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

# Methods of providing superelevation

Transportation Engineering I · Chapter 3: Geometric Design of Highway

- Asked in: 2079 Ashwin, 4 marks; 2077 Chaitra, 5 marks; 2074 Bhadra, 8 marks; 2071 Bhadra; 2068 Magh (old course), 8 marks (asked 5 times)
- Video: [Methods of Providing Superelevation on Highways](https://www.youtube.com/watch?v=yfeVoyRwe2Y) — CIVIL WALAY
- 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-methods
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-3

## Question

Describe the different methods of providing/introducing superelevation with neat sketches.

## Short answer

Superelevation is introduced by rotating pavement cross-section over transition length. Methods: (1) eliminate crown by rotating outer edge about crown or shifting crown diagonally; (2) rotate about centerline (outer edge raised, inner lowered equally); (3) rotate about inner edge (outer edge raised); (4) rotate about outer edge (inner edge lowered). Centerline rotation used on plains; inner edge rotation on hill roads for drainage.

## Answer

Superelevation is provided by rotating the pavement cross-section over the transition length (or partly on the tangent before the curve if there is no transition). The pavement is first changed from a cambered section to a flat or one-way section, and then to the full superelevation. The change should be gradual (rate 1 in 150 to 1 in 60, depending on the terrain).

#### 1. Eliminating the crown (removing the adverse camber)
- **Outer edge rotated about the crown:** the **outer half is rotated about the crown** until it is in line with the inner half (the normal camber is removed); then the whole pavement is rotated to give the required superelevation.
- **Diagonal crown (crown shifting) method:** the crown is gradually shifted towards the outer edge until the whole width has a one-way slope. It needs less change of edge level but is rarely used.
- Done over the first part of the transition length.

```text
 normal:   /\        flat:  ____    full e:     ___/
          /  \              ----           ___/
```

#### 2. Rotating about the centre line
- The pavement is turned about the **centre line:** the outer edge is raised and the inner edge lowered by equal amounts, each by half of the total difference.
- Advantages: the centre-line level stays fixed (profile unchanged), and the earthwork is balanced on the two sides. Mostly used on plains.
- Disadvantage: the inner edge drops below the ground profile, which may cause a drainage problem.

```text
   outer edge up   ____.-----   
   centre fixed ---+
   inner edge down ----'
```

#### 3. Rotating about the inner edge
- The inner edge is the fixed pivot and the **outer edge is raised;** the centre line also rises.
- Used where drainage is critical or the inner edge level cannot be changed (e.g. in cuttings, on hill roads).
- Disadvantage: the centre-line profile is changed and the outer edge is raised more, which affects levels and appearance.

```text
   outer edge up  ______----.
   centre line up    .--'
   inner edge fixed ---
```

#### 4. Rotating about the outer edge
- The outer edge level is kept fixed and the **inner edge is lowered;** used where the outer edge profile must be kept (for appearance, or on a curve on a hillside).

#### Remarks
- The pavement is generally rotated about the centre line on plain roads and about the inner edge in drainage-sensitive cases.
- If no transition curve is provided, about two-thirds of the superelevation run-off is placed on the tangent and one-third inside the circular curve (IRC). The extra widening is introduced over the same length.

## Check yourself

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

1. In the elimination of crown method, what is done first?
   A. Whole pavement is rotated to full e
   B. Inner edge is lowered
   C. Outer half is rotated about the crown until level with the inner half
   D. Centre is raised
   Answer: C. The outer half is first rotated to remove adverse camber, then the whole is rotated. (Key point: Eliminating crown)

2. In rotation about the centre line:
   A. Inner edge fixed
   B. Outer edge fixed
   C. Centre is raised
   D. Outer edge is raised and inner lowered equally, keeping the centre profile unchanged
   Answer: D. Each edge moves half of the difference; centre line profile is unchanged. (Key point: Centre line rotation)

3. Rotation about the inner edge is used where:
   A. Drainage is critical or inner edge level cannot be changed
   B. Plains with no drainage issues
   C. Outer edge must be fixed
   D. No superelevation
   Answer: A. Inner edge is kept as pivot, outer edge raised. (Key point: Inner edge rotation)

4. If no transition curve is provided, how is run-off placed?
   A. All on the curve
   B. All on the tangent
   C. One-third on tangent, two-thirds on curve
   D. About two-thirds on the tangent and one-third inside the circular curve
   Answer: D. IRC places about 2/3 on the tangent and 1/3 on the curve. (Key point: No transition)

## Related in Transportation Engineering I

- [Superelevation and conditions for providing it](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asuper-define-conditions) — Transportation Engineering I, chapter 3