Why the government wants self-driving cars to glow cyan

Self-driving cars may soon get distinct cyan-colored lights to indicate when they are being driven by a robot, according to a new proposal from the Department of Transportation's National Highway Traffic Safety Administration (NHTSA). The proposal, announced on October 23, outlines federal requirements for automated vehicle (AV) marker lamps, with the proposed cyan color chosen because it is unique and has industry backing.

SAE International, an aerospace and automotive professional association, supports the use of cyan for AVs, stating that a unique color would have a clear meaning, unlike standard light colors like amber, red, or white. The NHTSA's proposal is currently open to 30 days of public comment, as Administrator Jonathan Morrison emphasized the importance of establishing "clear performance standards for automated vehicle marker lamps" and paving the way for "safe innovation and setting clear rules of the road for automated vehicles."

Mercedes-Benz introduced turquoise lights in its EQS sedan and S-class in California and Nevada in 2023 to indicate when vehicles were set to the automaker's "Drive Pilot" mode. The company explained that the color was selected after consulting with engineers, compliance managers, data protection officers, and ethics experts, and that tests showed it was clearly distinguishable from traffic and emergency lighting.

The cyan color also fits the futuristic aesthetic of AVs, as it is commonly found in science fiction films, such as Disney's 2010 Tron: Legacy. This visual association could help motorists quickly identify autonomous, electric, or high-tech vehicles. Mercedes suggests that educational measures before and during market launch could help inform the public about the meaning of the cyan color, but even without this, the light's futuristic appearance effectively communicates automation.