---
title: "Design steps of superelevation"
subject: "Transportation Engineering I"
chapter: 3
key: "semester_6/transportation_engineering_i:super-design-steps"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/super-design-steps
site: BCT Engineering
---

# Design steps of superelevation

Transportation Engineering I · Chapter 3: Geometric Design of Highway

- Asked in: 2076 Baisakh; 2072 Ashwin; 2069 Bhadra (asked 3 times)
- Video: [TE- Design of super elevation](https://www.youtube.com/watch?v=G3FS9fOZU5k) — talk on civil engineering (TOCE)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/super-design-steps
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-3

## Question

List the design steps of superelevation.

## Short answer

Design steps: 1) Fix design speed V and radius R. 2) Compute e = V²/(225R) for 75% V. 3) Limit to e_max (7% plain, 10% hilly). 4) Minimum e not less than camber (2.5%). 5) Check friction f = V²/(127R) - e ≤ 0.15; adjust speed or R if exceeded. 6) Set introduction rate (1:150 plain, 1:60 hilly). 7) Choose rotation method. 8) Add extra widening along transition.

## Answer

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.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. The first computed superelevation uses:
   A. Full design speed with full friction
   B. 75% of design speed with no friction, e = V^2/225R
   C. Zero speed
   D. Twice the speed
   Answer: B. IRC takes e = V^2/(225R). (Key point: Initial superelevation)

2. Maximum superelevation in plain/rolling and hilly terrain is:
   A. 10% and 7%
   B. 5% and 5%
   C. 7% and 10%
   D. 15% and 20%
   Answer: C. 7% for plain/rolling and 10% for hills. (Key point: Maximum e)

3. After adopting e, the friction check at full speed is:
   A. f = V^2/127R - e <= 0.15
   B. f = e
   C. f >= 0.15
   D. f = V/R
   Answer: A. The friction required at full speed must not exceed 0.15. (Key point: Friction check)

4. If computed e is less than the camber:
   A. Use zero
   B. Provide camber value (about 2.5%) or a one-way cross fall
   C. Use 7%
   D. Ignore the curve
   Answer: B. Minimum is not less than camber. (Key point: Minimum e)

## Related in Transportation Engineering I

- [Superelevation design for 150 m radius](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-79j-super-150) — Transportation Engineering I, chapter 3
- [Design steps of surface drainage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asurface-drainage-design-steps) — Transportation Engineering I, chapter 4, asked 3×
- [Design steps of side drain](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aside-drain-design) — Transportation Engineering I, chapter 4
- [Derivation of superelevation expression](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asuper-derive) — Transportation Engineering I, chapter 3, asked 7×
- [Superelevation on 100 m radius curve](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-62j-super-100) — Transportation Engineering I, chapter 3

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