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visibility of DRL



 
 
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  #161  
Old April 9th 19, 03:44 PM posted to rec.bicycles.tech
SMS
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Posts: 9,477
Default visibility of DRL

On 4/9/2019 7:12 AM, jbeattie wrote:

snip

Yes, I turn on my front flasher and say "f*** that, I'm going for it!" Then I start racing down the middle of the road, going the wrong way -- "I'm king of the world!" And with my helmet, it's no holds barred!


Exactly. You're the prime example of risk-compensation.

But seriously, you experience risk-compensation without even being aware
of it. With a DRL, and with good lights in general, I know that vehicles
are much more aware of my presence and less likely to exit a parking lot
or a side street across my path. When I'm riding with only my dynamo
light I know that I'm much less conspicuous so I ride differently. You
often don't realize the risk compensation you engage in.

https://www.theguardian.com/science/2016/jan/24/bike-helmet-appetite-danger
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  #162  
Old April 9th 19, 03:52 PM posted to rec.bicycles.tech
Duane[_2_]
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Posts: 401
Default visibility of DRL

On 09/04/2019 10:12 a.m., jbeattie wrote:
On Tuesday, April 9, 2019 at 6:39:51 AM UTC-7, sms wrote:
On 4/8/2019 6:19 PM, Jeff Liebermann wrote:

The problem with DRL is that anyone can see that the light is flashing
or not flashing. Everyone in the test group knows that they have a
functional device and everyone in the control group knows that they
don't have anything to test. Expected results soon turn into actual
results. In other words, there's no way I could arrange a double
blind study for DRL safety and the results will tend to favor the
expected results.


Another issue is that the group with the DRLs will be taking more risks.
It's called " “risk compensation." In the Odense study, the results
would have been skewed by risk compensation. If all the riders had
somehow been forced to take the same risks, the conclusion would have
been different, with the riders using DRLs having even fewer incidents.


Yes, I turn on my front flasher and say "f*** that, I'm going for it!" Then I start racing down the middle of the road, going the wrong way -- "I'm king of the world!" And with my helmet, it's no holds barred!


Yeah, I find that pretty ludicrous. I understand risk compensation. My
kid does things on a snow board with a helmet that he wouldn't if he
weren't wearing one. But DRLs on my bike? I don't think so.

The safety mavens around here with their five flashers and three headlights, flags, vests, etc., etc. don't seem to be doing any compensating. The most consistently crazy are the ones with the least safety equipment.


Yeah, same here. Actually I think rather than risk compensation, choice
bias skews these "studies" as people that use flags and vests etc are
already more concerned with safety than the typical users.


  #163  
Old April 9th 19, 04:15 PM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 4,018
Default visibility of DRL

On Tue, 9 Apr 2019 06:39:46 -0700, sms
wrote:
If all the riders had
somehow been forced to take the same risks, the conclusion would have
been different, with the riders using DRLs having even fewer incidents.


I call to your attention (again) the data tweaking and fudging that
was apparently done to produce a result in favor of riders with DRLs.
See my cursory and superficial analysis at:
https://groups.google.com/d/msg/rec.bicycles.tech/CVAE2CuCHo8/VRIyIZ-cAgAJ
If you accept my suspicions, the actual results of the study, ignoring
a 28% fudging of the treatment group data, would be a 9% INCREASE in
accidents by the treatment group over the control group. So far,
nobody has commented on this problem and I could use a sanity check to
make sure I haven't screwed up somewhere.

If someone gave you a DRL to use on your bicycle in trade for filling
out a web form with your experiences, would you be:
[ ] More
[ ] Equally
[ ] Less
inclined to provide the data compared to filling out the same web form
if you were given nothing? It would be interesting to know if the
control group, that had NOT been provided with lights, were given free
lights at the end of the study.




