Govt to limit power of cycle lights ?

SA_SA_SA
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Re: Govt to limit power of cycle lights ?

Postby SA_SA_SA » 5 Apr 2013, 10:30am

cj said
car lamps are bigger and hence exhibit less glare at the same intensity.


so a car's fancy expensive projector headlamps should cause more glare than large old fashioned fresnel ones?

Car headlamp design now seems to be more about looks than function (minimising glare seems an important function to me)

Perhaps some extra rules for cars too, to minimise glare: eg limit blue component,
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Re: Govt to limit power of cycle lights ?

Postby meic » 5 Apr 2013, 11:01am

They will probably omit to put a restriction on the number of lights that can be fitted to your bike. So the future could involve bikes with a bank of lower power lights. This would give quite a good field of light with less dazzle for others.
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CJ
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Re: Govt to limit power of cycle lights ?

Postby CJ » 5 Apr 2013, 12:38pm

TonyR wrote:Another aspect of the problem is the 3.5º problem. Because lights have to be taken on and off bikes to avoid theft (dynamo lights excepted), even if you were careful, setting the lights when you put them back its unlikely you would be able to set them up to the necessary accuracy. And you just need to look at the number of people cycling around with their rear lights pointed at the ground, sky or sideways to realise the 3.5º measure is meaningless to most people.

Cyclists have a lot less trouble aiming their headlamps than rearlamps. It comes naturally. We've all done it, riding along, into the dark, oh whoops, my light isn't shining on the road (or too close to be useful), reach for the lamp, give it a twist, all good now.

And in any situation where the ambient light level is good enough that you can't easily see where your headlamp is pointed and don't need it enough to bother improving its aim, you won't be dazzling anyone anyway, because glare only happens against a much darker background.

People who've studied this, find that cyclists generally aim their front lights so the brightest bit of the beam hits the road 10m to 20m in front and have them mounted between ¾ and 1m above the road. In this very non-exact science of simply getting into the right ball-park, the assumption is made that bike headlamps are aimed down at 3.5º. (That's 12m throw for a lamp 0.75m above the road, 16m if it's 1m up, so you see, we're in the right ball-park.) The eyes of anyone who's in a position to be dazzled will be higher than the lamp, so regulations put a top limit on the intensity of light emitted in the zone 3.5º and higher above the beam centre.

That does not mean you have to mount your light at exactly 3.5º, or that the whole exercise is rendered completely pointless if you aim it higher. I aim my light a bit higher than that, because I like to see at least 20m down the road. But most observers' eyes are somewhat higher than where my lamp is mounted, so the angle subtended at the lamp may nevertheless be at least 3.5º. And if it isn't, that's not the end of the world, for if my lamp is non-dazzling at 3.5º it doesn't suddenly become a monster at 3.0º.

Glare is not an absolute phenomenon but a highly subjective matter that comes on gradually with increasing contrast between a light-source and the surroundings. The best that can be achieved is to reduce the number of times that someone will be dazzled and the severity of those events.

In the case of motor vehicles this is done by expecting that drivers will dip their headlamps for oncoming other road users and by not approving vehicles for use on the road if those lamps when dipped, emit more than 625cd in an offside above-horizontal direction.

In the case of pedal cycles, this is done in Germany by expecting that cyclists will aim their headlamps so as to see the road a sensible distance ahead and not approving any headlamps that emit more than 200cd at 3.5º or higher above the beam centre. (That works in Germany because you're not allowed to ride a bike even in daylight unless it's equipped with approved lights and Germans have a habit of obeying the law. Something different would be wanted here, obviously!)

Neither of those measures are 100% effective because nothing ever can be, but they're both a whole lot better than the anarchy that would reign if there were no limits. Previously, the technology didn't exist to let cyclists dazzle anyone, but that's come on in leaps and bounds, and in the vacancy left by out-of-date, unobserved and irrelevant or non-existent standards, a little bit of anarchy is breaking out.

I think it's best to admit and discuss how we would prefer to address this problem, than to deny it in the hope that our Government won't impose a draconian solution.
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Re: Govt to limit power of cycle lights ?

Postby kwackers » 5 Apr 2013, 1:11pm

I'm not sure why there's an issue.

