What feature is not characteristic of a dual carriageway?

A dual carriageway is designed for higher-speed traffic and typically includes features that enhance safety and efficiency. One characteristic that is common on dual carriageways is the presence of a central reservation, which separates the opposing lanes of traffic to reduce the likelihood of head-on collisions. A barrier may also separate the lanes, but it's not essential for a road to be classified as a dual carriageway.

While many dual carriageways incorporate a hard shoulder for emergencies, it is not a defining feature. Some dual carriageways might lack a hard shoulder entirely, focusing instead on the separation of lanes and the structure of the road itself. These roads can still maintain their classification with just the central reservation, multiple lanes, and potentially barriers.

Thus, the absence of a hard shoulder does not disqualify a road from being classified as a dual carriageway, making it the correct choice in this context.