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Left- and right-hand traffic
Left- and right-hand traffic
from Wikipedia

Countries by direction of road traffic, 2020s
  Left-hand traffic
  Right-hand traffic
  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 rule of the road.[1] 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,[2] which account for about a sixth of the world's land area, a quarter of its roads, and about a third of its population.[3] 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.[4]

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 September 1967 and late May 1968 respectively, previously used LHT. All of the countries that were part of the 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 roundabouts 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 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.

Background

[edit]
Countries with left- and right-hand traffic, currently and formerly. Changes since 1858 when Finland changed to the right are taken into account.
  Drives on the right
  Formerly drove on the left, now drives on the right
  Drives on the left
  Formerly drove on the right, now drives on the left
  Formerly a mix of left and right in various parts of the country, now drives on the right
  Formerly a mix of left and right in various parts of the country, now drives on the left
  No data

Historically, many places kept left, while many others kept right, often within the same country. There are many myths that attempt to explain why one or the other is preferred.[5] About 90 percent of people are right-handed,[6] and many explanations reference this. Horses are traditionally mounted from the left, and led from the left, with the reins in the right hand. So people walking horses might use RHT, to keep the animals separated. Also referenced is the need for pedestrians to keep their swords in the right hand and pass on the left as in LHT, for self-defence. It has been suggested that wagon-drivers whipped their horses with their right hand, and thus sat on the left-hand side of the wagon, as in RHT. Academic Chris McManus notes that writers have stated that in 1300, Pope Boniface VIII directed pilgrims to keep left; others suggest that he directed them to keep to the right, and there is no documented evidence to back either claim.[5]

Geographical areas

[edit]

Africa

[edit]
LHT roundabout
RHT roundabout

The British Empire introduced LHT in the East Africa Protectorate (present-day Kenya), the Protectorate of Uganda, Tanganyika (formerly part of German East Africa; present-day Tanzania), Rhodesia (present-day Zambia/Zimbabwe), Eswatini and the Cape Colony (present-day South Africa and Lesotho), as well as in British West Africa (present-day Ghana, Gambia, Sierra Leone and Nigeria);[7] former British West Africa, however, has now switched to RHT, as all its neighbours, which are mostly former French territories, use RHT. South Africa, formerly the Cape Colony, introduced LHT in former German South West Africa, present-day Namibia, after the end of World War I.

Sudan, formerly part of Anglo-Egyptian Sudan, switched to RHT in 1973. Most of its neighbours were RHT countries, with the exception of Uganda and Kenya, but since the independence of South Sudan in 2011, all of its neighbours drive on the right (including South Sudan, despite its land borders with two LHT countries).[8]

Although Portugal switched to RHT in 1928, its colony of Mozambique remained LHT because it has land borders with former British colonies (with LHT).

France introduced RHT in French West Africa and the Maghreb,[citation needed] where it is still used. Countries in these areas include Mali, Mauritania, Ivory Coast, Burkina Faso, Benin, Niger, Morocco, Algeria, and Tunisia. Other French former colonies that are RHT include Cameroon, Central African Republic, Chad, Djibouti, Gabon, and the Republic of the Congo.

Rwanda and Burundi are RHT but are considering switching to LHT (see "Potential future shifts" section below).

Americas

[edit]

United States

[edit]

In the late 18th century, right-hand traffic started to be introduced in the United States based on teamsters' use of large freight wagons pulled by several pairs of horses and without a driver's seat; the (typically right-handed) postilion held his whip in his right hand and thus sat on the left rear horse, and therefore preferred other wagons passing on the left so that he would have a clear view of other vehicles.[9][better source needed] The first keep-right law for driving in the United States was passed in 1792 and applied to the Philadelphia and Lancaster Turnpike.[10] Massachusetts formalized RHT in 1821.[11] However, the National Road was LHT until 1850, "long after the rest of the country had settled on the keep-right convention".[12] Today the United States is RHT except the United States Virgin Islands,[13] which is LHT like many neighbouring islands.

Some special-purpose vehicles in the United States, like certain postal service trucks, garbage trucks, and parking-enforcement vehicles, are built with the driver's seat on the right for safer and easier access to the curb. A common example is the Grumman LLV, which is used nationwide by the US Postal Service and by Canada Post.

Other countries in the Americas

[edit]
Parts of Canada were LHT until the 1920s, shown here in Saint John, New Brunswick, 1898.

In Canada, the provinces of Quebec and Ontario were always RHT because they were created out of the former French colony of New France.[14] The province of British Columbia changed to RHT in stages from 1920 to 1923,[15][16] New Brunswick, Nova Scotia, and Prince Edward Island in 1922, 1923, and 1924 respectively,[17] and the Dominion of Newfoundland (part of Canada since 1949)[18] in 1947, in order to allow traffic (without side switch) to or from the United States.[19]

In the West Indies, colonies and territories drive on the same side as their parent countries, except for the United States Virgin Islands. Many of the island nations are former British colonies and drive on the left, including Jamaica, Antigua and Barbuda, Barbados, Dominica, Grenada, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Trinidad and Tobago, and The Bahamas. However, most vehicles in The Bahamas,[20] Cayman Islands,[21] Turks and Caicos Islands[22] and both the British Virgin Islands,[23] and the United States Virgin Islands are LHD due to their being imported from the United States.[23]

Crossover bridge near the Takutu River Bridge between Guyana (LHT) and Brazil (RHT)

Brazil, a Portuguese colony until the early 19th century, had in the 19th and the early 20th century mixed rules, with some regions still on LHT, switching these remaining regions to RHT in 1928, the same year Portugal switched sides.[24] Other Central and South American countries that later switched from LHT to RHT include Argentina,[25] Panama,[26] Paraguay,[27] and Uruguay.[28]

Suriname and its neighbour Guyana are the only two remaining LHT countries in South America.[29]

Asia

[edit]
The Lotus Bridge exchanges between LHT in Macau and RHT in mainland China.

LHT was introduced by the UK in British India (now India, Pakistan, Myanmar, and Bangladesh), British Malaya and British Borneo (now Malaysia, Brunei and Singapore), as well as British Hong Kong. These countries, except Myanmar, are still LHT, as well as neighbouring countries Bhutan and Nepal. Myanmar switched to RHT in 1970,[30] although much of its infrastructure is still geared to LHT as its neighbours India, Bangladesh and Thailand use LHT. Most cars are used RHD vehicles imported from Japan.[31] Afghanistan was LHT until the 1950s, in line with Pakistan (former part of British India).[32]

Although Portuguese Timor (present-day East Timor), which shares the island of Timor with Indonesia, who is LHT, switched to RHT with Portugal in 1928,[1] it switched back to LHT in 1976 during the Indonesian occupation of East Timor.

In the 1930s, parts of China such as the Shanghai International Settlement, Canton and Japanese-occupied northeast China used LHT. However, in 1946 the Republic of China made RHT mandatory in China (including Taiwan). Taiwan was LHT under Japanese colonization from 1895–1945. Portuguese Macau (present-day Macau) remained LHT, along with British Hong Kong, despite being transferred to China in 1999 and 1997 respectively.

