Cyan lights proposed to mark self-driving cars on U.S. roads

The federal government wants a specific cyan light on self-driving vehicles. The National Highway Traffic Safety Administration announced Oct. 23 a proposal to standardize blue-green marker lamps that signal when an automated driving system, rather than a person, is operating a car. The proposal is open to a 30-day public comment period.

NHTSA said the color would let other motorists and law enforcement see when a vehicle is in automated mode. The agency said it settled on cyan because the color is not already assigned to other vehicle functions and because industry groups back it. The specifications under the proposal place the color apart from the blue lights some states reserve for law enforcement and towing vehicles.

SAE International, a professional association covering aerospace and automotive work, recommends cyan for automated vehicles. The group said a unique color carries a clear meaning, unlike amber, red or white. SAE International said it picked blue-green after surveying manufacturers, suppliers, research organizations and experts on several color options.

NHTSA administrator Jonathan Morrison said in a statement that the proposal establishes "clear performance standards for automated vehicle marker lamps" and supports "safe innovation and setting clear rules of the road for automated vehicles." Mercedes-Benz used turquoise lights starting in 2023 on its EQS sedan and S-class, which were permitted that year in California and Nevada, to show the cars were in the automaker's "Drive Pilot" mode. Mercedes-Benz said it consulted engineers, compliance managers, data protection officers and ethics experts on the color choice, and that tests showed teal stood apart from traffic and emergency lighting.