Turnout components: Which of the following statements about tongue (switch) and stock rails is correct?

Introduction / Context:
Safe turnout operation depends on adequate switch (tongue) rail length and the proper proportioning of stock rails. These details help ensure smooth wheel guidance, reduced impact at the toe, and sufficient support to avoid derailments.

Given Data / Assumptions:

• Standard practice for mainline turnouts.
• Rigid wheel base is the fixed distance between wheel centers on a vehicle without steering articulation.

Concept / Approach:
Longer tongue rails provide a gradual change of alignment, reducing flange impacts. Stock rails, being the running rails against which tongues close, should be longer to extend support and provide adequate lead for fittings. A minimum length ahead of the toe ensures structural integrity and better wheel transition behavior.

Step-by-Step Solution:
1) (a) Longer tongue than rigid wheel base enables gradual steering of wheels.2) (b) Stock rail longer than tongue rail provides extended guidance and support.3) (c) Maintaining at least 1.65 m ahead of toe is a common minimum to accommodate chairs/fastenings and reduce toe battering.4) Therefore, all statements are satisfied in standard design.

Verification / Alternative check:
Turnout design manuals depict stock rail extensions and tongue planing lengths based on speed and axle load categories, aligning with the statements.

Why Other Options Are Wrong:

• Partial selections omit at least one valid and necessary requirement.

Common Pitfalls:

• Underestimating tongue length, leading to higher impact and maintenance.

Final Answer:
All of the above.