In 1998, archaeologists found a well-preserved double track leading to a Roman quarry near Swindon, England. The grooves in the road on the left side (viewed facing down the track away from the quarry) were much deeper than those on the right side. These grooves suggest that the Romans drove on the left ... since carts would exit the quarry heavily loaded, and enter it empty. ... Ancient travellers on horseback generally rode on the left side of the road. As more people are right-handed, a horseman would thus be able to hold the reins with his left hand and keep his right hand free - to offer in friendship to passing riders or to defend himself with a sword, if necessary.

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