In our last “Ask the Experts” article, we corresponded with Danish Engineer, Soren Jensen, to help clarify the findings from his study titled, “Road safety and perceived risk of cycle facilities in Copenhagen”. Local Vehicular Cyclists had attempted to cite the study as reason for not developing bicycle infrastructure. At the conclusion of the article, Soren summarized that if Dallas in fact added Cycle Tracks to its roadways, it would actually see “much higher ridership”, and “greater safety to bicyclists”.
In our dialog, Mr. Jensen referenced an important study from Public Health Consultant, Paul L. Jacobsen, titled, “Safety in Numbers”. This study has been the basis many US and European city planners have cited to increase bicycle infrastructure within their communities. The summary of the study states: “The risk of an individual pedestrian or bicyclist being hit by a motor vehicle decreases as the number of pedestrians or bicyclists increases, respectively.” When combined with the Soren study, which notes that implementation of Cycle Tracks increases bicycle ridership, a correlation can be inferred.
Within our comment section, commenter Steve-A, dismissed the Jacoben study, and linked to a Cycle*Dallas article he’d written citing “random numbers” could be used to achieve the same results. He drew his conclusions using a method noted in an article written by Vehicular Cycling advocate, John Forester, who questioned the study’s findings.
BFOC communicated with Paul L. Jacobsen in California, to explain his study and counter the claims made by Cycle*Dallas and Forester, and followed up once again with Author/Engineer Dr. Lon D. Roberts, to also shine some light onto the dispute.
First will start with Mr. Jacobsen:
Hi Jason,
This question comes up every 6 months or so. There’s a website out there with this argument.
First off, this is not the way I did the analysis. The folks saying the data is manipulated need to read the Methods section of my paper. (http://safetyinnumbers.notlong.com)
Secondly, having a variable on both sides changes the exponent by one, and that’s the issue that matters. The other variables change slightly. The key point is that injury rate is non-linear with the amount of walking and biking. Take a look at Table 1 in this recent paper. Lots of researchers have found the injury rate to be non-linear.
Soren Jensen provided the data used in Figure 2 of my SIN paper.
Best wishes,
Peter
Next up, we asked Dr. Roberts to also review Forester’s argument:
The argument that some have posed that Jacobsen’s “Safety In Numbers” plots can be replicated by calculations involving random number is interesting but perhaps flawed — both mathematically and logically. For instance, the assertion that a plot created by paired data where the X-axis values are represented by the quotient of two uniformly distributed random variables, N divided by C, and the Y-axis values are represented by the quotient of two uniformly distributed random variables, C divided by P, results in a quasi-hyperbolic curve, “similar in shape” to Jacobsen’s, places undue emphasis on extreme outliers on both axes to dictate the shape of the curve. For instance, if N and C are randomly chosen values between 0 and 1, on average, half of the values for N will be 0.5 or less and half of the values for C will be 0.5 or less, if N and C are randomly chosen numerous times. Using Monte Carlo simulation to plot the value of N divided by C for 1000 samples in a run that I did, 75 percent of the values were less than 2, on the other hand the single most extreme value was 973. Since the theoretical values for N divided by C can range from zero to infinity, a computer generated plot of the “best fit” curve may vaguely resemble a hyperbolic function, if you choose to ignore the distribution of the data points, but it isn’t. (For any who are interested in how trend lines and correlation coefficients can be artificially manipulated, I would refer them to Anscombe’s Quartet.)
We’ve been raising quite a bit of funds recently through the sales of t-shirts, online fundraisers, and a homebrew fest. So far with the funds, we’ve got a couple more bike racks on order, some “share the road” signage plans, a September Bicycle event, and an entry point sign into Oak Cliff stating “Welcome to Oak Cliff. A Bike Friendly Community” on the way.
We also used some funds to pick up a pedicab (above)! So now, when you’re in Bishop Arts, be sure to keep an eye out for this three-wheeled wonder. The guys at Oak Cliff Bicycle Company are giving it a once over, and we’ll probably be painting it up, but once completed, it will be available to ferry visitors around the district and back and forth between Tyler Street, Bolsa, Bishop Arts, the Texas Theatre and more. All proceeds from tips and advertising go right back into more bicycle projects for the OC!
