Legal use of lights on public roads

This section was made using what I wrote in an email that I sent in answer to a question on how to know about legality of bicycle lamps in the EU:

The EU countries all have different requirements and the German StVZO rules are the strictest. So there is no simple rule that can tell whether a bicycle lamp is EU-legal (i.e. whether it's legal to use on all public roads in the EU, well, ok, by complying with StVZO you're fairly certain, but then you also need the K-markings for Germany, France and Uk have their own sets etc. It won't work to say "This is legal because it is legal in my country" because the rules have not been harmonised and each country may have their own rules in various areas).

But by reasoning you can deduce what you need to know. Despite what someone claimed about my reasoning about traffic laws on candlepower forums (as I showed that symmetric beams are illegal to use in Germany on helmets, not just implicitly, but also explicitly from the searchlight article in StVO), my reasoning is rock solid and thus the only way anyone who is a lawyer can get to a different conclusion is by dubious arguments...

The essence of all vehicle lighting is cutoff/non cutoff and in my view, all symmetric beam shapes are not ok simply because they hinder opposing traffic far too much.

It would not surprise me if in all countries there are rules saying that you may not blind oncoming traffic, such as there is in NL. Even though there is not a requirement for a cutoff beam in bicycles in NL, in essence there is a requirement for a cutoff beam (for sufficiently strong headlamps at least) by virtue of this general rule.

It's the same as with car headlamps: you may not use the non-dipped beam if there is oncoming traffic. Therefore it would be silly if on bicycles you would suddenly be able to do this (with strong headlamps at least, that are sometimes even stronger than the high beam of cars).

The real crux of the matter is that there are few bicycles running with strong headlamps, and thus it's not a priority for lawmaking nor even policing, and thus cyclists will be able to get away with this for now, but it could well be over soon, especially when harmonisation of EU laws on bicycle lighting gets underway, for which I'm sure the German model will be the basis. Then again, lawmaking is slow so it could take a decade...

Now we get to implicit rules: Not everything has to be written in a law, to be clear, to be legal/illegal. Though of course in the end a legal case will make such issues clear, should the need arise. The way laws are written and used it's often argued that if it's not included/disallowed, then it's allowed. I disagree strongly, this is moronic. You cannot predict all situations and events and describing all possible situations would take far too much text, would make laws way too long. Which they already are... So, use common sense! If this was not the case, then court cases would be not necessary, as then everything can be deduced from the rules. But this doesn't work because of the complexity of the rules (i.e. situations can slip through that the lawmakers didn't think of and different rules may actually be contradictory).

To measure the relevant value put a lightmeter somewhere at a distance, e.g. 10 metres in case of StVZO (for cars 25m is designated but you can calculate those from the values of 10m of course), and just measuring it. Somewhere in the middle will be the highest in most cases of a symmetric beam, and the value above the horizon will then be a bit lower as one can measure.

If you look at which values are allowed for cars, namely in Germany 6.25 lux above the horizon at 10 metres distance (StVZO, not sure if it's the same in all EU countries), then also it's obvious that anything above that value, which would not be allowed for cars, is not ok. This means that a symmetric beam of the magicshine/lupine etc. type which are really more designed for MTB riding, can be presumed to hinder oncoming traffic if they get above that amount. Which they do unless you aim it very close to the ground.

Note that with lamps such as the Edelux, if incorrectly set, you can hinder traffic even more than with a Magicshine. So the cyclist has final responsibility...

If you sell symmetric beam headlamps, I think the only thing you can do is point to the problem of blinding oncoming traffic. I would say by virtue of a fairly strong beam they are always illegal in case there is a general rule that blinding oncoming traffic is illegal. It can be argued as I wrote above, that such a non-blinding rule is implicit by virtue of the fact that the light output (and even beam shape) of lots of vehicles is limited by the law, and thus such a general rule is not needed to declare a non-described light type, on in this case a bicycle, as illegal. But, this is for e.g. a judge to decide should someone cause an accident or others in the lawmaking parts of the government, when someone should ask for clarification.

And on clarification: I tried to find out some things in Germany about dynamo headlamps and they wanted me to pay for looking into it. I declined, public rules should be clear enough, definitely for someone of my intelligence, so if they are not, then they have the obligation to provide an answer for free... That I'm not a German is irrelevant, as their rules can influence me e.g. if I want to ride on my bike through Germany.

So, what can be considered legal?

The limit I would say for being legal/illegal (without actually being stricly legal in case of rules such as StVZO) is the lux ratings that car headlamps are allowed to put out above the horizon. So aiming a symmectric beam on a public road, such that more than a few degrees above the horizon the lux rating is more than 6.25 (assuming no countries have lower limits for cars), is in my view, as explained above, enough indication for a legally 'dubious' (to put it mildly) position, no matter if in the country in question does not rule specifically on bicycle headlamp beam shape/intensity.

This does however not take into account the mounting position (nor emitter surface, which for a lamp is the reflector surface or lens size, which means for bicycles actually luminance is far higher than for cars when given the same illumination of the road surface thus luminance (which is important to understand how direct light which is mapped onto the eye's receptors, can hinder) can be higher even for less strong headlamps than of cars, see below for more on this). As I calculated on the StVZO page, drivers in cars can get more than the 2.0 lux into their eyes from bicycle lamps even if that bicycle headlamp puts out less than 2 lux at 3.4° above the horizon. It seems from estimates that actually the hindrance of motorists in a car with standard driver position (not a high one as in one of those stupid SUV vehicles) from cyclists is similar to the motorists hindering the cyclists. So perhaps StVZO should fix mounting height of bicycle and car lamps, or approve a lamp for a given mounting height. The same lamp that does not hinder at 0.70m could hinder (motorists with standard driver position) at 1.05m although my estimate is that in the worst case the motorist probably gets the same in return as he dishes out (note that StVZO at first seems unfair, in allowing cars 6.25 lux and bicycle lamps 2.0 lux at a few degrees above the horizon). This could also be one of the reasons why SUV type cars hinder far more than other cars, though perhaps the extra height at which the headlamps are mounted is not the issue but that these newer cars usually have Xenon lamps and asymmetric beams. In looking at the equivalent hinder (light above the horizon) I'm not taking into account the asymmetric beams of cars these days, which blind cyclists quite a bit on parallel roads. In the past cars didn't need this, and traffic signs only get better reflective surfaces, so why the need for asymmetric lights? But anyway, to counter this with more light would also mean blinding other cyclists.

Lux and Luminance: Experienced brightness due to emitting surface area

A final complication in the issue of how blinding a lamp is, is that this is also related to the emitting surface due to how the light is projected via the eye's lens onto the eye's receptors. This is the issue of luminance that I mentioned on the main page. I will give a brief explanation here: A small emitting surface area means that the light from the lamp that hits the lens of the eye, is projected onto a small area of the eye's photoreceptors resulting in a high experienced brightness, a larger area (as in car headlamps) results in the light from that lamp which hits the eye's lens, being projected onto a larger area, so although the lux rating at the position where the eyes are, may be the same, the actual experienced brightness can be vastly different. This is an aspect not (explicitly) taken into account in StVZO though the allowed lux rating for bicycles (above the cutoff) is lower than for cars. At first this seems unfair towards cyclists, but when taking luminance into account, it's not... And as the calculations show, even in lux values the actual intensity a driver of a car gets into his eyes from a bicycle lamp can be close to that of cyclists experiencing car headlamps. At least for the older style car headlamps, not the ones with light going upwards to the right which creates a huge problem for cyclists on parallel roads.

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