NHTSA wants self-driving cars to glow cyan when nobody is watching the road

America’s road-safety regulator wants to add a new color to the street. The National Highway Traffic Safety Administration has proposed letting vehicles that drive themselves carry cyan marker lamps on the front, sides and rear, switched on only while the car is in full control and nobody inside is expected to watch the road. For a pedestrian at a crosswalk, or a police officer walking up to a stopped car, that blue-green glow would answer a question nothing on the outside of a car answers today: who, or what, is driving.

Right now there is no standard way to tell. A driverless taxi and a car with a distracted human behind the wheel look the same from the sidewalk, and the companies that want to signal autonomy have improvised their own lights. NHTSA warns in its proposal that this patchwork could become a nuisance or a source of confusion, and the cyan lamp is its attempt to close that gap before it hardens.

The rules are precise. A car could carry one or two lamps on each face, so between four and eight in total, mounted at least 15 inches (38 cm) off the ground. They must burn steadily rather than flash, switch on and off together, and go dark as soon as a person is expected to take over monitoring. Because of that last condition, the driver-assistance systems sold on most new cars, which still need a human watching the road, would not qualify for the light at all.

Cyan won because the other colors are taken. Red, amber and white already carry fixed meanings on a vehicle, and the agency argues that the blue-green defined in SAE’s lighting standards is distinct from the blue of police lights and far dimmer. The specification largely follows SAE J3134, the industry standard for what engineers call ADS marker lamps, short for automated driving system.

Mercedes-Benz did much of the groundwork. It pitched cyan lamps to international regulators and ran a two-year road validation in California with five cars, in a state whose vehicle code already allows the lamps. The appetite seems to be there too: in a survey of more than 4,400 drivers in the US, UK, Japan and Germany cited by NHTSA, upwards of 80 percent of American and British respondents said self-driving cars should carry such a lamp.

The same package rewrites rules drafted for cars with steering wheels. Vehicles with no manual driving controls would no longer need a hand-operated turn-signal stalk, hazard switch or high-beam switch, only some non-manual way of running those lights. That clears a path for purpose-built robotaxis such as Tesla’s Cybercab, which have no place to put a lever.

The limits are just as clear. The lamps would stay optional, because NHTSA says it lacks the evidence to show a safety need for requiring them, and it admits it cannot estimate the benefit, partly because nobody knows how many such vehicles will be on the road. A manufacturer that would rather not advertise that its car is driving itself can simply leave the lights out. The lamps also say nothing about what the car is about to do: NHTSA is not allowing them to flash as a signal to pedestrians and says it knows of no research supporting that use. In Europe, the UN working party on automated vehicles has declined to recommend mandatory lighting, citing uncertainty.

The proposal covers only the United States, but China is moving in parallel. Its industry ministry has opened consultation on a draft national lighting standard that reserves turquoise lamps for cars with Level 3 automation or higher, bans them on anything less, and forbids switching them on or off by hand. Chinese regulators had already told automakers to stop fitting the unofficial “little blue lights” that spread across driver-assistance models.

NHTSA’s notice is scheduled to appear in the Federal Register on October 26, opening a 30-day public comment period under docket NHTSA-2026-1519 before the agency can write a final rule. China’s consultation closes on December 19, and its explanatory notes recommend the standard take effect on January 1, 2028.

If both drafts survive, the world’s two largest car markets will have settled on nearly the same blue-green signal for a car with no human in charge, before most drivers have ever shared a road with one.

Tags: autonomous vehicles, robotics, robotaxis, self-driving cars, NHTSA, Drive Pilot