Bicycle lighting

There are a few things on which most experienced cyclists agree, and one of these is that riding after dark without lights is pretty much suicidal. Buried beneath this apparent, consensus, though, is a world of disagreement, myth and counter-myth (it seems that wherever two or three cyclists are gathered together, there will be an argument about something on which they disagree only in minor detail).

There have been claims that dynamo lights are inherently unsafe because they go out when you stop, that they are inherently unsafe because 2.4 or 3W is not bright enough to be seen, that 0.2W of LED is sufficient to be seen from the side and prevent rear-quarter impacts (these two from the same source, no less!), that rechargables waste most of the light they throw, that they are "cheating", that they cannot achieve sufficient burn time for long night rides. And, as so often, when you look for any actual evidence to back up any of these positions, there is little or none save a list of other people who hold the same view. My expert is better than your expert.

One thing: I'm going to try not to say too much about individual models here because (contrary to the beliefs of the Department for Transport) the market is moving rapidly at the moment, with high-brightness LED and other technologies coming down in price and increasing in light output almost daily.

Just the facts please, Ma'am
The first and most surprising fact about bicycle lighting is this: there is little if any evidence showing that riding with lights at night is actually safer than riding without. If you don't believe me, go and look (and remember, the fact that Ken Kifer said "use lights" does not amount to evidence; it is possible and indeed quite common for whole communities of experts to be wrong about things). Don't get me wrong, I'm not saying you should ride without lights, only that I know of no robust evidence which says you should not. That said, I strongly recommend lights for two reasons: first, you can see better, and second, to ward off lawyers. In the UK at least (and in many other countries) it is illegal to ride at night without approved lights, and if you do, and you are hit, it may well be held to be your own fault. And if you can find any good solid evidence regarding light use and accident involvement, do be sure to let me know.

One thing which is known is that in the UK at least the law requires use of lights after dark (and in fog, if they are fitted to the bike). And the law is very specific: the lights must conform to BS 6102 Part 3: 1986. In theory even LED tail-lights like the Cateye TL-AU100 which is kitemarked to BS 6102 part 3 are not legal, because the amendment allowing use of LED lights is later than specified in the standard referenced in the Road Vehicles Lighting Regulations, 1989. We live in hope that this absurd situation will change. In practice you are unlikely to be in trouble as long as your lights comply to the current BS 6102 or an equivalent European standard. One of the better things to come out of Europe is the move to unified standards for vehicle construction and use; it makes for a much larger market base, much more attractive to large manufacturers. The range of BS 6102/3 kitemarked bike lights is not enormous. The law does not preclude the use of other lights in addition provided they are the right colour, and steady, not flashing. You may attach flashing lights to your person, or (it is said) to luggage, but definitely not to the bike.

In practice this may well mean you want more than one light at each end of the bike. This is good practice anyway, since if a light fails you want a backup at least for being seen.

The Two Functions Of Lights
Bike lights have two main purposes, other than warding off insurers: seeing and being seen. The lights you choose for the two purposes may well have very different characteristics, which is another reason why many regular cyclists have more than one light front and rear.

Be Seen, Be Safe
There is one school of thought which has it that whatever lights you put on your bike, motorists will continue to look right through you. There is another which says that this can be avoided, but only by using the brightest lights available, at present being high intensity discharge lights like the ARC. The truth probably lies somewhere between the two.

The truth, in this case, being rather difficult to get at. As stated above, evidence that lights do anything for safety is scant, and bike crashes (especially at night) are sufficiently rare that this is likely to remain so. So we have to go with what seems to work, which is rather unsatisfactory. It does seem to be the case that large numbers of people ride regularly at night using everything from the late unlamented Wonder Light up, and there is no significant reporting of problems. This is probably because the major need for being-seen lights is on urban roads, which generally have street lighting, so the drivers are more likely to see the cyclist him(her)self, especially if they use high visibility clothing.

And here's another aside: I don't know of any good evidence that high-visibility clothing makes a difference either, except in the specific case of sleeves. High-viz on the sleeves seems to get you more space, probably because you look wider (I'll dig out the reference when I have a minute). So don't go for a sleeveless yellow jacket.

In practice, workable front being-seen lights start these days with the Cateye HL-500, a halogen-powered, kitemarked battery light that can be had for a tenner, or in a blister pack with a tail light for under £20. You might take the view that these are too dim to be seen by a motorist. You may even be right - as above, the cyclist's body is probably more likely to be seen in an urban context anyway. If you sincerely believe that you can't be seen without joining the arms race of every-brighter lighting, then you must go straight to the very high intensity systems, high output LEDs and HID lights, which emit a fierce blue-white light. But bear in mind that the average car mounts up to 200W on the front (more if using "driving lights" - like headlights are not for driving!), has virtually unlimited electricity to burn, and HID lights are becoming standard on modern cars. We'll never win, and I don't think we even need to try, because I am convinced that road position is the key to being seen.

