About a quarter of the world drives on the left, and the countries that do are mostly old British colonies   like Australia , and Ireland. But Thailand, Indonesia and Japan also do so. This strange quirk   puzzles the rest of the world; however, there is a perfectly good reason . Up to the late 1700's , everybody travelled on the left side of the road because it's the most sensible option for feudal  , violent societies with mostly right-handed people. Soldiers with their swords under their right arm naturally passed on each other's right, and if you passed a stranger on the road, you walked on the left to ensure that your protective sword arm was between yourself and him. Revolutionary France, however, overturned this practice as part of its sweeping social rethink. A change was carried out all over continental Europe by Napoleon. It changed under Napoleon because he was left-handed. His armies had to march on the right so he could keep his sword arm between him and any opponent. From then on, any part of colonized by the French travelled on the right. After the American Revolutionary War (1775--1783), the US became independent and decided to make traffic drive on the right in order to cast off all remaining links with its British colonial past. As America became the center of the car industry, if you wanted a good reliable vehicle, you bought American right-hand-drive cars. From then on, many countries changed out of necessity. Today, the EU would like Britain to fall into line with the rest of Europe, but this is no longer possible. It would cost billions of pounds to change everything round. The last European country to change driving on the right was Sweden in 1967. While everyone was getting used to the new system, they paid more attention and took more care, resulting in a reduction of the number of road accidents. What is the main cause of the UK failing to adopt the new system?
Its high costs to change. Its increasing traffic accidents. Its influence on colonies. Its fast-developing car industry.