400-Nanometer Shift: Feds Propose Cyan Lights for Driverless Cars

A new federal proposal aims to settle a years-long debate over how driverless vehicles should announce their presence to the rest of the traffic.

The National Highway Traffic Safety Administration (NHTSA) has released proposed amendments to Federal Motor Vehicle Safety Standard No. 108, specifically targeting the lighting requirements for autonomous vehicles. The core of the update suggests that robotaxis use distinct cyan-colored marker lamps to indicate that an automated driving system is in control. This move seeks to replace the fragmented approaches currently used by various manufacturers with a single, nationally recognized visual cue. By standardizing the color, brightness, and placement of these lights, the agency hopes to eliminate confusion among other road users and law enforcement officers.

The choice of cyan is strategic, filling a specific gap in the current automotive lighting spectrum. Today, the industry relies on red for braking, amber for turn signals, white for headlights, and flashing blue or red for emergency vehicles. NHTSA argues that a blue-green hue would be easily distinguishable from these existing signals. There is already some precedent for this approach, as Mercedes-Benz previously received state-level approval to use turquoise lights on its Level 3 Drive Pilot systems. Although the automaker has since pivoted to a different system, the agency wants to establish a uniform national standard that operators like Waymo, Nuro, and Zoox, along with manufacturers such as GM and Mercedes, can adopt.

Under the proposed rule, cyan marker lights would not be mandatory for all manufacturers. Instead, the proposal creates an official framework for their use. If a company chooses to install these lights, they must adhere to the specified federal standards for color, intensity, and location. This ensures that any vehicle using the signal does so in a consistent and legally compliant manner, preventing a confusing mix of different colors or signal patterns across the fleet.

The proposal also addresses the physical controls inside the vehicle, which are often unnecessary for fully autonomous designs. Current rules require the presence of physical hazard switches, manual beam shifters, and turn levers. NHTSA proposes removing these requirements, acknowledging that they are often redundant in cars without a human driver. The agency is also updating the 12.8-volt testing standard to accommodate modern LED architectures, reducing administrative hurdles for automakers. Additionally, the proposal considers eliminating the current rule that dictates whether high-beam lights must sit above or below low-beam lights.

This regulatory update is part of a broader push by the Department of Transportation to streamline the deployment of autonomous vehicles. The goal is to make it easier for companies to build cars that lack traditional controls, such as steering wheels and pedals, which are primarily designed for human operation. By simplifying the certification process, the government aims to accelerate the introduction of driverless technology into the mainstream market.

However, the push for streamlined rules coexists with strict enforcement of current standards. Last month, NHTSA opened an audit query into the Tesla Cybercab. The investigation aims to examine the technical data and processes Tesla used when certifying the vehicle. The focus is on the absence of certain design features, such as sideview mirrors, pedals, and a steering wheel, which are currently required under FMVSS. This highlights the ongoing tension between enforcing existing rules written for human-driven cars and adapting them for the next generation of autonomous technology.