On CycleSmartDallas, a recent post titled “Friday Bike-Lane Special” uses the above photo to justify the failures of bicycle facilities with the added comment, “advocates for segregationist bicycle facilities like being treated this way”.
Given that we’re advocates for separated transit modes in urban environments like sidewalks, bus-only lanes, and cycle tracks, I’m assuming we’re being targeted. First and foremost, this is exactly the way we would not develop a street, and deplore being “treated that way” with or without a bike lane, for one simple reason: It prioritizes cars over people. With this in mind, let’s break down our goals for streets:
- Prioritize People Over Cars
- Increase Perception of & Actual Safety
- Increase Bicycle Ridership (and Public Transit)
- Accommodate for children, the elderly, the disabled, as well as the physically fit for non-motorized modes
Now even with the bike lane, we haven’t accomplished all of our stated objectives. First, the Arizona road uses the following street hierarchy: car first, then bicycle, last pedestrian . This actually may be appropriate if in a suburban environment, where sprawl has forced distant separation of business/residential zoning from third places, and completely dismantled community. Remember, we’re advocating for cycling facilities in urban environments, where community is intact (ie. men and women can bicycle short distances to work, young and old can walk to the park and play chess, couples can take strolls from home to coffee shop, and mom’s can quickly bicycle to school with children)…for Dallas, that would be well within Loop 12. (Side note: Germany is now showing, with new experiments in car-free towns and suburbs, that there is potential for this transect to be adapted as well)
Now, let’s imagine the AZ image is within an urban transect…the car is obviously given priority by the 5 wide lanes (with 1 turn lane). The adaption technique of Vehicular Cycling, encourages (and advocates for) this car-centric planning. Perception of safety is drastically reduced, as people attempting to bicycle without facilities are only given the “Swim with the Sharks” option to commute on. Dramatically low bicycle ridership reflects this as the young, and elderly have been marginalized completely from anything but being chauffeured to school/stores/parks/theaters. While bicyclists accident rates using VC methods may be low in this scenario, safety to pedestrians and for car commuters traveling at posted speeds of 40mph just outside of the residential neighborhood (seen in the top left portion of the photo) is decreased. Here, the bike lane is a band-aided after thought as the car is still top of the hierarchy. Pedestrians are at the bottom…though they do have a wide sidewalk, but absolutely no shade (this is Arizona, btw), no place to go (zoning), and a dangerous multi-lane high-speed street to cross. This model also emphasizes large over small businesses…in other words, Wal-Mart will build next to this road.
Here is an example of how we’d actually revision the above street:
Again, our objectives are:
- Prioritize People Over Cars
- Increase Perception of & Actual Safety
- Increase Bicycle Ridership (and Public Transit)
- Accommodate for children, the elderly, the disabled, as well as the physically fit for non-motorized modes
Now let’s break down this second image from Amsterdam (which could also have been found in Copenhagen, Munich, Bogota, Boulder, Portland, Vancouver, and is the trend slowly beginning to occur across the US). The community has changed their street hierarchies to the following “people-first” model:
Pedestrian, Bicyclist, Bus, Car, Truck
Perception of, and actual safety have increased for cyclists. VC’s would dispute this, but Copenhagen’s decimal point accident levels combined with massive ridership levels easily support this case. The young and elderly can (and do) bicycle comfortably in this model. Car lanes are thinned (naturally calming speeds), and posted speeds are slowed increasing safety to motorists, bicyclists, and pedestrians. Also, this model encourages residents to consider alternate transit, whereas the Arizona image encourages car ownership (which will now account for a lack in savings and become the second highest expenditure behind housing). This also encourages local business development, as many needs can be catered to with small store footprints (read: affordable for new business owner) at walking/bicycling distances and denser housing (ie. Wal-Mart won’t build on this two-lane street…Joe and Jane’s Neighborhood Cafe will) Other things we haven’t even delved into, but should be taken note of in “people first” planning is heightened sustainability, lowered CO2 emissions, community health (note obesity trends in US), and overall transit safety for all modes. Also, the elderly, which we’re about to experience a boom in, can continue to live and assist in this people-first community. In the car-first model, they’ll be shipped off to a distant nursing home shortly after they’re unable to drive…or become prisoners’ in their own homes.
