Flashing headlights on the trails

[hozn]

@jabberwocky 97720 wrote:

wonder how you people with 200-300 lumen lights manage. You must not ride very quickly, because I can override my 400L pretty easily.

I find 200-350 lumens is plenty. When it’s full dark, I run the Lezyne at 200 lumens, when it’s starting to get light, I drop it to 100L and when it’s not really needed for trail illumination, I set it at 50. Same for my NiteRider 350; I run it at the 250 setting unless I’m in the woods. And I run my NiteRider 250 at the 180 lumen (medium) setting.

Granted, this is not off-road riding. I would consider a brighter light for going through the woods. I have no problem with that light output for normal speeds — probably up to 25-30mph, depending on the roads. I’d crank it up to 350 for 30mph and probably would simply avoid going much faster than that in the full dark. I’m not going super fast in the AM (which is when it’s dark for me), though; looks like those rides average 16+/-0.5 mph.

[mstone]

@Brendan von Buckingham 97719 wrote:

What’s a lumen?

If it’s a serious question, the answer is that it’s the unit of measure for the total amount of light generated by a light source. It is derived from the candela, which is the unit used to measure the amount of light generated by a source over a specific angle. Any light source which has some sort of lens and/or reflector will have different candela measures depending on where the measurement is taken. The lumen is intended to normalize such measurements by conceptually “squashing” the light output into one square meter so that sources with different beam patterns can be directly compared. The fact that it is normalized in that manner makes it completely useless for comparing lights on the basis of “how much will this source light up the path in front of me”. For that, you need the “lux”, which is a measure of illumination rather than luminance–that is, how bright a surface is when it is lit by a particular source. The lux measurements can tell you how bright the road is 5 feet ahead, 30 feet ahead, 20 feet ahead and 10 feet off to the side, etc. (This is obviously much more complicated to communicate than a single number.)

[hozn]

@mstone 97723 wrote:

Really? Do you have any evidence of that actually happening or are you engaging in hysterics over something that annoys you?

I have witnessed a couple near accidents due to people being unable to see pedestrians, related to oncoming headlights. If you can’t see in front of you, the only way to be sure you’re not going to plow into a pedestrian is to stop your bicycle. [And then risk getting plowed into by the person you didn’t know was riding behind you.]

I think it’s pretty selfish to blast down the trail with 750L and not bother to shield your light to oncoming riders. Sure, I sometimes forget or am just not able to safely shield my light from oncoming riders.

I know we have this silly debate every year. I think rcannon summed it up nicely last year. The facts are pretty simple: a sizeable portion of the population finds it unsafe to be blinded while riding on the trail at night. It bothers them; they ask people to stop doing it. People are free to run whatever ridiculous level of light they want on the trail since this isn’t regulated. It’s just inconsiderate.

[Supermau]

@timo96 97718 wrote:

Seriously? You need 750 lumens on a multi-use trail? I hope you realize that you’re going to cause an accident at some point. You’re going to blind someone and they’re going to wreck right into you. But hey, at least you’ll see them coming, right?

Seriously. I do.

Much of the MVT is pitch black when I’m on it. I’ve tried lower settings and I always wind up back at 750. The one time I was called for blinding was when my light was new and I think I had it angled too high. It didn’t help that I was coming down hill while the other rider was coming up, making my light even more in his face. We did not crash however. Not even close.

A direct hit with 200 lumens is still pretty blinding. I make no apologies for my bright light. It’s got a pretty focused beam pointed down toward the road about four meters in front of me. That’s the best I can do right now.

I get blinded too on occasion. The best strategy I’ve found is to eyeball the trail, hold my line, and avoid the temptation to stare into the light. The whole thing is over as quick as it began.

[mstone]

@hozn 97725 wrote:

I find 200-350 lumens is plenty. When it’s full dark, I run the Lezyne at 200 lumens, when it’s starting to get light, I drop it to 100L and when it’s not really needed for trail illumination, I set it at 50. Same for my NiteRider 350; I run it at the 250 setting unless I’m in the woods. And I run my NiteRider 250 at the 180 lumen (medium) setting.

Granted, this is not off-road riding. I would consider a brighter light for going through the woods. I have no problem with that light output for normal speeds — probably up to 25-30mph, depending on the roads. I’d crank it up to 350 for 30mph and probably would simply avoid going much faster than that in the full dark. I’m not going super fast in the AM (which is when it’s dark for me), though; looks like those rides average 16+/-0.5 mph.

