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more validation for Jacobsen's Safety in Numbers effect

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more validation for Jacobsen's Safety in Numbers effect

Old 10-13-10, 09:21 AM
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Bekologist
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more validation for Jacobsen's Safety in Numbers effect

more reports validate's Jacobsen's Safety in Numbers hypothesis on bicyclist safety in a community. People and dilettante epistemologists have likely already seen these reports. This is a nice analysis of Jacobsen's theory in practice...

The Grist blog post there's safety in numbers for cyclists with links to recent studies affirming the safety in numbers effect.

It's more of an effect on motorist behvior...... from jacobsens' 2003 safety in numbers report,

Originally Posted by peter jacobsen
Whose behavior changes, the motorist's or that of the people walking and bicycling? It seems unlikely that people walking or bicycling obey traffic laws more or defer to motorists more in societies or time periods with greater walking and bicycling. Indeed it seems less likely. ... Adaptation in motorist behavior seems more plausible.
anyhoo, some food for thought. It's difficult to get more people cycling along roads that cater to motor vehicle traffic at the expense of bicyclist and pedestrian safety and access. Like ellie blue mentions in the tail end of her post,

"Jacobsen's research calls into question the foundation of a system in which the convenience of driving is exalted above the basic safety and mobility of people walking and bicycling."

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Old 10-13-10, 09:36 AM
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I think adaptation of cyclist behavior is possible too. A single cyclist riding on their own may feel that he gets to make up his own rules (many do). However, if he's on the road with another cyclist, and that cyclist stops at a stop light that the other guy has been running, he might change his behavior. Maybe not that time, but sometime in the future he may get nearly killed and rather than think "that ******* in the car should watch where I'm going!" he might think "Maybe that other guy is on to something, and I should stop at stoplights."
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Old 10-13-10, 09:38 AM
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Originally Posted by Bekologist View Post
more reports validate's Jacobsen's Safety in Numbers hypothesis on bicyclist safety in a community. People and dilettante epistemologists have likely already seen these reports. This is a nice analysis of Jacobsen's theory in practice...

Interesting spin on the post. I liked this part (which I imagine you left out because it seems to be a big mental blindspot for the juggernaut of your belief system:

Much of the ridership increase is due to cities' investments in bicycle-specific infrastructure. But the efficacy of that infrastructure for safety is often questioned. And there's one theory -- based on a growing body of data -- that suggests that a few painted lines on the road, bike racks, and traffic lights form only part of the safety equation. And maybe a smaller part than we tend to assume.
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Old 10-13-10, 10:08 AM
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Originally Posted by RazrSkutr View Post
Interesting spin on the post. I liked this part (which I imagine you left out because it seems to be a big mental blindspot for the juggernaut of your belief system:
Yeah I could see that bike racks hardly lend anything to the safety of cyclists. Of course having free parking for motorists everywhere does rather encourage motoring doesn't it? I wonder if the same might also be true of cycling.
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Old 10-13-10, 10:19 AM
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regardless of the juggernaut aside, It would be difficult if not impossible to separate increased ridership and its concurrent safety benefits from the infrastructure that built the ridership in the first place in most cities.

Gasoline and economic hardships aside, bike infrastructure appears to drive ridership more than any other factor influencing bicycling in industrialized countries IMO.
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Old 10-13-10, 10:21 AM
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Originally Posted by genec View Post
Yeah I could see that bike racks hardly lend anything to the safety of cyclists. Of course having free parking for motorists everywhere does rather encourage motoring doesn't it? I wonder if the same might also be true of cycling.
If one wants to encourage cycling vis a vis being a motorist, then the thing to do is CHARGE for motor vehicle parking and give free parking to cyclists.
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Old 10-13-10, 10:39 AM
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Does anybody notice that the money quote from Jacobsen there is a completely unscientific assumption about what "seems more plausible."

What seems more plausible to me is that much of the effect measured by Jacobsen and credited to increasing numbers and motorist behavior was actually primarily due to changes in the average age and experience level of the measured populations of bicyclists over time.