Photo: Reuters
As we discovered from a commenter, seven time Tour de France winner, Lance Armstrong, was born right here in Oak Cliff at Methodist Hospital and lived in the OC for a short while until moving to Richardson and later Plano. Curiously, Wikipedia notes Plano as his birthplace, but his biography lists first living here, and that his mom became pregnant while attending our own Adamson High School. In 1971, Plano would have been a very tiny town far to the north, which makes it all the more doubtful the wikipedia entry is correct.
He returned to the Tour after a 4 year hiatus, and has surprisingly shown good standing. After the 6th stage, he’s climbed to second place (and only one second behind the leader). Keep up with all of the details here: Tour de France Official Website
UPDATE:
Just received confirmation from Lance’s mom’s marketing group that he was in fact born at Methodist Hospital, in Oak Cliff.
Also from EcoVelo, ran across this great video of John Pucher discussing “Cycling for Everyone”. It’s fascinating to see the numbers of accidents, and rates of ridership among the elderly and more in Europe compared to the US. Something else he touches on is something we documented earlier from Danish planner, Jan Gehl, where car-centric planning in Europe caused precipitous drop in cycling (up to 80%) until major campaigns in the late 60’s and 70’s were implemented to focus on the creation of bicycle facilities. Since that time, Germany, Denmark, and the Netherlands have tripled there bicycle infrastructure and seen exponential ridership levels.
Ecovelo offers this thoughtful post regarding the Facility Advocate vs. Vehicular Cycling quibble.
A study released in Copenhagen titled “Road safety and perceived risk of cycle facilities in Copenhagen”, is sometimes referenced by local Vehicular Cyclists as proof that cycling infrastructure poses a greater safety risk, though they typically avoid the paper’s conclusion which clearly advocates in favor of infrastructure. Noting this confusion, a BFOC commenter posted the following request:
I’d appreciate a thoughtful post about this study, which is about the effects of bike infrastructure in Copenhagen. I have doubts about the methodology, it not being explained real well, but the conclusions include:
Cycle tracks increase cycling 18-20%
Cycle tracks increase accidents 9-10%
Cycle lanes were less effective at increasing cycling and it was unclear if they raised accidents more than cycle tracks
The paper did not discuss to what extent (if any) all this infrastructure caused cyclists to lose road riding rights they enjoyed previously.
To clarify the paper, we contacted the study’s Danish author, Soren Jensen, for a breakdown, and asked if bicycle facilities would benefit Dallas. We also communicated with Dr. Lon D. Roberts, author of SPC (Statistical Process Control) for Right Brain Thinkers and Professor of the course Gleaning Facts from Figures to provide a better understanding due to confusing concepts in statistical analysis. Before getting started, some definitions are in order…a cycle track (pictured above) is simply a dedicated bike lane, which is physically separated from car traffic, while a bike lane is simply a painted line on a street that has no physical barrier between auto lanes.
Below is our conversations, starting with Mr. Jensen:
Hello Jason,
The cycle tracks (kerb between drive lane and cycle track, and kerb between sidewalk and cycle track) increase cycling by 18-20%, whereas cycle lanes (only a 30 cm wide white marking to drive lane) increase cycling by 5-7%. These figures have been found for streets in Copenhagen. I do not know, what the figures would be in Dallas, but because cycle facilities are seldom in Texas, I believe the figures would be higher (much higher).
The cycle tracks have resulted in an increase of 9-10% in both accidents and injuries. The study accounts for confounding factors (general safety trends, changes in traffic volumes and regression-to-the-mean), i.e. the stated safety effect is truly the result of constructing cycle tracts. There are several reasons for the increase in accidents, however, the most dominating one is that construction of cycle tracks on main roads often leads to a parking ban on these roads, which then leads to many automobiles being driven onto sidestreets and being parked there – and this leads to many more accidents at intersections between main roads and side streets. If parking is not banned on the main road then there most often is no change in safety when cycle tracks are being constructed. The cycle lanes have resulted in an increase of 5-15% in both accidents and injuries – i.e. practically the same as cycle tracks. Both cycle lanes and cycle tracks are most often about 2.0 metres wide in Copenhagen. All investigated cycle tracks and cycle lanes are one-way, i.e. there is one cycle track/lane in each side of the road.
