(WHTM) — Driving in the United States is very common, with over 228 million people taking to the roads in 2019. But have you ever thought about why in The United States we drive on the right side of the road, and not the left?

According to National Geographic, around 75% of the world also drives on the right side of the road, with most of the United Kingdom and its colonies driving on the left side of the road. So why can’t there be a standard system when it comes to driving?

National Geographic states that driving a certain way on a road was a cultural custom. It also had to do with most people being right-hand dominant.

In Ancient Rome, Romans would drive their chariots with their more dominant hand, which would normally be the right hand. This would allow them to whip the horse with the less dominant left hand.

This was done so there was less of a risk of accidentally whipping a passing chariot. But if the driver needed to battle from the chariot, the right, more dominant hand was ready for battle. So they would drive on the left side of the road to account for this.

In later centuries, Henry Ford designed his Model T with the driver sitting on the left. That decision itself meant that cars would drive on the road’s right-hand side, so passengers in both the front and back seats could enter and exit the car onto a curb. This led many other countries, such as Canada and Italy to change to right-side driving in the 1920s.

National Geographic cities that it could be stubbornness on why 50 or so countries still drive on the left. It also could be city design. London, for example, was designed to accommodate left-handed driving, so changing it to right-side driving would not be easy to do. Having more and more cars on roadways also inhibits the change.