The big noise in his measurements is decreasing percentage of children among all bicyclists.

Sorry to rain on the happy parade.

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Old 10-13-10, 10:53 AM
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Originally Posted by RobertHurst View Post
Does anybody notice that the money quote from Jacobsen there is a completely unscientific assumption about what "seems more plausible."

What seems more plausible to me is that much of the effect measured by Jacobsen and credited to increasing numbers and motorist behavior was actually primarily due to changes in the average age and experience level of the measured populations of bicyclists over time.

The big noise in his measurements is decreasing percentage of children among all bicyclists.

Sorry to rain on the happy parade.
I wonder if that decreasing percentage of children cyclists is primarily due to the increased amount of chauffeuring by parents, which in turn increased the traffic around schools, and created the situation that "traffic around schools is too dangerous for children cyclists..." thus becoming a self fulfilling prophecy.

The fact that in some locations parents have to fight with administrators for the "privilege" to bike with their children to school, is something of an indicator of a system gone haywire.
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Old 10-13-10, 11:04 AM
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Originally Posted by genec View Post
I wonder if that decreasing percentage of children cyclists is primarily due to the increased amount of chauffeuring by parents, which in turn increased the traffic around schools, and created the situation that "traffic around schools is too dangerous for children cyclists..." thus becoming a self fulfilling prophecy.

The fact that in some locations parents have to fight with administrators for the "privilege" to bike with their children to school, is something of an indicator of a system gone haywire.
That's totally tangential to his point.

His point is that cycling went up while death/injury stayed flat because the makeup of cyclists went from mostly kids to mostly adults: Adults are safer riders than kids.

I tend to agree with Hurst's point (he's the one that changed my mind about safety in numbers a while back). Like much of the soft sciences these studies are poorly done and mostly useless.


I think there's more safety in an individual rider than there is in numbers. I believe we can do more to save cyclists by educating those who currently aren't listening about safe riding practices than we can by creating more of these types.

And I think we can do a lot by educating motorists as well. And by educate I mean punish when they kill, maim or endanger.

Edit: This could be misinterpreted. I don't mean that less riders is safer. I mean that a cyclists actions do more to make him safe than being surrounded by other cyclists does.
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Old 10-13-10, 11:09 AM
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State College just painted some bike lanes on one of the bike routes through town (Allen). For my purposes, they are a little closer to the curb than I feel comfortable riding. But if the placebo effect gets more people riding, then I'll live with that issue. The idea that cyclists may ride safer when there are more cyclists appeals to me. Hopefully we see proof of that.

Robert Hurst makes a good point if his assertion is true. When I was a kid, we rode everywhere, now you almost never see that. Of course, the distances I rode as a 10 year old wouldn't get you very far nowadays. I recall the very long ride across town to visit my friend in my old neighborhood. I recently checked the mileage, it was under 1.5 miles. I don't think my son has any friends that live within 5 miles of us. We were lucky my daughter's best friend only lives a mile away so we didn't have to drive her all the time like we do with my son. I also used to ride across town to play little league. My son's soccer is almost 10 miles away, and that's one of the closer fields.

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Old 10-13-10, 12:03 PM
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I redid the graph linked in the blog post for New York. I didn't like the scale used for the injuries. Of course it didn't give the numbers used for the graph, so I eyeballed them. These are numbers i used:
Year Riders Casualties
1998 83000 5000
1999 85000 4200
2000 78000 4100
2001 78000 3900
2002 80000 3200
2003 90000 2900
2004 105000 2800
2005 95000 3000
2006 140000 2700
2007 160000 2700
2008 180000
The graph:
NewYorkGraph..png
Click to enlarge.
Note the massive drop in injuries from 98-03. It's about a 40% decrease over the same period when ridership remained flat. Barring any other reasonable explanation, I suggest the NYC data is being manipulated and that there is a large number of injuries going unreported.
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Old 10-13-10, 12:25 PM
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Originally Posted by crhilton View Post
That's totally tangential to his point.

