Left- and right-hand traffic

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The terms left-hand traffic (LHT) and right-hand traffic (RHT) refer to the practice, in bidirectional traffic, to keep to the left side or to the right side of the road, respectively. A fundamental element to traffic flow, it is sometimes referred to as the rule of the road.

RHT is used in 163 countries and territories, with the remaining 78 countries and territories using LHT. Countries that use LHT account for about a sixth of the world's area with about 35% of humanity and a quarter of its roads. In 1919, 104 of the world's territories were LHT and an equal number were RHT. From 1919 to 1986, 34 of the LHT territories switched to RHT.

Many of the countries with LHT were formerly part of the British Empire. In addition, Japan, Indonesia, Thailand, Suriname and other countries have retained the LHT tradition. Conversely, many of the countries with RHT were formerly part of the French colonial empire or, in Europe, were subject to French rule during the Napoleonic conquests.

For rail traffic, LHT predominates in Western Europe (except Germany, Austria, Spain and the Netherlands), Latin America, and in countries formerly in the British and French Empires, whereas North American and central and eastern European train services operate RHT.

According to the International Regulations for Preventing Collisions at Sea, water traffic is RHT. For aircraft the US Federal Aviation Regulations suggest RHT principles, both in the air and on water.

In healthy populations, traffic safety is thought to be the same regardless of handedness, although some researchers have speculated that LHT may be safer for ageing populations since humans are more commonly right-eye dominant than left-eye dominant.

Video Left- and right-hand traffic

History

Ancient Greek, Egyptian, and Roman troops kept to the left when marching. In 1998, archaeologists found a well-preserved double track leading to a Roman quarry near Swindon, in southern England. The grooves in the road on the left side (viewed facing down the track away from the quarry) were much deeper than those on the right side, suggesting LHT, at least at this location, since carts would exit the quarry heavily loaded, and enter it empty.

The first reference in English law to an order for LHT was in 1756, with regard to London Bridge.

Some historians, such as C. Northcote Parkinson, believed that ancient travellers on horseback or on foot generally kept to the left, since most people were right-handed. If two men riding on horseback were to start a fight, each would edge toward the left. In the year 1300, Pope Boniface VIII directed pilgrims to keep left.

In the late 1700s, traffic in the United States was RHT based on teamsters' use of large freight wagons pulled by several pairs of horses. The wagons had no driver's seat, so the (typically right-handed) postilion held his whip in his right hand and thus sat on the left rear horse. Seated on the left, the driver preferred that other wagons pass him on the left so that he could be sure to keep clear of the wheels of oncoming wagons.

In France, traditionally foot traffic had kept right, while carriage traffic kept left. Following the French Revolution, all traffic kept right. Following the Napoleonic Wars, the French imposed RHT on parts of Europe. During the colonial period, RHT was introduced by the French in New France, French West Africa, the Maghreb, French Indochina, the West Indies, French Guiana and the Réunion, among others.

Meanwhile, LHT was introduced by the British in parts of Canada (Atlantic Canada and British Columbia), Australia, New Zealand, the East Africa Protectorate (now Kenya, Tanzania and Uganda), British India, Rhodesia and the Cape Colony (now Zambia, Zimbabwe and South Africa), British Malaya (now Malaysia, Brunei and Singapore), British Guiana, and British Hong Kong. LHT was also introduced by the Portuguese Empire in Portuguese Macau, Colonial Brazil, Portuguese Timor, Portuguese Mozambique, and Portuguese Angola.

The first keep-right law for driving in the United States was passed in 1792 and applied to the Philadelphia and Lancaster Turnpike. New York formalized RHT in 1804, New Jersey in 1813 and Massachusetts in 1821.

In the early 1900s some countries including Canada, Spain, and Brazil had different rules in different parts of the country. During the 1900s many countries standardised within their jurisdictions, and changed from LHT to RHT, mostly to conform with regional custom. Currently nearly all countries use one side or the other throughout their entire territory. Most exceptions are due to historical considerations and/or involve islands with no road connection to the main part of a country. China is RHT except the Special Administrative Regions of Hong Kong and Macau. The United States is RHT except the United States Virgin Islands. The United Kingdom is LHT, but its overseas territories of Gibraltar and British Indian Ocean Territory are RHT.

Maps Left- and right-hand traffic

Changing sides

Europe

Influential in Europe was the 1920 Paris Convention, which advised driving on the right-hand side of the road, in order to harmonise traffic across a continent with many borders. This was despite the fact that left-hand traffic was still widespread: in 1915 for example, LHT was introduced everywhere in the Austro-Hungarian Empire; however, three years later the Empire was split up into several countries, and they all changed eventually to RHT, notably including when Nazi Germany introduced RHT with almost immediate effect in Czechoslovakia in 1938-39.

