Friday, November 11, 2011

Bike Commuting Down the Tunnel of Night: Go Bright

A post on Seeing and Being Seen (SABS) on city streets at night on a bicycle

On a comment (link here) on his blog "Off the Beaten Path," on a post about hub generators and lights, Jan Heine wrote (in part), "I don’t like beams that are too bright, because it makes me ride in a tunnel of light in the dark night." At certain times, in certain places and in certain moods, I'm down with that. When commuting by bicycle on dark nights in a city of cars, however, I subscribe to the "brighter is better" approach, primarily because it helps both with seeing, and also with being seen. 

A little further down in the same thread, though, Jan wrote, "Regarding brightness, I agree that in the city, brighter can be better, but blinding oncoming traffic is not only discourteous, but also unsafe. So what you need is a bright light with a beam that is cut off at the top. In fact, that is how car headlights on low beam work…" I agree with that on the face of it, too, in other words, actually blinding, or even dazzling to the point of affecting driving or visibility, would be bad, and I don't want to do that. Being courteous on the streets is highly important to me, as readers of this blog will know. With that in mind, let's review some numbers comparing car headlight bulbs with my pretty bright bike headlight, to see where the courtesy bar is actually set:

Source Lumens
9011 (HIR1) bulb 2350 lumens
H9 bulb 2100 lumens
9012 (HIR2) bulb 1870 lumens
H7 bulb 1450 lumens
Tri-Newt bike light 3 LEDs, 486 lumens

While acknowledging that lumens alone don't give the whole picture, and while I did find slightly varying values for the car headlight bulbs, looking at this table and comparing it with what I experience while riding my bike at night, here's the thing: my bicycle headlight is not nearly as bright as most of the eye-level SUV and pickup truck lights that I face into every night on my ride home. These lights are much brighter, and mounted much higher, than my bike light. Which is bright, but not nearly as bright, blinding, or dazzling as those SUV and pickup lights. If they are permitted on the street, allowed, encouraged, then my bike light is well within, and probably below, the accepted illumination sources in use where I ride.

Therefore, I offer the official OSG SABS ruling:
It is not discourteous to equip your machine with illumination sources on a par with those used by the other machines sharing the same streets.

I was in no way advocating that cyclists should be discourteous or dangerous with bright lights on their bicycles at night. Only that I ride with a light similar to other users of the road. Beam pattern and aiming are also important, so I note in passing that my light has a beam pattern which flatter on the top, designed specifically for bicycles, and that I aim it slightly downwards. That doesn't come through in the photo below very well, but you can see it very clearly on the street or against a wall.

My road illumination source of choice. Go bright.

With this light mounted, while riding the city streets in Phoenix, I find that drivers see me coming, appear less inclined to pull out in front of me or turn right in front of me, and appear to be aware of my position in the lane on the street, and don't ignore it. These are important results for me riding at night. They increase my confidence and comfort level with riding in the darkness.

On the other hand, with lesser lights I've tried, cars pull out in front of me, act like they don't see me, and generally drive as if I'm not even there. Flashy "be seen" lights lessen this, but don't work well for me on the canal because I need to see the surface to scan for ruts, bumps, and sometimes bunnies sprinting across my path. One of the best flashy lights I use also has this nasty back-scatter problem that means it flashes back into my eyes in part, which is particularly unpleasant on this somewhat dark street, and on the dark canal.

Light IMBL

Bicycle lights significantly brighter than mine are available. Some of them are equal in rated lumens to those car light bulbs listed in the table above, but also keep in mind that cars have two headlights. I see a few other cyclists with nice bright lights riding the other direction, and I've tried staring directly into their lights. They do not exceed in brightness, blindingness, or dazzling-ness those of SUV or pickup truck headlights, and so I do not find them discourteous or dangerous at all.

I'm sure that some drivers who see us with lights which are brighter than a small flashlight duct taped to the handlebar are a bit surprised at them. As rare as cyclists are around here, even rarer cyclists with reasonably bright headlights. It may be a different story, too, on a street with hundreds of cyclists riding on it. That could get to be a bit much, and it's very possible that's a reason to consider hub generators with less-than-bright lights hooked up to them. Here, though, that middle picture is pretty accurate: it's typically just me and the cars out there, with a handful other cyclists, riding through the night. In that setting, I'll keep the OSG SABS ruling in mind, and go bright. There is no reason to do otherwise, and definitely no reason based on the mistaken notion that bicycles should have dimmer lights than other vehicles on the road.

at 11:11:11 on 11/11/11 I will be thinking of you all


  1. My P7 puts out 900 lumens and appears much brighter than my Daughter's VW high beams. I am concerned about the upper light cutoff - for the reasons you cite. So I only use the high on roads with a history of drivers coming through stop signs and on trails where more light is better. I also ride with the light dipped when on high.

  2. Steve on a side note let's talk about upgrading the high beams on the VW. On trails and dark empty, I really like the visibility a bright headlight gives, but occasionally find this also shines glare into an oncoming trail user, which I would like to avoid if possible.

  3. Blog I came across on Electronics Weekly about building a two-light solution for dynamo-powered bicycle lighting, one bright light, one "dipped", selected by toggle switch. Go ask Alice:


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