His point is that cycling went up while death/injury stayed flat because the makeup of cyclists went from mostly kids to mostly adults: Adults are safer riders than kids.

I tend to agree with Hurst's point (he's the one that changed my mind about safety in numbers a while back). Like much of the soft sciences these studies are poorly done and mostly useless.


I think there's more safety in an individual rider than there is in numbers. I believe we can do more to save cyclists by educating those who currently aren't listening about safe riding practices than we can by creating more of these types.

And I think we can do a lot by educating motorists as well. And by educate I mean punish when they kill, maim or endanger.

Edit: This could be misinterpreted. I don't mean that less riders is safer. I mean that a cyclists actions do more to make him safe than being surrounded by other cyclists does.
I see your point and understand.

I don't believe "surrounding cyclists with other cyclists" makes cyclists safer, but that frequent interaction between cyclists and motorists may tend to increase the awareness of motorists to the fact that there are cyclists about.

My comment regarding children merely means that we should expect a statistical drop in the number of "older experienced cyclists" in the future... more as a result of a self fulfilling prophecy than actual statistics indicating that cycling is dangerous... but that decrease in experienced cyclists could lead to a situation where the awareness of motorists to cyclists also drops, and cycling DOES become more dangerous.
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Old 10-13-10, 01:05 PM
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Originally Posted by genec View Post
Yeah I could see that bike racks hardly lend anything to the safety of cyclists. Of course having free parking for motorists everywhere does rather encourage motoring doesn't it? I wonder if the same might also be true of cycling.
Like all bike specific infrastructure that depends on whether it supplements or replaces existing ways of doing things.

I've been perfectly happy locking up to parking-meters, iron railings etc for a long while. On a couple of occasions now I've had people complain when I lock to parking meters because "there's a bike rack over there" where "over there" means a place which is out of sight from where I'll be shopping or even hundreds of meters away inconveniently across the street.

I've never, on the other hand, seen a superintended indoor bicycle parking structure which shelters my bicycle from snow, thieves and rain.

Like much BSI the intent may be good but the practice is counter-productive.
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Old 10-13-10, 02:32 PM
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Originally Posted by Bekologist View Post
regardless of the juggernaut aside, It would be difficult if not impossible to separate increased ridership and its concurrent safety benefits from the infrastructure that built the ridership in the first place in most cities.


The paper I linked addresses that very question. But since you don't like the conclusion it must not be worthwhile.
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Old 10-13-10, 03:27 PM
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Originally Posted by Bekologist View Post
regardless of the juggernaut aside, It would be difficult if not impossible to separate increased ridership and its concurrent safety benefits from the infrastructure that built the ridership in the first place in most cities.

Gasoline and economic hardships aside, bike infrastructure appears to drive ridership more than any other factor influencing bicycling in industrialized countries IMO.
Hmmm. In Davis, CA in the '70s and early '80s we had something very near 90% of all trips being made by bike or foot. In fact, one was considered quite strange if one chose to use a motor vehicle for an intracity trip. It is possible that a factor in this large ridership was the building of bike paths, striping out bike lanes and restricting motor vehicle access to the university campus, though most of us who were there just took for granted that it was a cultural thing (if you live in Davis, you ride and don't drive). The campus had a number of very large car parking lots that stood empty while people fought for more bike parking and dealt with the inevitable impoundments of illegally parked bikes.

However, as fuel prices plummeted in the mid '80s and '90s and tuition came to U.C. Davis there was a cultural transformation. By the time we got to the mid '90s there were so few people living car-free or even using their bikes for transportation that my family became known as "the bike family". I moved away from Davis in 2000, but my dentist, physician and family are still there so I ride through several times a year. Many times I would spend a week in town and go many days in a row without seeing a single person on a bike. (Thankfully there has been some improvement in the past 2 years.)

Now, all the infrastructure that was there in the in the '70s and '80s was still there in the '90s. In fact, quite a bit was added to it. Yet, in spite of all that infrastructure, ridership fell to levels so low that the people who were riding were the ones considered strange. A relative new-comer from someplace where people ride might even conclude that the infrastructure has a negative effect on ridership. (Another impact of the transition to cars was a very large increase in the ambient sound levels. There is a constant and loud background drone in Davis today that was not there 25 years ago.)

