Left- and right-hand traffic

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 a "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, Hong Kong, Macau 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, and Mozambique 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.

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]

LHT roundabout

RHT roundabout

Roundabout signs used in Southern African Development Community

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 and Zimbabwe), Eswatini, the Cape Colony (part of 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 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, 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).

A finales del siglo XVIII, el tráfico por la derecha comenzó a introducirse en los Estados Unidos debido al uso por parte de los carreteros de grandes carros de carga tirados por varias parejas de caballos y sin asiento de conductor; el postillón (típicamente diestro) sostenía su látigo en su mano derecha y, por lo tanto, se sentaba en el caballo trasero izquierdo, y por consiguiente prefería que otros carros pasaran por la izquierda para tener una visión clara de los demás vehículos. ^{[ 9 ]} La primera ley de circulación por la derecha en los Estados Unidos se aprobó en 1792 y se aplicó a la autopista de peaje de Filadelfia y Lancaster . ^{[ 10 ]} Massachusetts formalizó la circulación por la derecha en 1821. ^{[ 11 ]} Sin embargo, la Carretera Nacional fue de circulación por la izquierda hasta 1850, "mucho después de que el resto del país se hubiera establecido en la convención de circulación por la derecha". ^{[ 12 ]} Hoy en día, los Estados Unidos son de circulación por la derecha, excepto las Islas Vírgenes de los Estados Unidos , ^{[ 13 ]} que son de circulación por la izquierda como muchas islas vecinas.

En Estados Unidos, algunos vehículos especiales, como ciertos camiones del servicio postal, camiones de basura y vehículos de control de estacionamiento, están diseñados con el asiento del conductor a la derecha para facilitar y hacer más seguro el acceso a la acera. Un ejemplo común es el Grumman LLV , utilizado en todo el país por el Servicio Postal de Estados Unidos y por Canada Post .

En Canadá, las provincias de Quebec y Ontario siempre fueron de tipo RHT porque se crearon a partir de la antigua colonia francesa de Nueva Francia . ^{[ 14 ]} La provincia de Columbia Británica cambió a RHT por etapas de 1920 a 1923, ^{[ 15 ] [ 16 ]} Nuevo Brunswick , Nueva Escocia y la Isla del Príncipe Eduardo en 1922, 1923 y 1924 respectivamente, ^{[ 17 ]} y el Dominio de Terranova (parte de Canadá desde 1949) ^{[ 18 ]} en 1947. ^{[ 19 ]}

En las Indias Occidentales , las colonias y territorios conducen por el mismo lado que sus países de origen, excepto las Islas Vírgenes de los Estados Unidos . Muchas de las naciones insulares son antiguas colonias británicas y conducen por la izquierda, incluidas Jamaica , Antigua y Barbuda , Barbados , Dominica , Granada , San Cristóbal y Nieves , Santa Lucía , San Vicente y las Granadinas , Trinidad y Tobago y Las Bahamas . Sin embargo, la mayoría de los vehículos en Las Bahamas, ^{[ 20 ]} Islas Caimán , ^{[ 21 ]} Islas Turcas y Caicos ^{[ 22 ]} y tanto las Islas Vírgenes Británicas , ^{[ 23 ]} como las Islas Vírgenes de los Estados Unidos tienen el volante a la izquierda debido a que fueron importados de los Estados Unidos. ^{[ 23 ]}

Brasil , colonia portuguesa hasta principios del siglo XIX, tuvo durante el siglo XIX y principios del XX reglas mixtas, con algunas regiones aún bajo el sistema de mano izquierda (LHT), cambiando estas regiones restantes al sistema de mano derecha (RHT) en 1928, el mismo año en que Portugal cambió de bando. ^{[ 24 ]} Otros países de Centroamérica y Sudamérica que posteriormente cambiaron del sistema de mano izquierda al sistema de mano derecha incluyen Argentina, ^{[ 25 ]} Panamá, ^{[ 26 ]} Paraguay, ^{[ 27 ]} y Uruguay. ^{[ 28 ]}

Surinam y su vecino Guyana son los únicos dos países LHT que quedan en Sudamérica . ^{[ 29 ]}

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 IIOkinawa 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]

En un estudio del antiguo sistema de tráfico de Pompeya , Eric Poehler pudo demostrar que los conductores de carros circulaban por el centro de la calzada siempre que era posible. Esto ocurría incluso en calzadas lo suficientemente anchas para dos carriles. ^{[ 45 ] : 136} Sin embargo, las marcas de desgaste en los bordillos demuestran que, cuando había dos carriles de circulación y el volumen de tráfico hacía necesario dividirlos, los conductores siempre circulaban por la derecha. ^{[ 45 ] : 150–155} Estas consideraciones también pueden demostrarse en los hallazgos arqueológicos de otras ciudades del Imperio Romano . ^{[ 45 ] : 218–219}

