question: Why do island nations typically drive on the left (UK, Japan, Australia, etc) while mainland nations typically drive on the right (US, Canada, Mainland Europe, etc)?
comment: In the past, almost everybody travelled on the left side of the road because that was the most sensible option for feudal, violent societies. Since most people are right-handed, swordsmen preferred to keep to the left in order to have their right arm nearer to an opponent and their scabbard further from him. Moreover, it reduced the chance of the scabbard (worn on the left) hitting other people. Furthermore, a right-handed person finds it easier to mount a horse from the left side of the horse, and it would be very difficult to do otherwise if wearing a sword (which would be worn on the left). It is safer to mount and dismount towards the side of the road, rather than in the middle of traffic, so if one mounts on the left, then the horse should be ridden on the left side of the road. In the late 1700s, however, teamsters in France and the United States began hauling farm products in big wagons pulled by several pairs of horses. These wagons had no driver’s seat; instead the driver sat on the left rear horse, so he could keep his right arm free to lash the team. Since he was sitting on the left, he naturally wanted everybody to pass on the left so he could look down and make sure he kept clear of the oncoming wagon’s wheels. Therefore he kept to the right side of the road. 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 (Elizaveta Petrovna) officially issued an edict for traffic to keep to the right. In addition, the French Revolution of 1789 gave a huge impetus to right-hand travel in Europe. The fact is, before the Revolution, the aristocracy travelled on the left of the road, forcing the peasantry over to the right, but after the storming of the Bastille and the subsequent events, aristocrats preferred to keep a low profile and joined the peasants on the right. An official keep-right rule was introduced in Paris in 1794, more or less parallel to Denmark, where driving on the right had been made compulsory in 1793.
passages: Vietnam became RHT as part of French Indochina, as did Cambodia. In the latter country, RHD cars, many of which were smuggled from Thailand, were banned from 2001, even though they accounted for 80% of vehicles in the country.
  
  Section::::History.:Oceania.
  
  Many former British colonies in the region have always been LHT, including Australia, New Zealand, Fiji, Kiribati, Nauru, Papua New Guinea, Solomon Islands, Tonga, and Tuvalu.
   Egypt had been conquered by Napoleon before becoming a British dependency, and its traffic goes to the right.
  
  Section::::History.:North America.
  
  In what is now Canada, LHT was introduced by the British in British Columbia, which changed to RHT in stages from 1920 to 1923, and New Brunswick, Nova Scotia, and Prince Edward Island, which changed in 1922, 1923, and 1924 respectively. Newfoundland, then a British colony, changed to RHT in 1947, two years before joining Canada. Former parts of New France have always been RHT. 
   LHT was introduced by the British in British India (now India, Pakistan, Myanmar, and Bangladesh), British Malaya (now Malaysia, Brunei and Singapore), and British Hong Kong. All are still LHT except Myanmar, which switched to RHT in 1970, although much of its infrastructure still geared to LHT. Most cars are used RHD vehicles imported from Japan. Afghanistan was LHT until the 1950s, in line with neighbouring British India and later Pakistan.
   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.
  
  Section::::History.:Asia.
   BULLET::::- Uganda
  
  BULLET::::- Zambia
  
  BULLET::::- Zimbabwe
  
  Section::::In Australasia.
  
  BULLET::::- Australia and dependencies Christmas Island, Cocos (Keeling) Islands, and Norfolk Island
  
  BULLET::::- Fiji
  
  BULLET::::- Kiribati
  
  BULLET::::- Nauru
  
  BULLET::::- New Zealand and dependencies Cook Islands, Niue, and Tokelau
  
  BULLET::::- Papua New Guinea
  
  BULLET::::- Solomon Islands
  
  BULLET::::- Samoa (since 2009)
  
  BULLET::::- Tonga
  
  BULLET::::- Tuvalu
  
  BULLET::::- U.K. Overseas Territory Pitcairn Islands
  
  Section::::In Europe.
  
  BULLET::::- Republic of Ireland
  
  BULLET::::- Malta
  
  BULLET::::- The United Kingdom; also Guernsey, Jersey, and the Isle of Man
  
  Section::::In South America.
  
  BULLET::::- Guyana
  
  BULLET::::- Suriname
  
  Section::::Atlantic Ocean & West Indies.
  
  BULLET::::- Antigua and Barbuda
  
  BULLET::::- The Bahamas
  
  BULLET::::- Barbados
   Finland, formerly ruled as part of LHT Sweden, switched to RHT in 1858 as the Grand Duchy of Finland by Russian decree. 
  
  Rotterdam was LHT until 1917, although the rest of the Netherlands was RHT.
  
  Russia completely switched to driving on the right in the last days of the Tsars in February 1917.
  
