Design steps of superelevation

Design steps of superelevation (IRC practice, followed in NRS 2070 designs):

1. Fix the design speed $V$ (km/h) and the radius $R$ of the curve from the road class and terrain.
2. Compute the superelevation for 75% of the design speed with no friction: $$e = \frac{V^2}{225\,R}$$
3. Compare it with the maximum value: 7% for plain and rolling terrain (and snow-bound areas), 10% for hilly terrain (IRC). If $e$ is more than the maximum, adopt $e_{max}$.
4. Minimum value: not less than the camber (normally 2.5%); if the computed $e$ is smaller than the camber, provide the camber value as a one-way cross fall.
5. Check friction at the full design speed: $$f = \frac{V^2}{127\,R} - e \le 0.15$$ If $f > 0.15$, either restrict the speed to $V_a = \sqrt{127R(e+f)}$ with $f = 0.15$, or increase $R$.
6. Decide the rate of introduction of superelevation (1 in 150 in plain/rolling terrain, 1 in 60 in mountainous/steep terrain) and find the length of the transition.
7. Choose the method of attaining superelevation (about the centre line or the inner edge) and prepare the diagram of edge levels.
8. Provide the extra widening and introduce it along the same transition length.