Maximum Value of Superelevation in Highway Design

Superelevation is the slope provided on the horizontal curve of a highway to counterbalance the centrifugal force acting on a vehicle. The maximum value of superelevation provided in the design of horizontal alignment of a highway is 0.07.

Factors Affecting Superelevation

The following factors affect the selection of maximum superelevation in highway design:

1. Design speed: The maximum superelevation is directly proportional to the design speed of the highway. As the design speed increases, the maximum superelevation also increases.

2. Radius of curvature: The maximum superelevation is inversely proportional to the radius of curvature of the horizontal curve. As the radius of curvature decreases, the maximum superelevation increases.

3. Coefficient of friction: The maximum superelevation is directly proportional to the coefficient of friction between the tires of the vehicle and the road surface. As the coefficient of friction increases, the maximum superelevation also increases.

4. Vehicle characteristics: The maximum superelevation is also affected by the type of vehicle using the highway. Heavy vehicles require less superelevation compared to light vehicles.

Calculation of Maximum Superelevation

The maximum superelevation can be calculated using the following formula:

e(max) = V^2 / (127 R + f)

Where,
e(max) = maximum superelevation
V = design speed in km/h
R = radius of curvature in meters
f = coefficient of friction

For a design speed of 80 km/h and a coefficient of friction of 0.7, the maximum superelevation for a radius of curvature of 100 meters is calculated as:

e(max) = 80^2 / (127 x 100 + 0.7) = 0.07

Therefore, the maximum superelevation provided in the design of horizontal alignment of a highway is 0.07.