Traffic signals: A brief history | Washington State Magazine | Washington State University

Before automobiles even swarmed over the roads and streets, there was a need to control traffic to avoid accidents and keep vehicles moving smoothly.

The current systems have developed over more than a century, and they’re poised to change once again as vehicles become more connected and traffic control moves toward AI and complex computer-driven systems.



A signal history
December 10, 1868 — The first gas-lit traffic lights were installed outside the Houses of Parliament in London. Proposed by British railway engineer J.P. Knight to control the traffic of horse carriages, gas lights were manually controlled by a police officer using semaphore arms. At night, gas-lit red and green lights were used, but still changed by a police officer. The lights became a safety hazard as they sometimes exploded and injured police officers.