I've been down the high power led route (in fact they're still attached to my bike), I also have a B&M dynamo light.

If I cycle along an unlit path and put the high power (dual 5W) light on the world lights up, if I now switch on the B&M there's a visible improvement.
If I do this the other way around the hi-power light doesn't add much to the mix other than making everything in the periphery of my vision light up.

The B&M has proper optics and a very visible cut off, cars very obviously see it and I can ride unlit paths and roads at 20mph plus with no issues.

It's been obvious to me for some time as the brightness (and number) of lights attached to each bicycle has increased that sooner or later the sht would hit the fan.

Why anyone is surprised I'm not sure, what the problem is I'm not sure since from where I'm sat the answer already exists.

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Re: Govt to limit power of cycle lights ?

Postby CJ » 5 Apr 2013, 2:15pm

Tonyf33 wrote:Given we are now subjected to many unlit suburban roads across swathes of the country because councils are switching off lights after midnight I cannot see how 70 candela would even remotely be enough to see by nor even safe especially given the shocking state of the roads so that HAS to be changed sooner rather than later to a much more sensible figure. 652 would be fine as a starting point but as others have said what plod are going to bother to enforce it!

Some misunderstandings there. Even the totally out-of-date British Standard didn't expect you to light up the road with 70 candela. In the beam centre that standard required AT LEAST 400cd, which admittedly isn't much, but it's what we all used to get by with in the 1980s. Any light above the beam centre hits the road even further away and fails to light it perceptibly. All it does is illuminate road signs and advertise your presence to other road users, and a few dozen candles is plenty for that.

The 625cd also quoted is also an above-horizontal value - not intended to light up the road or anything - its just a limit of stray upward light that does nothing useful except attract the attention of an observer - which is also useful, but you don't need anything like 625 candles to do that at night.

A mere 70 is nevertheless an unreasonably low limit. We should want that raised to at least 200cd as per the German regulations. These regulations, by the way, require at least 700cd in the beam centre, and I believe the Germans plan to increase that to 1000cd. They do keep their regulations up to date and obeyed, allowed LEDs to be used as soon as they became practical, unfortunately they tend to scorn batteries as suitable only for toys (i.e. racing bikes weighing less than 11kg) whilst expecting any vehicle worthy of the description to be equipped with an alternator!

But I digress. We should be demanding a standard that has German-style lighting requirements without their prejudice against batteries. Unless there is also a legal mechanism to make it worth eveyone's while designing and manufacturing lamps to that standard however, it'll be ignored by the UK bike trade just like the old standard, and allowed to go out of date whilst it remains almost impossible to buy a really bright battery lamp that can be used on a bike without inadvertently dazzling people.

My suggested solution is to require, as is the case in France, approved lights to be fitted on all new bikes at the point of sale, whilst still allowing non-approved lights to be sold separately. That creates a volume demand for lights made to a standard without stifling the development and sale of new types and designs. It hasn't worked very well in France because France has an even more rubbish standard for bike lights than Britain! France is in the process of sorting that via a German-style ISO standard. We could adopt that too if they end up with something sensible.

There will be howls of protest from those who don't want any more lamps when they buy a new bike, but that's only a problem for a handful of enthusiasts like us who buy more bikes more often than we really need them. There's actually a whole lot of areas where it's safer for the general public if bikes are sold in a particular way, but safe enough to configure differently for use by a consenting expert rider. So I reckon there ought to be an option to purchase a non-conforming bike, subject to the purchaser signing a waiver that he/she understands that this bike is illegal to ride in the dark, has the front brake lever on the left (currently illegal to sell but legal to use), both brakes by one hand (currently illegal to sell and use but needed by one-armed cyclists), dangerous toe overlap... :wink: Worth thinking about?
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Re: Govt to limit power of cycle lights ?

Postby Tonyf33 » 5 Apr 2013, 3:02pm

I only buy second user bikes, so the having a new light fitted that meets the std at POS wouldn't really effect me. However thatadditional cost is passed onto consumers direct, many if not most will have no intention on riding at night so why should they be subjected to the additional cost involved?
Last edited by Tonyf33 on 6 Apr 2013, 3:38am, edited 1 time in total.

