to confuse other drivers, but the cars are now ready to hit the road with horns blaring.

During testing, the cars learned the difference between what Google called "false positives" - like a car driving the wrong way down the street versus a car facing the wrong way because it's making a three-point turn - and learned the proper response for different situations. If another vehicle is reversing toward a Google car, for example, the car will emit "two short, quieter pips as a friendly heads up," but will let out a louder, longer honk for more urgent or dangerous situations.

"Our self-driving cars aim to be polite, considerate, and only honk when it makes driving safer for everyone," Google wrote in the report.

"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 added.

Engineers also equipped the cars to make other sounds, like a hum that's more audible than the car's usual electric whir and changes in pitch when the vehicle accelerates and decelerates. Pedestrians, cyclists and the visually impaired rely on those sounds, the report said, and the cars have previously been too quiet.

And if the car's new noises sound familiar, it's because Google tested numerous sounds so make a personalized voice for its vehicles. The company said it tested the sound of an orca, consumer electronics and ambient art sculptures to create what it called "a voice that matches our face."

Google is currently testing a fleet o f 24 Lexus RX450h SUVs and 34 pod-shaped prototype vehicles on public roads in California and three other states. The company reported one accident in May: a prototype vehicle traveling 9 miles per hour in manual mode struck a median in in Google's hometown of Mountain View, California and sustained minor damage, but no other vehicles were involved.