Railway track materials: Which sleeper type most closely satisfies the requirements of an ideal sleeper in terms of durability, gauge holding, low maintenance, and resistance to environmental damage?

Introduction / Context:
In railway permanent way engineering, an “ideal sleeper” should maintain gauge accurately, distribute wheel loads effectively, resist decay and corrosion, allow good track elasticity with ballast, and require minimal maintenance over a long service life. This question checks recognition of the sleeper material that best meets these combined performance criteria on modern railways.

Given Data / Assumptions:

• Service on mainline track with typical ballast and fastenings.
• Key attributes: durability, stability, gauge retention, cost-effectiveness, and maintainability.
• Environmental resistance (moisture, pests, chemical attack) is desirable.

Concept / Approach:
Reinforced cement concrete (R.C.C.) sleepers provide long life, uniform behavior, and excellent gauge-holding due to higher weight and robust fastenings. They are immune to termite attack (unlike timber) and corrosion issues common with steel in aggressive environments. Compared with cast iron, R.C.C. gives better ballast interaction, fewer breakages, and standardized designs compatible with modern mechanized maintenance.

Step-by-Step Solution:

Verification / Alternative check:
Global practice on heavy-haul and passenger corridors has shifted to concrete sleepers because they minimize track geometry defects and support high axle loads with reduced life-cycle cost.

Why Other Options Are Wrong:

• Wooden sleepers: Good elasticity and easy handling but short life; prone to decay and termites.
• Steel sleepers: Durable but can corrode and may offer less ballast interlock; noise and stiffness concerns.
• Cast iron sleepers: Obsolete in many systems; brittle and maintenance-intensive.
• Composite sleepers: Niche usage; not as widely proven as standard R.C.C. for mainlines.

Common Pitfalls:

• Judging only initial cost; life-cycle and geometry retention matter more on trunk lines.
• Confusing local temporary solutions with mainline best practice.

Final Answer:
R.C.C. (reinforced cement concrete) sleepers