Autonomous vehicles have a communication problem that has nothing to do with software. Other road users need to know what the vehicle is doing, and eventually, whether anyone is doing anything inside it at all.
The proposed answer from federal regulators is cyan lighting. As The Verge reports, the National Highway Traffic Safety Administration wants to update Federal Motor Vehicle Safety Standard No. 108 so automated driving systems can use blue-green marker lamps to signal that the vehicle is operating without a human driver.
Cyan is becoming a shared language for autonomous vehicles
The color matters because vehicle lighting already carries a crowded set of instructions. Red generally means braking or stopping. Amber handles indicators. White belongs to headlights and other forward-facing functions. Flashing blue and red are associated with emergency vehicles. NHTSA’s proposed cyan signal would occupy a space that is visually distinct from those existing cues.
The proposal would make the cyan lamps optional, but it would define their color, brightness and placement if manufacturers choose to use them. That distinction is important. The agency is not simply asking every robotaxi to add another light. It is trying to prevent each company from inventing its own visual language.
That could give operators including Waymo, Nuro and Zoox a common way to communicate with pedestrians, police officers and other drivers. Automakers such as GM and Mercedes-Benz could use the same signal as autonomous systems move from controlled demonstrations into more ordinary streets.
There is already a small amount of precedent. Mercedes-Benz received state-level approval for turquoise lights on vehicles using its Level 3 Drive Pilot system, although the company later abandoned that direction in favor of a Level 2++ approach. The earlier experiment still shows why a shared standard is attractive: an unusual light can be useful only when people understand what it means.
The bigger change is removing assumptions built for human drivers
The cyan lamp is the most visible part of the proposal, but the deeper shift is inside the vehicle. NHTSA is also proposing to remove or revise requirements that assume a human is always controlling the car.
Those changes include rules covering physical hazard switches, manual beam shifters and turn levers. The agency is also considering changes to the 12.8-volt testing standard so manufacturers can design around newer LED architectures, along with removing requirements about whether high beams must sit above or below low beams.
This is regulation beginning to describe a new kind of object. A vehicle without a steering wheel, pedals or side-view mirrors cannot comply neatly with rules written around a person sitting behind the controls. The proposed updates would give manufacturers more room to build autonomous vehicles, while keeping a standardized public signal around them.
The tension is that modernization does not mean automatic approval. NHTSA opened an audit query into Tesla’s Cybercab last month over the technical and certification process behind a vehicle that lacks several features required under current FMVSS rules, including mirrors, pedals and a steering wheel.
That combination says more than the cyan light alone. Regulators appear willing to redesign the rules for vehicles that do not fit the old model, but they are still checking whether individual companies can justify their designs under the rules that remain.
For autonomous vehicle makers, the implication is practical. The future car will need to explain itself through its exterior behavior as much as through its software. A cyan light may become the simplest visible sign that driving has shifted from a person in the cabin to a system operating around everyone else.