  Today, four countries in Europe continue to use left-hand traffic, all island nations: the UK, Cyprus, Ireland, and Malta.
  
  Section::::History.:Africa.
   LHT was introduced in British West Africa. All of the countries formerly part of this colony have borders with former French RHT jurisdictions and have switched to RHT since decolonization. These include Ghana, The Gambia, Sierra Leone, and Nigeria. LHT was introduced by the British in the East Africa Protectorate (now Kenya, Tanzania and Uganda), Rhodesia, and the Cape Colony (now Zambia, Zimbabwe and South Africa). All of these have remained LHT. Sudan, formerly part of Anglo-Egyptian Sudan switched to RHT in 1973, as it is surrounded by neighbouring RHT countries. 
   The first reference in English law to an order for LHT was in 1756, with regard to London Bridge. The United Kingdom is LHT, but its overseas territories of Gibraltar and British Indian Ocean Territory are RHT. In the late 1960s, the UK Department for Transport considered switching to RHT, but declared it unsafe and too costly for such a built-up nation. Road building standards, for motorways in particular, allow asymmetrically designed road junctions, where merge and diverge lanes differ in length. 
   LHT was introduced by the Portuguese Empire in Portuguese Macau (now Macau) and Portuguese Timor (now East Timor). Both places are still LHT, despite Macau now being part of RHT China, requiring a right-to-left switching interchange at the Lotus Bridge which connects the two. East Timor shares the island of Timor with Indonesia, which is also LHT, although the former (then Portuguese Timor) switched to RHT along with Portugal in 1928 before changing back to LHT in 1976 during the Indonesian occupation of East Timor.
   Colloquially, the terms "freeway", "highway", and "motorway" are used synonymously. The term "expressway" is not common in South Africa. A freeway, highway or motorway refers to a divided dual carriageway with limited access, and at least two lanes in either direction. A central island, usually either with drainage, foliage, or high-impact barriers, provides a visible separation between the carriageways in opposite directions. As in the United Kingdom, Ireland, Australia, and Japan, South Africans drive on the left-hand side of the road and nearly all steering wheels are on the right-hand side of vehicles.
   Comparison of MUTCD-influenced traffic signs
  
  Road signs used by countries in the Americas are significantly influenced by the "Manual on Uniform Traffic Control Devices" (MUTCD), first released in 1935, reflecting the influence of the United States throughout the region. Other non-American countries using road signs similar to the MUTCD include Australia, Indonesia, Ireland, Japan, Malaysia, New Zealand, and Thailand. They are also the only countries listed here which drive on the left—with the exception of Liberia and the Philippines (though partial), both of which drive on the right.
   Section::::Left hand drive Vs Right hand drive.
  
  In Singapore, only right-hand-drive cars are permitted on the roads. There are exceptions for special-purpose vehicles, diplomatic vehicles, and foreign-registered vehicles, with the label placed at the back windscreen of the vehicles indicating "Left Hand Drive" to alert other motorist that the driver's seat is on the left side instead of on the right side.
  
  Section::::Petrol market.
  
  Section::::Petrol market.:Major companies in the retail petrol market.
   Driving in Singapore
  
  In Singapore, cars and other vehicles drive on the left side of the road, as in neighbouring Malaysia, due to its British colonial history (which led to British driving rules being adopted in India, Australia, New Zealand, and Hong Kong as well). As a result, most vehicles are right-hand drive. However, exemptions have been made to allow foreign vehicles and construction machineries to utilise the roadspace of Singapore. As such, vehicles with left hand drive configurations are required to either be driven with a sign indicating "LEFT-HAND-DRIVE" or towed.
   Motor vehicles are driven on the left-hand side of the road in both the British and the U.S. Virgin Islands, although the steering wheels on most cars are located on the left side (as is the norm for drive-on-the-right localities). In the Spanish Virgin Islands, vehicles are driven on the right-hand side of the road.
  
  Section::::See also.
  
  BULLET::::- Culture of the Virgin Islands
  
  BULLET::::- Music of the Virgin Islands
  
  BULLET::::- Virgin Islands Creole
  
  BULLET::::- Danish Virgin Islands
  
  BULLET::::- Dutch Virgin Islands
  
  BULLET::::- Virgin Islands patch reefs
  
  Section::::External links.
  
  BULLET::::- BVI.gov: British Virgin Islands government website
   Although many LHT jurisdictions are on islands, there are cases where vehicles may be driven from LHT across a border into a RHT area. Such borders are mostly located in Africa and southern Asia. The Vienna Convention on Road Traffic regulates the use of foreign registered vehicles in the 74 countries that have ratified it.
  
