Why are highway or railway tunnels often more advantageous than surface alternatives? Identify the comprehensive set of benefits that commonly justify tunnelling over a detour or open cut.

Difficulty: Easy

Correct Answer: All the above.

Explanation:


Introduction / Context:
Selecting between tunnelling and a surface alignment is a fundamental planning decision. Tunnels can provide straighter, shorter routes through mountains or dense urban areas, mitigate severe weather exposure, and minimize disruption to existing communities or land rights. This question evaluates understanding of the multifaceted advantages that make tunnelling attractive in feasibility studies.


Given Data / Assumptions:

  • Alternatives considered: detour around terrain obstacles, open cut through hills, or tunnel.
  • Performance factors: climate resilience, alignment length, costs, maintenance, and surface rights.
  • Goal: choose the option that aggregates the primary benefits.


Concept / Approach:
Tunnels reduce grades and curvature, resulting in shorter route length and operating savings. They are protected from surface snow/ice, improving reliability and reducing closures. Maintenance for stabilized underground works is often less than for long exposed cuts or high embankments. Additionally, tunnelling preserves surface land use and avoids complex right-of-way acquisition—crucial in urban or environmentally sensitive areas.


Step-by-Step Solution:

Compare alternatives: detour increases distance and travel time.Open cut: large excavation volumes, landslide/erosion risk, snow accumulation on approaches.Tunnel: shorter alignment, stable microclimate, limited surface impacts.


Verification / Alternative check:

Life-cycle costing that includes operations and maintenance typically shows tunnels becoming competitive or cheaper when surface works are extensive or weather exposure is severe.


Why Other Options Are Wrong:

Each single benefit is true, but only “All the above” captures the full set of common advantages.


Common Pitfalls:

Focusing solely on initial construction cost without factoring maintenance, closures, and right-of-way complications.


Final Answer:

All the above.

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