Red and green traffic lights have been around since the 1800s, when British traffic officers used to rotate gas lamps that burned red and green to control the movement of mostly horse-drawn vehicles.

Many cities are replacing their incandescent traffic lights with LEDs, despite the higher initial cost. Here's why that's ...

Traffic lights help traffic flow by directing specific lanes to go and others to stop. Some are more complex and include signals for buses. But at the end of the day, they're devices with red, yellow, ...