Definition – Turn-in-curve: In permanent-way terminology, a “turn-in-curve” is best described as which of the following?
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AA simple curve introduced between two straights
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BA standard reverse curve (S-curve) between straights
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CA reverse curve introduced in continuity of a turnout
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DA spiral transition curve
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ENone of these
Answer
Correct Answer: A reverse curve introduced in continuity of a turnout
Explanation
Introduction / Context:Special track geometry terms describe how diverging routes are connected. “Turn-in-curve” appears in turnout lead design and yard layouts.
Given Data / Assumptions:
- Term is specific to curves associated with a turnout.
- Reverse curvature near switches and crossings is common.
Concept / Approach:A turn-in-curve is a reverse curve arranged to smoothly connect the diverging route further into the turnout lead, maintaining alignment constraints and clearance envelopes.
Step-by-Step Solution:Recognize that the curve continues the turnout geometry.Identify reverse curvature within that continuity.Select the description: reverse curve in continuity of a turnout.
Verification / Alternative check:Design charts and practice notes label these as turn-in curves or similar terminology near switches.
Why Other Options Are Wrong:
- Simple curve between straights lacks the turnout context.
- Generic reverse curve not necessarily tied to a turnout.
- Spiral transition is a curvature-varying element, not specifically a reverse within a turnout.
Common Pitfalls:Equating any reverse curve with a turn-in-curve without the turnout linkage.
Final Answer:A reverse curve introduced in continuity of a turnout