Why some countries drive vehicles on the Right and some countries on the Left ?

Question

Any specific reason is there for it ?

Answer 1

All british colony (except US/Canada) are left side driving and rest of the world is right side which is 35:65 ratio. See the following image -

Now coming to the reason, reason lies to the behavior of armies as most of the people is right handed so Right-handed knights preferred to keep to the left in order to have their right arm nearer to an opponent. In the Europe first France switched to the right side (may be because they didn’t want to use the same rule of the road the English used) and others followed.