I think it works more like this: When you have a cultural change that leads to support for increased cycling, you get more cyclists. Since the social norm then defines cyclists in a positive way, motorists become less likely to attack them. Further, when cycling is seen in a positive light the political class begins to support infrastructure improvements for cyclists. Sadly, much of this infrastructure is poorly planned, built and maintained, so it often adds very little to the safety of cyclists; however it may be a factor in some people's decision to give the bike a try.

In the end, I suppose it does not matter what gets people on a bike. We simply need to get more people cycling, having cycling friends and viewing us in a positive light. Our goals are in concurrence, we just happen to disagree a little on how to get there. I don't object to road diets, increased striping of bike lanes (as long as they are not put in door zones) or the construction of bike paths (as long as they are not allowed to be overrun by pedestrian critical masses). In fact, I fully support those efforts. However, when they are poorly implemented I think they can do more harm than good. It is quite frustrating to watch expensive artsy bike bridges to nowhere being built that the general public thinks those of us riding asked for while we can't get the roads repaired to a level that doesn't cause bikes to needlessly break or traffic signals tuned to detect us.
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Old 10-13-10, 05:43 PM
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Originally Posted by invisiblehand View Post


The paper I linked addresses that very question. But since you don't like the conclusion it must not be worthwhile.
Construction of cycle tracks results in increases in numbers of cyclists, but that is offset by increases in crashes due to conflicts at intersections, and it's worse in urban areas than in rural areas.

fairly intuitive, I'd say.
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Old 10-13-10, 09:04 PM
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Originally Posted by unterhausen View Post
State College just painted some bike lanes on one of the bike routes through town (Allen). For my purposes, they are a little closer to the curb than I feel comfortable riding. But if the placebo effect gets more people riding, then I'll live with that issue. The idea that cyclists may ride safer when there are more cyclists appeals to me. Hopefully we see proof of that.
If only they could make the campus itself more bike-friendly, I'd think a lot more people would bike. As it is, with the exception of the closed portion of pollock rd, every road is dominated by cars and every pathway is dominated by pedestrians. Case in point: Shortlidge road up from College Ave, which is fairly steep and where they have random planters in the road at the perfect interval to prevent cars from passing.

Anyhow, why use sharrows if you're going to put them in the gutter?:
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Old 10-13-10, 10:04 PM
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Originally Posted by RobertHurst View Post
Does anybody notice that the money quote from Jacobsen there is a completely unscientific assumption about what "seems more plausible."

What seems more plausible to me is that much of the effect measured by Jacobsen and credited to increasing numbers and motorist behavior was actually primarily due to changes in the average age and experience level of the measured populations of bicyclists over time.

The big noise in his measurements is decreasing percentage of children among all bicyclists.

Sorry to rain on the happy parade.
That's not rain on the parade, Robert, it's hardly a drizzle. The rise in cyclist numbers in cities with fairly exploding ridership have not seen a correlative explosion in collisions or accidents. New York City and Portland trends tend to discredit rider savvy and education influencing the decline in the accident rate. Rather, with new riders on the roads the ratio of beginners to experienced traffic riders would likely be increasing.

additionally, the sharp rise in ridership in the last 3 or 5 years and the dropping accident rate does not get discredited by the demise of child cycling participation since the 1970s.

Theoretically taken to extremes, the Jacobsen safety in numbers effect holds true. I see no reason to dispute a theory that more bicyclists riding on the roads might become more of the expected road user makeup.

it's what can be called a "no brainer" hypothesis - more riders become better recognized road users so motorists are more aware of them is quite rational.

I personally feel and experience this as a palpable response over time from motorists that have become collectively more attuned to bicyclists as normal road users in cities that have greatly increased their ridership relative to other american cities less progressive in their bicycle planning.


why a decline in child participation in cycling from the 1970's would skew declining indexed accident rates seen in the last few years is a stretch.

