---
title: "Advantages of shoulder and extra widening"
subject: "Transportation Engineering I"
chapter: 3
key: "semester_6/transportation_engineering_i:shoulder-extra-widening-adv"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/shoulder-extra-widening-adv
site: BCT Engineering
---

# Advantages of shoulder and extra widening

Transportation Engineering I · Chapter 3: Geometric Design of Highway

- Asked in: 2079 Chaitra, 6 marks
- Video: [Extra widening on road | Extra widening on curve | HIGHWAY ENGINEERING](https://www.youtube.com/watch?v=jAm1n-bYmxY) — Engineer's Coach
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/shoulder-extra-widening-adv
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-3

## Question

What are the advantages of providing shoulder and extra widening in a road?

## Short answer

Shoulders provide lateral support, emergency stopping space, extra width for turning and overtaking, pedestrian/cyclist space, drainage, and psychological comfort. Extra widening accommodates off-tracking of long vehicles, gives extra clearance for passing, eases steering, prevents lane encroachment, and maintains capacity and speed on curves.

## Answer

#### Advantages of shoulders
1. **Lateral support** to the pavement edges; protects the pavement layers and prevents edge failure.
2. **Space for emergency stopping** and breakdown without disturbing the traffic; improves safety.
3. **Extra width** for turning, overtaking manoeuvres and better lateral clearance; increases capacity.
4. **Pedestrian and cyclist space** in rural roads.
5. **Drainage:** carries water away from the pavement; keeps water away from the pavement base and subgrade.
6. Space for **maintenance work, signs, snow storage** and utilities.
7. Gives **psychological comfort** to the drivers and improves sight distance in curves in cut.

#### Advantages of extra widening
1. Provides for **off-tracking** of the rear wheels of long vehicles on curves.
2. Gives **extra clearance** for vehicles to pass each other at the curve.
3. Compensates for the driver's difficulty in steering at the curve (psychological need).
4. Prevents the vehicles from **encroaching** on the neighbouring lane or shoulder, reducing accidents.
5. Maintains the **capacity and speed** of the road on curves.
6. Reduces edge damage and maintenance.

## Check yourself

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

1. How do shoulders protect the pavement structure?
   A. They increase the camber of the pavement
   B. They give lateral support to the pavement edges and prevent edge failure
   C. They carry the wheel load of heavy vehicles regularly
   D. They raise the design speed
   Answer: B. Shoulders support the pavement edges and keep water away from the base and subgrade. (Key point: Shoulder lateral support)

2. Which is a safety benefit of shoulders?
   A. They remove the need for sight distance
   B. They force vehicles to slow down
   C. They give space for emergency stopping without disturbing traffic
   D. They allow narrower carriageway lanes
   Answer: C. Broken-down vehicles can stop on the shoulder, so the traffic flow is not obstructed. (Key point: Shoulders for safety)

3. Why is extra widening provided on horizontal curves?
   A. To compensate for off-tracking of rear wheels of long vehicles
   B. To increase the radius of the curve
   C. To reduce the superelevation needed
   D. To provide a place for parking
   Answer: A. On a curve rear wheels follow a path inside the front wheels, so extra width is needed for off-tracking. (Key point: Off-tracking and extra widening)

4. Which is a benefit of extra widening, as stated in the answer?
   A. It lengthens the transition curve
   B. It prevents vehicles encroaching on the neighbouring lane or shoulder, reducing accidents
   C. It reduces the cost of earthwork
   D. It removes the need for shoulders
   Answer: B. Extra width gives clearance between passing vehicles and keeps vehicles in their lane, maintaining capacity and reducing accidents. (Key point: Extra widening effects)

5. Which role of shoulders relates to drainage?
   A. They store rainwater for later use
   B. They make the pavement impermeable
   C. They carry water away from the pavement and keep the base and subgrade dry
   D. They replace the side drains completely
   Answer: C. Shoulders carry water away from the pavement so the base and subgrade are not weakened. (Key point: Shoulder drainage)

## Related in Transportation Engineering I

- [Extra widening: reasons and derivation](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aextra-widening-derive) — Transportation Engineering I, chapter 3, asked 8×
- [Reasons for extra widening](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aextra-widening-reasons) — Transportation Engineering I, chapter 3, asked 3×