Traffic lights, traffic signals or stoplights, also known as robots in South Africa, are signalling devices positioned at road intersections, pedestrian crossings, and other locations to control flows of traffic.The world's first traffic light was a manually operated gas-lit signal installed in London in December 1868. It exploded less than a month after it was implemented, injuring its policeman operator. Earnest Sirrine from Chicago patented the first automated traffic control system in 1910. It used the words "STOP" and "PROCEED", although neither word was illuminated.Traffic lights are internationally standardised by the Vienna Convention on Road Signs and Signals. Traffic lights alternate the right of way accorded to users with a sequence of illuminating lamps or LEDs of three standard colours:

Red lightProhibits any traffic from proceeding. A flashing red indication requires traffic to stop and then proceed when safe (equivalent to a stop sign).

Amber light (also known as 'orange light' or 'yellow light')Warns that the signal is about to change to red, with some jurisdictions requiring drivers to stop if it is safe to do so, and others allowing drivers to go through the intersection if safe to do so. In some European countries (such as the UK), red and amber is displayed together, indicating that the signal is about to change to green. A flashing amber indication is a warning signal. In the United Kingdom and Ireland, a flashing amber light is used only at pelican crossings, in place of the combined red–amber signal, and indicates that drivers may pass if no pedestrians are on the crossing. The length of time that a traffic light remains green or red is known as a phase.

Green lightAllows traffic to proceed in the direction denoted, if it is safe to do so and there is room on the other side of the intersection.In the US and Canada, traffic signals will go into a flashing mode if the conflict monitor detects a problem, such as a fault that tries to display green lights to conflicting traffic. The signal may display flashing amber to the main road and flashing red to the side road, or flashing red in all directions. Flashing operation can also be used during times of day when traffic is light, such as late at night.