---
title: "Elements of cut and fill cross-section"
subject: "Transportation Engineering I"
chapter: 3
key: "semester_6/transportation_engineering_i:cut-fill-cross-section"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/cut-fill-cross-section
site: BCT Engineering
---

# Elements of cut and fill cross-section

Transportation Engineering I · Chapter 3: Geometric Design of Highway

- Asked in: 2068 Magh (old course), 8 marks
- Video: [Roadway Fundamentals - Introduction to road design, cross sections and alignments](https://www.youtube.com/watch?v=SNKuX5OTICg) — Tall Bridgeguy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/cut-fill-cross-section
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-3

## Question

Draw a typical cross section of a partially cut and filled road. Describe all its elements.

## Short answer

A hill road cross-section combines cut (excavation) and fill (embankment) to balance earthwork. Key elements include carriageway with camber, shoulders, side drain on cut side, cut slope with catch drain, fill slope with toe protection, retaining/breast walls, benching, parapets, and right-of-way. Slope protection uses bio-engineering.

## Answer

A road on a hillside or sloping ground is built partly in **cut** (excavation into the hill) and partly in **fill** (embankment on the lower side). This is the usual section in hill roads, because it balances the earthwork.

```text
         hill slope (natural ground)
              \
     catch     \ cut slope        carriageway
     drain      \   ____ side ___________ shoulder
        \  berm  \ /  drain      camber    \
  ground ---`----- \_|_______________________\ fill slope
                   |<---- formation width ---->\\
                   |                            \\ toe
                                             retaining/breast wall
```

#### Elements
1. **Carriageway:** the paved width for traffic, with camber (or inward slope on hill roads).
2. **Shoulders:** on both sides (1.0-1.5 m in hills), giving lateral support and space for emergency stop.
3. **Formation width:** carriageway + shoulders + side drain on the cut side.
4. **Side (hill-side) drain:** lined drain in the cut side for the surface water from the road and hill.
5. **Cut slope (back slope):** the excavated face; slope depends on soil/rock (e.g. 0.25:1 to 1:1 horizontal : vertical), with a berm (bench) in a high cut.
6. **Catch water drain:** above the cut slope to intercept the hill runoff.
7. **Fill slope (embankment slope):** side slope of fill, generally 1.5:1 to 2:1 (H:V) in earth; shown with toe protection.
8. **Toe of the fill** and **toe wall / retaining wall:** to stop the spreading, in steep ground.
9. **Breast wall:** at the cut side for vertical or unstable faces.
10. **Benching:** steps cut in the natural ground under the fill to bond the embankment.
11. **Parapet / guard rail** at the outer edge on high fill.
12. **Right of way:** total land acquired, including the slopes.
13. **Bio-engineering (turfing, plants)** for slope protection.

## Check yourself

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

1. Why is a partially cut and filled section used on hill roads?
   A. It balances the earthwork
   B. It eliminates drainage
   C. It avoids retaining walls always
   D. It needs no formation width
   Answer: A. Excavated material from the cut forms the fill on the lower side, balancing earthwork. (Key point: Why cut and fill)

2. Where is a catch water drain placed and why?
   A. Beside the carriageway to drain the pavement
   B. Above the cut slope to intercept hill runoff
   C. Under the fill to support it
   D. At the toe of the fill to hold soil
   Answer: B. It intercepts runoff coming from the hill above the cut slope. (Key point: Catch water drain)

3. What is the purpose of benching under the fill?
   A. To drain the road
   B. To widen the carriageway
   C. To bond the embankment with the natural ground
   D. To provide a footpath
   Answer: C. Steps cut in the natural slope bond the new embankment to the ground. (Key point: Benching)

4. A breast wall is provided
   A. at the outer edge of a high fill
   B. on the cut side for vertical or unstable faces
   C. at the crown of the road
   D. between lanes
   Answer: B. A breast wall supports unstable or vertical cut faces; retaining/toe walls support the fill side. (Key point: Breast wall)

## Related in Transportation Engineering I

- [Urban road cross-section elements](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aurban-road-cross-section) — Transportation Engineering I, chapter 3, asked 2×
- [Typical cross-sections of hill roads](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahill-cross-sections) — Transportation Engineering I, chapter 5, asked 9×
- [Cross-sectional elements of a highway](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Across-section-elements) — Transportation Engineering I, chapter 3, asked 2×

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- [Canal cross-section in cutting and filling](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Acanal-cross-section-cut-fill) — Irrigation and Drainage Engineering, chapter 3, asked 3×
- [Cut and fill volume, 20 m formation width](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Avolume-road-20m-width-cut-fill-1-1-1-2) — Surveying I, chapter 9
- [Transition elements; non-typical 3d element](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Atm-not-typical) — Engineering Chemistry, chapter 5