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Old 01-09-11, 02:40 AM   #1
smasha
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Cyclist visiblity at night

i've seen a few references to this recent study, but this is the first time i've seen the actual study. at six pages it's a very good read.

http://dl.dropbox.com/u/1079188/Stud...at%20night.pdf

i would like to see a study that skips the knee-reflectors, since i've never seen those incorporated into cycle clothing. at the same time, maybe this study will inspire such clothing.
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Old 01-09-11, 08:48 AM   #2
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Thanks for posting! It's nice to learn the differences between fluorescent and reflective materials. It got me thinking about replacing my leg bands and adding a reflective vest.
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Old 01-09-11, 01:19 PM   #3
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I'd think that a good portion of the reason why vests don't help much is because most car headlights really don't shine that high. Headlight patterns have been made with a good horizontal cutoff for quite a few years now (of course that assumes that they're aimed correctly, but let's be honest -- MOST vehicles out there DO have correctly-aimed headlights), and they really don't illuminate very much above level -- which is maybe knee-level for cyclists.

Do an image search via Google to see what I mean; use "headlight cutoff" and you'll get plenty of results.

FWIW, I've been able to read street signs much more clearly with a helmet light or a bright handlebar light than I have with my car's headlights. Not because the bike lights are any brighter -- which they're not -- but because they have more glare.
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Old 01-09-11, 01:34 PM   #4
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The article barely makes mention of head and tail lights - which are required by law in many states. I think bright flashing red lights are far more effective than any amount of reflective material you could outfit yourself with.

The study almost antiquates itself by failing to use mounted lights in its study.
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Old 01-09-11, 01:38 PM   #5
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^^^ On the other hand, it does succeed in focusing on wearable visibility gear.

And, if we bring lights into it, we've got to remember that a lot of the little blinkies you can buy off the shelf are almost as inadequate as dark clothing. We know that bright lights are good, but how many do you really see being used?
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Old 01-09-11, 02:16 PM   #6
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Quote:
Originally Posted by twobadfish View Post
The article barely makes mention of head and tail lights - which are required by law in many states. I think bright flashing red lights are far more effective than any amount of reflective material you could outfit yourself with.
last year I volunteered on a 1200km brevet. I overtook one of the riders in the fog at night, and the reflective gear he was wearing was far more striking than his tail light. The tail light was plenty bright, but there was only one spot, whereas the vest and ankle bands he was wearing were distributed over a fairly large area. Fog may have had something to do with this, I don't know.
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Old 01-10-11, 12:51 PM   #7
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Review: Interventions for increasing pedestrian&cyclist visibility for the prevent...

For a review of the subject, see Kwan I, Mapstone J.Interventions for increasing pedestrian and cyclist visibility for the prevention of death and injuries. Cochrane Database Syst Rev. 2006 Oct 18;(4):CD003438.

At one time the full article was available on the web at no cost, but that link seems to no longer exist.

CORRECTION, Google advanced search restricted to PDF files locates the entire review HERE. Dozens of studies are included in this review.

Last edited by Giro; 01-10-11 at 12:58 PM.
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Old 01-10-11, 10:20 PM   #8
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Quote:
Originally Posted by twobadfish View Post
The article barely makes mention of head and tail lights - which are required by law in many states. I think bright flashing red lights are far more effective than any amount of reflective material you could outfit yourself with.

The study almost antiquates itself by failing to use mounted lights in its study.
it may not make sense at first, but basic scientific method requires isolating different variables. this study just isolates parts of the reflectives variable (and completely trashes the flouro-at-night variable, for anyone who didn't know that previously). at some point in the future i hope they follow up with a similar experiment studying blinkies or reflectives & blinkies.

i'd be impressed to see how they standardize a blinky and mounting for an experiment... part of the problem is that blinkies are all marketed in terms of power consumption (eg, 1W, 1/2W, etc) but that only loosely (at best) translates into visible light output and still ignores optics, mounting variables, etc. there are countless variables to a blinky study, not least of which is the fact that there are countless blinkies of very different light output and optical characteristics.

just as this study points out the difference in perception of visibility vs actual visibility in regards to reflectives and flouros, i think there's an even bigger gap between the perception and reality of blinkies. if you haven't seen your bike being ridden in traffic by someone else, then you really have no idea what it looks like from a car. i think most cyclists would be disappointed. that blinky that seemed crazy-bright at arms length while standing in the LBS is barely visible half-way down the block to a car moving at +40MPH (in a 25MPH zone) - or +65KPH in a 40KPH zone.

i think the most important part of the study, the way i read it, is that 20% of old people who are driving cars shouldn't be driving!
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Old 01-13-11, 11:55 PM   #9
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I was slogging away at ~12mph yesterday morning in pitch darkness and a driving rain and another cyclist overtook me and rode off ahead. He had a helmet mounted rear blinky and a seatpost mounted rear blinky and they were all I could see! There was absolutely no outline at all of a human being just those two tailights flashing their merry patterns in the air. FWIW.

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