Terrain classification by cross slope If the natural cross slope of the country exceeds 60%, the terrain is classified as:

Introduction / Context:
Terrain classification influences geometric design standards, costs, and earthwork estimates. Agencies categorize terrain by the natural cross slope of the ground.

Given Data / Assumptions:

• Cross slope threshold for terrain classes.
• We need the class for cross slope > 60%.

Concept / Approach:
Typical classification: Plain (0–10%), Rolling (10–25%), Mountainous (25–60%), Steep (> 60%). This reflects increasing alignment difficulty and earthwork challenges.

Step-by-Step Solution:
Given cross slope > 60%.Match to category limits → Steep terrain.

Verification / Alternative check:
Design manuals adopt similar limits; exact cutoffs may vary slightly, but >60% is consistently “Steep.”

Why Other Options Are Wrong:

• Plain, rolling, mountainous: all correspond to lower cross slope ranges.

Common Pitfalls:
Confusing longitudinal grade with natural cross slope used for terrain classification.

Final Answer:
steep