What defines a dual carriageway?

A dual carriageway is defined by the presence of a central reservation that separates lanes of traffic moving in opposite directions. This central divider enhances safety by preventing head-on collisions and allows for higher speed limits compared to roads without such separation. The two carriageways on a dual carriageway both typically have two or more lanes, which facilitates efficient traffic flow.

In contrast, a road exclusively for heavy vehicles does not encompass the characteristics of a dual carriageway, as it is meant for particular vehicle types rather than general traffic. A multi-lane road without any separators would not qualify as a dual carriageway because it lacks the essential central reservation that provides the necessary separation of traffic flow. Lastly, while some dual carriageways may have a speed limit of 50 mph or less, the defining feature of a dual carriageway is the structure itself—central reservation—rather than the speed limit.