Which strategy of using the bicycle light should I select?

Question

I use my bicycle for commuting, mostly over the secondary roads closed for the majority (not all) car traffic. There are other cyclists, dog walkers and runners on these roads.

Using the light often, I would like to find some grounded answer, how they should be used in the most safest way. When I start do dig deeper, multiple solutions appear and the things start contradicting each other. Looks like there the following strategies are generally possible:

• Rotate your (StVZO certified) headlight into the ground ten meters in front of you, all done and ignore complains from bystanders about the intensity. The major concern here is, unlike a car driver, I frequently encounter random people standing on my road. I am afraid not to see them in time if I only illuminate the road and they shoes. I was ten minutes from buying Supernova AirStream 2 but ran into this #2 Google hit negative review.

• Rotate your (StVZO certified) headlight into the ground ten meters in front of you and reduce the intensity till everyone is happy. So we have done everything not to disturb the other traffic but this may not be fully adequate for spotting some black dressed runner carrying not even passive reflector.

• Buy dual beam light so you can switch off the high beam when you see other traffic. The main danger here is, the object may disappear after switching the beam, as once happened to me when I ad hoc shifted the light by hand (there was also a light fog). Also, people not carrying they own lights or at least reflectors, can be spotted in time to avoid them but not early enough to adjust the beam (and some later yell).

• Use wide and high beam and adjust how it is better for you. Simply reduce intensity until nobody complains (that is possible to achieve) and then move on with the speed still good enough for your light that now melds nicely with twilight. This technique is described in this document as "Weak headlights with wide diffuse beam technology". So far this was my compromise between the "peace with community" and "perceived safety". Is it really so bad, has any serious analysis ever been done about this approach?

• Use narrow beam. I found it unsafe in turns, basically turning into darkness. While not encountered, I also think that people may wander into the beam (and path of your bicycle) from the side much closer than this nice far view.

The ideal answer would provide some statistical safety comparison or at least in depth analytical comparison. Surely any lamp manufacturer claims they product is the best. I wonder if any more serious analysis has ever been done. The country where I am does not have very specific or strict light requirements beyond the sane mind.

Answer 1

I don’t think it’s a matter of brightness but more a matter of adjustment — assuming you already use an StVZO compliant light with a proper cut-off.

I’ve always liked this diagram from this (German) article: https://www.velototal.de/2020/09/29/modernes-fahrradlicht-richtig-einstellen/

The middle picture is the correct adjustment, top one is angled up, bottom on is angled down too much.

Basically the idea is that your beam should only go downwards and therefore shouldn’t hit anything above handlebar height. You can check by riding towards a wall or towards parked cars. Your light should never (brightly) illuminate anything above ~1m or so. If it is, it’s not only dazzling oncoming drivers or pedestrians, it’s also wasting light.

Within this constraint you are pretty much free to adjust as you want. Angle the light downwards and you’ll have brighter illumination but only close to you. Angle it more horizontally and you’ll have far and wide illumination but it might be too weak to see properly (unless your light is very strong).

I regularly encounter cyclists with badly adjusted headlights or headlights which don’t have a proper cut-off. The difference is very noticeable. You can usually tell even if you ride behind such a cyclist because they’ll illuminate trees and other things far above the ground.

Make sure your headlight mount is sturdy and doesn’t get loose.

Of course when you go over bumps or over the crest of a hill you might temporarily blind oncoming traffic, but this also happens with cars and can’t really be avoided.

Fun story: I once almost ended up on a 3 lane highway because the reflective Autobahn road signs were so big and tall that my light didn’t illuminate it, even though it’s a fairly powerful Lezyne Lite Drive Pro 80 StVZO. That’s really the only disadvantage of the cut-off and the reason why mountainbikers use lights without it in order to see trees and branches.

Answer 2

Generally, there are two kinds of lights on a bike.

BE SEEN lights show your position, and their colour shows your orientation/direction. They are for the benefit of other road users.

SEEING lights are for the rider of that one bike, and are so you can determine what's coming up in the roadway.

Rear lights are exclusively the former, and front lights can be either.

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You mention StVZO a lot, so presumably you're in Europe. I'm not, so my go-to for directed lighting is a focused torch/flashlight on my helmet. While riding normally the beam is about 5/10 metres on the ground in front of me. I also ride with a handlebar headlight too for lighting my direct path.

If something happens, or if I choose to illuminate something, like a car that looks to be turning I will raise my chin, turn the head, and intentionally light-up, or "paint" the thing.
That might be something like a driver's side mirror, or a pedestrian that looks to be about to step out, a car who has to give way to me but might not, or I can send some light sideways around a corner before my handlebar light could illuminate.

This is probably not permitted in Europe, where the vast majority of your roads will be lit. In contrast, almost 1/3 of my winter commute is on black roads with zero street lighting, and a posted speed limit of 80 km/h.

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For strategy, figure out what the worst part of your ride is, and set up for that level of lighting.

Avoid harsh-blinking lights. StVZO discounts flashing anyway from memory, but abrupt strobing is nasty to pedestrians. Aim for solid lights, or perhaps slow throbbing if permitted.

Costs come into it too - a light worth more than your bike might be overkill, or it might be quite reasonable depending on your needs.