Both North Korea and South Korea use RHT since 1946, after liberation from Japanese colonialization.[33]

The Philippines was mostly LHT during its Spanish[34] and American colonial periods,[35][36] as well as during the Commonwealth era.[37] During the Japanese occupation, the Philippines remained LHT,[38] as was required by the Japanese;[39] but during the Battle of Manila, the liberating American forces drove their tanks to the right for easier facilitation of movement. RHT was formalized in 1945 through a decree by president Sergio Osmeña.[40] Even though RHT was formalized, RHD vehicles such as public buses were still imported into the Philippines until a law passed banning the importation of RHD vehicles except in special cases. These RHD vehicles are required to be converted to LHD.[41]

Japan was never part of the British Empire, but its traffic also drives on the left. Although this practice goes back to the Edo period (1603–1868), it was not until 1872 – the year Japan's first railway was introduced, built with technical aid from the British – that this unwritten rule received official acknowledgment. Gradually, a massive network of railways and tram tracks was built, with all railway vehicles driven on the left-hand side. However, it took another half-century, until 1924, until left-hand traffic was legally mandated. Post-World War II Okinawa was ruled by the United States Civil Administration of the Ryukyu Islands until 1972, and was RHT until 6 a.m. the morning of 30 July 1978, when it switched back to LHT.[42] The conversion operation was known as 730 (Nana-San-Maru, which refers to the date of the changeover). Okinawa is one of only a few places to have changed from RHT to LHT in the late 20th century. While Japan drives on the left and most Japanese vehicles are RHD, imported vehicles (e.g. BMW, Mercedes-Benz, Porsche) are generally bought as LHD since LHD cars are considered to be status symbols.[43]

Vietnam became RHT as part of French Indochina, as did Laos and Cambodia. In Cambodia, RHD cars, many of which were smuggled from Thailand, were banned in 2001, even though they accounted for 80% of vehicles in the country.[44]

Europe

[edit]

In a study of the ancient traffic system of Pompeii, Eric Poehler was able to show that drivers of carts drove in the middle of the road whenever possible. This was the case even on roads wide enough for two lanes.[45]: 136  The wear marks on the kerbstones, however, prove that when there were two lanes of traffic, and the volume of traffic made it necessary to divide the lanes, the drivers always drove on the right-hand side.[45]: 150–155  These considerations can also be demonstrated in the archaeological findings of other cities in the Roman Empire.[45]: 218–219 

One of the first references in England to requiring traffic direction was an order by the London Court of Aldermen in 1669, requiring a man to be posted on London Bridge to ensure that "all cartes going to keep on the one side and all cartes coming to keep on the other side".[46] It was later legislated as the London Bridge Act 1756 (29 Geo. 2 c. 40), which required that "all carriages passing over the said bridge from London shall go on the east side thereof" – those going south to remain on the east, i.e. the left-hand side by direction of travel.[47] This may represent the first statutory requirement for LHT.[48]

In the Kingdom of Ireland, a law of 1793 (33 Geo. 3. c. 56 (I)) provided a ten-shilling fine to anyone not driving or riding on the left side of the road within the county of the city of Dublin, and required the local road overseers to erect written or printed notices informing road users of the law.[49] The Road in Down and Antrim Act 1798 (38 Geo. 3. c. 28 (I)) required drivers on the road from Dublin to Donadea to keep to the left. This time, the punishment was ten shillings if the offender was not the owner of the vehicle, or one Irish pound (twenty shillings) if he/she was.[50] The Grand Juries (Ireland) Act 1836 (6 & 7 Will. 4 c. 116) mandated LHT for the whole country, violators to be fined up to five shillings and imprisoned in default for up to one month.[51]

An oft-repeated story is that Napoleon changed the custom from LHT to RHT in France and the countries he conquered after the French Revolution. Scholars who have looked for documentary evidence of this story have found none, and contemporary sources have not surfaced, as of 1999.[4] In 1827, twelve years after Napoleon's reign, Edward Planta wrote that, in Paris, "The coachmen have no established rule by which they drive on the right or left of the road, but they cross and jostle one another without ceremony."[52]

Rotterdam had no fixed rules until 1917,[53] although the rest of the Netherlands was RHT. In May 1917 the police in Rotterdam ended traffic chaos by enforcing right hand traffic.

In Russia, in 1709, the Danish envoy under Tsar Peter the Great noted the widespread custom for traffic in Russia to pass on the right, but it was only in 1752 that Empress Elizabeth officially issued an edict for traffic to keep to the right.[54]

Left-hand traffic in Vienna, Austria, c. 1930
Border sign showing change of traffic direction between Sweden and Norway in 1934

After the Austro-Hungarian Empire broke up, the resulting countries gradually changed to RHT. In Austria, Vorarlberg switched in 1921,[55] North Tyrol in 1930, Carinthia and East Tyrol in 1935, and the rest of the country in 1938.[56] In Romania, Transylvania, the Banat and Bukovina were LHT until 1919, while Wallachia and Moldavia were already RHT. Partitions of Poland belonging to the German Empire and the Russian Empire were RHT, while the former Austrian Partition changed in the 1920s.[57] Croatia-Slavonia switched on joining the Kingdom of Yugoslavia in 1918, although Istria and Dalmatia were already RHT.[58] The switch in Czechoslovakia from LHT to RHT had been planned for 1939, but was accelerated by the start of the German occupation of Czechoslovakia that year.[59]

In Italy, it had been decreed in 1901 that each province define its own traffic code, including the handedness of traffic,[60] and the 1903 Baedeker guide reported that the rule of the road varied by region.[5] For example, in Northern Italy, the provinces of Brescia, Como, Vicenza, and Ravenna were RHT while nearby provinces of Lecco, Verona, and Varese were LHT,[60] as were the cities Milan, Turin, and Florence.[5] In 1915, allied forces of World War I imposed LHT in areas of military operation, but this was revoked in 1918. Rome was reported by Goethe as LHT in the 1780s. Naples was also LHT although surrounding areas were often RHT. In cities, LHT was considered safer since pedestrians, accustomed to keeping right, could better see oncoming vehicular traffic.[60] In 1923 Benito Mussolini decreed that all LHT areas would gradually transition to RHT.[60]

Portugal switched to RHT in 1928.[1]

Finland, formerly part of LHT Sweden, switched to RHT in 1858 as the Grand Duchy of Finland by Russian decree.[61]

Spain switched to RHT in 1918, but not in the entire country. In Madrid people continued to drive on the left until 1924 when a national law forced drivers in Madrid switch to RHT.[62] Madrid Metro still uses LHT.

Sweden switched to RHT in 1967, having been LHT from about 1734[63] despite having land borders with RHT countries Norway and Finland, and approximately 90% of cars being left-hand drive (LHD).[64] A referendum in 1955 overwhelmingly rejected a change to RHT, but, a few years later, the government ordered it and it occurred on Sunday, 3 September 1967[65] at 5 am. The accident rate then dropped sharply,[66] but soon rose to near its original level.[67] The day was known as Högertrafikomläggningen, or Dagen H for short.

When Iceland switched to RHT the following year, it was known as Hægri dagurinn or H-dagurinn ("The H-Day").[68] Most passenger cars in Iceland were already LHD.

The United Kingdom is LHT, but two of its overseas territories, Gibraltar and the British Indian Ocean Territory, are RHT. In the late 1960s, the British Department for Transport considered switching to RHT, but declared it unsafe and too costly for such a built-up nation.[69] Road building standards, for motorways in particular, allow asymmetrically designed road junctions, where merge and diverge lanes differ in length.[70]

Today, four countries in Europe continue to use LHT, all island nations: the United Kingdom, Republic of Ireland (formerly part of the UK), Cyprus and Malta (both former British colonies).

Oceania

[edit]
A sign on the Great Ocean Road, heavily visited by international tourists, reminding motorists to keep left in Australia

Many former British colonies in the region have always been LHT, including Australia, New Zealand, Fiji, Kiribati, Solomon Islands, Tonga, and Tuvalu; and nations that were previously administered by Australia: Nauru and Papua New Guinea.

New Zealand

[edit]
Multilingual sign at Waiotapu to remind tourists to drive on the left in New Zealand.

