Undivided carriageway describes a deck where traffic loads share the same surface and are not separated.

• A. Corrugated Steel Deck
• B. Timber Deck
• C. Double-Decked Bridges
• D. Undivided Carriageway

Answer: (D)

The idea being tested is whether the deck carries all traffic on a single, continuous surface. An undivided carriageway means there is one shared surface for all traffic, with no physical barrier or separation between lanes or directions. In practice, even if there are multiple lanes, if there’s no median barrier or divider, the surface is considered undivided—the loads from all lanes transfer through the same deck surface.

That’s why this option is the best description: it explicitly states that traffic loads share the same surface and are not separated. The other choices describe different concepts: corrugated steel deck refers to the deck’s construction form, not whether traffic is divided; timber deck indicates material; double-decked bridges involve two separate levels for traffic, i.e., a divided arrangement, not an undivided single surface.