Provision of check rails on sharp curves (Broad Gauge): Beyond what curve sharpness (degree of curve) are check rails provided on the inner side of the inner rail?

Introduction / Context:
Check rails are installed on sharp curves to improve flange guidance and reduce the risk of flange climb, rail wear, and rolling contact fatigue. On Broad Gauge (BG), standards prescribe a threshold curve sharpness for fitting check rails.

Given Data / Assumptions:

• Curve sharpness is expressed as degree of curve (central angle subtended by standard chord).
• Inner side of inner rail is the gauge face reference location.
• Standard Indian practice for BG is considered.

Concept / Approach:
As curvature increases, the angle of attack of wheelsets grows, increasing flange contact and risk at the gauge corner. Check rails restrain the flange path, reducing lateral forces and wear. Thresholds are set so that only sufficiently sharp curves receive check rails, optimizing maintenance cost and safety.

Step-by-Step Solution:
Identify BG threshold for check-rail provision.Use standard rule: provide check rails on curves sharper than about 5° on BG, depending on traffic and speed.Choose 5° as the specified value in the options.

Verification / Alternative check:
Maintenance and P&Way manuals corroborate that about 5° is the commonly cited trigger for check rails on BG, with local adjustments for traffic density.

Why Other Options Are Wrong:

• 3°: Too mild for mandatory check rails.
• 6° or 8°: These are sharper curves; waiting until these values could increase wear risk.

Common Pitfalls:
Confusing BG with MG/NG thresholds; assuming check rails are needed on all curves, which is uneconomical and unnecessary.

Final Answer:
5°