Stop Light

The history of the stop light is one that few Americans know. Instead, we hop in our cars and drive to work, school, or recreation without thinking of the stop light at the end of the road or the other traffic signals that light our way. The stop light is one of the inventions many schoolchildren learn about during Black History Month in February. African American inventor Garrett Morgan came up with the idea for an electric stop light in 1914 after seeing several failures in other areas. London had a lantern to direct traffic in the 1860s, but these lanterns could catch fire and cause injury. William Potts, a Detroit police officer, came up with a similar idea, but Morgan is credited with the invention because he made it something that could be made more easily.

When traffic engineers needed to determine the universal colors for the traffic signals, they chose red, yellow, and green. While we know what these colors mean, most people do not know about the thought process behind this decision. The engineers borrowed their theory for the stop light signals from railroad systems. Red signified danger for centuries, and the engineers believed that most people would understand the signal for stop. The engineers also adopted green for “go.” Initial testing with clear for go did not work because people could not see the light.

The engineers installed the first stop light in Cleveland, Ohio, Morgan’s hometown, with only red and green. After a while, they discovered that motorists need something to let them know to prepare to stop, and they added in the caution color - yellow. Although it seems obvious now, putting together the electrical system and signaling mechanism for the stop light was a brilliant invention that helped pave the way for city streets to hold more traffic.