  LHT Thailand has three RHT neighbors: Cambodia, Laos, and Myanmar. Most of its borders use a simple traffic light to do the switch, but there are also interchanges which enable the switch while keeping up a continuous flow of traffic.
   A plan to move to driving on the left was first announced by the Samoan government in September 2007. Prime Minister Tuilaepa Aiono Sailele Malielegaoi said that the purpose of adopting left-hand traffic was to allow Samoans to use cheaper right-hand-drive vehicles sourced from Australia, New Zealand or Japan, and so that the large number of Samoans living in Australasia could drive on the same side of the road when they visited their country of origin. He aimed to reduce reliance on expensive, left-hand-drive imports from America.
   The Portuguese Empire, then LHT, introduced that to Portuguese Mozambique and Portuguese Angola. Although Portugal itself switched to RHT in 1928, these territories remained LHT as they have land borders with former British colonies. Other former Portuguese colonies in Africa that switched sides in 1928 including Guinea-Bissau, São Tomé and Príncipe, and Cape Verde.
   The Henry E. Rohlsen International Airport serves St. Croix and the Cyril E. King International Airport serves St. Thomas and St. John.
  
  The U.S. Virgin Islands is the only US jurisdiction that drives on the left. This was inherited from what was then-current practice on the islands at the time of the 1917 transfer of the territory to the United States from Denmark. However, because most cars in the territory are imported from the mainland United States, the cars in the territory are left-hand drive.
   List of countries with left-hand traffic
  
  This is a list of 75 countries and territories with left-hand traffic. Left-hand traffic (LHT) is the practice, in bidirectional traffic, of keeping to the left side of the road.
  
  Section::::Asia.
  
  BULLET::::- Bangladesh
  
  BULLET::::- Bhutan
  
  BULLET::::- Brunei
  
  BULLET::::- Special administrative regions of China:
  
  BULLET::::- Hong Kong
  
  BULLET::::- Macau
  
  BULLET::::- Cyprus
  
  BULLET::::- East Timor
  
  BULLET::::- India
  
  BULLET::::- Indonesia
  
  BULLET::::- Japan
  
  BULLET::::- Malaysia
  
  BULLET::::- Nepal
  
  BULLET::::- Pakistan
  
  BULLET::::- Singapore
  
  BULLET::::- Sri Lanka
  
  BULLET::::- Thailand
  
  Section::::In Africa.
  
  BULLET::::- Botswana
  
  BULLET::::- Eswatini
  
  BULLET::::- Kenya
  
  BULLET::::- Lesotho
  
  BULLET::::- Malawi
  
  BULLET::::- Mozambique
  
  BULLET::::- Namibia
  
  BULLET::::- South Africa
  
  BULLET::::- Tanzania
   Used vehicles must, with some exceptions, be right-hand drive, and they must comply with recognised European, Australian, Japanese, or American emission and safety standards, or they are ineligible for import to New Zealand.
  
  In some cases a left-hand drive vehicle can be imported into New Zealand if it meets certain conditions or is a specialized vehicle. Left-hand drive vehicles 20 years or older normally do not have to meet any special requirements but must weigh no more than 3500 kg.
  
  Section::::By country.:Ireland.
   Generally, the convention is to mount a motorcycle on the left, and kickstands are usually on the left which makes it more convenient to mount on the safer kerbside as is the case in LHT. Some jurisdictions prohibit fitting a sidecar to a motorcycle's offside.
  
  Section::::Road vehicle configurations.:Headlamps and other lighting equipment.
   Section::::Driving.
  
  In the UK, vehicles are driven on the left and on multi-lane carriageways drivers are generally expected to keep to the left lane except when overtaking or turning right. In Great Britain, the Highway Code applies to drivers. In Northern Ireland, the Highway Code for Northern Ireland applies.
   The Philippines was mostly LHT during its Spanish and American colonial periods, as well as during the Commonwealth era. During the Japanese occupation, the Philippines remained LHT, also because LHT had been required by the Japanese; but during the Battle of Manila, the liberating American forces drove their tanks to the right for easier facilitation of movement. RHT was formalised in 1945.
   RHT is used in 165 countries and territories, with the remaining 75 countries and territories using LHT. Countries that use LHT account for about a sixth of the world's area with about 35% of its population and a quarter of its roads. In 1919, 104 of the world's territories were LHT and an equal number were RHT. From 1919 to 1986, 34 of the LHT territories switched to RHT.
   Section::::History.:South America.
  
  Brazil was a colony of Portugal until the early 19th century and during this century and the early 20th century had mixed rules, with some regions still on LHT, switching these remaining regions to RHT in 1928, the same year Portugal switched sides. Other Central and South American countries that later switched from LHT to RHT include Argentina, Chile, Panama, Paraguay, and Uruguay. 
  
  Suriname, along with neighbouring Guyana, are the only two remaining LHT countries in South America.
  
  Section::::Changing sides at borders.
  