Right- and left-hand traffic

The terms right-hand traffic and left-hand traffic refer to regulations requiring all bidirectional traffic, unless otherwise directed, to keep to the right or to the left side of the road, respectively. This is so fundamental to traffic flow that it is sometimes referred to as the rule of the road. Today, about 65% of the world's population lives in countries with right-hand traffic and 35% in countries with left-hand traffic. About 90% of the world's total road distance carries traffic on the right and 10% on the left. Right-hand traffic predominates across the continental landmasses, while the majority of the world's island nations and territories drive on the left.