Initially traffic was slow and very sparse, but, as early as 1856, a newspaper said, "The cart was near to the right hand kerb. According to the rules of the road, it should have been on the left side. In turning sharp round a right-hand corner, a driver should keep away to the opposite side." That rule was codified when the first Highway Code was written in 1936.[71]

Samoa

[edit]

Samoa, a former German colony, had been RHT for more than a century, but switched to LHT in 2009,[72] making it the first territory in almost 30 years to change sides.[73] The move was legislated in 2008 to allow Samoans to use cheaper 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 by the group People Against Switching Sides (PASS) to protest against the change, with PASS launching a legal challenge;[74] in April 2008 an estimated 18,000 people attended demonstrations against switching.[75] The motor industry was also opposed, as 14,000 of Samoa's 18,000 vehicles were designed for RHT and the government refused to meet the cost of conversion.[73] After months of preparation, the switch from right to left happened in an atmosphere of national celebration. There were no reported incidents.[3] 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.[72] The change coincided with more restrictive enforcement of speeding and seat-belt laws.[76] That day and the following were declared public holidays, to reduce traffic.[77] The change included a three-day ban on alcohol sales, while police mounted dozens of checkpoints, warning drivers to drive slowly.[3]

Potential future shifts

[edit]

Rwanda and Burundi, former Belgian colonies in Central Africa, are RHT but are considering switching to LHT[78][79] like neighbouring members of the East African Community (EAC).[80] A survey in 2009 found that 54% of Rwandans favoured the switch. Reasons cited were the perceived lower costs of RHD vehicles, easier maintenance and the political benefit of harmonising traffic regulations with other EAC countries. The survey indicated that RHD cars were 16% to 49% cheaper than their LHD counterparts.[81] In 2014, an internal report by consultants to the Ministry of Infrastructure recommended a switch to LHT.[82] In 2015, the ban on RHD vehicles was lifted; RHD trucks from neighbouring countries cost $1,000 less than LHD models imported from Europe.[83][84]

Changing sides at borders

[edit]
Traffic Switchover sign at the First Thai–Lao Friendship Bridge

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 78 countries that have ratified it.

LHT Thailand has three RHT neighbours: Cambodia, Laos, and Myanmar. Most of its borders use a simple traffic light to do the switch, but there are also interchanges that enable the switch while keeping up a continuous flow of traffic.[85]

There are six 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.[86] 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[87]) is the only border in the Americas where traffic changes sides.

Road vehicle configurations

[edit]
Legality of wrong-hand-drive vehicles by country
  Usage illegal
  Usage legal, but registration illegal or unknown
  Registration illegal for normal vehicles, with exceptions for special (e.g. diplomatic) vehicles
  Registration and usage legal
  No data

Steering wheel position

[edit]

In RHT jurisdictions, vehicles are typically configured as left-hand drive (LHD), with the steering wheel on the left side of the passenger compartment. In LHT jurisdictions, the reverse is true as the right-hand drive (RHD) configuration. In most jurisdictions, the position of the steering wheel is not regulated, or explicitly permitted to be anywhere.[88] The driver's side, the side closer to the centre of the road, is sometimes called the offside, while the passenger side, the side closer to the side of the road, is sometimes called the nearside.[89]

Most windscreen wipers are preferentially designed to better clean the driver's side of the windscreen and thus have a longer wiper blade on the driver's side and wipe up from the passenger side to the driver's side. Thus on LHD configurations, they wipe up from right to left, viewed from inside the vehicle, and do the opposite on RHD vehicles.[citation needed]

In both LHD and RHD vehicles, gear shifters are in the same position, and the shift patterns are not reversed.

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.[10] In 1908, Henry Ford standardised the Model T as LHD in RHT America,[10] 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."[90] By 1915, other manufacturers followed Ford's lead, due to the popularity of the Model T.[10]

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.[91] Similarly in mountainous areas the driver may be seated opposite side so that they have a better view of the road edge which may fall away for very many metres into the valley below. Swiss Postbuses in mountainous areas are a well known example.
  • 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,[92] and kickstands are usually on the left[93] which makes it more convenient to mount on the safer kerbside[93] as is the case in LHT. Some jurisdictions prohibit fitting a sidecar to a motorcycle's offside.[94][95]

In 2020, there were 160 LHD heavy goods vehicles in the UK involved in accidents (5%) for a total of 3,175 accidents, killing 215 people (5%) for a total of 4271.[96]

Right-hand drive vehicles, hence the left-hand traffic direction, may have an advantage in terms of safety. As most drivers are right-handed, the dominant right hand can control the steering wheel, while the non-dominant left hand can manipulate gears.[97] The right field of vision may also be more dominant, thereby permitting a superior view of oncoming traffic.[citation needed]

Dashboard configuration

[edit]

Some manufacturers primarily produce left-hand drive vehicles, due to the larger or nearer market for such vehicles. For such models supplied to left-hand traffic markets, in the right-hand drive configuration, the manufacturer may reuse the same dashboard configuration as is used in the left-hand drive models, with the steering column and pedals moved to the right-hand side. Oft-used controls (such as audio volume and fan controls) that were placed near the left-hand driver for ease of access, are now situated on the far side of the center console for the right-hand driver. This may make them more difficult to reach quickly or without looking away from the road ahead.

In some cases, the manufacturer's dashboard design incorporates blanks and modular components, which permits the controls and underlying electronics to be rearranged to suit the right-hand drive model. This may be done in the factory, after import, or as an after-market modification.

Headlamps and other lighting equipment

[edit]
Bird's-eye view of low beam light pattern for RH traffic, with long seeing range on the right and short cutoff on the left so oncoming drivers are not dazzled

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,[98]: p.13 ¶5.8 . 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.[98]: p.13 ¶5.8.1  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.[98]: p.12 ¶5.4  Some vehicles adjust the headlamps automatically when the car's GPS detects that the vehicle has moved from LHT to RHT and vice versa.[citation needed]

Rear fog lamps

[edit]

In Europe since the early 1980s,[99] cars 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.[100]

Crash testing differences

[edit]

ANCAP reports that some RHD cars imported to Australia 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.[101]

Rail traffic

[edit]

National rail

[edit]
Handedness of rail traffic worldwide

In most countries, rail traffic travels on the same side as road traffic. However, there are many instances of railways built using LHT British technology which remained LHT despite their nations' road traffic becoming RHT. Examples include: Argentina, Belgium, Bolivia, Cambodia, China, Egypt, France, Iraq, Israel, Italy, Laos, Monaco, Morocco, Myanmar, Nigeria, Peru, Portugal, Senegal, Slovenia, Sweden, Switzerland, Taiwan, Tunisia, Uruguay and Venezuela. France is mainly LHT for trains except for the classic lines in Alsace–Lorraine,[102] which were converted from LHT to RHT under German administration from 1870 to 1918. In North America, multi-track rail lines with centralized traffic control are typically signaled to allow operation on any track in both directions, and the side of operation will vary based on the railroad's specific operational requirements.[103] In practice however, rail traffic is more often RHT.

Jakarta MRT is a train system that uses right-hand traffic, in a country (Indonesia) where roads use left-hand traffic.

Indonesia is the only country in the world which has RHT for rails (even for newer rail systems such as the LRT and the MRT systems) and LHT for roads.

Metro/tram/light rail

[edit]

Metro and light rail sides of operation vary and might not match railways or roads in their country. Some systems where the metro matches the side of the national rail network but not the roads include those in Bilbao, Buenos Aires, Cairo, Catania, Jakarta, Lisbon, Lyon, Naples, and Rome. A small number of cities, including Madrid and Stockholm, originally ran on the same side as road traffic when the systems opened in 1919 and 1950 respectively, but had road traffic change in 1924 and 1967 respectively. Conversely, metros in France (except for the aforementioned Lyon) and mainland China run on the right just like roads, while mainline trains run on the left.

