A self-driving start-up in Silicon Valley is exploring emojis as a robotic response to the honks, nods, waves and other signals exchanged between human road users.

Drive.ai is beginning a test near its Mountain View headquarters of autonomous cars fitted with digital signage on their roofs. The display, which also incorporates an array of cameras and sensors for navigation, can show text and pictures, as well as making sounds, to provide cues to human drivers of the robot’s intentions.

“If you take the driver out of the equation, how do other human beings communicate with this car? A self-driving car needs to emote intention, understand what the other cars are doing and signal to them what it wants to do,” said Carol Reiley, co-founder and president of the year-old company.