NHTSA proposes cyan exterior lighting standard and relaxed manual controls for autonomous robotaxis
The National Highway Traffic Safety Administration published sweeping revisions to FMVSS No. 108, establishing a standardized blue-green visual indicator for driverless operations while eliminating obsolete mandates for steering levers and high-beam foot switches.
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Federal automotive safety regulators on Friday issued a major proposed rulemaking that establishes a nationwide visual signaling standard for driverless vehicles, moving to eliminate confusing patchwork communications across municipal streets and highways. Under a notice of proposed rulemaking updating Federal Motor Vehicle Safety Standard (FMVSS) No. 108, the National Highway Traffic Safety Administration (NHTSA) proposed introducing optional cyan-colored exterior marker lamps that illuminate exclusively when an automated driving system (ADS) is in active control of a vehicle.
For years, autonomous vehicle developers have debated how to communicate operational status to law enforcement, emergency responders, and pedestrians—experimenting with rooftop LED displays, text marquees, and exterior chime tones. NHTSA determined that a dedicated color would provide immediate clarity without visual ambiguity. While red is reserved for braking and rear visibility, amber for turn indicators, white for forward illumination, and flashing blue and red for emergency responders, cyan (a blue-green wavelength) fills an unused spectral niche that human eyes can rapidly distinguish across varied ambient lighting conditions.
While the cyan marker lamps would remain optional for vehicle manufacturers, any automaker or fleet operator choosing to deploy them must adhere to strict federal photometric standards dictating chromaticity coordinates, minimum candela output, and mounting geometry. The standardized lighting seeks to prevent a fragmented landscape where different operators deploy conflicting visual cues. Mercedes-Benz previously secured state-level approvals in California and Nevada for turquoise indicator lights on Level 3 Drive Pilot vehicles; NHTSA’s nationwide proposal provides a unified framework scalable to Level 4 commercial robotaxis deployed by Waymo, Zoox, and GM Cruise.
In addition to the cyan signaling standard, the proposed rule eliminates several legacy requirements designed solely for human occupants. Driverless vehicles without manual controls will no longer be required to incorporate physical turn signal levers, manual headlamp beam selectors, or dashboard hazard switches. The agency is also modernizing testing procedures by lifting the decades-old 12.8-volt testing baseline to accommodate modern solid-state LED architectures, and removing rigid rules dictating whether high-beam elements must be positioned physically above or below low-beam projectors. Public comments on the proposed rulemaking will remain open for 60 days following Federal Register publication.