Traffic lights with slatted covers -why?

[silverfoxcc]

There are several sets of lights near me where there are Traffic Lights with these slatted covers on them, so when it is green you cannot see the light until you are right on top of it. Otherwise from some distance away it looks like a TL that has failed

Would love to hear the reasons behind it

[Chris Bertram]

There are several sets of lights near me where there are Traffic Lights with these slatted covers on them, so when it is green you cannot see the light until you are right on top of it. Otherwise from some distance away it looks like a TL that has failed

Would love to hear the reasons behind it

It's usually to avoid "read-through" where sets of lights are close together, but the first set might be at red while the following set is showing green - you don't want traffic at the first set to see a green and set off prematurely, with potentially catastrophic consequences. It's possible that there may be overuse of this, with the amber also being covered by a louvre (I think this is the correct term?), but the principle of it has been around for a very long time, even going back pre-Mellor signals. Extended visors is another means of restricting visibility, in this case from acute angles rather than straight on. Pedestrian signals sometimes have louvres as well.

[rileyrob]

They are also used in situations like the Lochybridge Roundabout in Fort William. Heading south on the A82, into town, there is a pelican just beyond the roundabout, so the greens are louvred to prevent traffic entering the roundabout 'on green' in error.

[OLD GIT]

As said , being seen from right place, but possibly also due to sunlight problems.

[WHBM]

Many of the louvred signals in London are so heavily covered that you can't easily make out the aspects from any direction, especially in daylight. Here's a typically bad one I've noticed

https://maps.google.co.uk/?ll=51.510896 ... 97,,0,6.03

In the US/Canada they tend to use ground glass optics on the lens instead, which work much better, suddenly coming in to full view at a certain angle.

[Chris5156]

Many of the louvred signals in London are so heavily covered that you can't easily make out the aspects from any direction, especially in daylight. Here's a typically bad one I've noticed

Yes, there's quite a few around London like that - even at the stop line it's difficult to see whether there's a green light showing. Most drivers seem to assume that, as long as they can't see the red, they can pass.

[Piatkow]

I agree that some implementations can make the light too difficult to see but this location is an exmple of where they were needed.

Its not clear from Streetview but it's a downhill approach to this staggered junction. The phasing is designed to hold the mainline against the crossing flow so the two lights are never green at the same time.

When first installed without louvres the second set of lights were the ones naturally in the driver's eyeline as he came downhill. When I first used the junction I went straight through the first red, luckily nothing was crossing. I discussed this with two other local drivers and both had done the same thing. It was obviously a common problem as the louvres appeared a couple of months later.

[AndyB]

They are used where seeing the green at all but close quarters might give a false impression. That includes on filter lanes where the lights are immediately followed by a Give Way line.

The main point is so that an approaching road user can see whether they need to stop at that signal - as usual, if a red lens on a louvred signal has failed, the other signals will show the red, and if all the louvred signals have failed, so will the other signals at the junction.

[quarella]

https://www.google.co.uk/maps/@51.52203 ... K5q-4g!2e0
This set of lights now has louvres over them but to prevent the red aspect being seen close up. People were turning left out of Litchard Terrace and stopping, treating West Plas Road as a separate junction and not the staggered crossroads it actually is. The red and amber aspects are perfectly clear from the stop line on Litchard Cross.

[thetrafficlightman]

https://www.google.co.uk/maps/@51.56011 ... !5s2009-04

This example has the covers on the red aspect they are bicycle traffic lights not normal ones.

[flyingscot]

I remember seeing in the USA the lenses that meant the light looked blank until you approached. I thought that was smart and probably better than our blinds! Can't find any info on the web though, unless anyone else knows better.

[WHBM]

I remember seeing in the USA the lenses that meant the light looked blank until you approached. I thought that was smart and probably better than our blinds! Can't find any info on the web though, unless anyone else knows better.

See

In the US/Canada they tend to use ground glass optics on the lens instead, which work much better, suddenly coming in to full view at a certain angle.

above.

[Helvellyn]

I remember seeing in the USA the lenses that meant the light looked blank until you approached. I thought that was smart and probably better than our blinds! Can't find any info on the web though, unless anyone else knows better.

That might give people the impression that the lights have failed, whereas with the louvres it's clearly a case of simply not being able to see it.

[Fahad]

https://www.google.co.uk/maps/@51.56011 ... !5s2009-04

This example has the covers on the red aspect they are bicycle traffic lights not normal ones.

I hope the louvres are calibrated to be pointing at the average eye-level of a cyclist, somewhat higher than the average eye-level of a motorist. Some around London are acceptable in a car but near impossible to see on a bicycle. Others are just completely wrong and useless for everybody, e.g. WHBM's example on Upper Thames Street.