Four-lane divided highways: To prevent head-on collisions between vehicles moving in opposite directions, which measure is primarily adopted on such roads?
-
AMarkings on the road are provided
-
BPhysical dividers (raised medians or barrier medians) are provided
-
CArea dividers are provided
-
DMedians of wide area are provided
-
ENone of these
Answer
Correct Answer: Medians of wide area are provided
Explanation
Introduction / Context:Head-on collisions are among the most severe crash types because closing speeds are high. Highway engineers therefore design four-lane facilities as divided carriageways so opposing streams are fully separated. The question asks which measure specifically addresses head-on collisions on four-lane roads.
Given Data / Assumptions:
- A four-lane road carries two lanes in each direction.
- Opposing streams are to be separated to prevent encroachment into the opposite carriageway.
- Standard traffic control devices like markings may supplement, but not replace, physical separation for high-speed facilities.
Concept / Approach:
Centerline (or lane) markings provide guidance but cannot physically block errant vehicles. A raised, landscaped, or barrier median forms a continuous longitudinal separator. This median (also called a physical divider) is the primary design element to prevent head-on conflicts by eliminating opposing traffic face-to-face interaction on the same carriageway.
Step-by-Step Solution:
Identify the crash mode → head-on collision between opposing directions.Map countermeasures → guidance (markings), channelization (area dividers), and separation (medians/physical dividers).Select the measure that physically separates opposing streams → a wide or barrier median.Verification / Alternative check:
Design manuals for divided highways emphasize a central median or continuous longitudinal barrier as the definitive treatment for eliminating head-on conflicts on multi-lane high-speed facilities. Markings alone are insufficient at higher speeds or volumes.
Why Other Options Are Wrong:
- Markings on the road: provide delineation but no physical separation; cannot reliably prevent head-on crashes.
- Area dividers: a vague term for pavement markings/islands; not a continuous physical separator.
- None of these: incorrect because medians are the standard solution.
Common Pitfalls:
- Confusing lane markings with medians; markings help guidance, not physical crash prevention.
- Assuming urban channelization islands are equivalent to highway medians; islands are intermittent and local.
Final Answer:
Medians of wide area are provided.