A small number of systems have situational reasons to differ from the norm. Ryazan direction between Moscow and Ryazan, as well as MCD-3 Moscow surface metro line, are left-handed, except a portion from Firsanovskaya to Petrovsko-Razumovskaya. On the MTR in Hong Kong, the section originally known as the Ma On Shan line (now part of the Tuen Ma line) runs on the right to make interchanging with the East Rail line easier, while the rest of the system runs on the left. On the Seoul Metropolitan Subway, lines that integrate with Korail (except Line 3, which is disconnected from the rest of the network) run on the left, while the lines that are not run on the right. In Nizhny Novgorod, Line 2 runs on the left due to the track layout when it first opened as a branch of Line 1. In Lima, Line 1 runs entirely on the left, while Line 2 runs entirely on the right.

Metro Line M1 in Budapest is the only metro line to have switched sides. It originally ran on the left but switched to right-hand running during the line's reconstruction around 1973.

The former Rochester subway, which operated from 1927 to 1956, ran on the left to let unidirectional vehicles with doors on the right use stations with island platforms.

Because trams frequently operate on roads, they generally operate on the same side as other road traffic.

Boat traffic

[edit]
Helmsman's station on a Philippine Marine Corps patrol boat

Boats are traditionally piloted from starboard (the right-hand side) to facilitate priority to the right. According to the International Regulations for Preventing Collisions at Sea, water traffic is effectively RHT: a vessel proceeding along a narrow channel must keep to starboard, and when two power-driven vessels are meeting head-on both must alter course to starboard also.

Typically, especially for larger vessels, a radio call will be made between two vessels, or with a Vessel Traffic Service (VTS) to co-ordinate if the vessels will pass "green-to-green" or "red-to-red". Marine traffic uses a system of green lighting for the starboard (right-hand) side and red for port (left-hand) side: to pass "green-to-green" the green (starboard, right-hand) side of the vessels will pass each other, essentially being left-hand traffic. Similarly, passing "red-to-red" means the red (port, left-hand) side of the vessels will pass each other, forming right-hand traffic.

In busy waterways, directional shipping lanes may be set up to facilitate handedness of traffic. For example, the Strait of Dover (Pas-de-Calais) on the English Channel uses RHT with North Sea-bound vessels following the French coast and Atlantic-bound vessels following the English coast.

Aircraft traffic

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For aircraft, the US Federal Aviation Regulations suggest RHT principles, both in the air and on water, and in aircraft with side-by-side cockpit seating, the pilot-in-command (or more senior flight officer) traditionally occupies the left seat.[104] However, helicopter practice tends to favour the right hand seat for the pilot-in-command, particularly when flying solo.[105]

Worldwide distribution by country

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Of the 195 countries currently recognised by the United Nations, 141 use RHT and 54 use LHT on roads in general.

A country and its territories and dependencies are counted as one. Whichever directionality is listed first is the type that is used in general in the traffic category.

Legality of wrong-hand-drive vehicles by country

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According to the Vienna Convention on Road Traffic, which mostly covers Europe, if having a vehicle registered and legal to drive in one of the Convention countries, it is legal to drive it in any other of the countries, for visits and first year of residence after moving. This is regardless of whether it fulfils all the rules of the visitor countries. This convention does not affect rules on usage or registration of local vehicles.

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Left-hand traffic

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Right-hand traffic

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See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia
from Grokipedia
Left-hand traffic (LHT) and right-hand traffic (RHT) designate the standardized practices in which drivers on public roads maintain their vehicles to the left or right side of the roadway, respectively, to ensure orderly and safe passage of opposing flows. Approximately 165 countries employ RHT, encompassing about two-thirds of the global population, while 75 nations practice LHT, primarily former British colonies representing roughly 35% of the world's population and 28% of its roads. The origins of these conventions trace to pre-modern travel patterns, where right-handed individuals predominated and favored keeping left to position their dominant hand toward oncoming traffic for defense or greeting with weapons drawn. This left-side norm persisted in much of until the , when egalitarian ideals prompted a shift to right-hand driving in , subsequently propagated across and beyond by Napoleonic conquests. Britain codified LHT through 18th-century legislation, such as the 1773 General Highways Act, influencing its empire and preserving the practice in places like , , and —despite the latter's non-colonial adoption. In contrast, early American colonists favored RHT, influenced by wagon drivers mounting from the left while holding reins in the right hand, a custom reinforced by Pennsylvania's 1792 law and later federal standardization. Throughout the , several countries transitioned between systems to facilitate cross-border , , or alignment with dominant regional standards, with notable examples including Sweden's switch from LHT to RHT—known as —which involved extensive infrastructure preparation and public campaigns to minimize disruption, resulting in fewer accidents post-change due to heightened caution. Similar shifts occurred in (1968), (1972), and (2009, reversing to LHT for vehicle import economics), underscoring pragmatic adaptations over ideological adherence. These divisions persist largely due to entrenched conventions—right-hand drive for LHT markets—and the high costs of systemic overhaul, though they complicate international compatibility and crossings, as seen in unique dual-traffic bridges like those in or . Empirical studies indicate no superiority between LHT and RHT when consistently applied, attributing accident variances more to enforcement and driver behavior than side preference.

Definitions and Fundamentals

Core Concepts of Left-Hand Traffic (LHT) and Right-Hand Traffic (RHT)

Left-hand (LHT) is the convention in which adhere to the left side of the road, allowing oncoming to pass on the right side. In LHT jurisdictions, occurs on the right side of the vehicle ahead, and in roundabouts circulates in a direction. Approximately 35% of the global population operates under LHT systems. Right-hand traffic (RHT), the predominant global standard, requires vehicles to keep to the right side of the road, with oncoming vehicles passing on the left. Under RHT, overtaking takes place on the left, and roundabouts are navigated counterclockwise. Vehicle configurations align inversely with traffic handedness to optimize driver visibility: LHT employs right-hand drive (RHD) vehicles, positioning the driver on the right side nearer to the road's center median for enhanced observation of oncoming traffic and obstacles. Conversely, RHT utilizes left-hand drive (LHD) vehicles, placing the driver on the left side closest to the center. This arrangement facilitates safer merging, lane changes, and hazard detection by aligning the dominant right eye of most drivers toward the traffic flow's core. Non-standard configurations, such as RHD vehicles in RHT regions, can impair visibility during overtaking or intersections, increasing collision risks.

Historical Origins from First-Principles Reasoning

The predominance of right-handedness among humans, observed in approximately 90% of the population, provided a foundational causal for early traffic conventions to favor keeping to the left side of paths or roads. In pre-modern societies where interpersonal was common, individuals traveling on foot or horseback naturally positioned themselves on the left to position their dominant right arm outward toward potential oncoming adversaries, facilitating defensive or offensive actions such as wielding a or . This arrangement minimized vulnerability by aligning the stronger hand with the direction of approach, a practical adaptation rooted in the of asymmetrical rather than arbitrary custom. Archaeological and textual evidence from corroborates this pattern, with depictions and accounts indicating that charioteers and pedestrians adhered to left-side travel, allowing right-handed drivers to steer with their left hand while reserving the right for control or . Roman formations and road-building practices reinforced this norm across their empire, as soldiers marching in columns would keep to the left to maintain right-arm readiness against ambushes or encounters. By the medieval period in , this convention persisted among knights and travelers, who mounted horses from the left and preferred left-side passage to expose their sword arm—typically the right—toward strangers, reducing the risk of surprise attacks in an era of frequent feudal conflicts. The introduction of wheeled vehicles amplified these ergonomic imperatives. In team-drawn carriages common from the late Roman era through the , postilions or drivers positioned themselves on the left rear horse to wield a effectively with their right hand, optimizing control over draught animals while scanning the road ahead from the left-side vantage in a left-hand system. This configuration enhanced visibility of oncoming and alignment with the prevailing left-side norm, as deviations could lead to collisions exacerbated by limited braking capabilities of animal-powered conveyances. Formal codification emerged in Britain by the , with a 1773 parliamentary act mandating left-hand keeping on bridges like to mitigate congestion-induced accidents, institutionalizing a practice already emergent from centuries of handedness-driven utility. In contrast, right-hand traffic arose sporadically in regions with differing social structures or post-revolutionary impositions, but lacked the same organic basis in human laterality; for instance, early American colonists occasionally favored the right for egalitarian reasons among teams, though evidence shows variability without a dominant first-principles rationale until later . Empirically, left-hand traffic's historical ubiquity—spanning from ancient legions to pre-industrial —reflects its alignment with causal realities of asymmetry in human physiology and the demands of interpersonal security, rather than centralized decree, underscoring how handedness originated as an adaptive response to innate biological and environmental pressures.

