‘Keep to the left’ rules have been around at least since Roman ages where Roman carts and soldiers travelled on the left. In 1300AD it was Pope Boniface VIII declared the first ‘rules of the road’for pilgrims to travel on the left.
However, contrary to this history, Napoleon’s France enforced a ‘common’ right in 1792 across French territories. Meanwhile, the British solidified the left side trend, by ruling that traffic over the crowded London Bridge keep to the left to avoid collisions. This was later brought in across the country and Empire by 1835. These colonial legacies can still be seen today, though the story of the left/right side dichotomy is deep and based in individual histories. As it stands, 65% of the world has adopted the right side, whilst Britain, India and Japan among others remain stubbornly on the left.