Editing Left- and right-hand traffic (section)

{{short description|Directionality of traffic flow by jurisdiction}}
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{{redirect|Traffic direction|the task performed by traffic officers|traffic police}}
[[File:Countries driving on the left or right.svg|thumb|upright=1.35|Countries by direction of road traffic, 2020s
{{legend|#204A87|Left-hand traffic}} {{legend|#CC0000|Right-hand traffic}} {{legend|#808080|No data}}]]

'''Left-hand traffic''' ('''LHT''') and '''right-hand traffic''' ('''RHT''') are the practices, in [[bidirectional traffic]], of keeping to the left side or to the right side of the road, respectively. They are fundamental to [[traffic flow]], and are sometimes called the ''[[Traffic#Rules of the road|rule of the road]]''.<ref name="kincaid">{{Cite book |last=Kincaid |first=Peter |title=The Rule of the Road: An International Guide to History and Practice |publisher=Greenwood Press |date=December 1986 |pages=50, 86–88, 99–100, 121–122, 198–202 |isbn=978-0-313-25249-5}}</ref> The terms right- and left-hand ''drive'' refer to the position of the driver and the [[steering wheel]] in the vehicle and are, in automobiles, the reverse of the terms right- and left-hand ''traffic''. The rule also includes where on the road a vehicle is to be driven, if there is room for more than one vehicle in one direction, and the side on which the vehicle in the rear overtakes the one in the front. For example, a driver in an LHT country would typically overtake on the right of the vehicle being overtaken.

RHT is used in 165 countries and territories, mainly in the Americas, [[Continental Europe]], most of Africa and mainland Asia (except [[South Asia]] and [[Thailand]]), while 75 countries use LHT,<ref name="chartsbin">{{cite web|title=Worldwide Driving Orientation by Country|url=http://chartsbin.com/view/edr|access-date=13 December 2016|archive-date=25 December 2018|archive-url=https://web.archive.org/web/20181225111225/http://chartsbin.com/view/edr|url-status=live}}{{Circular reference|date=November 2020}}</ref> which account for about a sixth of the world's land area, a quarter of its roads, and about a third of its population.<ref name="wsj">{{cite news |last1=Barta |first1=Patrick |title=Shifting the Right of Way to the Left Leaves Some Samoans Feeling Wronged |url=https://www.wsj.com/articles/SB125086852452149513 |work=The Wall Street Journal |access-date=4 December 2016 |archive-date=5 June 2022 |archive-url=https://web.archive.org/web/20220605100337/https://www.wsj.com/articles/SB125086852452149513 |url-status=live }}{{subscription required}}</ref> In 1919, 104 of the world's territories were LHT and an equal number were RHT. Between 1919 and 1986, 34 of the LHT territories switched to RHT.<ref name="watson">{{cite web|last1=Watson|first1=Ian|title=The rule of the road, 1919–1986: A case study of standards change|url=http://www.ianwatson.org/rule_of_the_road.pdf|access-date=30 November 2016|archive-date=10 October 2021|archive-url=https://web.archive.org/web/20211010161416/http://www.ianwatson.org/rule_of_the_road.pdf|url-status=live}}</ref>

While many of the countries using LHT were part of the [[British Empire]], others such as [[Indonesia]], [[Japan]], [[Nepal]], [[Bhutan]], [[Macau]], [[Thailand]], [[Mozambique]] and [[Suriname]] were not. [[Sweden]] and [[Iceland]], which have used RHT since [[Dagen H|September 1967]] and [[H-dagurinn|late May 1968]] respectively, previously used LHT. Most of the countries that were part of the [[French colonial empire|French Colonial Empire]] adopted RHT.

Historical switches of traffic handedness have often been motivated by factors such as changes in political administration, a desire for uniformity within a country or with neighboring states, or availability and affordability of vehicles.

In LHT, traffic keeps left and cars usually have the steering wheel on the right (RHD: right-hand drive) and [[roundabout]]s circulate clockwise. RHT is the opposite: traffic keeps right, the driver usually sits on the left side of the car (LHD: left-hand drive), and roundabouts circulate counterclockwise.

In most countries, rail traffic follows the handedness of the roads; but many of the countries that switched road traffic from LHT to RHT did not switch their trains. Boat traffic on [[Body of water|bodies of water]] is RHT, regardless of location. Boats are traditionally piloted from the [[starboard]] side (and not the port side like RHT road traffic vehicles) to facilitate [[priority to the right]].

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