Superelevation development: Before rotating the carriageway to provide superelevation, the portion between the crown and the outer edge is first made…

Introduction / Context:
Superelevation tilts the pavement to counteract lateral acceleration on curves, improving safety and comfort. The process of developing superelevation from a crowned section to a fully rotated surface must be staged to avoid abrupt crossfall changes and water ponding.

Given Data / Assumptions:

• Two-lane crowned pavement transitioning into a curve.
• Standard method is by rotating about the centerline or the inner edge depending on practice.
• Drainage and ride comfort are key constraints.

Concept / Approach:

In the commonly adopted method, the outer half of the carriageway is raised progressively. The first action is to eliminate the adverse camber on the outer half by bringing the segment between crown and outer edge to a horizontal line. Subsequent rotation then provides the required outward upward cross slope.

Step-by-Step Solution:

Verification / Alternative check:

Profile templates and field superelevation runouts show an initial “zeroing” of the outer half crossfall before adding the designed tilt, thereby preventing a sharp kink and ensuring drainage continuity.

Why Other Options Are Wrong:

• Reduced fall: still leaves adverse camber; not the standard first step.
• Same slope as inner half: would double crown height; not intended.
• None of these: incorrect because the established first step is to make it horizontal.

Common Pitfalls:

• Too short a transition length causes abrupt crossfall changes and discomfort.
• Ignoring shoulder crossfall adjustments alongside the carriageway.

Final Answer:

Horizontal (leveled from crown to outer edge).