Why do Americans drive on right side while UK drives on left?

In Europe, Napoleon Bonaparte and in the United States, Henry Ford are often credited with introducing left and right driving; however, the truth is that it goes further back than either Ford or Bonaparte, CNN reported.

Back in the early 1700s, big wagons, with their tall, arched cloth roofs, became icons of America's westward expansion.

As trade increased, America's first major highway, the Turnpike Road between Philadelphia and Lancaster, was built in 1795. Its charter stated that all traffic was to keep to the right.

In 1804, New York became the first state to enforce that traffic remain to the right on all roads and highways.

Because Ford Motor Company placed the steering wheel on the left side of their wildly successful Model T in 1908, some people attribute Henry Ford's decision to bring about the standardisation of right-side driving in the US.

Whereas in the UK, one of the most popularly accepted ideas about why the British drive on the left dates back to ancient Roman times, The Collector reported.

Back then, travellers faced the constant threat of invasion or mugging. Since the majority of Romans were right-handed, riding on the left meant they could keep their right hand free to fight if anyone attacked. 

This practice was carried on by subsequent civilisations.

The first officially sanctioned rule for driving on the left was enshrined by Pope Boniface VIII in 1300 CE when he declared that all travelling pilgrims visiting the Roman Empire must remain on the left.

In 1773, the government introduced the General Highways Act, which stated that all travellers must remain on the left side.