Federal Regulators Propose Cyan Lights to Mark Driverless Vehicles

Federal safety regulators have put forward a single answer to a question the autonomous vehicle industry has debated for years: how should a driverless car tell everyone around it that no human is at the wheel? Their proposal is a distinctive blue-green light known as cyan.

The National Highway Traffic Safety Administration (NHTSA) released proposed amendments to Federal Motor Vehicle Safety Standard No. 108, which governs vehicle lighting. The rewrite is aimed at autonomous vehicles and combines two goals: easing regulatory burdens for designs that have no human driver, and standardizing how robotaxis communicate with their surroundings.

According to the agency, the cyan marker lamps would "clearly and consistently signal to law enforcement and other road users when an automated driving system is operating the vehicle." The color was chosen because the auto industry already uses red, amber, white, and flashing blue or red lights for functions such as braking, turn signals, headlights, and emergency vehicles. Cyan could, in theory, fill a visual gap without causing confusion on the road.

There is some precedent. Mercedes-Benz won state-level approval for turquoise lights on its Level 3 Drive Pilot vehicles, although the automaker has since dropped that approach in favor of a Level 2++ system. NHTSA nonetheless wants a national standard that companies such as Waymo, Nuro, and Zoox, along with automakers including GM and Mercedes, could all adopt in the same way.

Under the proposal, the cyan lights would be optional for manufacturers. By setting federal requirements for their color, brightness, and placement, however, NHTSA wants any company that chooses to install them to use a consistent and legal configuration, rather than a patchwork of different colors and signals.

The agency also proposes to scrap lighting requirements that make little sense in a vehicle without a human driver. Current rules call for physical hazard switches, manual beam shifters, and turn levers inside the vehicle, and NHTSA would remove those. It would also update the 12.8-volt testing standard so manufacturers can build around modern LED systems without administrative hurdles, and it is considering dropping rules about whether high-beam lights must sit above or below low-beam lights.

The changes fit into a wider push by the Department of Transportation to speed up the deployment of autonomous vehicles. The government wants to make it easier for automakers to build cars without traditional controls, such as steering wheels and pedals, which are designed for human drivers.

Regulators are still enforcing existing rules as written, though. Last month, NHTSA opened an audit query into the Tesla Cybercab "to examine the process and technical data on which Tesla relied when certifying the Cybercab and related issues." The concern is the absence of certain design features, including sideview mirrors, pedals, and a steering wheel, all of which are required under the current federal standards.