Road gradients terminology: The steepest gradient ordinarily permitted in geometric design (while still considered desirable under normal conditions) is termed what?

Introduction / Context:
Gradients affect traction demand, heavy-vehicle performance, drainage, and safety. Highway design classifies gradients to distinguish everyday desirable values from absolute or exceptional limits that may be allowed under constraints.

Given Data / Assumptions:

• Ordinary conditions; no extraordinary topographic constraints.
• Design speed and class appropriate to the facility.
• Focus on terminology rather than a numeric gradient value.

Concept / Approach:

Ruling gradient is the desirable upper bound used most frequently over long stretches. Maximum gradient is steeper and permitted for limited distances when necessary. Exceptional gradient is even steeper and allowed only over very short lengths with special justification. A floating gradient relates to grades that balance tractive effort and resistance, often discussed in economic operation concepts rather than geometric limits.

Step-by-Step Reasoning:

Verification / Alternative check:

IRC guidelines define class- and terrain-specific values for ruling, maximum, and exceptional gradients, with ruling used predominantly.

Why Other Options Are Wrong:

• Maximum/Exceptional: permitted but not “ordinary” or “desirable” over long stretches.
• Floating gradient: different concept context.

Common Pitfalls:

• Confusing naming with numeric values; always refer to the project’s terrain and class table.

Final Answer:

Ruling gradient.