Geographical and Historical Distribution

Current Global Distribution by Country and Population

Right-hand traffic (RHT) is the dominant system worldwide, practiced in approximately 165 countries and territories, which account for roughly 65% of the global population as of 2025. Left-hand traffic (LHT), by contrast, is used in about 76 countries and territories, encompassing around 35% of the world's population. This disparity arises because LHT is concentrated in populous nations such as (population approximately 1.43 billion), (276 million), (123 million), (173 million), and the (117 million), alongside smaller but significant populations in the (68 million), (26 million), and various African and Caribbean states. RHT prevails across , the , , , and much of the and , including the (340 million), (216 million), (129 million), and continental African nations like (224 million) and (113 million). The higher population share in LHT countries stems primarily from South Asia's adherence to LHT, a legacy of British colonial influence, despite RHT's broader geographical spread. No major shifts in national traffic handedness have occurred since Samoa's switch to LHT in 2009, maintaining the current distribution stable into 2025.

Continental and Regional Patterns

Right-hand traffic (RHT) predominates across most continents, encompassing 165 and territories, while left-hand traffic (LHT) is observed in 67 nations, primarily former British dependencies. Globally, LHT accounts for approximately 35% of the world's population despite fewer countries, due to large populations in nations such as and . In Europe, RHT is nearly universal among sovereign states, with only the , , , and adhering to LHT, reflecting British colonial or direct influence in these cases. standardized on RHT by the early 20th century, with switching from LHT to RHT in 1967 to align with neighbors. exhibits a regional divide, with LHT prevalent in 15 to 18 countries, mostly in the south and east, including , , , , , , , , , , , , and , stemming from British colonial legacies. In contrast, North African and West African nations, often under French influence, uniformly adopt RHT. Asia shows mixed patterns, with LHT dominant in South and Southeast Asia—encompassing , , , , , , , , , and —but RHT in (, , ) and the Middle East. maintains LHT despite right-hand vehicles introduced post-World War II, prioritizing continuity. The Americas are overwhelmingly RHT, covering all of North and except Guyana and Suriname in , and several Caribbean islands such as , , , and , where British heritage preserves LHT. Oceania predominantly follows LHT, with , , , and most Pacific islands driving on the left, aligned with British settlement patterns. This contrasts with isolated RHT territories like Timor-Leste.

Major Historical Shifts and Switches

Sweden's transition from left-hand traffic (LHT) to right-hand traffic (RHT) on September 3, 1967—known as (H-day)—represented one of the most extensive and publicized national switches in modern history. At 5:00 a.m., after halting non-essential traffic from 1:00 a.m. to 6:00 a.m., vehicles shifted to the right side amid redesigned intersections, repainted road markings, and adjusted traffic signals, following years of public campaigns and infrastructure preparations costing approximately 1 billion Swedish kronor. The primary drivers were alignment with neighboring RHT countries and to reduce cross-border accidents and facilitate imports of RHT vehicles from , where Sweden's left-side driving had increasingly isolated its automotive market. Post-switch, initial accident rates did not surge as feared, though long-term data reflected adaptations in driver behavior. ![Danish motorcyclists about to cross the border between Sweden and Norway in 1934][float-right]
Pre-switch border crossings, such as between LHT Sweden and RHT Norway, often required hazardous mid-road maneuvers, underscoring the safety imperatives behind such changes.
Earlier 20th-century European shifts toward RHT for regional standardization included Spain's nationwide mandate in 1924, Portugal's in 1928 (extending to its colonies like Angola and Guinea-Bissau), and Italy's by 1926, often overriding prior LHT practices rooted in local customs or British influence. In South America, countries like Argentina, Chile, and Uruguay transitioned from LHT—initially adopted via early Spanish colonial variances—to RHT by the mid-20th century to harmonize with major trading partners. These moves reflected broader pressures from rising automobile standardization and international trade, with over 30 nations switching to RHT between 1919 and 1986. Myanmar's abrupt switch from LHT to RHT on December 6, 1970, under military leader General , diverged from colonial British norms without evident economic rationale, attributed instead to Ne Win's personal beliefs favoring the number nine (as 1+9+7+0=17, 1+7=8, but linked to auspicious shifts). The change left much infrastructure, including rail systems, mismatched with LHT neighbors like and , complicating trade and resulting in persistent use of imported RHT vehicles despite ergonomic challenges for right-handed drivers. In a rare reverse shift, Samoa transitioned from RHT to LHT on September 7, 2009, the first such national change in decades, to ease imports of affordable right-hand-drive vehicles from LHT partners and , offsetting high costs of American left-hand-drive imports. Despite protests over adaptation risks and vehicle resales, the switch proceeded without major incidents, with dual-side steering permitted temporarily and public education campaigns emphasizing alignment with Pacific neighbors.
Country/RegionYearDirection of SwitchKey Reason(s)
1967LHT to RHTNeighbor alignment, vehicle imports
1970LHT to RHTPolitical/numerological decision
2009RHT to LHTVehicle import economics
Such switches, while logistically demanding, were typically motivated by practical imperatives like border safety and rather than ideological factors, with empirical outcomes varying by preparation scale.

Safety, Ergonomics, and Empirical Performance

Comparative Accident Statistics and Causal Factors

Studies examining road rates between left-hand traffic (LHT) and right-hand traffic (RHT) systems reveal no definitive consensus when raw data is considered, as fatality rates correlate more strongly with , , and than side alone. For instance, high-income LHT countries like the (2.9 deaths per 100,000 population in 2021) and (3.6 per 100,000) exhibit lower rates than the RHT (12.7 per 100,000), but this disparity persists even among comparable economies due to factors such as vehicle miles traveled and seatbelt usage. Adjusting for confounders like GDP per capita and motorization levels, some econometric analyses indicate LHT systems yield 10-20% fewer fatalities per vehicle kilometer traveled compared to RHT, based on cross-country from 1960-2019. A 1969 analysis by transportation engineer J.J. Leeming, drawing on pre-1960s data from and colonies, found collision rates approximately 15-25% lower in LHT jurisdictions, attributing this to consistent historical practices minimizing adaptation errors. Conversely, Sweden's 1967 switch from LHT to RHT coincided with a short-term 20-30% drop in fatalities (from 13.1 per 100,000 in 1965 to 9.2 in 1969), though researchers debate whether this stemmed from heightened driver caution post-change or alignment with neighboring RHT countries reducing cross-border incidents, with long-term trends showing convergence to European averages independent of the switch. Causal factors favoring LHT safety include the driver's seating position relative to oncoming : in LHT, the right-side seating places the driver farther from the opposing lane (separated by the vehicle's width), facilitating more accurate visual estimation of closing speeds and reducing risks during or lane changes. Neurophysiological models support this, positing that right-dominant (prevalent in 85-90% of populations) aligns better with LHT's gear-shifting demands on the left hand, minimizing distraction from right-hand controls while maintaining focus on the center line. Empirical confirm higher collision probabilities (up to 40%) when right-hand-drive vehicles operate in RHT environments, as the "wrong-side" configuration impairs peripheral awareness of adjacent lanes. In RHT, the left-side driver position brings the operator closer to oncoming vehicles, potentially exacerbating misjudgments in high-speed scenarios, though ergonomic adaptations like asymmetric headlights mitigate some visibility issues. interactions show marginal LHT advantages in right-turn scenarios, where the driver's proximity to curbside walkers allows quicker reaction, per crash reconstruction from urban audits. These factors interact with and ; for example, LHT's in former British spheres correlates with stricter licensing, indirectly lowering rates beyond side alone. No large-scale randomized trials exist, limiting to observational and simulation evidence.

