The terms right-hand traffic (RHT) and left-hand traffic (LHT) 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.

About two thirds of the world's population (163 countries and territories) are RHT, with the remaining 76 countries and territories LHT. Countries that use LHT account for about a sixth of the world's area and a quarter of its roads. In the early 1900s some countries like Canada, Spain, and Brazil, had different rules in different parts of the country. During the 1900s many countries standardised within their jurisdictions, and changed from LHT to RHT, mostly to conform with regional custom. In 1919, 104 of the world's territories were LHT, and an equal number were RHT. From 1919 to 1986, 34 of the LHT territories switched sides.

Of the African countries mentioned only Mozambique drives on the left hand side of the road. In Angola, Egypt and Nigeria cars are driven on the right hand side of the road.

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