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The terms right-hand traffic (RHT) and left-hand traffic (LHT) refer to regulations requiring all bidirectional traffic, unless otherwise directed, to keep to the right or to the left side of the road, respectively. This is so fundamental to traffic flow that it is sometimes referred to as the rule of the road.
Contents
- History
- Europe
- The Americas
- Asia and the Pacific
- Africa
- Changing sides at borders
- Driver seating position
- Headlamps
- Worldwide distribution by country
- References
About two-thirds of the world's population (163 countries and territories) use RHT, with the remaining 76 countries and territories using LHT. Countries that use LHT account for about a sixth of the world's area and a quarter of its roads. 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. 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 are former British colonies in the Caribbean, Southern Africa, Southeast Asia, Australia, and New Zealand. In Europe, only four countries still drive on the left: the United Kingdom, Ireland, Malta, and Cyprus, all of which are islands. Japan, Thailand, Nepal, Bhutan, Mozambique, Suriname, East Timor, and Indonesia are among the few LHT countries outside the former British Empire.
Nearly all countries use one side or the other throughout their entire territory. Most exceptions are due to historical considerations and involve islands with no road connection to the main part of a country. China is RHT except the Special Administrative Regions of China 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.
According to the International Regulations for Preventing Collisions at Sea, water traffic is RHT. For aircraft the US Federal Aviation Regulations provide for passing on the right, both in the air and on water.
Light rail vehicles generally operate on the same side as other road traffic in the country. Many countries use RHT for automobiles but LHT for trains. In some countries this occurred because rail traffic remained LHT after automobile traffic switched to RHT, for example in China, Brazil, and Argentina. However, France, Belgium, and Switzerland have used RHT for automobiles since their introduction but operate trains using LHT.
There is no technical reason to prefer one side over the other. In healthy populations, traffic safety is thought to be the same regardless of handedness, however researches have speculated that LHT may be safer for ageing populations since humans are more commonly right eye dominant than left.
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. 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 a postilion sat on the left rear horse and held his whip in his right hand. 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 traffic was introduced by the British in Atlantic Canada, Australia, New Zealand, the East Africa Protectorate, the British India, Southern Rhodesia and the Cape Colony (now Zimbabwe and South Africa), British Guiana, and British Hong Kong. LHT was also introduced by the Portuguese Empire in Portuguese Macau, Colonial Brazil, East Timor, Portuguese Mozambique, and 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 formalised RHT in 1804, New Jersey in 1813 and Massachusetts in 1821.
Europe
In 1915, LHT was introduced everywhere in the Austro-Hungarian Empire. In 1918 the Empire was split up into several countries, and they all changed eventually to RHT, as in the switch to right-hand traffic in Czechoslovakia.
Sweden was LHT from about 1734 to 1967, despite having land borders with RHT countries, and virtually all the cars on the road in Sweden being left hand drive (LHD). 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 ("The H-Day"), the 'H' being for Högertrafik or right traffic. When Iceland switched the following year, it was known as H-dagurinn, again meaning "The H-day".
In the late 1960s the UK Department for Transport considered switching to RHT, but declared it unsafe and too costly. Road building standards, for motorways in particular, allow asymmetrically designed road junctions, where merge and diverge lanes differ in length.
The Americas
During the planning of the Pan American Highway from Alaska to Cape Horn in the 1930s, it was decided that the road should use RHT on its entire length. Many countries changed to RHT. Guyana and Suriname are the only two remaining countries in the mainland Americas that drive on the left.
Much of the Caribbean is LHT.
Asia and the Pacific
China adopted RHT in 1946. Taiwan changed to driving on the right at the same time. Hong Kong and Macau continue to be LHT.
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 40 years to switch. The move was legislated in 2008 to allow Samoans to use cheaper right hand drive (RHD) vehicles 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 & American colonial periods, the latter despite America's switch to RHT in the 1930's (see above); as well as during the Commonwealth era. During the Japanese occupation the Philippines remained LHT, nonwithstanding an LHT edict; but during the Battle of Manila the liberating American forces drove their tanks to the right for easier facilitation of movement. RHT was formally finalized by Executive Order No. 34 signed by President Sergio Osmeña on 10 March 1945.
Africa
Ghana switched from LHT to RHT in 1974.
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.
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. The Vienna Convention on Road Traffic regulates the use of foreign registered vehicles in the 72 countries that are parties to the 1968 agreement.
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 between the UK and France.
Some countries have borders where drivers must switch from LHT to RHT and vice versa.
LHT Thailand has three RHT neighbours: 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.
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:
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.
Headlamps
The projection of light from low-beam headlamps is asymmetrical. The kerbside lamp projects light forwards, while the other headlamp dips the beam down and away from oncoming traffic, so as not to dazzle drivers coming in the opposite direction. 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 is done by affixing masking strips or prismatic lenses to a designated 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 cars have a built in adjustment to adapt the projection mechanically.
Worldwide distribution by country
Of the 193 countries currently recognised by the United Nations, 139 use RHT and 54 use LHT. A country and its territories and dependencies is counted once.