Can you use you knowledge of the structure of the human eye to explain this...?

Question

You may have used underground traffic tunnels and noiced that there are far more lights switched on in daytime than at night. This is a safety precaution.

Can you explain the reason(s) behind this please?

Answer 1

I would agree with "K".

Answer 2

Also at night time people usually have their headlights on which offsets the need for so many lights.

Answer 3

Good question!!

At the back of your eye is a light-sensitive structure known as the retina. Your retina has structures that we refer to as cones and rods. Cones are primarily used to distinguish colors, while rods are responsible for night vision and accommodation to light.

When you drive during the day, your rods are adjusted to a "bright" setting. Drive into a tunnel that's dark, and you will notice that you will either have:

1. An afterimage of light streaks.

2. A hard time adjusting to the low-light setting.

This is the reason why more lights are on during the day: to help the driver accommodate gradually to low light settings.

During the night, those lights are turned off so as not to blind a driver. Your pupils(the black hole) need to contract to allow just the right amount of light to hit your retina. It's potentially dangerous to travel from a minimal light environment to one that is extremely bright because your eyes will be slow to adapt.

The key here is gradual accommodation to light. During the day(light--> light=more lights), whereas during the night(dark-->dark=less lights).

Answer 4

Never actually noticed this myself, and I use the Clyde Tunnel regularly.  Anyhoo, they probably do this so that your eyes don't have to accustom themselves to darkness / light when entering or exiting the tunnel.