Chromacity of Traffic Signals
The CIE Chromacity Diagram — released in 1931 — is based on about two dozen people matching a projected area of color (covering about 2 degrees of their field of vision) with a color they mixed themselves from red, green and blue light sources.
Our LED traffic signals are designed to meet federal color standards established in the Code of Federal Regulations (23 CFR 655), which specify exact CIE chromaticity coordinates for traffic control devices. These regulations require that signal colors fall within precise boundaries on the 1931 CIE Chromaticity Diagram to ensure consistent color recognition. This standardization helps drivers instantly recognize red as "stop," yellow as "caution," and green as "go" regardless of weather conditions or viewing angle.
By following these federal chromacity specifications, our signals deliver colors that meet the same scientific standards used across all U.S. traffic control devices. The 1931 CIE standard remains the foundation of these federal requirements because it established the fundamental principles of human color perception that are still used to define acceptable color boundaries in modern traffic signal regulations.