Placement rule for check rails at a crossing: how much of the check rail length is kept ahead (in front) of the nose of crossing?

Introduction / Context:
Check rails are fitted opposite the crossing to control the wheel flange path and prevent it from striking the nose of crossing. Correct longitudinal placement of check rails is essential to safe guidance and reduced wear.

Given Data / Assumptions:

• Standard turnout/crossing geometry is considered.
• “Ahead of the nose” means toward the approaching traffic direction.

Concept / Approach:

The greater portion of a check rail must lie ahead of the nose to guide the wheel well before it reaches the critical crossing region. A commonly used rule-of-thumb is to place about two-third of its total length in front of the nose, the remaining one-third trailing behind.

Step-by-Step Solution:

Verification / Alternative check:

Typical permanent-way manuals illustrate check rail layouts with longer leading lengths to align and restrain flanges prior to the crossing gap.

Why Other Options Are Wrong:

One-third ahead is insufficient; three-fourths ahead is excessive and may reduce trailing protection; symmetric placement does not prioritize the critical approach area; all-behind offers no advance guidance.

Common Pitfalls:

Confusing “ahead” with “behind”; overlooking directionality of traffic dominance in layouts.

Final Answer:

Two-third of its length ahead of the nose