Imagine arriving in Britain, renting a car and seeing another vehicle coming towards you on what feels like the wrong side of the road. For British drivers, however, the left is the correct side. Travel to France or Slovakia, and everyone drives on the right. Why did countries choose different systems? There is no single, certain answer. The custom began long before cars existed, when people travelled on foot, on horses or in carriages. One popular theory says that travellers often stayed on the left for safety. Since most people were right-handed, this position allowed them to use their right hand to greet another traveller or protect themselves. A person riding on the left could also hold a sword in the hand closer to someone coming from the opposite direction. This explanation sounds reasonable, although historians do not have enough…