Federal agencies pick a blue-green light for driverless cars

The National Highway Traffic Safety Administration has proposed a specific visual signal for driverless vehicles, identifying a cyan-colored light as the standard way for autonomous cars to indicate that no human is at the wheel. This move resolves years of industry debate regarding how robotaxis should communicate their status to other road users, law enforcement, and pedestrians.

The proposal represents a significant shift in Federal Motor Vehicle Safety Standard No. 108, rewriting existing rules to accommodate the unique design needs of autonomous systems. By establishing a single, recognizable color, regulators aim to create a uniform language for the road. This standardization is intended to help operators like Waymo, Zoox, and Nuro, as well as major automakers such as General Motors and Mercedes-Benz, adopt a consistent approach without confusion.

The choice of cyan is driven by the need for visual distinctiveness. Current automotive lighting conventions heavily rely on red, amber, white, and flashing blue or red for functions such as braking, turn signals, headlights, and emergency responses. A blue-green hue fills a gap in the existing color spectrum, allowing autonomous vehicles to signal their automated status without being mistaken for a standard taxi or an emergency vehicle.

There is precedent for this type of signaling, though it has not been universally adopted. Mercedes-Benz previously received state-level approval to use turquoise lights on its Level 3 Drive Pilot vehicles. However, the automaker later abandoned that specific feature in favor of a Level 2++ system. Despite this, NHTSA is pushing for a national standard to ensure that any future autonomous vehicle uses a legally defined and consistent lighting setup.

Under the proposed rule, the installation of cyan marker lamps would remain optional for manufacturers. The primary goal of the regulation is not to force every car to have the light, but to ensure that if a manufacturer chooses to include one, it meets specific federal criteria for color, brightness, and location. This prevents a fragmented market where different companies use varying colors or intensities, which could confuse drivers and pedestrians.

The agency is also proposing to eliminate several lighting requirements that are obsolete for vehicles without human drivers. Current regulations mandate the presence of physical hazard switches, manual beam shifters, and turn signal levers inside the vehicle. Since these components are unnecessary for an automated driving system, NHTSA seeks to remove them from the standard. This allows automakers to design cleaner interiors and more efficient electrical systems.

Administrative updates are also included in the proposal to modernize testing procedures. The agency plans to update the 12.8-volt testing standard to align with modern LED architecture. This change is designed to reduce bureaucratic hurdles for manufacturers building with contemporary technology. Additionally, NHTSA is considering removing rules that dictate the vertical placement of high-beam lights relative to low-beam lights, offering more flexibility in design.

These changes are part of a broader effort by the Department of Transportation to streamline the deployment of autonomous vehicles. The federal government aims to make it easier for companies to build cars that lack traditional human-centric controls, such as steering wheels and pedals. By updating the safety standards to reflect the reality of driverless technology, regulators hope to accelerate the introduction of these vehicles into the public marketplace.

However, the path to a fully streamlined regulatory environment is not yet clear. Regulators continue to enforce existing rules as they are currently written while new standards are debated. Last month, NHTSA opened an audit query into the Tesla Cybercab to examine the technical data and processes used in its certification. The inquiry focused on the absence of features like sideview mirrors, pedals, and steering wheels, which are still required under current Federal Motor Vehicle Safety Standards.