Until now, if you got in the way of one of Google's self-driving cars, it would do its best not to hit you.
But now it might just honk and assume you'll get out of the way.
"The human act of honking may be (performance) art, but our self-driving cars aim to be polite, considerate, and only honk when it makes driving safer for everyone," the Google self-driving car team said in its latest monthly update.
The cars learned when to honk, and when to keep their rage under wraps, through a series of tests with on-board passengers.
"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."
After a while they started testing the horn on the outside, using different sounds for different situations.
"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 next step is getting the self-driving cars to learn what human drivers are trying to tell them when they're honked at.
Because the cars are electric they make very little noise, so Google has also developed a range of 'hum' sounds to help cyclists, pedestrians and the visually impaired know when they're coming.
In May, there was only one recorded instance of a Google self-driving car crashing -- it was going 15km/h and bumped into a median. No one was hurt.
"Our self-driving cars are designed to see 360 degrees and not be distracted, unlike human drivers, who are not always fully aware of their surroundings," Google said.