Indian Broad Gauge (BG) rail sections: Which of the following rail sections is <em>not</em> used on Indian BG tracks?

Introduction / Context:
Rail sections are designated by their weight per unit length (legacy “R” series in lb/yd and modern kg/m series). Indian BG tracks historically used heavier sections to carry higher axle loads, whereas very light sections were associated with MG/NG or sidings.

Given Data / Assumptions:

• BG main lines require adequate rail section weight to resist bending and wear.
• Options show legacy “R” sections of varying weights.

Concept / Approach:
Among the listed sections, 35 R is very light and unsuitable for BG mainline service. BG has used heavier “R” sections (e.g., 60 R, 75 R, 90 R in older practice) and later 52 kg/m and 60 kg/m rails.

Step-by-Step Solution:
Identify which section is clearly too light for BG main line duty.35 R lacks the required stiffness/strength for BG operations.Conclude 35 R is not used on Indian BG tracks.

Verification / Alternative check:
Historical track standards show BG progressively migrating to 52 kg/m and 60 kg/m. Light “R” sections were phased out or limited to lighter gauges.

Why Other Options Are Wrong:

• 40 R, 45 R, 55 R: Heavier than 35 R and historically closer to use on heavier-duty lines, though now largely superseded by metric rails.
• None of these: Incorrect, because 35 R is indeed not a BG standard.

Common Pitfalls:
Assuming any “R” section is acceptable for BG; confusing historical usage on MG/NG with BG practice.

Final Answer:
35 R