(WHTM) — Driving in the United States is very common, with over 228 million people taking to the roads in 2019. But have you ever wondered why, in the U.S., 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 while most of the United Kingdom and its colonies drive on the left side. 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, then the right, more dominant hand would be ready for that. So they would drive on the left side of the road to account for this.

It was a similar situation for people who operated Conestoga wagons, which were introduced in the U.S. around 1750, according to the Federal Highway Administration (FHA). The wagons were operated by a postilion driver riding on the left or by a driver walking or sitting on a “lazy board” on the left-hand side of the vehicle.

“He kept to the left in both cases in order to use the right hand to manage the horses and operate the brake lever mounted on the left-hand side,” Historian M. G. Lay told the FHA.

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.

“By 1915, the Model T had become so popular that the rest of the automakers followed Ford’s lead,” wrote Richard F. Weingroff, an information liaison specialist for the FHA.

Other countries, such as Canada and Italy, followed suit and also changed to right-side driving in the 1920s.

National Geographic states 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.

Lay also told the FHA that there are truly “no technical reasons for preferring driving on either the left or the right side of the road.”