Assuming you’re talking about a medium width circular beam pattern, that’s simply not enough light for me–I cannot clearly see an obstacle on the road far enough ahead to be confident about avoiding it when moving at 20+MPH with that much light. It would be sufficient for me to clearly see 25-50 feet out, and I want to see more like 50-100. Eyes are different. Lights are also different, so some beam shapes will more illuminate further than others, and it may be that the 250lm light has a great beam which would be fine. (Note that such a beam would also have a vertical cutoff and wouldn’t be causing issues for oncoming riders in the first place.) In general, though, if people are talking about 500+lm lights they’re talking about round beams, for which you need a pretty bright source to illuminate the distant road as well as the trees above and to either side.

[rcannon100]

@Brendan von Buckingham 97719 wrote:

What’s a lupin?

[mstone]

@hozn 97728 wrote:

I have witnessed a couple near accidents due to people being unable to see pedestrians, related to oncoming headlights. If you can’t see in front of you, the only way to be sure you’re not going to plow into a pedestrian is to stop your bicycle. [And then risk getting plowed into by the person you didn’t know was riding behind you.][/quote]

The question I asked, was “do you have any evidence of that actually happening”? Not, “can you speculate on what might happen”. (And I should probably add the clause, “where the blinded person had adequate lighting and wasn’t relying on their super-hero night vision” since I am aware of non-lighted cyclists hitting people but I’m not going to accept blaming anybody else’s light for that.) We’ve been over all this before, and I truly believe that if you personally go completely blind in the presence of an oncoming light, you shouldn’t be riding at night, period. No amount of bellyaching on this forum is going to make oncoming headlights go away, and if you are so sensitive that you pose an ongoing danger to yourself and others you have an obligation to take yourself out of that situation. I have been dazzled by oncoming lights, but never to the point of being completely blind. Since I have adequate lighting myself, I know whether there are any pedestrians within at least 100 feet, and if I were to be blinded to the point of not being able to see ahead of me, of course I’d STOP MOVING well within that 100 foot range (so I can’t imagine running into someone barring extremely unlikely/contrived scenarios).

Quote:

I think it’s pretty selfish to blast down the trail with 750L and not bother to shield your light to oncoming riders. Sure, I sometimes forget or am just not able to safely shield my light from oncoming riders.

Again, the lumen measure is pretty irrelevant. The key point is how much light is being focused on a given surface, for which the luminosity is only an upper bound. I fully support the idea that nobody should be shooting light up into the sky ahead of them on a trail for a variety of reasons. Either direct the light downward, or to the side, or get a light with a vertical cutoff. That said, I know that a lot of people are going to just strap a flashlight to the front of their bike, and I’d rather have that than a ninja cyclist running into ninja joggers. Loudly proclaiming that some specific lumen value is the thin line between the virtuous and the damned misrepresents how lights are measured and focusing so obsessively on sending the message that people’s lights are too bright encourages them to take the counterproductive step of dimming their lights so they see less clearly rather than encouraging them to get as bright a light as they need to see, while making sure it is aimed in such a way as to minimize inconvenience to others.

[cyclingfool]

@rcannon100 97736 wrote:

Dennis Moore
Dennis Moore
Riding through the night…

[dkel]

I run 300 lumen most of the time, and rarely will go up to 350. I find this is enough to see, but I don’t feel like I see very well. I have a pretty strong prescription to correct nearsightedness, and I’m also older than I used to be; I don’t know if that has anything to do with it. I lust after one of those German dyno systems, not because it would be brighter, but because it would be more effective (and because it’s a dyno system). I think that is what I’m missing with my current light: I can see up close, but the light just gets dimmer and dimmer the further out it goes (much like my vision, now that I think about it :p).

[jabberwocky]

It probably depends where you ride, as well. Closer to the city, you get a lot of ambient light due to all the light pollution. Out in the burbs, not so much. I know when I used to do the tysons-reston commute down the W&OD in the evening, I had a lot easier time seeing as I got closer to Reston Town Center. There is enough ambient light there that you can make stuff out pretty far ahead even if your light isn’t illuminating it. Between Vienna and Reston it was pretty much pitch black though.

More power to you if you can commute safely on a less powerful light.

[Geoff]

I’m not sure what to make of the discussion when it turns to how much light you need at 20+ mph. Maybe my legs aren’t as good as other people’s, but the only time I hit those speeds on my commute is a few downhill sections that have good sightlines and good lighting. Most stretches, whether on roads or trails, have too many intersections or turns or bumps to make it worthwhile to build up speed. The turns are a problem on the Custis in particular; given the limited sightlines, there are few places where 20+ is safe in broad daylight.

For the record, my headlight is set at 200 lumens and is angled down. I don’t often cover it because I want my hands on the handlebars and the brake levers. Too many bumps and ninjas on the trail.

[AFHokie]

@Supermau 97729 wrote:

Seriously. I do.

