Railway yard planning: Which statements about gathering lines and economical yard layout are correct?

Introduction / Context:
Railway yards must fit many sidings into limited space and still allow efficient movements. Gathering lines (lead lines) and the angles they make with sidings determine both the capacity and economy of layout.

Given Data / Assumptions:

• Multiple parallel sidings branch off from a lead line (gathering line).
• Main track access is required.
• Limiting angle concept: the steepest practical turnout/gathering angle permitted by standards and operational constraints.

Concept / Approach:
A gathering line collects sidings and connects them to a main line. If the gathering line is laid diagonally, sidings placed farther away have shorter usable length unless geometry is compensated. Using a diagonal at one end and a parallel gathering line at the other balances lengths. Working at the limiting angle economizes space and turnout usage.

Step-by-Step Solution:
Define gathering line as the lead that provides access from multiple sidings to the main line.Note that a diagonal lead causes length reduction for sidings farther from the main.Provide a parallel gathering line opposite the diagonal end to equalize siding lengths.Adopt limiting angle to minimize land take and material while respecting turnout geometry.

Verification / Alternative check:
Yard design handbooks illustrate equalizing siding lengths using combined diagonal and parallel leads, and recommend near-limiting angles for compact yet functional yards.

Why Other Options Are Wrong:
Each individual statement is correct; hence selecting any single one underestimates the complete design guidance. The only comprehensive choice is “All the above.”

Common Pitfalls:
Using a single diagonal without compensating geometry; ignoring operational clearances (fouling marks) that further reduce effective siding length.

Final Answer:
All the above.