All rear lights are being-seen lights. There is some research which shows that flashing lights are more visible than steady ones; there is other evidence which says that rapidly flashing lights are confusing and hard to place. One thing is for sure: flashing red LEDs are these days widely associated with bikes, so a blinkie (on your person if not your bike) may well be a good idea. Ideally of course you want both. The Cateye TL-LD1000 combines both: you can have half the LEDs flash and the other half steady. That's OK until the battery goes flat, then you've lost both kinds of light at once (a flashing LED uses less power than a steady one, so lasts longer per battery). I like to mount my rear lights high, to be seen above bonnet level in traffic jams, and I do use exclusively LED rear lights (TL-AU100, Busch & Muller Toplight etc). Some are dynamo powered, some battery powered. LED rear lights last a long time even on rechargeable AA cells, on alkaline cells even longer, so unless you are ethically opposed to these (and they are an environmental menace) even dynamo users often power their rear lights with batteries.

All the better to see you with, my dear
Seeing-with lights are likely to be brighter than being-seen lights, and will often have better optics (although cheap battery lights have surprisingly good beam patterns, to get sufficient illumination out of a low-wattage lamp). Here the "right" choice will depend more than anything else on where, and how fast, you ride. The smallest light I've ever been able to actually ride by was a Cateye HL-EL 400 compact opticube LED front light. This is my emergency light, the main light was battery powered and went flat. This produced enough light to see my way at about 8-10mph on unlit roads, walking pace on a path, and was of course not really needed for seeing-with on urban roads. The white versions of cheap LED blinkies which I have used before now as additional being-seen lights, do not (in my experience) produce enough light to see. If you are hooning down singletrack there's nothing short of a HID system which is likely to be sufficient. So what you actually need for everyday riding is something between a candle and an arc light. Job done.

OK, so perhaps that's not too helpful. Let me say up front that I know next to nothing about night-time offroad riding. I do, on the other hand, have a lot of experience of road riding at night in all weathers. My experience of road riding is this:


 * At normal speeds (up to about 18-20mph) if you have reasonable night vision, a 2.4W dynamo light is good enough on all but the darkest roads (pitch black, moonless, under trees) and will still allow reasonable progress even then. 3W is slightly better, worth it if you are not going the 12V route below. 5W rechargeable is a bit dim in the gloomy bits but fine on the open road especially if there is a decent moon. 10W rechargeable is in my experience slightly brighter than 3W dynamo.
 * Adding a second light in a 12V setup (as per this page) should be satisfactory at all normal road speeds, say up to about 30mph. As indeed will adding the 5W and 10W together.
 * Around town, a 2.4W halogen dynamo light has never been insufficient for my needs, but then, neither has the cheap and cheerful Cateye battery light, albeit you need to keep feeding it batteries.
 * In bad weather, rotationally symmetrical lights are a menace on unlit roads. Far too much of the light comes back at you. A dynamo headlight with good beam focus is far better, and it's best to mount it low down (on the fork leg, for example) in fog or heavy rain. If I have an additional being-seen light on my bars I always need to turn it off in bad weather on dark roads.

Bear in mind, this is my eyes (and, more importantly, my neck). If you have poor night vision, you may well need more light. You can see what I mean here; Andreas Oehler took a number of different lights and compared the beam pattern and brightness. Note how the pillar-box-slot effect of the Bisy FL (same as the SON E6) means you get the same amount of usable light ahead as the 5W Lumicycle MR11 spot, and more concentrated on the road ahead.

Output
Lights are sold, in the main, by companies who have more interest in selling you lights than in informing you about how well they really work. These are some of the terms you'll see used in adverts (and with apologies to any who are offended by the gross oversimplifications occasioned by my memory of basic physics):

Don't be dazzled, then, by talk of Watts or lumens per Watt, it's the luminous intensity which enables you to see!

Terminology
Thank you for flying with Pedant Airlines.

Front Lamps
These are the common front lamp types:

Rear Lamps
These are the common rear lamp types:

Some rear lamps are available which are powered off your rechargeable battery system, but these are not very commonly used, not least because an LED |blinkie will often run for several months' worth of riding on a set of alkaline cells.

What does everybody else think?
It used to be the case that most offroad riders used rechargeable lighting systems, most long-distance riders (e.g. audax) used dynamos, and commuters used whatever seemed appropriate given their journey. Actually this is still pretty much true, but with improving battery technology the number of audax riders using rechargeables has increased somewhat, and with the increasing availability of rechargeable systems (and the lack of availability in bike shops of dynamos in some countries) rechargeables have a larger share of the commuting market as well. While the former is a reflection of the improving quality of rechargeables, the latter is not. In countries like Germany and the Netherlands, dynamo systems are the norm, valued for their "always there" suitability for use on utility bikes. For the higher mileage rider they will always be a sound choice. For the middle distance it largely comes down to personal preference these days, and for short distances traditional battery lights will always be a strong contender. Off-road riders will always prefer the greater light output of rechargeable systems.