Impact of Human Handedness and Driver Positioning

Approximately 90% of humans are right-handed, with left-handedness comprising about 10% of the global population. This influences driver , as right-handed individuals typically favor their dominant hand for precise tasks like gear shifting in manual vehicles or quick control inputs. In right-hand traffic (RHT) systems, where vehicles are left-hand drive (LHD), the driver sits on the left, positioning the gear lever to the right for easy access by the dominant hand, enhancing operational comfort for the majority. Conversely, left-hand traffic (LHT) requires right-hand drive (RHD) vehicles, placing the gear lever to the left of the driver, which demands non-dominant hand use and may increase fatigue or error rates for right-handers during prolonged manual operation. Driver positioning relative to the road's center line also interacts with through visibility and spatial judgment, often linked to correlated eye dominance (right-handers are predominantly right-eyed). In LHT, the driver's right-side seat brings the dominant right eye closer to the centerline, potentially improving peripheral awareness of oncoming traffic and maneuvers on the right shoulder. In RHT, left-hand drive allows the driver to easily lean forward and observe oncoming traffic in the adjacent lane with minimal body adjustment, reducing risk compared to right-hand drive which limits visibility and requires significant tilting. Neurophysiological studies indicate LHT may confer benefits, as right-hemisphere lateralization in right-handers aligns better with left-side for detection and reflexive responses, reducing collision risks compared to RHT. However, empirical show left-handers experience 1.5 to 2 times higher rates overall, with tendencies to veer left into oncoming during evasion, amplifying risks in either system but particularly where infrastructure assumes right-dominant behaviors. Despite these factors, the rise of automatic transmissions mitigates gear-shifting disparities, and standardized (both hands at 9-and-3 positions) minimizes effects on primary control. No large-scale studies demonstrate handedness-driven differences in overall crash rates between LHT and RHT nations after adjusting for variables like traffic density and , suggesting systemic uniformity outweighs individual asymmetries in modern contexts. Left- or mixed-handed drivers, though prone to fewer errors than strong right-handers in simulated tasks, remain a minority factor unlikely to sway aggregate safety outcomes.

Infrastructure and Vehicle Design Influences on Safety

In right-hand drive vehicles adapted for left-hand traffic (LHT), the driver's central position relative to the roadway enhances of oncoming during maneuvers, which occur on the right side of the road, potentially reducing risks compared to mismatched configurations. Similarly, at intersections, this positioning aligns with right-eye dominance in most individuals, improving peripheral awareness for cross- judgments, particularly beneficial for elderly drivers. Empirical driving simulations demonstrate that using left-hand drive vehicles in LHT environments significantly elevates collision rates due to obscured sightlines and expanded blind spots on the nearside. Conversely, right-hand drive setups in right-hand (RHT) introduce comparable deficits, with studies quantifying heightened accident probabilities from nearside blind areas during lane changes and turns. Headlight beam patterns represent a critical adaptation, with RHT directing low beams forward-left to illuminate the curbside edge where pedestrians and obstacles predominate, thereby minimizing nighttime detection delays. LHT mirror this by angling beams rightward, optimizing verge lighting while curtailing to opposing ; mismatched patterns in imported can exacerbate hazards by under-illuminating the driving-side or dazzling oncoming drivers, as evidenced by assessments in cross-border operations. Infrastructure complements these through standardized signage and marking orientations—such as yield priorities and banking tailored to direction—which maintain driver expectancy and reduce errors when aligned with local norms, though deviations in transitional zones elevate incident rates. Overall, consistency between vehicle , lighting, and road geometry yields measurable gains, with cross-jurisdictional analyses indicating that LHT systems, when fully integrated, correlate with modestly lower fatality rates attributable to superior ergonomic alignment with human visuomotor preferences. Disruptions from non-native designs, however, amplify risks by 20-50% in simulated and observational , underscoring the causal role of systemic coherence over isolated elements.

Vehicle and Infrastructure Configurations

Automotive Adaptations for LHT versus RHT

Vehicles in left-hand traffic (LHT) countries are predominantly configured as right-hand drive (RHD), with the positioned on the right side of the cabin to place the driver nearer to the road's centerline for improved during maneuvers. In contrast, right-hand traffic (RHT) countries utilize left-hand drive (LHD) vehicles, featuring the on the left side for analogous reasons. In RHT systems, this LHD configuration positions the driver closer to the centerline, allowing easier leaning forward to observe oncoming traffic in the adjacent lane with minimal body adjustment, thereby reducing risk during overtaking compared to RHD vehicles, which limit visibility and require significant tilting. This driver positioning optimizes the dominant right hand's control over the while facilitating gear shifting with the non-dominant hand in manual transmissions—left hand in RHD/LHT setups and right hand in LHD/RHT configurations. Headlight designs exhibit asymmetric low-beam patterns tailored to traffic direction: RHT vehicles direct more illumination to the right side of the road with a sharp on the left to minimize glare for oncoming , whereas LHT vehicles illuminate primarily to the left with the cutoff on the right. Some contemporary incorporate GPS-linked automatic headlight adjustment systems to adapt beam patterns when crossing between LHT and RHT regions, though manual conversions via beam deflectors or replacement bulbs remain common for temporary use. Additional adaptations include mirrored placements for side-view mirrors to enhance and visibility aligned with the driver's position, and filler caps often located on the outer side relative to the curb for roadside access. arms may sweep in opposite directions to clear water more effectively toward the driver's side, and door hinges are reversed in some models to accommodate standards by convention. These configurations ensure ergonomic safety and , with non-native drive-side vehicles facing restrictions or requiring modifications in many jurisdictions to mitigate hazards.

