In rail terminology, a Viaduct refers to which of the following?

• A. A tunnel section
• B. A bridge over water
• C. A culvert under a roadway
• D. A bridge longer than 100 meters

Answer: (D)

A viaduct is a long bridge made up of multiple spans that crosses valleys, gorges, or uneven terrain. The defining idea is length and the series of smaller spans rather than a single simple span. That’s why the option describing a bridge longer than a certain length fits best—practically, viaducts are long, multi-span structures, often exceeding a noticeable length like 100 meters.

A tunnel is an enclosed passage through ground, so it isn’t a bridge. A culvert is a small drainage passage under a roadway or railway, not a long multi-span crossing. A bridge over water can be a viaduct, but the distinguishing feature of a viaduct is its length and multiple spans crossing land or varied terrain, not just crossing water.