The Traffic Act in Denmark clearly states that if a road has cycle tracks or lanes, then the bicyclists must use them, i.e. they must not ride on drive lanes or sidewalks – only children up to 6 years old may ride on sidewalks.
In the past 5-8 years, the construction of cycle tracks have often been a part of a more comprehensive “campaign” in order to get more people cycling in many communities in Denmark. The size of the possible spil-over or synergy effect on cycle traffic volumes, which might come from mixing new cycle facilities with campaigning, is unknown – and is also may have implication on safety. But I do not know if an increase in bicycle traffic in Dallas will lead to better or worse safety overall (total number of road deaths etc.) – but I do know that it will lead to better safety for the bicyclists.
Kind regards,
Søren Underlien Jensen
Soren,
Could you clarify one part for me? You stated that
“The cycle lanes have resulted in an increase of 5-15% in both accidents and injuries “
but ended by stating “I do know that it will lead to better safety for the bicyclists.”
If you’re seeing an overall increase in accidents, would this not lead to less safety for bicyclists?
Jason
Hi Jason,
There exists clear relationships between the traffic density and traffic safety for all travel modes (from walking to aviation – probably even space shuttles). This relationship says – higher density, better safety. An example is P L Jacobsens paper http://injuryprevention.bmj.com/cgi/content/abstract/9/3/205
Chers
Søren Underlien Jensen
Got that? I too was a bit unclear. So, I contacted Dr. Lon D. Roberts, author of Statistical Process Control for Right Brain Thinkers to explain in greater detail.
Jason,
Like with most studies involving statistical analysis, one must be careful as a case can be made for and against a particular position, depending on how the users of the data choose to “cherry pick” the results. Looking at the big picture, based on Soren’s study, his comments to you, and the other study he referenced, there is a simple syllogism to use that can be backed up by the numbers and percentages that shows favor for the development of bicycle facilities.
* The likelihood an individual bicyclist will experience an accident goes down as the number of bicycle riders go up.
* So, if an increase in bicycle ridership leads to a lower likelihood that a particular individual will have an accident, how do we increase bicycle ridership? According to Soren’s study, the way to do this is to construct more cycle tracks and cycle lanes.
* Conclusion: construct more cycle lanes and tracks.
In formal logic this would be expressed as follows:
Major Premise: The per capita likelihood of a bike accident decreases as the number of bike riders increases.
Minor Premise: The number of bike riders increases as the number of bike lanes and bike tracks increases.
Conclusion: Increasing the number of bike lanes reduces the per capita likelihood of a bike accident.
Keep in mind that “inferences” can be drawn from statistics, but this is not the same as saying the statistics “prove” a particular conclusion. (Every statistician will tell you that you can’t “prove” anything with statistics.)
While the bike lanes do not seem to have an effect one way or the other, if someone tried to use Soren’s study to “prove” that an increase in cycle tracks increased accidents by 9%, they’d be guilty of cherry picking the numbers. The accident rate may have increased by 9%, but the number of bicyclists increased by 18-20%. (This is consistent with the Major Premise cited above.)
Using Soren’s percentages, here’s an example starting with the assumption that 10 bicyclists out of 10,000 will experience an accident over a certain period of time if there are no bike tracks:
1. On an individual basis, there’s a 10 out of 10,000 (or 0.1%) chance that an individual biker will experience an accident if there are no bike tracks
2. When the bike tracks were added, the accident rate increased by 9%. In other words, if there are 10 accidents without the tracks, the number of accidents increases 10.9 (or approximately 11). On the other hand, the number of bike riders increased by 18%, from 10,000 to 11,800. Therefore, on an individual basis the likelihood of an accident with the tracks added is now 11 out of 11,800, or 0.09%, as opposed to 0.1% without the lanes/tracks.
Even if you assume there are 1000 bike accidents out of 10,000 without the lanes/tracks, the likelihood on an individual level is 9% with the lanes/tracks rather than 10% without the lanes/tracks.