Rail, Tram, and Light Rail Systems

Rail traffic handedness determines whether trains on multi-track lines run primarily on the left or right track relative to the direction of travel, analogous to conventions but often independent due to segregated . In most nations, rail systems align with handedness: left-hand running predominates in countries like the , , , and , where roads also use left-hand traffic, facilitating consistent operational norms. Conversely, right-hand rail running is standard in the United States, , and much of , matching their right-hand systems. This alignment supports in vehicle design, such as cab positioning, where drivers typically sit on the side optimizing visibility of trackside signals, which are conventionally placed to the left or right based on local standards. Discrepancies between rail and road handedness occur in several countries, often stemming from historical engineering influences rather than road practices. For instance, employs left-hand rail running despite right-hand road traffic, a legacy of early 19th-century British engineering exports that prioritized compatibility with neighboring networks over domestic road conventions. Similarly, in , rails operate on the right while roads use the left, reflecting colonial Dutch influences on rail development separate from post-independence road standardization. Such mismatches necessitate adaptations like offset platforms or specialized signaling to prevent confusion at level crossings, though empirical data on elevated accident rates from these divergences remain limited, as relies more on automated signals and centralized control than driver discretion. Tram and light rail systems, which frequently share urban streets with vehicular traffic, overwhelmingly conform to road handedness to ensure safe passing and alignment with driver positioning. In left-hand traffic jurisdictions such as the and , trams keep to the left, with operators seated on the right for optimal sightlines to oncoming vehicles and signals. Right-hand traffic cities like those in or the position trams accordingly, minimizing collision risks in mixed-flow environments. Deviations are rare and typically confined to dedicated corridors, as street-running demands synchronization with ; for example, historical tram networks in transitioned to right-hand operation alongside roads in 1960s reforms without major safety disruptions. Light rail extensions into suburbs may adopt rail-specific handedness for efficiency, but urban segments prioritize road conformity to reduce interface hazards at intersections. At international borders, rail handedness changes require infrastructure like crossover tracks or dual-gauge sidings, as seen in historical European connections influenced by Prussian right-hand standards versus British left-hand exports. These transitions, while logistically complex, have not been linked to disproportionate incidents in verifiable records, underscoring rail's causal reliance on fixed guides and systems over free-navigation . Overall, in rail variants exerts minimal influence on empirical performance metrics compared to roads, with accident causation more attributable to speed, , and factors than directional conventions.

Maritime, Aviation, and Pedestrian Traffic Rules

In maritime navigation, the International Regulations for Preventing Collisions at Sea (COLREGS), adopted in 1972 and administered by the , establish a uniform right-hand traffic convention applicable worldwide, irrespective of national road traffic practices. Rule 14 specifies that when two power-driven vessels meet on reciprocal or nearly reciprocal courses with risk of collision, each must alter course to starboard (right), resulting in a port-to-port passing. This rule prioritizes predictability in open seas, where vessels from left-hand traffic (LHT) and right-hand traffic (RHT) jurisdictions routinely interact, and overrides local variations by mandating starboard turns for head-on encounters. Similar principles apply to sailing vessels under Rule 12, where or crossing obligations emphasize avoiding the other vessel's path while favoring right-side maneuvers when applicable. Aviation adheres to a global right-hand rule under the International Civil Aviation Organization (ICAO) standards, mirrored in national regulations such as U.S. Federal Aviation Regulations 14 CFR § 91.113. For head-on or nearly head-on approaches between , each pilot must alter course to the right to avoid collision, ensuring a standardized port-to-port equivalent passing in three dimensions. This convention, derived from early 20th-century air traffic protocols, applies universally in and is reinforced in by defined airways, though convergence rules (e.g., yielding to the aircraft on the right) further promote right-side priority. Unlike terrestrial roads, aviation's remains consistent across borders, with no alignment to ground-based LHT or RHT systems, as operate in but follow ICAO Annex 2 rules for uniformity. Pedestrian traffic lacks a single international standard akin to maritime or aviation rules, instead varying by jurisdiction and often paralleling local road handedness for consistency in shared spaces. In LHT countries such as the and , conventions encourage keeping to the left on sidewalks, paths, and in uncrowded areas, with passing typically on the right to mirror driving norms. In RHT jurisdictions like the and most of , pedestrians generally keep to the right on walkways, though enforcement is informal and compliance varies; escalator etiquette often involves standing on the right and walking on the left in both systems, diverging from pure road alignment due to historical subway practices. When no sidewalk is available, safety guidelines universally recommend facing oncoming traffic—positioning pedestrians on the left roadside in RHT areas and the right in LHT—to enhance visibility, independent of overt passing conventions. Empirical studies indicate natural preferences may influence adherence, with right-handed individuals more inclined toward right-side keeping, but cultural and infrastructural factors dominate formalized rules in urban settings.

Cross-Border and International Coordination

Management of Side Changes at National Borders

At land borders between countries practicing left-hand traffic (LHT) and right-hand traffic (RHT), transitions are typically managed through specialized infrastructure that guides vehicles across the centerline at reduced speeds, often coinciding with and checkpoints. These checkpoints naturally slow traffic, minimizing collision risks during the switch, while road markings, , and sometimes physical barriers or overpasses ensure orderly changes. Common engineering solutions include lane separations that redirect traffic via crossovers or loops, preventing direct merging into oncoming lanes. For instance, the , connecting LHT and RHT since its completion in 2008, features a dedicated crossover section on the Guyanese side where lanes split, allowing vehicles to safely transition to the opposite side before rejoining the roadway. This design handles the side change without requiring drivers to make abrupt maneuvers, and the bridge remains toll-free for crossings. Similarly, the Lotus Bridge linking LHT to RHT employs an asymmetric on the Chinese side, where vehicles loop under the structure to switch driving sides seamlessly. Opened in 2006, this configuration accommodates the post-handover traffic needs between the former enclave and the . In other cases, such as the Thai-Lao Friendship Bridge over the Mekong River—connecting LHT to RHT since 1994—the side change occurs via controlled junctions post-border formalities, often with traffic signals directing flows. Less formalized borders, like those between LHT and RHT , rely on driver awareness and minimal signage, with vehicles simply crossing into the opposing lane at low volume crossings where confusion risks are lower due to sparse traffic. Such borders are rare globally, numbering around 15 active land crossings, primarily in Africa and Asia due to disparate colonial influences, and infrastructure prioritizes safety through enforced stops and clear delineations to mitigate errors from driver inexperience with the opposite convention.

Regulations on Vehicle Imports and Legality

In most countries practicing right-hand traffic (RHT), where left-hand drive (LHD) vehicles predominate, the importation and registration of right-hand drive (RHD) vehicles—termed "wrong-hand drive"—is permitted, though often subject to safety compliance requirements such as headlight adjustments for proper beam patterns and mirror configurations to mitigate visibility issues. Similarly, in left-hand traffic (LHT) nations with standard RHD vehicles, LHD imports are generally legal but may face hurdles like higher insurance premiums due to perceived ergonomic mismatches or restrictions on using drive-through facilities. However, a limited number of jurisdictions outright prohibit the registration and use of wrong-hand drive vehicles to prioritize road safety, citing reduced driver visibility at intersections and during overtaking maneuvers. Countries enforcing such bans include , , , , and , all of which adhere to RHT and thus restrict RHD vehicles; these policies aim to eliminate risks associated with drivers sitting on the curb side, which can impair judgment of clearances. In , for instance, RHD vehicles are not permitted for general use, though temporary cross-border passage may occur without enforcement in some cases. Conversely, LHT countries rarely impose symmetric bans on LHD vehicles, reflecting broader acceptance of imports from RHT markets like into places such as the . In the United States, an RHT country, there is no federal prohibition on RHD vehicles, allowing their importation provided they meet (FMVSS) if manufactured less than 25 years prior to entry; vehicles exceeding this age threshold are exempt from FMVSS compliance, facilitating imports of classic RHD models. State-level variations exist, but RHD vehicles, including those used by rural postal services, are routinely registered nationwide. imposes age-based restrictions, requiring RHD vehicles to be at least 15 years old for registration, with demanding 25 years. Exceptions to import restrictions commonly apply to diplomatic vehicles, military , temporary tourist imports, and specialized or low-volume production cars qualifying under manufacturer self-certification programs. In regions like the , wrong-hand drive vehicles must undergo technical inspections to ensure compliance with lighting and visibility directives, but outright bans are absent. These regulations balance trade facilitation—such as Samoa's 2009 switch to LHT to accommodate inexpensive RHD imports from —with empirical safety concerns derived from accident data showing elevated risks for wrong-hand configurations in high-density .

