The Ins and Outs of LED Traffic Lights
The very first traffic signal was actually a set of semaphore arms installed in London back in 1868 and it was lit by gas so a police officer could turn it by hand to warn horse-drawn carriages of oncoming trains. The electric version we would recognise today came along in the early 1900s in the United States, with the familiar red, amber and green sequence becoming standard by the 1920s. For most of the twentieth century, these signals ran on incandescent bulbs, which worked well enough but once LED technology matured enough to handle the brightness and reliability needed for road use they changed the way modern traffic lights operate.