In highway engineering for high-traffic corridors, what functional requirements should properly designed shoulders satisfy to ensure safety, durability, and serviceability?

Introduction / Context:
Shoulders are the immediate strips flanking the carriageway on highways and expressways. For routes with high traffic volumes, well-designed shoulders improve safety (breakdowns and evasive maneuvers), protect the pavement edge, and aid drainage. The question tests understanding of these multi-role requirements and the consequences if any requirement is neglected.

Given Data / Assumptions:

• Facility type: high-traffic roadway.
• Shoulders are contiguous with the main pavement.
• Emergency use by vehicles is expected.
• Moisture control and edge support are essential.

Concept / Approach:
Effective shoulders serve three core functions: (1) safety refuge and operational flexibility, requiring year-round stability and adequate structural strength; (2) structural protection of the pavement edge, reducing edge-stress concentrations and ravelling; and (3) drainage control, using cross-slope and surface integrity to keep water out of the subgrade, which otherwise weakens and deforms under traffic loads.

Step-by-Step Solution:
Identify emergency functionality: shoulders must sustain occasional wheel loads without rutting.Recognize structural role: shoulders prevent edge failure by providing lateral confinement.Address drainage: shoulders need cross-fall and sealed shoulders (or well-compacted granular) to avert subgrade ingress.All three statements are correct; choose “All the above”.

Verification / Alternative check:
Design manuals specify minimum width, cross-slope (often 2–4%), and surface types (paved/partially paved) to meet these roles. Performance histories show fewer edge failures and safer breakdowns where shoulders are properly maintained.

Why Other Options Are Wrong:

• Each single statement captures only part of the requirement; all are simultaneously necessary.
• “None of these” is false because the listed properties are standard practice.

Common Pitfalls:

• Poor compaction or inadequate shoulder drainage causing pumping and edge cracking.
• Neglecting maintenance, which quickly erodes emergency usability.

Final Answer:
All the above.