Answer: C. 1 in 30
On the recommendations of Indian Road Congress, the ruling gradient in plains, is 1 in 30.
Ruling/Design Gradient: It is the maximum gradient, by which roads are designed.
Limiting Gradient: It is steeper than Design Gradient. This gradient is used when construction cost is high.
Exceptional gradient: It is steeper among all the gradients. This is generally used where any steepy obstruction of length less than 100 m arises.
Gradients for different types of terrain are represented as follows.
Ruling Gradient (in %)
Limiting Gradient (in %)
Exceptional gradient (in %)
Plain and Rolling
Mountainous or hilly ( Elevation > 3000m )
Steepy ( Elevation > 3000m )
Ruling gradient in plains: 3.3 % or 1 in 30.
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