The story goes way back to the times when there were no cars. Since most people are right-handed, back then men with swords opted to stay to the left side of the road so that their right arm is nearer to an opponent. Moreover, it reduced the chance of the scabbard : a sheath for the blade of a sword hitting other people. ( worn on the left )
Also think about it, If you were right-handed , you would find it easier to mount a horse from the left side of the horse, especially with a sword worn on the left. Rather than getting down to the middle of traffic, it is easier to get down towards the left than the right. Now you may ask, but it contradicts the way we get out of car these days in india then. We do get to the street if we park and get out. Well ! let’s find out why ?
In 1700s, France and the United States was transporting large amounts of agriculture products in huge wagons pulled by at least 2-6 horses, in pairs. There was no dedicated driver seat and the driver sat on the left rear horse so that he could keep his right hand free to lash the horses. Since he can only see the left side clearly, he would want everybody to pass on the left so he could look down and make sure he kept clear of the oncoming wagon’s wheels. Thats how these countries ended up having right side driving.Several factors including Napolean , WW1 and British colonies helped spread the system that we live in .Reading isn’t your thing ?