---
title: "Components of highway drainage system"
subject: "Transportation Engineering I"
chapter: 4
key: "semester_6/transportation_engineering_i:drainage-components"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/drainage-components
site: BCT Engineering
---

# Components of highway drainage system

Transportation Engineering I · Chapter 4: Highway Drainage

- Asked in: 2075 Bhadra
- Video: [Highway Drainage - Transportation Engineering - I](https://www.youtube.com/watch?v=74_mP-_38zk) — Ekeeda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/drainage-components
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-4

## Question

What are the components of the highway drainage system?

## Short answer

Highway drainage components include camber, shoulders, side drains, catch drains, mitre drains, cross-drainage structures, sub-surface drainage, erosion control works, urban components like gullies and storm sewers, and disposal outlets. Together they remove surface and ground water safely. Each component prevents water from damaging the road.

## Answer

The components of a highway drainage system are:

1. **Camber and cross-slope of the carriageway and shoulders**: first stage of removing the surface water.
2. **Side drains (longitudinal drains)**: open or lined drains along the road edge; kerb and channel in urban areas.
3. **Catch / intercepting drains**: above cut slopes to stop hill-side runoff reaching the road.
4. **Mitre (turnout) drains and outfalls**: take water from side drains into natural ground.
5. **Cross-drainage structures**: culverts, causeways, minor bridges (and inverted siphons or aqueducts where needed).
6. **Sub-surface drainage**: trench drains with perforated pipe, drainage blankets, cut-off layers, horizontal drains and weep holes in retaining walls.
7. **Erosion control and energy dissipating structures**: check dams, drop structures, aprons, rip-rap, stilling basins, bio-engineering.
8. **Urban components**: gully inlets, catch basins, storm sewers and manholes.
9. **Disposal**: natural streams, soak pits or storage ponds.

## Check yourself

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

1. The first stage of removing surface water is:
   A. Camber and cross slope
   B. Storm sewer
   C. Culvert
   D. Siphon
   Answer: A. Camber and cross slope of carriageway and shoulders start the process. (Key point: First stage)

2. Catch drains are placed:
   A. Above cut slopes
   B. At the river
   C. In the pavement
   D. Under the culvert
   Answer: A. They stop hillside runoff from reaching the road. (Key point: Catch drains)

3. Mitre drains and outfalls:
   A. Break capillary rise
   B. Support pavement
   C. Carry water under road
   D. Take water from side drains into natural ground
   Answer: D. They discharge side-drain water to a safe outlet. (Key point: Mitre drains)

## Related in Transportation Engineering I

- [Requirements of highway drainage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Arequirements-highway-drainage) — Transportation Engineering I, chapter 4, asked 6×
- [Define highway drainage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Adefine-highway-drainage) — Transportation Engineering I, chapter 4, asked 5×
- [Importance of highway drainage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Adrainage-importance) — Transportation Engineering I, chapter 4, asked 4×
- [Classification of highway drainage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aclassify-highway-drainage) — Transportation Engineering I, chapter 4
- [Surface drainage system](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asurface-drainage-system) — Transportation Engineering I, chapter 4
- [Components of transportation system](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Atransport-components) — Transportation Engineering I, chapter 1, asked 6×

## Related in other subjects

- [Layout planning of surface drainage system](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Asurface-drainage-layout-planning) — Irrigation and Drainage Engineering, chapter 9
- [Components of canal irrigation system](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Acanal-components-sketch) — Irrigation and Drainage Engineering, chapter 3, asked 7×
- [Bridge components; tunnel drainage and ventilation](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Abridge-components-tunnel-drainage-ventilation) — Transportation Engineering II, chapter 5
- [Bridge components; tunnel drainage and ventilation](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Abridge-components-tunnel-drainage-ventilation-problems) — Transportation Engineering II, chapter 5