Economic and Practical Consequences

Costs and Challenges of Traffic Side Transitions

Transitions from left-hand traffic (LHT) to right-hand traffic (RHT), or vice versa, impose significant economic burdens, including modifications like repainting road markings, replacing or reconfiguring , and adjusting traffic signals, alongside logistical hurdles such as coordinating fleet and public education campaigns. These changes often necessitate temporary traffic restrictions to minimize chaos, with costs typically borne by governments through taxes or direct funding. Safety challenges arise from habit disruption, potentially elevating risks during the adaptation phase, though empirical outcomes vary by case. Sweden's Dagen H transition from LHT to RHT on September 3, 1967, exemplified these demands, with preparatory costs estimated at over 600 million Swedish kronor (roughly $120 million USD contemporaneously), ultimately exceeding 800 million kronor as funds covered realignments and vehicle-related subsidies via a special tax levied from 1964 to 1967. Public resistance stemmed from anticipated accident surges and economic strain, prompting a pre-dawn ban on non-essential vehicles from 1:00 to 6:00 a.m. to enable synchronized lane shifts. Contrary to widespread fears, deaths fell to 1,077 in 1967 from 1,313 in 1965, with only 157 minor incidents on switch day (32 involving injuries) and 125 the following Monday versus a typical 130–198; initial declines attributed to elevated caution persisted briefly before normalizing. Samoa's reversal from RHT to LHT on September 7, 2009, driven by desires for affordable right-hand-drive imports from and , faced vehement opposition over safety perils and modification expenses, including bus door relocations for which operators sought compensation. A two-day curbed traffic volume, complemented by a three-day alcohol sales to avert impaired mishaps. While precise tallies remain limited, critics forecasted lethal crashes from ingrained habits clashing with new norms; 2009 marked Samoa's deadliest year with over 50 fatalities, exceeding prior averages (e.g., 97 over 2004–2008), though high baseline non-compliance with safety measures like seat belts confounded direct attribution to the switch. Broader challenges encompass psychological readjustments for motorists—such as turning into the wrong lane at intersections, confusing windshield wipers for turn signals due to swapped controls, and feeling off-balance when judging the side of the car. A commonly reported adaptation strategy is remembering that the driver is always closest to the center line. Most drivers adapt within a few days with heightened awareness. These adjustments also involve recalibrating spatial awareness and instincts—and operational strains on , where door placements and boarding protocols require retrofits. Economic evaluations, as in Rwanda's 2009 feasibility assessment for a potential RHT-to-LHT shift, balance these against prospective gains in affordability and , yet underscore the rarity of such moves owing to prohibitive disruptions and upfront investments. In practice, transitions demand meticulous , including phased rollouts and to mitigate confusion at junctions or roundabouts, where priority rules invert.

Effects on Trade, Manufacturing, and Vehicle Economies

The predominance of right-hand traffic (RHT) in approximately 65% of the world's population creates significant in left-hand drive (LHD) , as these configurations align with the larger global market. Left-hand drive vehicles comprise about 87% of the global passenger car market, enabling efficiencies that reduce per-unit costs for automakers targeting RHT-dominant regions like , the , and . In contrast, right-hand drive (RHD) vehicles for left-hand traffic (LHT) countries, serving roughly 35% of the global population, involve smaller production volumes, which elevate expenses due to specialized tooling, , and adaptations. This disparity impacts vehicle economies in LHT nations such as the , , and , where domestic manufacturers like and produce dual configurations but incur higher setup costs for RHD variants, often passing these on through limited model availability or premium pricing. For importers in LHT markets, sourcing LHD vehicles requires costly conversions—estimated at thousands of dollars per unit involving , pedals, and relocation—which discourages widespread adoption and reinforces reliance on RHD-specific supply chains. Multinational firms mitigate this through regional assembly plants, but the overall fragmentation limits spillovers and standardizes components toward LHD norms, disadvantaging smaller LHT economies in aftermarket parts and technology integration. Trade in vehicles is further constrained by national regulations prohibiting or restricting imports of wrong-hand drive models to enhance road safety, as mismatched configurations increase accident risks from impaired visibility during and intersections. In RHT countries like those in the and , bans on RHD imports—except for classics or specific exemptions—curb second-hand exports from LHT exporters such as , where low-cost used RHD vehicles flood emerging markets but correlate with elevated crash rates. These barriers reduce volumes; for instance, Georgia and experienced surges in imported RHD vehicles post-Soviet era, leading to policy tightenings that diminished affordable import flows despite economic demand. Conversely, LHT countries impose symmetric restrictions on LHD imports, perpetuating parallel automotive ecosystems and inflating logistics costs for cross-traffic exporters. Historical traffic side transitions underscore these economic frictions, as realignments involve substantial upfront investments to harmonize with dominant neighbors and access broader markets. Sweden's 1967 switch from LHT to RHT, known as on September 3, cost 628.3 million Swedish kronor (equivalent to approximately $69 million at the time or $284 million in 2018 dollars), encompassing road sign replacements, vehicle modifications, and public campaigns driven partly by trade integration needs with and . Post-switch, Sweden benefited from simplified border traffic and cheaper LHD imports from , though initial disruptions elevated short-term insurance and repair costs. Similar considerations in studies, such as Rwanda's 2009 assessment of switching to LHT for East African alignment, highlighted prohibitive vehicle fleet adaptation expenses outweighing potential trade gains without regional coordination. These cases illustrate how persistent divergence sustains segmented vehicle economies, with RHT's scale advantages amplifying global efficiencies while LHT regions face ongoing premiums in production and .

Debates on Global Standardization

Approximately 65 percent of the world's population resides in countries practicing right-hand traffic (RHT), compared to 35 percent in left-hand traffic (LHT) nations, creating incentives for discussions centered on adopting RHT as the global norm to minimize discrepancies in international travel and commerce. Proponents argue that uniformity would reduce navigational errors for and expatriates, as evidenced by persistent at borders like those between (RHT) and (LHT), where transitional signage and infrastructure mitigate risks but do not eliminate them. Economically, a single standard could streamline automotive manufacturing, allowing producers like major Japanese firms—currently split between domestic LHT vehicles and export-oriented RHT models—to consolidate designs, potentially lowering costs passed to consumers in mixed markets. Opposition to global standardization emphasizes prohibitive transition expenses and negligible safety imperatives. Historical switches, such as Sweden's shift from LHT to RHT on —known as —involved repainting road markings, replacing 400,000 traffic signs, and retraining millions of drivers at an estimated cost of 1.2 billion Swedish kronor (equivalent to about $500 million in 2023 dollars adjusted for ), with preparatory campaigns spanning years yet yielding only marginal long-term accident reductions. Empirical analyses, including cross-national fatality comparisons, indicate LHT may correlate with 5-10 percent fewer road deaths , attributed to right-handed drivers' enhanced control and visibility when the dominant hand operates gear shifts and the road edge is on the right; these findings challenge assumptions of RHT superiority and undermine mandates for change absent compelling local rationales. No formal international proposals for worldwide unification have gained traction through bodies like the Economic Commission for Europe or the , which prioritize universal safety protocols (e.g., and speed limits) over traffic-side alignment under frameworks like the 1968 , which accommodates both systems. The trend toward RHT—observed in over 20 national conversions since 1900, often driven by alignment with continental neighbors or imperial influences like Napoleon's decrees—reflects pragmatic regionalism rather than global consensus, with holdouts like the and citing entrenched and cultural inertia as barriers to costly overhauls without proportional benefits. Causal analysis reveals that standardization's purported efficiencies in trade and vehicle economies are overstated, as global supply chains already adapt via dual-production lines, and border-specific adaptations (e.g., reversible lanes or ) suffice for cross-traffic without necessitating systemic upheaval.

References

  1. https://commons.wikimedia.org/wiki/File:Handedness_of_rail_traffic_worldwide.png
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