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From: Frank Krygowski <frkrygow@sbcglobal.net>
Newsgroups: rec.bicycles.tech
Subject: Re: Some traffic stats
Date: Thu, 14 Mar 2024 17:06:08 -0400
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On 3/14/2024 1:53 AM, Jeff Liebermann wrote:
> On Thu, 14 Mar 2024 00:00:45 -0400, Frank Krygowski
> <frkrygow@sbcglobal.net> wrote:
> 
>> On 3/13/2024 4:06 PM, Zen Cycle wrote:
>>> On 3/13/2024 3:44 PM, Frank Krygowski wrote:
>>>> On 3/13/2024 11:34 AM, AMuzi wrote:
>>>>> https://www.cityofmadison.com/police/newsroom/incidentreports/incident.cfm?id=30855
>>>>
>>>>   From that site:
>>>>
>>>> * On average, every day, twenty pedestrians are killed by a moving
>>>> vehicle in the United States.
>>>>
>>>> * Approximately 76,000 pedestrians and 47,000 bicyclists are injured
>>>> in roadway crashes annually in the United States.
>>>>
>>>> I'll note that the figures for pedestrians are far worse than for
>>>> bicyclists. Yet the general public thinks of bicycling as much more
>>>> dangerous than walking.
>>>
>>> I think if you compare injuries per participants or injuries per miles
>>> traveled, you'll see they're probably correct.
>>
>> That's far from certain.
>>
>> Powell et. al., “Injury Rates from Walking, Gardening, Weightlifting,
>> Outdoor Bicycling and Aerobics”, Medicine & Science in Sports &
>> Exercise, 1998, Vol. 30 pp. 1246-9 polled over 5000 people who had
>> chosen at least one of those activities for exercise. One question was
>> whether the participant had incurred an injury during the previous month.
>>
>> The results:
>> Weightlifting: 2.4% of participants injured
>> Gardening or yard work: 1.6%
>> Aerobic Dance: 1.4%
>> Walking for exercise: 1.4%
>> Outdoor bicycling: 0.9%
> 
> Such surveys require a control group to be valid.  I suspect that if
> someone was able to do NOTHING for one month, they would still have
> been involved in some kind of accident.

Sorry, that makes no sense. First, we're talking about _relative_ risk, 
comparing various activities. And how would you define a control group? 
A group that does NOTHING for one month might have to be nearly 
catatonic, and certainly would have to be confined to bed. The 
"accidents" suffered by people like that are medical deaths. Although 
yesterday, I was told about a friend of a friend who fell out of bed and 
broke her neck. Not fatally, but serious enough to require surgery, so 
there is that...

> 
>> And while injuries =/= fatalities, Dr. John Pucher of Rutgers has
>> published (in "Making Walking and Cycling Safer: Lessons from Europe")
>> an estimate from U.S. data that bicyclists suffer 109 fatalities per
>> billion km ridden.  Pedestrians suffer 362 fatalities per billion km,
>> three times as bad!
>>
>> Pucher's number works out to 5.7 million miles ridden per fatality for
>> cyclists, 1.7 million miles walked per fatality for pedestrians. And
>> Pucher's later work, as well as other sources, show he greatly
>> overstated the bicycling risk. It's now widely accepted that Americans
>> ride over ten million miles between fatalities.
> 
> Americans ride over 10 million miles between fatalities?  Most
> Americans don't ride after their first fatality.  The value of
> exercise after death has been greatly overrated.

:-)  I'd say we don't know that! I'm hoping that my riding after death 
will be scenic, in beautiful weather, and all gently downhill with a 
tailwind.

> 
>> British data for decades has consistently found more pedestrian
>> fatalities per mile traveled than bicycling fatalities per mile. AFAIK,
>> there have been only a couple years in the past 20 where the reverse was
>> true. I've also seen Australian data showing the same result.
>>
>> In any case, for most Americans the far bigger danger is sitting on the
>> couch.
> 
> If someone asked you "what is your favorite sport ...

Please. For ~99% of cyclists, bicycling is not a "sport."

> ...and how many times
> have you been injured in the previous month", would you produce an
> accurate number, or would you minimize the number of injuries?  My
> past experience working with such surveys suggests that most people
> would not admit to an injury.  

Really? I don't see why that would be. I believe I'd answer honestly - 
why not? - but my answer would almost always be "zero." I don't injure 
myself much at all.

(Anecdote alert: The last injury I recall was a [GASP!] head injury. One 
of my two garage doors is a manually lift. About two weeks ago, at 
night, I raised it not all the way, entered the garage to get the trash 
can, and bumped my head on the way out. Got a slight scratch.)

(Hmm. Is that a walking injury? I suppose if I were getting a rake 
instead of the trash can, it would be a gardening injury.)

> I also find it odd that the survey
> would ask if "the participant had incurred an injury" instead of
> asking how many injuries.  Why only one month?  Were they worried that
> if they extended the time period to one year, a much larger percentage
> would probably have been injured at least once.  

<sigh> Another study addressed that point. See
https://pubmed.ncbi.nlm.nih.gov/21068616/

"Bicycle commuter injury prevention: It is time to focus on the 
environment", Melissa R. Hoffman, et.al., Journal of Trauma, V 69, no. 
5, Nov. 2010 reports on exhaustive surveys of Portland, OR bike 
commuters. Hoffman's team feared that injury surveys underestimate 
injury counts due to people forgetting an injury, so they recruited just 
under 1000 commuters who agreed to repeated queries. They contacted them 
once per month, specifically because they figured it would take at least 
a month to forget an injury.

(Which raises the question, if an injury is so mild as to be forgotten 
in six weeks, does society _really_ need to be concerned?)

So they contacted everybody each month, asking something like "Were you 
injured? Yes or no." and "Did you show the injury to any medical person? 
Yes or no." (A company nurse would qualify.)

If the person answered yes to the latter, the authors dubbed it a 
"serious injury," probably not minding that someone might have asked for 
a tiny Band-aid. Their motivation, pretty obvious from the title, was to 
"prove" that more bike lanes were needed, even though bike lanes and 
quiet streets dominated their injury counts.

Results? Crunching their breathless numbers, the commuters averaged 6667 
commuting miles per boo-boo (AKA _any_ injury, no matter how small) and 
25,600 commuting miles between injuries that got _any_ medical 
attention, even a Band-aid. That's a very low level of danger.

> Also, was the month the same for everyone in the survey > I suspect not or the question
> would have been phrased differently.  For cycling, if they selected a
> month which has a high accident rate, typically when everyone is
> cycling, the survey results would have been very different had they
> selected a month with a low accident rate.

I don't think that's necessarily true. There's a contingent of Bicycling 
Advocates who put great store in "Safety In Numbers," claiming that if 
there are lots of cyclists about, they will be safer on average, because 
motorists will be less surprised by their presence, facilities will be 
better maintained, etc.

Admittedly, I'm not a member of that contingent, at least regarding 
America's levels of bicycle use. I think a bike mode increase from 0.3% 
to 0.4% is negligible in that regard as well as other regards. And it 
frosts me that  "Safety In NUmbers" is used to justify some atrocious 
facility designs, via claims that "It doesn't matter. As long as we get 
more people riding, they'll be safer."

But to me, we're pretty far off into the weeds. I think it's clearly a 
fact that normal bicycling is not an unusually dangerous activity, 
nowhere near as dangerous as most people seem to believe. And that 
pretending it is dangerous does no good for bicyclists or for society as 
a whole.

-- 
- Frank Krygowski