Why did driving on the right become the norm in some countries?
It was a combination of technical advances, revolution and plain old practicalities that saw many countries switch to right hand driving, such as the increased use of freight wagons and the rise of Napoleon.
Freight wagons pulled by several horses, were popular in France and America, but instead of having a central driving seat like a horse drawn coach, wagon drivers would sit on the horse at the very back, on the left-hand side. Being in this position meant that he (because women didn’t usually do that kind of stuff in those days) could control all his horses with his dominant hand – typically, his right.
But sitting on the horse on the left-hand side whilst driving on the left meant that riders couldn’t see if oncoming traffic would get tangled in their wagon wheels (remember them?) So, the practical to solution to this…was to drive on the right.