It isn’t about weight

Posted on May 27, 2010 by jsallen

“Your 25-pound bicycle is no match for a 10,000 pound truck.” You’ve probably heard that before.

So, if you collide with a 10,000 pound truck, the impact will be much, much worse than if you collide with a passenger car, or another bicyclist, or a pedestrian, because the truck weighs so many times more than your bicycle.

By the same reasoning, you should be much worse off yet if you simply fall and collide with the planet Earth. It is so much heavier than that truck…

Hmm, but we’ve all fallen off our bicycles a few times, mostly without serious injury.

I don’t want to collide with a truck — or a car, or another bicyclist, or the planet Earth. But let’s look at some basic physics.

First of all, the mass of the bicycle isn’t the issue. The rider accounts for most of the mass of the bicycle/rider system.

But also, the severity of a collision doesn’t increase directly with mass. It depends on the severity of the impact.

Consider two bicyclists, a perfect match for each other, riding toward each other at the same speed and colliding exactly head-on. They will both come to a complete stop. This impact would be the same if you put a brick wall, or a sheet of paper, between the two bicyclists.

Now, suppose that the truck is headed toward the bicyclist at the same speed as the other bicyclist. How much more severe is the impact?

Not hundreds of times, but four times. The energy dissipated in a head-on crash is as the square of the speed. The square of 2 is 4. The truck is so much more massive that the bicyclist is pushed back at almost the truck’s speed. It’s almost the same as riding into a brick wall at twice the bicyclist’s speed.

Severity of impact is much more about speed than about mass. The severity of a bicyclist’s collision with a motor vehicle is almost entirely in proportion to the square of closing speed, all other things being equal. The only exception is if you go underneath and get run over. Then, the vehicle’s mass does matter. Getting run over either by a car or a or by a truck is very likely deadly.

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Guest posting: P. M. Summer on a new breed of bicycle professionals

Posted on May 27, 2010 by jsallen

P. M. Summer is the former bicycle coordinator of Dallas, Texas, who was removed from his job because of his conservative approach to bicycle facilities. I post the following with his permission:

There is a whole new breed of bicycle professional out there. They aren’t what we usually think of as cyclists, much less traffic engineers or transportation planners. They are most often urban planners and landscape architects, who have become virtual social engineers. They see their job as changing the way dumb old Americans live in favor of the ways enlightened Low-Country Europeans live.

The bicycle is a means to that end. In their eyes, the bicycle isn’t a vehicle (as code defines it), and never has been. It’s a shoe with wheels. Cynically, they usually add “pedestrian” to their title, while short-shifting pedestrians in favor of “pedalcyclists”.

Most of these new bicycle professionals have never used a bicycle as a regular transportation device (including the gentleman hired to replace me), believe the road (any road) is inherently unsafe for cyclists, and believe that a segregated network is the enlightened (and sole) way to dramatically change mode share.

It’s almost impossible to argue with folks like this, because the only common point of reference is the word “bicycle”, and by “bicycle”, they mean something very different than what I, or others who think like me, do.

The problems we point out about how traffic operates don’t register, because bicycles can never be “traffic” in their eyes. Traffic is always the bicycle’s enemy, and never the bicycle’s environment. People who operate bicycles are like swimmers in shark-infested waters to them. The brave and fool-hardy only need apply. “Normal” people know better, and stay on the side-path/walk/track/gutter.

Fifteen years ago I had the Texas DOT Bicycle Coordinator plead with me to quit defending placing bicycle facilities (signed bike routes) on streets with lanes less than 14 ft. wide. When I explained to him that I preferred 10 ft. lanes, I thought he was going to have a heart attack. “You can’t put cyclists in the way of cars!” he said.

There is a growing “bikes belong off the road” sentiment. Cycling Advocates are slow to support cyclists like Eli [Damon], or Reed Bates, or Fred U., [who have been harassed by police for exercising their legal right to use the road] because to defend them would be to say that it’s not unsafe to ride on the roads… and LAB, ABW, and APBP [the League of American Bicyclists, Alliance for Bicycling and Walking and the Association of Bicycle and Pedestrian Professionals] can’t afford to admit that.

