Right- and left-hand traffic
Left-hand traffic (LHT) and right-hand traffic (RHT) are the practice, in bidirectional traffic, of keeping to the left side or to the right side of the road, respectively. A fundamental element to traffic flow, it is sometimes referred to as the rule of the road.
RHT is used in 163 countries and territories, with List of countries with left-hand traffic|the remaining 78 countries and territories using LHT. Countries that use LHT account for about a sixth of the world's area with about 35% of its population and a quarter of its roads.