Traffic lights - why are they shaded ?

Question

Many traffic lights, especially in London, have a grill like a tiny, circular Venetian blind, across the glass. Why ?

Answer 1

It's an attempt to aim the signal at only the lane that is supposed to see it. Old traffic signals were unshaded and at a big intersection it was possible for drivers to accidentally follow a signal that was not meant for them.

Answer 2

I can think of 2 purposes, One would be so that drivers that are stopped cannot attempt to guess when the change will be and thus jump the gun and two would be so that drivers that are controlled by that light can see it well when the sun is at such an angle so as to cause a glare on the signal. I would assume that both are correct.

Answer 3

Here in the US they do this as well. I mostly notice it at intersections with more than 2 streets crossing. I think it is so you can't see the light change for the other people and get confused or try to go then.
Just a theory

Answer 4

It is because, at some junctions, without these directional filters, the traffic signals could be viewed from a direction from which they are not intended to apply.

Often they are applied to pelican crossings immediately beyond a junction signal. Without these filters, traffic waiting at the red light of the junction may misinterpret them as applying to the junction (and not the pelican crossing).

Answer 5

To eliminate sun glare. The sun can give the illusion that the green light is illuminated, which can cause a nasty scene at the intersection.

Answer 6

So you can see it in direct sun light
The grill cast a shadow on the light so you can see it.
We have the same thing here in the states.

Answer 7

So that you can't see the light color changes from the intersecting street, which might cause you to "jump" the light -- start before your light turns green.

Answer 8

to stop the glare of the sun making the traffic lights unable to be seen, safety!!

Answer 9

Eliminate glare, particularly in the spring when the sun is low.

Answer 10

this is to stop bright sunlight from shining directly onto the light and causing a reflection which makes drivers think that the light is on