Why can’t these new bicycle advocates admit that bicycles can easily operate as part of the transportation mix, instead of having to be segregated from it? To admit that makes the extravagant demands for special facilities clearly just that: extravagant demands. Andy Clarke, then of BikeFed [the Bicycle Federation of America, now the National Center for Bicycling and Walking; now Clarke is President of the League of American Bicyclists] once described the cost for a segregated bicycle facility as being “mere decimal dust” compared to the cost of automobile projects. That ‘decimal dust’ has turned into hundreds of millions of dollars in consultant and lobbyist fees, as well as “bicycle planner” salaries. Admitting that most of these facilities aren’t necessary for safe and easy bicycle transportation endangers too much money currently being poured into the new cottage industry of “Amsterdamning America”, and threatens too much personal power. Politicians, eager for popular (if unproven) quick fixes, are far more likely to endorse feel-good projects using other people’s money than they are to call for better educated and trained cyclists.

You may find more from P.M. Summer on his own blog.

Posted in Bicycling, Bike lanes, Cycle tracks, Sidepaths | Tagged , , , , , , , , , , , , , , , , | 1 Comment

Research says bicyclists should run red lights?

Posted on May 20, 2010 by jsallen

Dr. Anne Lusk made an interesting comment on red lights: (quote is here):

Female bicyclists in England are being killed at a higher rate than
males because females wait for the green light to proceed and then are
hit by turning trucks,” said Anne Lusk, a Research Fellow at the
Harvard School of Public Health and active supporter of the BCU. She
suggests that the majority of car drivers and bicyclists are
conscientious and that warnings, instead of tickets, would improve
safety, increase bicycling, and foster good will.

Lusk is neglecting issues with bicyclist behavior that lead to such a result. Consider the probable mechanism:

Scofflaw male cyclist runs red light, and usually gets ahead of first-in-line turning motor vehicle before it turns.

Law-abiding female cyclist waits to the left (in England) of that vehicle and gets left-hooked when the light changes.

So, Lusk is making an argument for — what? Running red lights? — based on different kinds of poor behavior by males and females, exacerbated by traffic lights that cause delay when there is no cross traffic.

Those of us who understand the risks neither run red lights nor position ourselves where we are endangered by turning traffic. My advice is to merge far enough from the edge of the road to forestall a hook turn, and if filtering forward, to wait behind the first vehicle, where the driver of the second one can see me and yield to me.

And that in spite of a healthy a level of testosterone!

Posted in Bicycling, Bike lanes, Crashes, Laws | Tagged , , , , , , , , , | 1 Comment

Comments on a safety-in-numbers study

Posted on May 3, 2010 by jsallen

The University of California has published a study of pedestrian crashes in Oakland, California,

The Continuing Debate about Safety in Numbers—Data from Oakland, CA
Judy Geyer, Noah Raford and David Ragland, Traffic Safety Center;
Trinh Pham, Department of Statistics, UC Berkeley
UCB-ITS-TSC-2006-3

The full report is available online:

http://www.escholarship.org/uc/item/5498×882

John Forester, founder of the Effective Cycling program of cyclist education, and statistician, has demonstrated that the Safety in Numbers claim of Jacobsen (also cited in the Oakland paper) is faulty. Due to faulty math, a random set of numbers will generate the curve that apparently shows a decreasing crash rate with increasing numbers of users. This is not to say that the safety-in-numbers claim is false, but rather that Jacobsen has provided no evidence to support it. (Forester also questions Jacobsen’s explanation for safety in numbers as applied to bicyclists, but that’s a different issue.)

The Oakland report expresses the same complaint about Jacobsen’s math, and goes on to use better math to look for answers. Here’s a quote from page 5 (PDF numbering) of the Oakland report:

However, others are concerned that correlating collision rate (C/P) with pedestrian volume (P), (where C equals collisions and P equals pedestrian volume) will almost always yield a decreasing relationship due to the intrinsic relationship of the variable P and the fraction 1/P.

Tom Revay has generated a Microsoft Excel Workbook demonstrating how Jacobsen’s curve may be generated with  random data. Press the F9 key on a PC to refresh the random data. (Press Command [Apple] and = at the same time on a Mac. I thank Dan Carrigan for this information)

The Oakland study came up with some interesting and intriguing results. Here are a few; please correct me if I am wrong:

Pedestrians vs. Collisions/Pedestrian

Figure 4, p. 17, Pedestrians vs. Collisions/Pedestrian

  • The graph on p. 17, PDF numbering (click to see a larger version) shows the characteristic downward curve due to faulty math. However, the curve slopes back upwards for the intersections with the very highest numbers of pedestrians.
    p. 16, Pedestrians vs. Collisions

    Figure 3, p. 16, Pedestrians vs. Collisions

    A better graph (graph on p. 16, PDF numbering, click to see a larger version) shows crashes increasing with a steeper slope for the higher-volume intersections, worst at the intersections with the highest volume. Crash numbers are low enough, though, that the results for individual intersections are not statistically significant.