Una de las primeras referencias en Inglaterra a la necesidad de dirigir el tráfico fue una orden del Tribunal de Aldermen de Londres en 1669, que exigía que se colocara a un hombre en el Puente de Londres para asegurar que "todos los carros que iban se mantuvieran en un lado y todos los carros que venían se mantuvieran en el otro lado". ^{[ 46 ]} Posteriormente se legisló como la Ley del Puente de Londres de 1756 ( 29 Geo. 2 c. 40), que exigía que "todos los carruajes que pasaran por dicho puente desde Londres debían ir por el lado este del mismo"; los que iban hacia el sur debían permanecer en el este, es decir, en el lado izquierdo según la dirección del viaje. ^{[ 47 ]} Esto puede representar el primer requisito legal para el LHT. ^{[ 48 ]}

En el Reino de Irlanda , una ley de 1793 (33 Geo. 3. c. 56 (I)) establecía una multa de diez chelines para cualquiera que no condujera o viajara por el lado izquierdo de la carretera dentro del condado de la ciudad de Dublín , y exigía a los supervisores de carreteras locales que colocaran avisos escritos o impresos informando a los usuarios de la carretera sobre la ley. ^{[ 49 ]} La Ley de Carreteras en Down y Antrim de 1798 (38 Geo. 3. c. 28 (I)) exigía a los conductores en la carretera de Dublín a Donadea que se mantuvieran a la izquierda. En este caso, el castigo era de diez chelines si el infractor no era el propietario del vehículo, o de una libra irlandesa (veinte chelines) si lo era. ^{[ 50 ]} La Ley de Grandes Jurados (Irlanda) de 1836 ( 6 & 7 Will. 4 c. 116 ) estableció el LHT para todo el país, y los infractores serían multados con hasta cinco chelines y encarcelados en caso de impago hasta por un mes. ^{[ 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]

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).

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.

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, 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]

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 harmonizing 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] Rwanda launched a study on switching to LHT, but has decided to stay RHT due to the high costs of switching infrastructure to LHT.

There is no country with a conformed proposal or date where that country will switch the side of the road that they drive on.

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.

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.

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]

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.

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,^{[97]: 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.^{[97]: 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.^{[97]: 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.

In Europe since the early 1980s,^[98] 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.^[99]

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.^[100]

En la mayoría de los países, el tráfico ferroviario circula por el mismo lado que el tráfico rodado. Sin embargo, existen numerosos casos de ferrocarriles construidos con tecnología británica de doble sentido (LHT), que mantuvieron la circulación por ambos lados a pesar de que el tráfico rodado de sus países pasó a circular por la derecha (RHT). La razón principal es que el cambio de sentido del tráfico ferroviario es más difícil y costoso que el cambio de sentido de las carreteras. Algunos ejemplos son: Argentina, Bélgica, Bolivia, Brasil, Camboya, China, Egipto, Francia, Irak, Israel, Italia, Laos, Mónaco, Marruecos , Myanmar , Nigeria , Perú , Portugal , Senegal , Eslovenia , Suecia , Suiza , Taiwán , Túnez , Uruguay y Venezuela . En Norteamérica , las líneas ferroviarias de múltiples vías con control de tráfico centralizado suelen estar señalizadas para permitir la circulación en cualquier vía en ambas direcciones, y el lado de circulación varía según los requisitos operativos específicos del ferrocarril. ^{[ 101 ]}

Handedness of rail traffic in a country may differ due to historical or other reasons. For example, in Spain the broad-gauge lines that belong to the historic Compañía de los Caminos de Hierro del Norte de España , like León–A Coruña route and several branches run on the left, while the rest of the lines run on the right. Sweden, which had LHT till 1967, did not switch the direction of its trains, but the line from the north of Malmö, which leads to the border with Denmark and further south uses RHT. Russian railways are RHT, but a small number of routes like Moscow – Ryazan line run on the left. 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 Austria, the Semmering Railway, which had LHT on the line, was converted to the RHT, except the Bruck an der Mur – Graz section. Switzerland has LHT for the trains, except for the German border areas. In Finland, several lines of Helsinki commuter rail, like the line to Helsinki Airport uses LHT, while the metro and the rest of lines uses RHT. Slovenia is LHT for trains but Zidani Most – Dobova runs on the right because of the connection with RHT Croatia.

Philippines railways are one of the few instances nowadays that had switched sides. It originally ran one the left until 2010, but switched to the RHT to confront the roads in the country, which also are RHT.

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.

