As a visitor, one of the most disorienting parts of being in the UK is crossing the street. While traffic in almost all of the world passes on the right side, cars in Britain and many of its former colonies drive on the left. Just why do Brits drive on the opposite side of the road from most other countries?

The practice far predates cars, according to The Telegraph. In fact, it goes back to the Middle Ages. In ye olden days, when traveling down a highway put you at risk of being attacked or robbed, traveling on the left was a matter of safety. Since most people were (and still are) right-handed, passing on the left meant leaving your sword-hand free to take on any challengers. Whether on foot, horseback, or in a carriage, you needed to be able to whip out your lance, sword, pitchfork, or staff in response to a threat—and quickly.

According to the BBC, this practice was widespread outside of Britain, too, potentially dating back as far as ancient Greece and Rome. The UK wasn’t the only place with dangerous roads, after all. But various pressures eventually shifted travelers to the right.

Notably, Napoleon was a fan of right-side driving, and brought the practice to territories he conquered (as did French colonists). That included Germany, and Hitler continued to spread the tradition across Europe as he took power, forcing Czechoslovakia and Austria (where half the country drove on the left side of the road and the other half drove on the right) to switch to right-side driving.

America has been driving on the right side of the road since colonial times, according to the Federal Highway Administration’s research, likely both as a rejection of British customs and because it made it easier to control a wagon. Drivers either sat on the left of their wagon or led their horses on foot on the left-hand side, so it was much easier to see oncoming traffic by traveling on the right side of the road. Plus it made it less likely that you’d end up in a ditch. Pennsylvania regulated right-side traffic on a new turnpike in 1792, and New York regulated right-hand driving on all public highways in 1804. Many states followed suit, but Henry Ford really cemented the practice; he chose to put the Model T’s steering column on the left, and the car’s immense popularity meant that the rest of the car industry followed suit.

Britain has previously considered switching over to right-side driving (as Sweden did in 1967), but the idea isn’t likely to take hold anytime soon. In 2009, Samoa became one of the few nations in the world to switch from right-side driving to left-side driving, in a bid to make cheap cars from Australia and New Zealand available there.

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