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Passing Study U of Minnesota

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Passing Study U of Minnesota

Old 07-26-19, 10:36 PM
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debade
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Passing Study U of Minnesota

Interesting study about the distance motorists pass bicyclists, especially women. https://genderpolicyreport.umn.edu/b...EMg0PJvh4VL9Kk
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Old 07-27-19, 04:06 AM
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Car drivers encroach upon/close pass women more often than they do men. It's easy; with a male, subconsciously motorists think (sub) or consciously there's a chance for an altercation that could result in physical violence if they get stopped in traffic and are approached by the cyclist.
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Old 07-27-19, 06:33 AM
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Interesting article!

With 33 total encroachments out of close to 3,000 encounters, I'm not sure their data is sufficient to show a gender bias even though 24 out of the 33 were to women (actually only one woman in the 3 rider study group). I couldn't grab a copy of the actual published study so I don't know how well it was designed. For instance, how did they address the possibility of gender ambiguity, i.e. the motorist not recognising the rider as either male or female? Was there something about the riding style of the sole woman in the study group that resulted in more encroachments? Knowing the intent of the study, did she unconsciously position herself to achieve a higher number of encroachments? Was time of day an uncontrolled factor? I'm also curious about how the equipment was mounted. The article said "on the handlebars", but does that mean at the end or at a set point from center line? Handlebars vary in width. I also wonder how they controlled for cyclist size. It's possible that a bigger rider is given more passing distance regardless of their genders.

Anyhow, I think that the results may be valid, but for the time being I'll have my peer-reviewer hat on in anticipation of reading the actual study.

My own experience as a male rider is that I have very few close passes - maybe 1 every thousand miles riding in urban traffic. If I estimate 10 passes per mile, that would calculate to an encroachment rate of 1 in 10,000 or a tenth of the rate for the UMinn riders. Maybe the motorists here in NC are less aggressive than the MN ones!
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Old 07-27-19, 11:36 AM
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Did this study account for lane positioning? The distance at which I get passed corresponds directly to whether I take up more of the lane (good passes) or ride far to the right (close passes). If this factor wasn't accounted, perhaps women are getting passed closely more often because they ride too far to the right more often thinking they'll put themselves in less danger. We already know women take fewer risks than men (https://journal.sjdm.org/jdm06016.pdf), and it is often instinctual to ride far to the right thinking it's less risky.
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Old 07-27-19, 05:18 PM
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This study has the same flaw as the famous University of Bath study. The test subjects themselves could be a source of bias. What puzzles me is that they could do a purely observation based study by just putting up video cameras and watching the bike traffic, then using fairly conventional image analysis to tease out the data.
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Old 07-29-19, 08:18 PM
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Originally Posted by JW Fas
Did this study account for lane positioning?
"Working with county staff, students marked ½-mile routes and riding positions on six types of roadways with different types of bicycle facilities. "

So, I'm assuming this means lane positions were established for every type of road regardless of the rider's gender.

Originally Posted by Gresp15C
The test subjects themselves could be a source of bias. What puzzles me is that they could do a purely observation based study by just putting up video cameras and watching the bike traffic, then using fairly conventional image analysis to tease out the data.

"the students used the handle-bar-mounted radar to measure passing distances"So no bias there. Observation was done by instrumentation.

Last edited by Daniel4; 07-29-19 at 08:26 PM.
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Old 07-29-19, 08:38 PM
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Originally Posted by Daniel4
"Working with county staff, students marked ½-mile routes and riding positions on six types of roadways with different types of bicycle facilities. "

So, I'm assuming this means lane positions were established for every type of road regardless of the rider's gender.


"the students used the handle-bar-mounted radar to measure passing distances"So no bias there. Observation was done by instrumentation.
The bias could have been in the behavior of the riders. This is a feature of all studies based on trained participants. However, for all of that, I suspect that as with most preliminary studies in the social sciences, the effect diminishes upon replication and better experimental design. They could still take the conscious actions of the riders out of the picture by using video footage of actual riders.

I'm certainly not trying to downplay the way that female riders are treated by drivers, something that seems credible based on talking to friends who ride. But I've learned to be skeptical of studies -- especially when they confirm my opinions.

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Old 07-30-19, 07:15 AM
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Let's put it this way--if your subjects consist of two men and one woman, how can you possibly control for the importance of variables other than sex? There will be no variation of other variables for women, and coin flips for the men.

It's way too early to even discuss the importance of the results, at this point, it's little more than a proof of concept of the experimental design. Yes, they can judge passing distance by radar measurements.
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Old 07-30-19, 10:05 AM
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Oh, brother.

"In total, the students used the handle-bar-mounted radar to measure passing distances for 2,949 passing events: 1,408 for male riders and 1,541 for the female rider. "

I guess the extra 133 females throws off the whole study by 9%.

Next topic: Flat Earth.
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Old 07-30-19, 02:18 PM
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Originally Posted by Daniel4
Oh, brother.

"In total, the students used the handle-bar-mounted radar to measure passing distances for 2,949 passing events: 1,408 for male riders and 1,541 for the female rider. "

I guess the extra 133 females throws off the whole study by 9%.

Next topic: Flat Earth.
What? You do get that there was only one female rider and two male riders, right? What throws the study off is that is that there are too few riders to know if there's any systematic differences within the different sex groups--in other words, we really can't tell if something other than sex is actually causing the measured differences.

Is it your experience that all women ride or look alike or that all men do so?
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Old 08-08-19, 04:54 PM
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Insufficient data to draw their conclusions. What you need to do is perform an ANOVA of all passing distances and determine if there's a statistically significant difference, regardless of whether the passing distances are considered encroaching. Pretty sloppy work, if you ask me.
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Old 08-09-19, 12:20 AM
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Originally Posted by Hokiedad4
Insufficient data to draw their conclusions. What you need to do is perform an ANOVA of all passing distances and determine if there's a statistically significant difference, regardless of whether the passing distances are considered encroaching. Pretty sloppy work, if you ask me.
The design is so poor that statistical significance will not mean anything. Because there's only one woman rider, there's no way to control for variables other than sex.
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