Editing Traffic light (section)

{{Short description|Signaling device to control competing flows of traffic}}
{{about|lights used for signalling}}
{{redirect|Stoplight}}
{{Use British English|date=March 2025}}
{{pp-pc|small=yes}}
{{Use dmy dates|date=February 2024}}
[[File:Modern British LED Traffic Light.jpg|thumb|An LED 50-[[watt]] traffic light in [[Portsmouth]], United Kingdom]]
'''Traffic lights''', '''traffic signals''', or '''stoplights''' – also known as '''robots''' in [[South Africa]],<ref>{{cite web|url=https://en.oxforddictionaries.com/definition/robot|archive-url=https://web.archive.org/web/20180814235213/https://en.oxforddictionaries.com/definition/robot|url-status=dead|archive-date=14 August 2018|title=robot – definition of robot in English – Oxford Dictionaries|website=Oxford Dictionaries – English}}</ref><ref>{{cite web |title=see robot – definition of robot in Dictionary of South African English. |url=https://dsae.co.za/entry/robot/e06032 |website=Editor's Note: The origin of 'robot' used as 'traffic light' is from the English translation of the play [[R.U.R.]] by [[Karel Čapek]] which debuted in England in 1923 and introduced the term 'robot' to an English audience. For a short time in England it was fashionable to use 'robot' for 'traffic light' from the late 1920s, when traffic lights were being installed in England. This usage travelled to South Africa in the early 1930s, when they had their first traffic lights installed, and where it continues to be used almost 90 years later, while 'robot' for 'traffic light' fell out of usage in England. See Foster, B. 1970. The changing English language. Harmondsworth, Middlesex: Penguin.}}</ref> [[Zambia]], and [[Namibia]] – are signaling devices positioned at [[intersection (road)|road intersections]], [[pedestrian crossing]]s, and other locations in order to control the flow of traffic.<ref>{{cite journal |last1=McShane |first1=Clay |title=The Origins and Globalization of Traffic Control Signals |journal=Journal of Urban History |date=March 1999 |volume=25 |issue=3 |pages=379–404 |url=https://sites.tufts.edu/carscultureplace2010/files/2010/09/McShane-traffic-signals-1999.pdf |access-date=27 October 2019 |doi=10.1177/009614429902500304 |s2cid=110125733}}</ref>

Traffic lights usually consist of three signals, transmitting meaningful information to road users through colours and symbols, including arrows and bicycles. The usual traffic light colours are red to stop traffic, [[Amber (color)|amber]] for traffic change, and green to allow traffic to proceed. These are arranged vertically or horizontally in that order. Although this is internationally standardised,<ref name=":5">{{cite book | publisher=United Nations. Economic Commission for Europe. Transport Division | title=Convention on Road Signs and Signals of 1968; European Agreement Supplementing the Convention; and, Protocol on Road Markings, Additional to the European Agreement : (2006 consolidated versions) | url = https://unece.org/transport/publications/convention-road-signs-and-signals-1968-european-agreement-supplementing | publication-place=New York | date=2007 | isbn=978-92-1-139128-2 | oclc=227191711}}</ref> variations in traffic light sequences and laws exist on national and local scales.<ref>see [[Variations in traffic light operation]]</ref>

Traffic lights were first introduced in December 1868 on [[Parliament Square]] in [[London]] to reduce the need for police officers to control traffic.<ref name=":7">{{Cite web |last=Thames Leisure |title=12 Amazing Facts About London |url=http://www.thamesleisure.co.uk/12-amazing-facts-london/ |url-status=dead |archive-url=https://web.archive.org/web/20170107005431/http://www.thamesleisure.co.uk/12-amazing-facts-london/ |archive-date=7 January 2017 |access-date=25 January 2017}}</ref> Since then, electricity and computerised control have advanced traffic light technology and increased intersection capacity.{{sfnp|Sessions|1971|p=141}} The system is also used for other purposes, including the control of pedestrian movements, variable lane control (such as [[Reversible lane|tidal flow]] systems or [[smart motorway]]s), and railway [[level crossing]]s.