Partially right. Napoleon had a preference, but more importantly, those in carriages or carts with a horse-team, sat to the left of the seat, in order to use the whip with their right hand, given the extremely high prevalence of right handedness, since you're sitting on the left side, seeing opposing traffic is easier if they pass on your left, meaning that the traffic direction reversed as a matter partially of popular usage, and partly of the successes of Napoleon, and later, Germany in imposing their standard on the countries they conquered.<br/><br/>There is, I think, no 'correct' side to drive on. The public has no real need of free sword-hands in their vehicles, I should hope. :P