  • The Oakland study examines different intersections in the same community over the same time period rather than the same intersections at different times, or different communities with different volumes of pedestrian and vehicular traffic. The study can establish whether the safety in numbers effect applies only under the conditions it examined. Data from different times of day might possibly be checked against traffic volumes, though the results would be less robust and effects of lighting, alcohol use etc. would make them harder to interpret.
  • It is clear that a few intersections are outliers, with many more crashes than others. These intersections would be high on a priority list for improvements — though the actual numbers for individual intersections, again, are too low to be statistically significant.  The problem with lack of statistical significance highlights the importance of applying research data and operational analysis in determining where to make infrastructure improvements — crash data for an individual intersection are not statistically robust unless the intersection has an extremely bad problem. You apply research results and operational analysis so you can avoid collecting data on each intersection by killing and injuring people.
  • (See Results, p. 9, PDF numbering) Number of lanes on the primary and secondary streets, and number of marked and unmarked crosswalks, did not correlate with crash rates! (But note that this result is consistent with data on bicycling showing that riding on arterials is safer than on residential streets).
  • Despite the safety-in-numbers finding, the intersections with the largest numbers of crashes are still those with high pedestrian volumes. Increasing numbers decrease the rate of crashes, but not the number of crashes.
  • p. 18, Vehicles vs.Collisions/Pedestrian

    Figure 5, p. 18, Vehicles vs.Collisions/Pedestrian

    The crash rate increases for pedestrians as the number of vehicles increases (page 18, PDF numbering), though less rapidly than the number of vehicles. Is there a safety in numbers effect for vehicle operators as the number of vehicles increases? Yes, the likelihood that any particular driver will collide with a pedestrian decreases with the amount of vehicular traffic passing through an intersection — though the study doesn’t report this. The study doesn’t answer whether the result is achieved by improved signalization at high-volume intersections, or by depressing pedestrian volume (risk homeostasis), or by what other effect. The study also doesn’t say anything about crashes overall, as it doesn’t report on crashes not involving pedestrians.

All in all — interesting, intriguing, and careful research — but more research is needed!

Posted in Bicycling, Crashes | Tagged , , , , , , , , , , | 11 Comments

Dutch traffic jams

Posted on April 29, 2010 by jsallen

Many bicycle planners and advocates would like to suggest that increases in bicycle use lead to a decrease in motor vehicle use. The Netherlands is often held up as an example. The reality there is different.

Here’s a quote from a recent Time magazine article:

The Netherlands may be known overseas for its cycling culture, but outside the country’s city centers, gridlock is the more dreary reality. Vehicle use has risen sharply over the years, but road capacity has yet to catch up — in part due to lack of space.

Dutch people like their bicycles, but evidently they also like their cars. Despite the highest bicycle mode share of any industrialized country and high fuel prices, motor-vehicle use has been, as the article says, rising sharply. Here is a slide from a presentation given in Cambridge, Massachusetts, USA in the fall of 2008 by Hans Voerknecht of the Dutch government’s Fietsberaad (bicycling research institute).

Dutch feelings about motoring, bicycling and public transportation

Dutch feelings about motoring, bicycling and public transportation

Also, and rather surprisingly to this author, the Dutch are much less happy with public transportation than with either bicycling or motoring — not very good news as far as bicycling is concerned, because the bicycling and public transportation  complement one another.

There’s a lesson here somewhere. What is it? What keeps public transportation from being more appealing in the Netherlands, a rather small and wealthy country which ought to be able to afford high-quality service? What would succeed in making public transportation more appealing there? What would succeed in reducing use of private motor vehicles, or at least its societal costs in lost time, use of space, and environmental degradation? What lessons does the situation hold for the USA?

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German cycling organization’s comments on cycle tracks

Posted on March 29, 2010 by jsallen

Here are the comments in English.

The translation is posted with permission granted by Heinz Brockmann of the ADFC (German Cycling Federation) Bottrop chapter. Many thanks!

