Why does two-third (or three-quarters according to some) of the world drives on the right side? And why is the world divided over such a matter?

There clearly is a historical mystery to solve: in the past, most societies travelled in the left side of the road for a very simple reason: most people are right-handed and at the time swordsmen, warriors and knight kept moving on the left side of the road for their right arm to be able to hold a weapon to be able to face an eventual opponent.

The question now is how could it change over time? The answer came from France and United States in the 18^th century that began using large wagons (to transport farm products) pulled by pairs of horses or mules with no driver’s seat. Therefore, the driver had to seat on a left rear horse to use the right arm to guide the other horses. Naturally, the drivers preferred others to pass on the left for them to ascertain that the carriage will keep clear from being damaged.

 In addition to this explanation, in France, aristocracy drove carriage on the left side forcing peasants to the right. It only was after the French Revolution events in 1789, that aristocracy chose to keep low profile and drive on the right side. Yet, how this new custom, that became a law in 1794, could reach a global impact? The answer is Napoleon that imposed to the conquered nations the “rightism” traffic. This is how Belgium, Netherlands, Luxembourg, Switzerland, Germany, Poland, Russia, Spain, Italy got to drive on the right side of the road while Great Britain and its colonies (India, Australasia and African British colonies) kept the ancestral tradition to drive left (more or less official in 1872, written as a law in 1924). Hitler then imposed the right-hand traffic to Czechoslovakia and Austria in 1930s. Finally, in Japan, that never has been part of British colonies, always drove left for the same reasons all society drove left in the first place and had no reasons to change. Over times several countries around the world changed sides such as Gibraltar, China, Sweden and Korea that changed to right-hand traffic for various reasons such as war and political influences.

 Recently (7 September 2009), Samoa, a Pacific island swap sides from the right to the left side of the road for economic reasons: open the territory to low cost autos from left-driving countries such as Australia and New Zealand.