Sorry, Robert, but if more riders are riding and there's less accidents in cities that are planning for roadway bike traffic, that's not rain, it's actually quite the sunny forecast.

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Old 10-14-10, 05:23 AM
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Those of you who think infrastructure isn't needed should come to the suburbs of Detroit. There is no bike infrastructure apart from some graveled rails to trails. There are a few casual riders and almost no commuters. I wonder if that's a coincidence. Nah, couldn't be...
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Old 10-14-10, 06:52 AM
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And in contrast to the vehicular cyclists' paradise of Metro Detroit there's places like Davis California.....


streetfilms.org film- cycling in Davis








Originally Posted by B.carfree
A relative new-comer from someplace where people ride might even conclude that the infrastructure has a negative effect on ridership.
maybe if the person was blind and addled. there's no way a "newcomer" to davis from 'someplace where people ride" would conclude infrastructure has a negative effect on ridership. Davis is a city in the USA with incredible participation in bicycling, kids bike to school, 17 percent of the workers in Davis commute by bike. Davis is rated by the League of American Bicyclists as one of three platinum rated bike friendly communities in the USA.



this thread is about how the safety in numbers theory continues to get validation in cities that are planning for bicycles as normal daily transport like Portland and New York City. Global research suggests these are closely intertwined. So does Davis. The decline in ridership in Davis since the 1970's is largely attributable to the rise of the long distance commute. 17 percent of workers continue to commute by bike in Davis.

Complaints about a Davis being a city full of bike infrastructure yet vacant of bicyclists is not very accurate. I find B. Carfree's commentary about Davis somewhat dubious.
Many times I would spend a week in town and go many days in a row without seeing a single person on a bike.
Statements like this lack credibility when discussing an American city where 17 percent of the workforce commutes by bike and there are no school buses for the kids.

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Old 10-14-10, 07:11 AM
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Originally Posted by genec View Post
I don't believe "surrounding cyclists with other cyclists" makes cyclists safer, but that frequent interaction between cyclists and motorists may tend to increase the awareness of motorists to the fact that there are cyclists about.
I think this is a fair assumption: few drivers actively try to hit cyclists but many simply don't have any consciousness that they should be LOOKING for them. What's sad about the typical driver excuse "I just didn't see him" or "He came out of nowhere" is that, for that from the viewpoint of that driver, it was probably true. Until the collision, they had no idea that the cyclist was there. (Obviously they SHOULD know, but that's the whole point.)

I recently moved to from the U.S. to Madrid (Spain). In the central city, bicycles (and bike infrastructure) are still a pretty small presence, but what do exist in huge numbers are scooters & motorcycles of various kinds. Now, it is legal here for two-wheeled vehicles to filter forward at stoplights, and there are dozens of people doing it at every intersection. As a result, car drivers seem to have a FAR greater awareness of what's going on to the side/rear of their vehicle than I'm accustomed to. The fact that drivers generally KNOW you are there has made cycling here far more pleasant than I had imagined after many visits here where I was only on foot/public transport.

Originally Posted by RazrSkutr View Post
I've never, on the other hand, seen a superintended indoor bicycle parking structure which shelters my bicycle from snow, thieves and rain.
Such things do exist: I used to park my bike here when I worked in downtown Seattle (my building had indoor parking, but charged almost as much as a car-parking spot for it).
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Old 10-14-10, 09:11 AM
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Originally Posted by randya View Post
Construction of cycle tracks results in increases in numbers of cyclists, but that is offset by increases in crashes due to conflicts at intersections, and it's worse in urban areas than in rural areas.

fairly intuitive, I'd say.
That is right. Safety in numbers is explicit in their model which they seem to parameterize based on papers that I can't even read the title. (I assume it is in Dutch) But from the discussion in the papers, they talk about how certain designs result in more collisions than others. Now there are some important considerations and caveats; for instance, was facility-type endogenous with intersection risk. But nonetheless, I think that it is very good support for thinking clearly about design if a facilities strategy is going to be pursued and that certain designs should be unacceptable.

