Trains run on the left in many countries. This practice stems from the traditions of the English knights in the Middle Ages. Mostly right-handed, they rode on the left side of the road to be able to defend themselves with their strong arm in case of attack. Over the centuries, this custom has become proper traffic regulation for all vehicles in England. When the railway was invented in the heart of England in the nineteenth century, engineers drew inspiration from English traditions to create the first railway lines.