For a standard Broad Gauge (B.G.) single track, the typical design width of the ballast section (top width over sleepers including shoulders) is kept approximately

Introduction / Context:
The ballast section provides load distribution, drainage, and track stability. Its top width (including shoulders beyond sleeper ends) is a practical design choice that balances mechanical stability and material economy for a given gauge and traffic density.

Given Data / Assumptions:

• Gauge: Indian Broad Gauge.
• Typical main-line design with standard sleeper lengths.
• Ballast shoulder width selected to maintain lateral stability and drainage.

Concept / Approach:

Empirical practice sets shoulder widths and total ballast top width to ensure adequate confinement of sleepers, prevent lateral spread under dynamic loads, and promote drainage. For B.G., a commonly used top ballast width is about 3.35 m in many standard sections.

Step-by-Step Solution:

Verification / Alternative check:

Standard drawings and schedules for B.G. single track show ballast top width values around this figure for typical routes; heavy-haul or high-speed corridors may adopt larger shoulders.

Why Other Options Are Wrong:

2.35 m or 2.53 m are too narrow to give proper shoulder; 3.53 m is larger than typical standard design for ordinary routes; “None” is unnecessary since 3.35 m is standard practice.

Common Pitfalls:

Confusing ballast top width with formation width (which is larger) or sleeper spacing; neglecting drainage when reducing widths.

Final Answer:

3.35 m