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Old March 19th 17, 01:05 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Default More About Lights

On 3/18/2017 5:35 PM, sms wrote:


In the Odense study, cyclists with daytime bicycle lights had 32% fewer
accidents than the control group. The effect was particularly noticeable
during the summer season when the reduction is up to 40%. So it's when
the sun is brighter that there is even more of an advantage to DRLs.


Let's talk about the origin and the details of that study.

First, it was initiated by Reelight, the company selling the lights. For
most scientifically competent people, that would at least indicate that
the details need critical examination.

Second, the group who got the lights was self-selected. Self-selection
is always regarded with high suspicion, because those choosing the
measure under study are almost guaranteed to be different than those who
do not make that choice.

In this case, the company offered free lights to those who would
participate. It's very likely that those choosing to get the lights
were the most fearful and careful cyclists - those who would have the
lowest crash rate in any case. IOW, the difference in crash rates
between self-selected and control groups would probably be as great if
the offer was for magic key fobs.

You can see the same thing in your own town. It's especially noticeable
when cyclists are in a bicycle lane, closer to the curb than in a
traffic lane. They tend to blend in with the other stuff on the right
side of the road, such as parked cars.


Don't ride in the gutter, Stephen.

--
- Frank Krygowski
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