what is a dual carriageway

A dual carriageway, also known as a divided highway, is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation or median. It is a road that has a barrier separating two directions of traffic. Dual carriageways have improved road traffic safety over the years and typically have higher speed limits as a result. A road without a central reservation is known as a single carriageway regardless of how many lanes there are. Roads with two or more carriageways which are designed to higher standards with controlled access are generally classed as motorways, freeways, etc., rather than dual carriageways. Dual carriageways are used to separate high-speed traffic, allow usage of the middle of the road, or accommodate new lanes.