Which structure allows passage of a highway under a railroad?

• A. Overhead
• B. Overpass
• C. Undercrossing
• D. Underpass

Answer: (D)

The structure that allows the passage of a highway under a railroad is called a underpass. An underpass is specifically designed to provide clearance for vehicles traveling beneath a railway line, ensuring safe passage without interference from the trains above. This design helps to maintain traffic flow and can prevent accidents by separating road traffic from rail traffic.

In contrast, an overpass is a structure that allows a road to pass over another roadway or pathway, which is the opposite of what is required in this scenario. An overhead structure might refer more broadly to any construction above the ground, but it does not specify the context of allowing traffic beneath it. An undercrossing typically describes a similar concept but is more commonly associated with pedestrian or smaller pathways rather than the specific context of highway and railroad interactions. Hence, the appropriate term for a highway passing under a railroad is an underpass, as it succinctly captures the function and purpose of the structure.