Sweden was LHT from about 1734 to 1967, despite having land borders with RHT countries, and approximately 90 percent of cars being left-hand drive (LHD) vehicles. A referendum was held in 1955, with an overwhelming majority voting against a change to RHT. Nevertheless, some years later the government ordered a conversion, which took place at 5 am on Sunday, 3 September 1967. The accident rate dropped sharply after the change, but soon rose back to near its original level. The day was known as Dagen H ("H-Day"), the 'H' being for Högertrafik ("right traffic"). When Iceland switched the following year, it was known as H-dagurinn, again meaning "H-Day".

In the late 1960s, the UK Department for Transport considered switching to RHT, but declared it unsafe and too costly for such a built-up nation. Road building standards, for motorways in particular, allow asymmetrically designed road junctions, where merge and diverge lanes differ in length.

Today, four countries in Europe continue to use left-hand traffic, all island nations: the UK, Cyprus, Ireland, and Malta.

Asia and the Pacific

Nationalist China adopted RHT in 1946. This convention was preserved when the CCP took the mainland and the KMT retreated to Taiwan. Hong Kong and Macau continue to be LHT.

Both North Korea and South Korea switched to RHT in 1945 after liberation from Japanese colonial power.

Myanmar switched to RHT in 1970.

Samoa, a former German colony, had been RHT for more than a century. It switched to LHT in 2009, being the first territory in almost 30 years to switch. The move was legislated in 2008 to allow Samoans to use cheaper right-hand drive (RHD) vehicles--which are better suited for left-hand traffic--imported from Australia, New Zealand or Japan, and to harmonise with other South Pacific nations. A political party, The People's Party, was formed to try to protest against the change, a protest group which launched a legal challenge, and an estimated 18,000 people attending demonstrations against it. The motor industry was also opposed, as 14,000 of Samoa's 18,000 vehicles are designed for RHT and the government has refused to meet the cost of conversion. After months of preparation, the switch from right to left happened in an atmosphere of national celebration. There were no reported incidents. At 05:50 local time, Monday 7 September, a radio announcement halted traffic, and an announcement at 6:00 ordered traffic to switch to LHT. The change coincided with more restrictive enforcement of speeding and seat-belt laws. That day and the following day were declared public holidays, to reduce traffic. The change included a three-day ban on alcohol sales, while police mounted dozens of checkpoints, warning drivers to drive slowly.

The Philippines was mostly LHT during its Spanish and American colonial periods, as well as during the Commonwealth era. During the Japanese occupation the Philippines remained LHT, also because LHT had been required by the Japanese; but during the Battle of Manila the liberating American forces drove their tanks to the right for easier facilitation of movement. RHT was formally finalised by Executive Order No. 34 signed by President Sergio Osmeña on 10 March 1945.

Africa

A number of non-contiguous former British colonies in West Africa originally drove LHT and switched to RHT in the early 1970s to match the surrounding countries. Sierra Leone switched to RHT in 1971, Nigeria in 1972 and Ghana in 1974. Before this period The Gambia, a country entirely contained within RHT Senegal, had officially switched to RHT in 1965.

Rwanda, a former Belgian colony in central Africa, is RHT but is considering switching to LHT, to bring the country in line with other members of the East African Community (EAC). A survey, carried out in 2009, indicated that 54% of Rwandans were in favour of the switch. Reasons cited were the perceived lower costs of RHD vehicles as opposed to LHD versions of the same model, easier maintenance and the political benefit of harmonisation of traffic regulations with other EAC countries. The same survey also indicated that RHD cars are 16 to 49 per cent cheaper than their LHD equivalents. In 2014 an internal report from consultants to the Ministry of Infrastructure recommended a switch to LHT. In 2015, the ban on RHD vehicles was lifted; RHD trucks from neighbouring countries cost $1000 less than LHD models imported from Europe.

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Safety

In one study, researchers concluded that left-hand traffic may be safer for elderly drivers, since humans are more commonly right-eye dominant than left-eye dominant. Comparing accident statistics between countries operating either LHT or RHT, Leeming concluded that LHT is superior. However, Watson has criticised the small sample size and dismisses the notion.

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Changing sides at borders

Although many LHT jurisdictions are on islands, there are cases where vehicles may be driven from LHT across a border into a RHT area. Such borders are mostly located in Africa and southern Asia. The Vienna Convention on Road Traffic regulates the use of foreign registered vehicles in the 74 countries that have ratified it.

LHT Thailand has three RHT neighbors: Cambodia, Laos, Myanmar. Most of its borders use a simple traffic light to do the switch, but there are also interchanges which enable the switch while keeping up a continuous flow of traffic.