El sentido de circulación del metro y del tren ligero varía y puede no coincidir con el de las vías férreas o carreteras de cada país. Algunos sistemas donde el metro coincide con el sentido de la red ferroviaria nacional, pero no con el de las carreteras, incluyen los de Bilbao , Buenos Aires , El Cairo (excepto el monorraíl ), Catania , Yakarta , Lisboa , Lyon , Nápoles y Roma . Un pequeño número de ciudades, como Madrid y Estocolmo , originalmente circulaban por el mismo lado que el tráfico rodado cuando se inauguraron los sistemas en 1919 y 1950 respectivamente, pero el tráfico rodado cambió de sentido en 1924 y 1967 respectivamente. Por el contrario, los metros de Brasil (excepto en Belo Horizonte y Porto Alegre ), Francia (excepto la mencionada Lyon), Corea del Sur y China continental circulan por la derecha, al igual que las carreteras, mientras que los trenes de larga distancia circulan por la izquierda.

Un pequeño número de sistemas tienen razones situacionales para diferir de la norma. La línea D-3 de los Diámetros Centrales de Moscú utiliza el tráfico por la izquierda como parte de la dirección Ryazan mencionada anteriormente entre Moscú y Ryazan, excepto un tramo de Firsanovskaya a Petrovsko-Razumovskaya. En el MTR de Hong Kong, la sección originalmente conocida como la línea Ma On Shan (ahora parte de la línea Tuen Ma) corre por la derecha para facilitar el intercambio con la línea East Rail, mientras que el resto del sistema corre por la izquierda. En el Metro Metropolitano de Seúl , las líneas que se integran con Korail (excepto la Línea 3, que está desconectada del resto de la red) corren por la izquierda, mientras que las líneas que no lo están (excepto la Línea Shinbundang ) corren por la derecha. En Nizhny Novgorod , la Línea 2 corre por la izquierda debido al trazado de las vías cuando se inauguró como ramal de la Línea 1. En Lima , la Línea 1 corre completamente por la izquierda, mientras que la Línea 2 corre completamente por la derecha. En Barcelona , ​​un tramo de la Línea 2, desde Tetuán hasta Paral•lel, circula por la izquierda, mientras que el resto del sistema circula por la derecha.

La línea M1 del metro de Budapest es la única que ha cambiado de sentido de la circulación. Originalmente circulaba por la izquierda, pero pasó a circular por la derecha durante la reconstrucción de la línea alrededor de 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^[103]. The same situation with the undeground parts of first phases of Volgograd and Kryvyi Rih Metrotrams, they both use LHT on those parts.

Because trams frequently operate on roads, they generally operate on the same side as other road traffic, but there are some exceptions. Apart from the abovementioned Volgograd and Krivyi Rih, they are for example, the part of Gothenburg tram from Hjallbo to Angered and Alvik — Alléparken section of Nockebybanan and some parts of Lidingöbanan of Stockholm tram network, which use LHT while the rest of the systems run on the right.

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.

Para aeronaves, las Regulaciones Federales de Aviación de EE. UU . sugieren principios de RHT, tanto en el aire como en el agua, y en aeronaves con cabinas contiguas, el piloto al mando (o el oficial de vuelo de mayor rango) tradicionalmente ocupa el asiento izquierdo. ^{[ 104 ]} Sin embargo, en la práctica de helicópteros se tiende a favorecer el asiento derecho para el piloto al mando, particularmente cuando vuela solo. ^{[ 105 ]}

De los 195 países reconocidos actualmente por las Naciones Unidas , 141 utilizan la circulación por la derecha (RHT) y 54 utilizan la circulación por la izquierda (LHT) en las carreteras en general.

Un país, sus territorios y dependencias se consideran como una sola entidad. La direccionalidad que aparece primero es la que se utiliza generalmente en la categoría de tráfico.

Según el Convenio de Viena sobre Circulación Vial , que abarca principalmente Europa, si un vehículo está matriculado y tiene permiso de circulación en uno de los países signatarios del Convenio, es legal conducirlo en cualquier otro país, tanto para visitas como durante el primer año de residencia tras la mudanza. Esto se aplica independientemente de si el vehículo cumple con todas las normas del país de destino. Este Convenio no afecta a las normas sobre el uso o la matriculación de vehículos locales.

• Gancho de giro
• Señalización y funcionamiento de los semáforos
• Foro Mundial para la Armonización de las Reglamentaciones sobre Vehículos

• Marcadores de Google Maps de los cruces fronterizos donde el tráfico cambia de lado (archivo de marcadores, requiere Google Earth ).
• Los Extraordinarios Ferrocarriles Urbanos de Asunción, Paraguay