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What is Superelevation in Highway Engineering?Superelevation is the transverse slope provided to counteract the effect of centrifugal force and reduce the tendency of vehicle to overturn and to skid laterally outwards by raising the pavement outer edge with respect to inner edge. superelevation is represented by “ e ”.
Analysis of superelevationLet us say Design speed = V m/s Radius = R m
Various forces acting on the vehicle:Where e = rate of superelevation in % f = lateral friction factor = 0.15 V = velocity of vehicle in m/s g = acceleration due to gravity = 9.81 m/s2 R = radius of circular curve in meters.
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%
Limits for minimum superelevationMinimum superelevation = camber or cross slope Camber: Slope provide in the transverse direction to drain off rain water quickly is known as Camber or Cross slope. This will also prevents slipping and skidding of vehicles.
IRC Recommendations for Camber
|Type of pavement||Light rainfall intensity||Heavy rainfall intensity|
|C.C pavements and thick bituminous pavements||1 in 60||1 in 50|
|Thin Bituminous Pavements||1 in 50||1 in 40|
|W.B.M and Gravel Pavements||1 in 40||1 in 33|
|Earthen Pavements||1 in 33||1 in25|