Standard Traffic Light 

Traffic Light Pole

Traffic lights, traffic signals, or stoplights – also known as robots in South Africa and Namibia – are signaling devices positioned at road intersections, pedestrian crossings, and other locations in order to control the flow of traffic.

Traffic lights normally consist of three signals, transmitting meaningful information to road users through colours and symbols, including arrows and bicycles. The regular traffic light colours are red, yellow (also known as amber), and green arranged vertically or horizontally in that order. Although this is internationally standardised,^[4] variations in traffic light sequences and laws exist on national and local scales.^[5]

Traffic lights were first introduced in December 1868 on Parliament Square in London to reduce the need for police officers to control traffic.^[6] Since then, electricity and computerised control has advanced traffic light technology and increased intersection capacity.^[7] The system is also used for other purposes, including the control of pedestrian movements, variable lane control (such as tidal flow systems or smart motorways), and railway level crossings.

The first system of traffic signals, which was a sephamore traffic signal, was installed as a way to replace police officer control of vehicular traffic outside the Houses of Parliament in London on 9 December 1868. This system exploded on 2 January 1869 and was thus taken down. But, this early traffic signal led to other parts of the world implementing similar traffic signal systems. In the first two decades of the 20th century, semaphore traffic signals like the one in London were in use all over the United States. These traffic signals controlled by a traffic officer who would change the commands on this signal to direct traffic.^[8]

In 1912, the first electric traffic light was developed by Lester Wire, a policeman in Salt Lake City, Utah.^[9] It was installed by the American Traffic Signal Company on the corner