--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #164  
Old April 9th 19, 09:52 PM posted to rec.bicycles.tech
Andre Jute[_2_]
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Posts: 10,422
Default visibility of DRL

On Tuesday, April 9, 2019 at 4:15:19 PM UTC+1, Jeff Liebermann wrote:

I call to your attention (again) the data tweaking and fudging that
was apparently done to produce a result in favor of riders with DRLs.
See my cursory and superficial analysis at:
https://groups.google.com/d/msg/rec.bicycles.tech/CVAE2CuCHo8/VRIyIZ-cAgAJ
If you accept my suspicions, the actual results of the study, ignoring
a 28% fudging of the treatment group data, would be a 9% INCREASE in
accidents by the treatment group over the control group. So far,
nobody has commented on this problem and I could use a sanity check to
make sure I haven't screwed up somewhere.


Seems about right to me.

But I don't know why you're surprised. Peer review has been a sham for a long time. For instance, if twenty-some years ago the reviewers of Michael Mann's first two "hockey stick" articles were not his students, who basically passed the article as good without asking for either the underlying data or an account of the adjustments made, the world would never have wasted trillions on the myth of global warming, which has since become a touchy-feely religion much in evidence among the more sanctimonious class of cyclists, and others of course: I enjoyed those kids abusing Senator Diane Feinstein about it...

Ande Jute
Wide awake
  #165  
Old April 9th 19, 11:13 PM posted to rec.bicycles.tech
jOHN b.
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Posts: 2,421
Default visibility of DRL

On Tue, 9 Apr 2019 06:39:46 -0700, sms
wrote:

On 4/8/2019 6:19 PM, Jeff Liebermann wrote:

The problem with DRL is that anyone can see that the light is flashing
or not flashing. Everyone in the test group knows that they have a
functional device and everyone in the control group knows that they
don't have anything to test. Expected results soon turn into actual
results. In other words, there's no way I could arrange a double
blind study for DRL safety and the results will tend to favor the
expected results.


Another issue is that the group with the DRLs will be taking more risks.
It's called " “risk compensation." In the Odense study, the results
would have been skewed by risk compensation. If all the riders had
somehow been forced to take the same risks, the conclusion would have
been different, with the riders using DRLs having even fewer incidents.


The Odense study showed that solo accidents were also reduced by the
lights. Which does tend to make one think that simply participating in
the study as a part of the "lighted fraternity" had a tendency to make
one a bit more careful.
--
cheers,

John B.

  #166  
Old April 10th 19, 03:11 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 10,538
Default visibility of DRL

On 4/9/2019 10:12 AM, jbeattie wrote:
On Tuesday, April 9, 2019 at 6:39:51 AM UTC-7, sms wrote:

Another issue is that the group with the DRLs will be taking more risks.
It's called " “risk compensation." In the Odense study, the results
would have been skewed by risk compensation. If all the riders had
somehow been forced to take the same risks, the conclusion would have
been different, with the riders using DRLs having even fewer incidents.


Yes, I turn on my front flasher and say "f*** that, I'm going for it!" Then I start racing down the middle of the road, going the wrong way -- "I'm king of the world!" And with my helmet, it's no holds barred!


Here's a possible mechanism for risk compensation with DRLs: An
edge-riding cyclist coasting northward down a hill sees a car either
driving south with its left turn signal on, or a car rushing to a stop
sign from the east. The rider thinks "It's OK, they'll see my DRL" and
doesn't bother to pay attention, keep his hands on the brakes, watch for
a potential escape route, keep pedaling* etc. The car crosses his path,
and he's not ready for it.

(*I do keep pedaling in those situations, even if I'm spinning the
cranks against zero resistance. It's a way of telegraphing that I'm not
planning on stopping, and the motion may enhance conspicuity. Is that
partly why I don't get people pulling out in front of me? I can't say.)

The safety mavens around here with their five flashers and three headlights, flags, vests, etc., etc. don't seem to be doing any compensating. The most consistently crazy are the ones with the least safety equipment.


I agree that those Scharf imitators probably don't consciously take
extra risks. But I do think most of them are edge riders who lose some
of their conspicuity due to bad lane position.

And since I tend to believe data: Two pieces of data that are not
usually gathered after bike crashes, but really should be, are 1)
details on the use (or absence) of lights and reflectors, and 2) details
on lane position.

One colleague of mine tried hard to lobby for better collection of that
data in the latest revision of accident reporting forms. She wasn't able
to succeed.

--
- Frank Krygowski
 




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