There are four road border crossing points between Hong Kong and Mainland China. In 2006, the daily average number of vehicle trips recorded at Lok Ma Chau was 31,100. The next largest is Man Kam To, where there is no changeover system and the border roads on the mainland side Wenjindu intersect as one-way streets with a main road.

The Takutu River Bridge (which links LHT Guyana and RHT Brazil) is the only border in the Americas where traffic changes sides.

Although the United Kingdom is separated from Continental Europe by the English Channel, the level of cross-Channel traffic is very high; the Channel Tunnel alone carries 3.5 million vehicles per year, by rail, between the UK and France.

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Road vehicle configurations

Driver seating position

In RHT jurisdictions, vehicles are configured with LHD, with the driver sitting on the left side. In LHT jurisdictions, the reverse is true. The driver's side, the side closest to the centre of the road, is sometimes called the offside, while the passenger side, the side closest to the side of the road, is sometimes called the nearside.

Historically there was less consistency in the relationship of the position of the driver to the handedness of traffic. Most American cars produced before 1910 were RHD. In 1908 Henry Ford standardised the Model T as LHD in RHT America, arguing that with RHD and RHT, the passenger was obliged to "get out on the street side and walk around the car" and that with steering from the left, the driver "is able to see even the wheels of the other car and easily avoids danger." By 1915 other manufacturers followed Ford's lead, due to the popularity of the Model T.

In specialised cases, the driver will sit on the nearside, or kerbside. Examples include:

• Where the driver needs a good view of the nearside, e.g. street sweepers, or vehicles driven along unstable road edges.
• Where it is more convenient for the driver to be on the nearside, e.g. delivery vehicles. The Grumman LLV postal delivery truck is widely used with RHD configurations in RHT North America. Some Unimogs are designed to switch between LHD and RHD to permit operators to work on the more convenient side of the truck.

Generally, the convention is to mount a motorcycle on the left, and kickstands are usually on the left which makes it more convenient to mount on the safer kerbside as is the case in LHT. Some jurisdictions prohibit fitting a sidecar to a motorcycle's offside.

Headlamps and other lighting equipment

Most low-beam headlamps produce an asymmetrical light suitable for use on only one side of the road. Low beam headlamps in LHT jurisdictions throw most of their light forward-leftward; those for RHT throw most of their light forward-rightward, thus illuminating obstacles and road signs while minimising glare for oncoming traffic.

In Europe, headlamps approved for use on one side of the road must be adaptable to produce adequate illumination with controlled glare for temporarily driving on the other side of the road,. This may be achieved by affixing masking strips or prismatic lenses to a part of the lens or by moving all or part of the headlamp optic so all or part of the beam is shifted or the asymmetrical portion is occluded. Some varieties of the projector-type headlamp can be fully adjusted to produce a proper LHT or RHT beam by shifting a lever or other movable element in or on the lamp assembly. Some vehicles adjust the headlamps automatically when the car's GPS detects that the vehicle has moved from LHT to RHT and vice versa.

Because blackout strips and adhesive prismatic lenses reduce the safety performance of the headlamps, most countries require all vehicles registered or used on a permanent or semi-permanent basis within the country to be equipped with headlamps designed for the correct traffic-handedness.

Without sidecars attached, motorcycles, motor scooters, mopeds, and bicycles are almost symmetric with their handlebars in the centre. However, motorcycles are often equipped with automotive-type asymmetrical-beam headlamps that likewise require adjustments or replacement when brought into a country with opposite traffic-handedness.

Rear fog lamps

In the European Union, vehicles must be equipped with one or two red rear fog lamps. A single rear fog lamp must be located between the vehicle's longitudinal centreline and the outer extent of the driver's side of the vehicle. Rear fog lamps are also being found on vehicles produced for Australia, New Zealand and South Africa.

Crash testing differences

An Australian news source reports that some RHD cars imported to that country did not perform as well on crash tests as the LHD versions, although the cause is unknown, and may be due to differences in testing methodology.

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Worldwide distribution by country

Of the 194 countries currently recognised by the United Nations (and the unrecognised Palestine and Kosovo), 140 use RHT and 54 use LHT. A country and its territories and dependencies is counted once.

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Traffic rules

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Rail traffic

Several states in Europe have RHT for roads but LHT for trains. France has mainly LHT for trains, except in Alsace-Lorraine, an eastern French territory which belonged to Germany for much of its history.

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Gallery

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See also

• Bidirectional traffic
• Hook turn
• Traffic-light signalling and operation
• World Forum for Harmonization of Vehicle Regulations

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References

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External links

• Google Maps placemarks of border crossings where traffic changes sides (browser-based), also available as a Google Earth placemarks file (requires Google Earth)
• The Extraordinary Street Railways of Asunción, Paraguay

Source of article : Wikipedia