On hill roads where several hairpin bends are necessary, what minimum intervening distance between successive hairpin bends is generally maintained to ensure safety and stability?
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A20 m
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B40 m
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C60 m
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D100 m
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E
Answer
Correct Answer: 60 m
Explanation
Introduction / Context:Hairpin bends (switchbacks) are sharp 180-degree turns used to rapidly gain elevation on steep terrain. Spacing these bends properly is essential for safety, sight distance, vehicle maneuverability, and slope stability.
Given Data / Assumptions:
- Standard two-lane hill road geometry.
- Typical design vehicles include buses and medium trucks.
- Terrain and right-of-way permit recommended spacing.
Concept / Approach:Providing a minimum intervening distance helps in accommodating transition lengths, superelevation runoff, driver comfort, and drainage works between curves. A commonly adopted minimum is about 60 m under Indian hill-road practice.
Step-by-Step Solution:
Assess required space for curve transition and super-elevation development.Ensure adequate sight distance and room for protective works (retaining, breast walls, drains).Adopt 60 m as the minimum safe intervening distance between hairpins where feasible.Verification / Alternative check:Where terrain allows, larger spacing (e.g., 100 m) may be used for improved comfort; however, 60 m is widely accepted as the lower bound.
Why Other Options Are Wrong:20–40 m are too short for safe transitions and sight distance; 100 m, while safe, is not the typical minimum and may be impractical in steep terrain.
Common Pitfalls:Placing bends too close due to right-of-way constraints; neglecting super-elevation runoff length between successive hairpins.
Final Answer:60 m