On Indian Railways, the angle of crossing associated with the V-crossing (frog) is commonly calculated by which method?

Introduction / Context:
The angle of crossing determines the geometry of the V-crossing (frog) in a turnout or diamond. Several geometric conventions exist for defining and computing this angle for design and manufacture.

Given Data / Assumptions:

• Indian Railways practice allows more than one accepted method in standards and literature.
• Focus is on common calculation conventions rather than numerical value.

Concept / Approach:

Two widely taught approaches are Cole’s method and the centre-line method. Both yield consistent, practically usable definitions for specifying and checking crossings. The isosceles-triangle method is more of a didactic geometric construct and not the usual specification basis.

Step-by-Step Solution:

Verification / Alternative check:

Handbooks present tables with crossing numbers convertible between methods for checking and procurement.

Why Other Options Are Wrong:

Using only one of the two omits a commonly accepted method; the isosceles-triangle method is not the common specification basis; “parabolic transition method” is unrelated to crossing angle definition.

Common Pitfalls:

Confusing crossing angle with turnout angle or switch angle; misinterpreting crossing number (1 in N) as a direct degree measure.

Final Answer:

Both Cole’s and Centre-line methods