---
title: "Short note: importance of lighting in tunnel"
subject: "Transportation Engineering II"
chapter: 5
key: "semester_7/transportation_engineering_ii:short-note-tunnel-lighting-importance"
source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/short-note-tunnel-lighting-importance
site: BCT Engineering
---

# Short note: importance of lighting in tunnel

Transportation Engineering II · Chapter 5: Introduction to Bridge and Tunnel Engineering

- Asked in: 2066 Bhadra, 4 marks
- Video: [M5 ESD L6 Roadway Lighting](https://www.youtube.com/watch?v=I088X1Qk9aY) — Babu Thomas
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/short-note-tunnel-lighting-importance
- Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-5

## Question

Write a short note on importance of lighting in tunnel.

## Short answer

Tunnel lighting prevents the black-hole effect as drivers enter from bright daylight, enabling safe vision. It uses a sequence of luminance zones (threshold, transition, interior, exit) for eye adaptation. Proper illumination ensures traffic flow at design speed, reduces fatigue, and supports emergency evacuation.

## Answer

Lighting in a tunnel is important for safe driving and easy adaptation of the eyes.
- Daytime drivers moving from bright outside into a dark tunnel suffer the **black-hole effect**; lighting reduces temporary blindness and accidents.
- Gradual luminance reduction (**threshold, transition, interior and exit zones**) lets the eye adapt.
- It lets drivers see the road, obstacles, signs, and pedestrians, so traffic flows at the design speed.
- It gives comfort and reduces fatigue in long tunnels, and helps maintenance staff work.
- Emergency lighting helps evacuation and rescue in power failure or fire.
- Good lighting design follows CIE 88 and IRC:SP:91 with energy-efficient luminaires like LED lamps.

## Check yourself

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

1. What is the black-hole effect in tunnel lighting?
   A. Glare from too many lamps inside the tunnel
   B. Loss of power that blacks out the tunnel
   C. Temporary blindness of a driver moving from bright daylight into a dark tunnel
   D. Dust that collects in the tunnel roof
   Answer: C. The eye cannot adapt instantly, so the tunnel entrance looks like a black hole; lighting reduces this temporary blindness and accidents. (Key point: Black-hole effect)

2. Why is luminance reduced gradually through threshold, transition, interior and exit zones?
   A. To save energy only
   B. To let the driver's eyes adapt gradually
   C. To make the tunnel look longer
   D. To reduce the heat from the lamps
   Answer: B. Gradual reduction of luminance gives the eye time to adapt from outside brightness to the tunnel interior. (Key point: Lighting zones)

3. What is the purpose of emergency lighting in a tunnel?
   A. To help evacuation and rescue during power failure or fire
   B. To raise the interior luminance during daytime
   C. To replace the threshold zone lighting permanently
   D. To dry the tunnel walls
   Answer: A. Emergency lighting helps people evacuate and rescuers work when power fails or a fire occurs. (Key point: Emergency lighting)

## Related in Transportation Engineering II

- [Tunnel lighting factors; river bank protection methods](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Atunnel-lighting-factors-river-bank-methods) — Transportation Engineering II, chapter 5
- [Tunnel lighting and ventilation: importance and methods](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Atunnel-lighting-ventilation-importance-methods) — Transportation Engineering II, chapter 5