Note that there is a difference between the total derivative and a partial derivative. What I think your getting at is the total derivative is negative but the partial is positive. Possibly true, if we attribute the entire change (or a big component) in ridership to facilities. But simply based on a documentary and a few articles, I recall that several important things changed in Copenhagen. I don't know if the science is there to confidently decompose the change further.
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Old 10-14-10, 09:40 AM
  #23  
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Originally Posted by Bekologist View Post
why a decline in child participation in cycling from the 1970's would skew declining indexed accident rates seen in the last few years is a stretch.
I don't think he was talking about a decline in the number of child cyclists, but rather a change in the mix of cyclists. The more adult cyclists there are, the lower the proportion of child cyclists. Kids on bikes are relative crash magnets compared to adults. Increasing the number of adults riding would decrease the number of injuries/rider because adults on bikes injure themselves less.

A very simplified example:
1,000 children and 1,000 adults ride in an area. In a given year, half the children are injured while only one in 10 adults are. The number of injuries/cyclists is 0.3. The next year, 500 additional adults start riding, while the number of children stay the same. The number of injuries/cyclists drops to 0.26. The next year, the same thing happens, and the number of injuries/cyclists drops to 0.233.

It may not be safety in numbers, but rather a safer mix of cyclists.
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Old 10-14-10, 09:50 AM
  #24  
RobertHurst
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Originally Posted by Bekologist View Post
That's not rain on the parade, Robert, it's hardly a drizzle. The rise in cyclist numbers in cities with fairly exploding ridership have not seen a correlative explosion in collisions or accidents. New York City and Portland trends tend to discredit rider savvy and education influencing the decline in the accident rate. Rather, with new riders on the roads the ratio of beginners to experienced traffic riders would likely be increasing.
The ratio of adult beginners to adult veterans may have been increasing.

At the same time, the percentage of child cyclists has been decreasing, and completely changing the make-up of the total cyclist population.

When a 7 or 8-year-old kid rides out of his driveway or off the sidewalk into the path of a vehicle and is squished, that is a pedalcyclist traffic fatality, classified just the same as if you or I get squished. It's been that way since they started keeping these stats. Fatalities involving kids under 16 used to be a HUGE percentage of total cyclist fatalities, when lots of kids rode bikes on a regular basis. The percentage has gone down from about half in the 1970s to about 15% today. This trend has continued in recent years. Between 1996 and 2006 the percentage of pedalcyclist fatalities involving children under 14 declined 56%. !!!

That's huge. That will jack your numbers. To put it another way, that's a nuclear bomb that invalidates the Safety in Numbers Theory. At least, until someone culls out the wrecks involving kids (and other non-commuters) and takes another look at those numbers.

Anybody who counts adult commuters, then compares that count to total pedalcyclist casualties without accounting for the wrecks involving children (and other non-commuters, like late-night drunks), is making the oldest and dare I say silliest mistake in bicycling advocacy. That unfortunately includes Jacobsen, Bek, Grist blog and huge amounts of other folks who have been very eager to jump to a happy conclusion on this one. This is a fine example of how precious personal biases can ruin peoples' judgment.

And let me ask one more thing: How come Safety in Numbers has not worked one iota for motorcyclists, who face many of the same sort of 'vulnerable road users' issues faced by cyclists? As their numbers skyrocketed, the accident rate for motorcyclists actually went up.

Also, in the 'last few years' as you mention some interesting things have happened, for instance, the number of bike commuters counted in Portland in 2009 declined by 5% over 2008.

For the record, I actually believe in the Safety in Numbers Theory, to an extent. I do believe increasing numbers have a positive safety effect for individual cyclists. I just don't think this effect explains the overall accident numbers trends. I highly doubt such an effect would present clearly in the stats at all. And if it does, you or I have no way of knowing that from Jacobsen, because his study was so ... well...bogus.
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Old 10-14-10, 09:57 AM
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Originally Posted by Zizka View Post
[...]

It may not be safety in numbers, but rather a safer mix of cyclists.
Exactly.
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