This Is Why Americans and Brits Drive on Different Sides of the Road

In the old days, almost all of us traveled on the left side of the road, according to BBC America. However, the mode at that time differs a lot from today as the popular transport was horses instead of cars. For Medieval swordsmen on horseback, it made sense for them to travel on the left side of the road so their right arms are ready in case there were attacks from opponents.

Mounting and dismounting were also easier from the left side of the house and of course safer by the side of the road. So perhaps the question here should be, why did people stop traveling on the left?