There was once a theory that the reason for the difference in which side a vehicle is driving on the road today, stems from whether a country had many stretches of untamed wilderness with lots of bandits. So if there was a high likelihood that whoever you met on the road was a danger, the horsecart driver preferred passing them on the side of their sword arm (right hand as default), while if you did not have to take that into account, you would pass them on the left hand side.
The theory has now largely been abandonded as spurious, but it does remain a fact that there were dangerous stretches of roads in older times in Europe as well.
There was once a theory that the reason for the difference in which side a vehicle is driving on the road today, stems from whether a country had many stretches of untamed wilderness with lots of bandits. So if there was a high likelihood that whoever you met on the road was a danger, the horsecart driver preferred passing them on the side of their sword arm (right hand as default), while if you did not have to take that into account, you would pass them on the left hand side.
The theory has now largely been abandonded as spurious, but it does remain a fact that there were dangerous stretches of roads in older times in Europe as well.