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Re: Govt to limit power of cycle lights ?

Postby mark a. » 5 Apr 2013, 3:42pm

Thanks for the details, CJ. I wasn't surprised by the B&M light (which I own, so I know has a decent, non-blinding beam pattern), nor the cheap-ish Magicshine (which is essentially an LED in a bit of reflector). I was surprised at things like the Exposure Strada, which is specifically marketed as a road light.

I know that in the MTB community the lumens war is rather comical. But there you usually want as much light spread as possible so you can see low branches or see where you're going no matter which way your bike is pointing, so basic optics generally work fine. But these lights are not so good on the road because they have no horizontal cut-off.

I agree that the incentives are currently wrong. Customers want brighter lights at lower cost, so the manufacturers spend the money on the latest LED and as little as possible on the optics. A decent law would provide more sensible options.

Perhaps manufacturers could use clever optics which bleed only a little useful light upwards, or an easily switchable beam pattern.

By the way, I find my Ixon IQ (a couple years old), is still barely adequate on the darkest roads. It doesn't give enough light bleed for peripheral vision.

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Re: Govt to limit power of cycle lights ?

Postby snibgo » 5 Apr 2013, 4:45pm

Good work, report and thinking from CJ as always. I hadn't realised that some lights were that stupidly crazy (for road use).

I doubt that the government would have the appetite for banning any particular lights on bikes. As far as I know I can fit any number of eye-frying lights to my car, provided the ordinary ones comply with the standards. While that remains true, who will claim that cyclists should not be permitted the same freedom?

The answer has to be to encourage manufacturers to make good bike lights. Modern LEDs have ample light output but they need good optics to put the light where we need it, and not where we don't. In sufficient bulk, I don't see why these need cost more than £10 a piece.

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Re: Govt to limit power of cycle lights ?

Postby Nettled Shin » 6 Apr 2013, 2:49am

I would be glad of some guidance, if not legislation, on bicycle lights. It is true they are not as powerful as car headlights, but the radiance of the emitting surface is a lot higher with modern LEDs, to the point where it is almost painful to pass another cyclist with a Magic Shine-style light. From this perspective, bicycles are more of a nuisance than cars. If these lights are pulsating, the discomfort is even worse. The car headlight bulbs I have seen contain a mirrored surface to prevent light shining directly forward else they too would be similarly annoying. Batwing-style LED emitters are available, which emit very little forward light, and maybe these are the ones that should be used in bicycle lights. A normal LED could instead be mounted facing backwards, and I have seen this on some bicycle lights. Of course, a good quality reflector is then essential to collect the light and redirect it forwards. Lowering the colour temperature is also helpful, and a lot more pleasant from the rider's vantage in my experience, but the highest luminous efficacy LEDs tend to give off very blue-white light. If people are prepared to sacrifice some efficiency, they could have something a more mellow yellow.

Bicycle lights are never going to be as large as car headlights, but by preventing the emitter surface from being directly visible, and using larger reflectors, things could be made more tolerable, without needing to reduce the intensity of road illumination.

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Re: Govt to limit power of cycle lights ?

Postby TonyR » 6 Apr 2013, 8:35am

Nettled Shin wrote:Batwing-style LED emitters are available, which emit very little forward light, and maybe these are the ones that should be used in bicycle lights. A normal LED could instead be mounted facing backwards, and I have seen this on some bicycle lights.


Much of the advance in LED brightness has been from getting the heat out of the chip better which means attaching it to a good thermal mass and radiator. Mounting the chip facing backwards makes that difficult because a good thermal mass and conduction path will get in the way of the beam that eventually goes forward.

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Re: Govt to limit power of cycle lights ?

Postby TonyR » 6 Apr 2013, 8:43am

CJ wrote:Glare is not an absolute phenomenon but a highly subjective matter that comes on gradually with increasing contrast between a light-source and the surroundings. The best that can be achieved is to reduce the number of times that someone will be dazzled and the severity of those events.


