Definition – Turn-in-curve: In permanent-way terminology, a “turn-in-curve” is best described as which of the following?

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