---
title: "Factors affecting stopping sight distance"
subject: "Transportation Engineering I"
chapter: 3
key: "semester_6/transportation_engineering_i:ssd-factors-only"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/ssd-factors-only
site: BCT Engineering
---

# Factors affecting stopping sight distance

Transportation Engineering I · Chapter 3: Geometric Design of Highway

- Asked in: 2073 Bhadra, 5 marks; 2069 Bhadra (asked 2 times)
- Video: [CET 206 - T E | Mod 1 - Lec 5 | Sight Distance - Factor's Affecting & Its Types  | KTU Civil - S4](https://www.youtube.com/watch?v=u01DSrmMbbA) — Alex -E Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/ssd-factors-only
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-3

## Question

Enumerate the various factors affecting the stopping sight distance.

## Short answer

Vehicle speed, driver reaction time (PIEV time), coefficient of longitudinal friction, road gradient, braking efficiency, weather and visibility, driver characteristics, and tyre type and condition.

## Answer

The factors affecting stopping sight distance are:

1. **Speed of the vehicle:** the lag distance increases in proportion to speed and the braking distance with the square of speed.
2. **Total reaction time of the driver (PIEV time):** a longer time increases the lag distance; 2.5 s is adopted in design.
3. **Coefficient of longitudinal friction $f$** between tyre and road, which depends on the road surface (smooth, wet, rough) and tyre condition.
4. **Gradient of the road:** a descending grade increases the braking distance, and an ascending grade decreases it.
5. **Efficiency of brakes** and the loading of the vehicle.
6. **Weather and visibility:** rain, fog, night; height of the driver's eye and of the object.
7. **Driver characteristics:** age, fatigue, alertness, alcohol.
8. **Tyre type and condition.**

## Check yourself

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

1. How does SSD vary with speed?
   A. It is independent of speed
   B. It increases roughly with the square of speed
   C. It decreases as speed rises
   D. It increases linearly only
   Answer: B. Braking distance depends on V^2, so SSD increases roughly with the square of speed. (Key point: Speed)

2. The total reaction time (PIEV time) adopted in design is
   A. 1.0 s
   B. 5 s
   C. 2.5 s
   D. 0.5 s
   Answer: C. A longer reaction time increases the lag distance; 2.5 s is adopted. (Key point: Reaction time)

3. A wet or smooth road surface (lower f) causes SSD to
   A. decrease
   B. stay the same
   C. become zero
   D. increase
   Answer: D. Lower longitudinal friction lengthens the braking distance and thus SSD. (Key point: Friction)

4. How does gradient affect SSD?
   A. A descending grade increases the braking distance; an ascending grade decreases it
   B. An ascending grade increases it
   C. Both grades increase it equally
   D. Gradient has no effect
   Answer: A. Downgrade makes stopping harder, upgrade helps braking. (Key point: Gradient)

## Close variants set in other exams

- [Stopping distance and stopping sight distance](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Astopping-distance-relation) — Transportation Engineering I, chapter 3, asked 3×

## Related in Transportation Engineering I

- [Stopping sight distance and derivation](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Assd-factors-derive) — Transportation Engineering I, chapter 3, asked 6×
- [Stopping sight distance at 50 kmph](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-66m-ssd-50) — Transportation Engineering I, chapter 3
- [Overtaking sight distance derivation](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aosd-derive) — Transportation Engineering I, chapter 3, asked 6×
- [Percent grade from stopping distance difference](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-71bh-grade-ssd) — Transportation Engineering I, chapter 3
- [Vertical curve with intermediate sight distance](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-81a-vc-intermediate) — Transportation Engineering I, chapter 3
- [Intersection sight distance numerical](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-81c-intersection-sd) — Transportation Engineering I, chapter 3

## Related in other subjects

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- [Stopping distance and brake energy](https://www.bctengineer.com/question.md?key=semester_5%2Fautomotive_technology%3Abraking-distance-energy-numerical) — Automotive Technology, chapter 7
- [Factors affecting water demand; variation](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Afactors-affecting-demand) — Water Supply Engineering, chapter 3, asked 5×
- [Factors affecting bearing capacity; water table](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Abearing-capacity-factors-water-table) — Foundation Engineering, chapter 6, asked 5×