Traffic lights, traffic signals, or stoplights
-known also as robots in South Africa are signalling devices positioned at road intersections,
pedestrian crossings, and other locations in order to control flows of traffic.
Traffic lights consist normally of three signals,
transmitting meaningful information to drivers and riders through colours and symbols
including arrows and bicycles.
The regular traffic light colours are red, yellow,
and green arranged vertically or horizontally in that order.
Although this is internationally standardised,
variations exist on national and local scales as to traffic light sequences and laws.
The method was first introduced in December 1868 on Parliament Square in London
to reduce the need for police officers to control traffic.
Since then, electricity and computerised control
has advanced traffic light technology and increased intersection capacity.
The system is also used for other purposes, for example,
to control pedestrian movements, variable lane control
(such as tidal flow systems or smart motorways), and railway level crossings.