Superelevation Design

Superelevation In Highway Design

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Superelevation design is part of the design of the horizontal alignment of a highway. Superelevation is provided to counteract the effect of centrifugal force on the horizontal curves.

Why super elevation is needed?

When a vehicle is negotiating on a horizontal curve on a highway, it experiences the centrifugal force acting on it in the direction outwards the curve it tracing.
To counteract this centrifugal force, a vehicle has two options
– to get assist with the lateral friction between the road and the vehicle
As per Indian Standards, the value of coefficient of friction to prevent lateral skidding is limited to 0.15 for design purposes
– Vehicle counteracts by creating an overturning moment

This is when superelevation comes into the picture. When we provide superelevation we can help vehicles counteract the centrifugal force. Superelevation is simply the transverse inclination in the pavement also called ‘cant’ or ‘banking’

Attainment of superelevation

  1. By elimination of the crown of the cambered section
  2. Rotation of pavement to attain full superelevation

Superelevation is introduced by a rise in the outer edge of the pavement at a rate of not exceeding 1 in 150 in plain and rolling terrain and 1 in 60 in mountainous terrain.

IRC Recommendations for Camber

Type of PavementLight Rainfall IntensityHeavy Rainfall Intensity
C.C pavements and thick bituminous pavements1 in 601 in 50
Thin Bituminous Pavements1 in 501 in 40
W.B.M and Gravel Pavements1 in 401 in 33
Earthen Pavements1 in 331 in25

Limits for Maximum Superelevation

According to IRC the Maximum Superelevation in Areas Which Are Bound by Snow fall – 7% Which are not bounded by Snowfall – 10%

Important Links For Transportation Engineers-
AASHTO – Official site
Indian Road Congress – Official Site
Other Relevant Posts-
IRC 112-2011 [PDF Download]
Necessity, Benefits and Ill effects of irrigation

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