Traffic light

Traffic lights, also called traffic signals or stoplights, are signalling devices used at road intersections, pedestrian crossings, and other locations to control traffic flow. They usually use red, amber, and green signals, sometimes with arrows or bicycle symbols, to direct road users. First introduced at Parliament Square in London in December 1868, they have evolved through electrical and computerized control and are also used for pedestrian, lane, and railway-crossing management.

Usual colours

Red, amber, and green

First introduced

December 1868, Parliament Square in London

Primary use

Controlling traffic flow