There are two other aspects of glare that make it subjective. One is the cleanliness of the car windscreen and any glasses the driver is wearing and the other is any incipient cataracts they might be suffering from. All those are addressable by the driver not the cyclist. While windscreen wipers help very few drivers regularly clean the inside of their windscreens which tend to build up a thin scattering film that becomes most obvious when driving towards a setting sun.

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Re: Govt to limit power of cycle lights ?

Postby Nettled Shin » 6 Apr 2013, 12:10pm

TonyR wrote:Much of the advance in LED brightness has been from getting the heat out of the chip better which means attaching it to a good thermal mass and radiator.
Thermal mass isn't going to affect the steady-state temperature, is it.
TonyR wrote: Mounting the chip facing backwards makes that difficult because a good thermal mass and conduction path will get in the way of the beam that eventually goes forward.
Like how the secondary mirror gets in the way in a Newtonian telescope?
Yes, on second thoughts, look how effective a design mounting the LED rearward is; any heatsink can be directly exposed to airflow, keeping the sink smaller or cooler through forced convection cooling---ideally complemented by dynamo power!

TBH, the LED could be mounted in the side of the lamp housing if heat rejection and light obscuration is a real issue for you. My major point was that our being able to see the tiny radiating LED surface directly is what makes them so uncomfortable for us to look at. O&O.

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Re: Govt to limit power of cycle lights ?

Postby tatanab » 6 Apr 2013, 3:20pm

Nettled Shin wrote:Yes, on second thoughts, look how effective a design mounting the LED rearward is; any heatsink can be directly exposed to airflow, keeping the sink smaller or cooler through forced convection cooling.
B&M and Philips lights that I've been using for some years already do this, both in battery and dynamo guises.

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Re: Govt to limit power of cycle lights ?

Postby squeaker » 6 Apr 2013, 4:38pm

SA_SA_SA wrote:Perhaps some extra rules for cars too, to minimise glare: eg limit blue component,
+1 to that: IME it's been a problem for a while. Presumably the legal C&U light measurement kit has some sort of spectral weighting function? IMO it needs tweaking to emphasise the blue end of the spectrum more.

Good work by, and thanks for the clear explanations from, CJ :)
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Re: Govt to limit power of cycle lights ?

Postby SA_SA_SA » 7 Apr 2013, 12:49pm

CJ wrote:That does not mean you have to mount your light at exactly 3.5º, or that the whole exercise is rendered completely pointless if you aim it higher. I aim my light a bit higher than that, because I like to see at least 20m down the road. But most observers' eyes are somewhat higher than where my lamp is mounted, so the angle subtended at the lamp may nevertheless be at least 3.5º. And if it isn't, that's not the end of the world, for if my lamp is non-dazzling at 3.5º it doesn't suddenly become a monster at 3.0º.


Mr http://swhs.home.xs4all.nl/fiets/tests/verlichting/index_en.html#licht-bundel-vorm says he gets blinded by opposing low power cycle lamps set high (to see further) on unlit paths. He views the Trelock 885* as one that encourages itself to be set too high: but if the top of the beam hits the ground, I would have thought if it as still dipped. He sets his own philips dynamo lamp to have a long throw (40-50m) but likes it because of its sharp cutoff.

With more powerful LEDs meaning cyclists wish to see further perhaps that 3.5degrees angle should be lowered (requiring a sharper cutoff)?

Could a front cycle dynamo K~ lamp aimed 1 or 2 degrees below horizontal manage to be worse than a dipped car headlamp for unwanted brightness (in candela rather than perception)? Perhaps the cold blue of cycle lamps may be making the glare worse than it would otherwise be due to brightness alone?

Is there some way of building an aim guide into the lamps optics (a rather unlikely but neat example would be for the words "Dip me" ("written" using darker "lines") to appear in the beam pattern when set too high) ?

As I have complained about blue-ish car lamps, to be fair, I also think proper front cycle lamps should be required to be less blue-ish: eg neutral white (4000K) or better. I suspect cold white is now a marketing decision caused by caused by car xenon HID lamps: warmer colours do not seem to cost too much in terms of raw lumens per watt (and if the excess blue lumens are unwanted anyway.....)


* http://swhs.home.xs4all.nl/fiets/tests/verlichting/koplampen/Trelock_ls885/index_en.html
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