Much of the MVT is pitch black when I’m on it. I’ve tried lower settings and I always wind up back at 750. The one time I was called for blinding was when my light was new and I think I had it angled too high. It didn’t help that I was coming down hill while the other rider was coming up, making my light even more in his face. We did not crash however. Not even close.

A direct hit with 200 lumens is still pretty blinding. I make no apologies for my bright light. It’s got a pretty focused beam pointed down toward the road about four meters in front of me. That’s the best I can do right now.

I get blinded too on occasion. The best strategy I’ve found is to eyeball the trail, hold my line, and avoid the temptation to stare into the light. The whole thing is over as quick as it began.

Like mstone’s points out; beam design is more important than XX lumen output. My 25yr old Maglite with a krypton bulb produces less than half the lumens of my 350 lumen LED Niterider light, but throws a beam much farther…again, beam design over lumen output. Unfortunately, I find mounting a 2D cell flashlight on my bike unwieldy.

I checked out Cygolite’s webpage and while they don’t tell you how far their lights put out a beam they do show a photo of the light output from a cyclist perspective on a road. It looks more like a fan vice a beam however you will outrun even a highly focused beam if you point it at the ground only four meters in front of you. I’d guess that is why you need it at the 750 setting in order to keep from overrunning it.

IIRC, Niterider includes a distance chart on the packaging, but when I checked their webpage, I couldn’t find anything regarding distance. Incidentally, I also checked Surefire’s webpage as well and they don’t state the effective distance of their flashlights. They all only state the number of lumens produced. Maglite’s webpage is the only one I could find that included beam distance and they only had the data for their LED lights. For incandescent, they only showed ‘coming soon’.

The best part of a helmet light is also the worst part; there’s always light wherever you look. Great for you…annoying for anyone you look at in the eyes.

[mstone]

@dkel 97741 wrote:

I think that is what I’m missing with my current light: I can see up close, but the light just gets dimmer and dimmer the further out it goes (much like my vision, now that I think about it :p).

Yes, that’s exactly the thing that asymmetric beam optics can address; by focusing a larger portion of the available luminosity on the far field, you can achieve more consistent illumination over the whole field.

Also, FWIW, B&M uses the same optics on its generator lights and its non-generator lights. This will not help justify a dynamo hub to the spouse.

[hozn]

@jabberwocky 97742 wrote:

More power to you if you can commute safely on a less powerful light.

I think people are just different or you get used to lower light. I can see people, even non-reflective, quite far off in the distance. I likely have my lights angled up more / more even than you do.

FWIW, I don’t find that the shaped beam provides any salient advantage over a similarly bright round beam. I realize it’s fancy and German and everything, but both lights do fine illuminating the narrow W&OD trail. Likely would be different if I was doing more riding in the dark on roads than trail. But I don’t think they’re worth the difference in price.

[hozn]

@mstone 97737 wrote:

The question I asked, was “do you have any evidence of that actually happening”? Not, “can you speculate on what might happen”. (And I should probably add the clause, “where the blinded person had adequate lighting and wasn’t relying on their super-hero night vision” since I am aware of non-lighted cyclists hitting people but I’m not going to accept blaming anybody else’s light for that.) We’ve been over all this before, and I truly believe that if you personally go completely blind in the presence of an oncoming light, you shouldn’t be riding at night, period. No amount of bellyaching on this forum is going to make oncoming headlights go away, and if you are so sensitive that you pose an ongoing danger to yourself and others you have an obligation to take yourself out of that situation. I have been dazzled by oncoming lights, but never to the point of being completely blind. Since I have adequate lighting myself, I know whether there are any pedestrians within at least 100 feet, and if I were to be blinded to the point of not being able to see ahead of me, of course I’d STOP MOVING well within that 100 foot range (so I can’t imagine running into someone barring extremely unlikely/contrived scenarios).

The evidence was anecdotal, but that is evidence enough for me that it adds danger. It is fairly intuitive that even “dazzled” cyclists, whatever state of vision that implies, are a greater risk to others on the trail than those that can see clearly. I find it perplexing that you could actually maintain otherwise. Though I also am also perplexed that I would still find this perplexing.

I can only conclude that we must commute on different trails / roads [in the dark]. Or maybe you just happen to cross paths with more courteous cyclists. 90% of the cyclists I encounter are using “normal-power” lights, and I only find it mildly annoying when they shine in my face. There are, however, a few people riding east-bound on the W&OD in the AM with what are probably 1000+L lights that are absolutely ridiculous. There are also some people that ride with extremely bright lights but do shield them; I thank them. I don’t have sensitive eyes in any other scenario (e.g. driving), so as convenient as it may be to think other people are just genetically unfit for being on the road at night, I don’t think that’s what’s going on here.

[Author]

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