Why Do Some Countries Drive on the Left?

If you drive in the United States or France, you have to stay on the right side of the road. In Japan, however, cars keep to the left, just like in the UK. Why is the world divided like this?

Driving on the left is less common, but it is far from rare. About seventy-five countries and territories drive on the left, and together they are home to roughly a third of the world's population. They include Ireland, India, Australia, Thailand and Indonesia, as well as the UK and Japan.

Historians are not certain how the habit began, but there are several popular theories. One theory says that travelers with swords kept left, so their right hand was nearer to anyone coming the other way. In Japan, a similar story is often told about samurai, who wore their swords on the left side. However, it is hard to prove these ideas.

What we do know is that the custom was gradually written into law. In Britain, a 1756 law about London Bridge is one of the earliest known rules for keeping left. In Japan, keeping left became a national rule for road traffic in the 1920s. Some people link this to the British engineers who helped build Japan's early railways, but this is also debated.

Interestingly, one part of Japan has driven on both sides. After World War II, Okinawa was under American control, and cars there drove on the right. On July 30, 1978, the whole prefecture switched back to the left overnight. Local people still remember the change as Nana-san-maru, which means seven-three-zero.