So to sum up, individual accident rates dropped when bicycle infrastructure was added, and taking that a step further, Soren’s follow-up correspondence recommends that if Dallas added cycle tracks, ridership would be “much higher”, and “that it will lead to better safety for the bicyclists.” He even recommends maintaining parking on streets to further decrease accident rates.
Special thanks to Søren Underlien Jensen, Dr. Lon D. Roberts, and our commenter, Steve A., for requesting the post.
A BFOC member forwarded us the following video and article showing the new painted sharrow lane in Long Beach. This is pretty groundbreaking, as it’s not a bike lane, but simply a painted marking for cyclists. Features interviews with bike shop owners, activists, and cyclists to get their first impressions. Looks like it’s a hit.
If you’ve ever strolled through the Bishop Arts District and in front of Zola’s Everyday Vintage shop, you’ve undoubtedly seen this classic 3-speed chained to the tree out front. We always wondered about it, and recently went in to ask the store’s owner, Annette, its history. She told us some details about a girl who has since passed away, but worked in the shop next door, which used to be a floral business. She mentioned that her name was Marie, and that she would carry her two small dachshunds in the rear panniers which she had lined with cardboard. Beyond that, there weren’t a lot of other details, but Annette promised to contact Phillip, the owner of the former floral shop, to provide more information. This weekend I received the following email from him:
I was in at Zola’s tonight and Annette said that you were interested in the story behind the bicycle in front of their store.
My partner, Don Allen, and I used to own Bishop Arts Floral. Gloria Marie (Marie) Clevenger was an employee of ours and it was her bike. She lived off of Center Street near Tyler here in Oak Cliff with her long time boyfriend…and she did not own a car.
When Marie was younger she had spent some time modeling and quite a bit of time as a visual design assistant to several photographers. We never did learn exactly what caused her to walk away from the fast paced life….but in about 2000 just before Valentines day she showed up at our shop and basically hired herself on. She said that she knew we’d be swamped…and she wasn’t a floral designer…but she had helped out in other shops…she could run the register, take orders on the phone, etc.. And she was right, we did need help….so she helped out for the holiday. For the next couple of years we’d only see her just before major floral holidays…and she’d work a week or so for us. Marie was very outgoing…she could (and would) talk to anyone. If we had a slow time, she’d stand at the door and beckon people inside. Then in 2003 she started as a part time employee. She worked 20 or so hours a week that year. Every day she worked she rode her bicycle…rain or shine. If we worked late for some reason, we’d load the bike into our van and drive her home, but her bicycle was her mode of transportation.
Marie had asthma…..and late in 2003 we got a phone call from her boyfriend saying that she’d died of an asthma attack in the ambulance on the way to Parkland hospital.
They had no money and she had no local relatives. So a few of the merchants in Bishop Arts, who were all fond of Marie chipped in to pay for her funeral.
By the time Marie passed, her bicycle was something of a fixture in the district. The girls at Zola’s (Diedra and Annette) talked with her boyfriend and we all agreed to keep the bike as a kind of memorial to Marie. So now whenever Zola’s is open, they put the bike out. It may be decorated for different holidays, or have lights on it at Christmas, but those of us that knew Marie always think of her when we see it, and it’s a good memory. Marie was a kind soul, a gifted artist and a poet and she touched us all.
I’d be happy to answer any more questions you may have, but the back story behind the bicycle itself is pretty simple. It was the way that she had to get around….and she made the most of it.
Thanks for your inquiry,
Phillip Wheless
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Notable:
Dallas Tops Bicycle Magazine's Worst Cities for Cycling
“There are times I ride in Austin, and I’m afraid of cars...Imagine what the beginner cyclist must feel like?”
- Lance Armstrong
"As long as I'm the bike coordinator for the city, Dallas will never have on-street bike lanes."
- PM Summer, Dallas FORMER Bike Coordinator
Portland Metro: 174 Miles of On-street bikelanes, 8% bicycle ridership, 0 Fatalities in 2008
Dallas Metro: 0 Miles of On-Street bike lanes, .2% bicycle ridership, 6 Fatalities in 2008
"Our story is build it and they will come. We’ve built it and we now are approaching 6-8% mode split."
- Roger Geller, Bike Coordinator for Portland
The Reason Dallas Doesn't Have Bike Lanes 
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