technology
Smart Traffic Lights: How Cities Cut Delays and Pollution
April 20, 2026
Traffic lights used to be simple. Back in the 1860s they were just mechanical arms that changed manually. By the 1910s they became electric, and by the 1920s they turned red, yellow, and green. Today there are about 300, 000 of them in the U. S. alone. Their main job is safety—keeping cars, bikes, a
