Highway engineering – definition of an exceptional gradient on a road A road gradient is termed an “exceptional gradient” when its steepness, intended only for very short lengths in difficult terrain, is how related to the usual (ruling) gradient adopted for the route?

Introduction / Context:
In highway geometric design, different gradient categories are used to balance vehicle performance, safety, and construction economy. “Ruling gradient” is the desirable maximum used for most of the alignment, while “exceptional gradient” is steeper and permitted only for very short stretches where topography or cost makes gentler slopes impractical.

Given Data / Assumptions:

• We are classifying gradients on a road alignment.
• Ruling gradient represents the normal design limit for the route class.
• Exceptional gradient is permitted sparingly (short length) and with suitable traffic considerations.

Concept / Approach:
Vehicle tractive effort reduces on upgrades, increasing fuel consumption and reducing speeds. Therefore, highway standards specify a hierarchy: ruling gradient (used widely), limiting gradient (occasionally), and exceptional gradient (only in unavoidable short sections). By definition, an exceptional gradient is steeper than the ruling gradient and is allowed over very limited lengths with adequate sight distance and safety provisions.

Step-by-Step Solution:

Verification / Alternative check:
Standard design texts list recommended values for ruling, limiting, and exceptional gradients for various terrains. The numerical values differ with terrain, but the relationship among categories remains: exceptional > limiting > ruling (in terms of steepness).

Why Other Options Are Wrong:
Less than average gradient has no codal meaning for classification. Floating gradient relates to economics of vehicle operation on level stretches. Less than minimum or more than maximum mixes unrelated ideas; gradient classification is not stated that way.

Common Pitfalls:
Confusing limiting with exceptional; using exceptional lengths too long; ignoring sight distance and safety on steep segments.

Final Answer:
More than the ruling gradient