Safe Speed Forums

From yesterday’s Daily Wail (well, I got it for free)


My bold.

This is an area which I know a little something about.
Medical studies have concluded that the blue sensitive rods of the eye does indeed become relatively more sensitive at lower light levels, but it’s not quite as straightforward as that. Peripheral vision is dominated by the rods, so blue illumination would aid identification of hazards when viewed from the corner of the eye (applied to drivers: pedestrians walking into the road). However, the number of these rods reduce substantially at the fovea, falling to nil in the central fovea – this is the part of the retina you are using right now to read this text, as well as to identify specific objects when driving at speed (tunnel vision (we all do it) is dominated by the cones). This is also why people have more difficulty reading blue text on a black background (or yellow text on white background).

Applied to pedestrians: I would say there are more serious underlying problems if people can’t spot two 48W headlamps (emitting a considerable amount of blue light) directed at them.


I fear this is another ill-conceived solution to a relatively simple problem.


Thoughts?

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

I've always felt that sodium street lights somehow give a 'sharper' image. perhaps that's why. I'd guessed it might have been something to do with the monochromatic output, but I've never looked into it.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

So we should start requiring pedestrians to wear blue reflective clothing in the evenings?

A lot of streetlights have been replaced with white lamps which are much much better than the old sodium lamps.

Now when I am in an area lit with sodium lights it feels very gloomy.

On the downside I need some very heavy curtains.

Ah, round these 'ere parts & back in 'Ye Olde Mystes of Tyme' we HAD white mercury vapour streetlighting. The nasty, tiny little 'oval' downlighters that gave off miniscule amounts of light with that 'near UV' tinge to the white. Then they replaced them gradually with crappy low pressure sodiums (orange), which led to no colour definition except white, orange & black being 'seen' (idiots), and now are starting to replace them AGAIN with high pressure sodiums (very bright/pale orangey white) in an effort to [captain couragous voice] 'combat crime' [/captain courageous voice]....that'll be one of the places my council tax is going....again.

I find those yellow 'night vision' glasses very good.

Mebbe it's just MY eyes?

Why were ships (and subsequently aircraft) equipped with a red light on the left, and a green light on the right? Because these were the colours proven to be most visible at night.

Yeah, but being highly visible isn't necessarily the same thing as giving good illumination is it? I thought that ship lights were more about vessels being able to see where other vessels are and which way they're going rather than lighting up their own courses. And IIRC (comp. crew book isn't handy so I may be wrong) but they show a white light from the front.

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Make everything as simple as possible, but not simpler - Einstein

Good point.
Perhaps we need a special kind of headlight (so we can see), and a set of different coloured "running lights", so we can be seen.

I've been thinking about this, and I reckon what we have on cars already does the job pretty well. Two red lights in the distance is the back of a vehicle, two white ones are the front, they're in pairs so you know where the corners are, single red/white lights are the same except it's a biker, turn signals do what they say on the tin and so on. The only problems are wits who forget to turn them on (mainly the indicators) or off (mainly the fog lights) and blown bulbs which I feel too few people check for regularly. That said I thought the purpose of the sidelights was to be seen in dim light, and driving back from the west country around sunset most cars had their headlights on already even though there was ample ambient light still. I felt like the only one using just side lights, though I'm sure there were others. No big deal, but they weren't illuminating anything and they could be seen as easily with side lights as with the headlights on.

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Make everything as simple as possible, but not simpler - Einstein

The essence of marine lighting is basically threefold... To allow vessels to see other vessels at night. To let them identify what direction they are going. To identify what type and size of vessel it is. (There are also lighting schemes that identify what the vessel is doing - but it can get very esoteric, see the COLREGS..). As Gatsomate says, ship lights aren't for seeing where you're going - it's a little known fact but it's an absolute bugger to fix catseyes to the sea..


To make it more fun, they also show white to the rear. But the way the lights are arranged, make it easy to work out direction... If you can see white with either red, green or both - it's heading towards you (if they're equidistant it's heading straight at you!), if you can see just white it's heading away. Edited to add that a boat under sail doesn't show white at the front, only at the rear.

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"Politicians are the same the world over... We build bridges where there aren't any rivers." - Nikita Kruschev

I understood red and green were chosen as they cannot be confused with paler yellow / blue lamps which may or may not look white.

YELLOW light creates an illusion of higher contrast within the eye/brain.
WWII pilots goggles had pale yellow lenses, and French cars for years had yellow lenses fitted.

Sodium lights emit light in a very narrow bandwith, which makes it impossible to identify colour - only different shades of grey.
I would expect a broader spectrum lamp to provide more useful illumination, since more colours would be reflected to be gathered by the eye.

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Time to take responsibility for our actions.. and don't be afraid of speaking out!

When discussing the relative merrits of various colours for signals and lighting one should remember that arround 10% of men and 1% of women are colour blind.

in most cases this is red/green colour blindness.

what this means (at risk of stating the obvious ) is that reds and greens are sometimes dificult to distingush. though the effect can be quite subtle and can affect other colours aswell.

In my case I do not have too much dificulty distinguishing between red and green trafic lights, however the "Red" and the "Amber" are pretty much the same colour for me and are dificult to distinguish from the old "Dull" yellow street lights.

Interestingly the "Red" lights are noticably dimmer than the green and amber. suggesting that my "deficency" is with sensing red

In practace this doesnt present me with too many problems. The colour vision that I do have along with positional information tells me all I need to know and the trend towards using "Bright" sodium lights (particularly at junctions) eliminates any confusion between the red traffic lights and the background streeet lighting.

but if there are to be any changes in the way coloured lights are to be used then attempting to improve the situation for colour blind people, or at least not make it worse should be given a priority.

Dusty

Ps, Anecdotal evedence suggests that the "Advantage" of colour blindness is far superior low light level vision. I (and all the other colour blind people I have spoken too) can not only see *much* better in dim light than "Normal" people, we can also "Dark Adapt" a lot quicker aswell

My vision is basically like a cats, poor colour resolution, not terribly sharp but I can see in the dark and am very sensitive to movement in my periferal vision

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"The road to a police state is paved with public safety legislation"