And here is the same document in the original German.

Please note that the ADFC is not a spandex and speed bike club; its membership of approximately 100,000 consists almost entirely of utility cyclists. The ADFC advocates for their concerns and interests.

Posted in Bicycle facilities, Bicycling, Bike lanes, Cycle tracks, Sidepaths | Tagged , , , , , , , , , , , , , | 1 Comment

Our hero, Lance Armstrong

Posted on March 25, 2010 by jsallen

Who is the cyclist wearing sunglasses, a white T-shirt and gray cargo shorts in the video? Lance Armstrong, 7 times winner of the Tour de France.

Everyone is riding brakeless fixies. First instance of blowing a red light (0.52) — video is cut abruptly while only the first couple of cyclists is in the intersection. Swerving around cars, speeding between them and startling the drivers (1:11 and elsewhere). Riding four and five across, taking up the entire road. Camera motor scooter passes a moving vehicle on the right (1:19). Riding while carrying a beer keg in one hand (1:48). Another red light run — especially brazen, while passing a waiting vehicle on the right, then turning left at high speed into moving cross traffic (1:56). Passing a through vehicle on the left, some cyclists then turning right in front of it while others including Lance merge in front of it inside the intersection, motorist blows horn (2:10). Riding around the left side of a traffic circle (2:16).

Ride draws attention from the police (2:35), and this is included in the video. Our hero appears to have special status with the police — the ride continues unabated. Trick riding in the street facing backwards on the bicycle (3:15). Foul language and a clear shot of the beer keg (4:20). More trick riding in the street (4:29), cyclist riding on handlebars. More trick riding (4:47, two cyclists leaning against each other). What appears to be vandalizing of a signal control box (5:13). Lots of shots that are cut just as a critical situation develops. Few helmets.

I’m no slave to authority, thank you. Think about how our great country got its start. But what’s the point here? The video only builds the image of cyclists as scofflaws, rowdies and daredevils, and it has the imprimatur of our nation’s most famous cyclist. As this is a heavily-edited video, I can imagine that the ride included more craziness than was shown.

A cyclist who cared about the reputation of cycling would not ride with this group, or if taken by surprise, would refuse to continue, or to be included in the video. Instead, Lance was a willing and eager participant. And he was in his mid-30s and the father of three children when this was shot — with enough life experience, I would hope, to understand the responsibility that accompanies fame, and the importance of his example to younger folks.

I read his book, It’s Not About the Bike, and so got to experience in some small way the drama of his illness and recovery. I rooted for him in the Tour de France, year after year. I saw him on the Charlie Rose show a few years ago, and he is an impressive interviewee. But now he has lost his creds with me as a spokesman for cycling. It’s like — it’s like Shoeless Joe Jackson, the baseball player who conspired to throw the World Series in the 1919 Chicago Black Sox scandal. A boy is reported to have uttered the immortal line “say it ain’t so, Joe” as Jackson left the courthouse after pleading guilty.

The video has over 330,000 views as of March 25, 2010. The Youtube page has lots of semi-literate comments heavy with admiration and foul language.

I suppose that times have changed.

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Audible warnings

Posted on March 24, 2010 by jsallen

Some jurisdictions require a bicyclist to have an audible warning device, commonly a bell or horn.

My bicycle has an audible warning device. Well, actually, I have only one warning device which I move to whatever bicycle I happen to be riding: my operatically-trained voice. Though less courteous than a bell or horn to warn pedestrians, my voice can transmit messages, not only a warning — “bicycle behind you”; “passing on your left.” My voice can be modulated from a whisper to a shout, which is more likely to be audible inside motor vehicles than any bell or horn commonly sold for use on a bicycle (except an air horn, which would startle pedestrians right out of their shoes every time). Bells and little squeeze-bulb horns make the most sense on multi-use paths, but they are rather pointless when riding in the street.

My voice also operates without my having to remove a hand from a brake lever.

I live and ride in Massachusetts, USA. which requires an audible warning when overtaking a pedestrian, but doesn’t specify a device. That works for me.

Some bicyclists don’t like to install a bell on their bicycle; one claim is that there is limited “dashboard” space on drop bars.

I think that a more common objection is that these bicyclists don’t want to look geeky or add the horrifying couple of ounces of extra weight. After all, if there’s room for a bicycle computer one side of the handlebar stem, there’s room for a bell on the other side — or on the stem itself.

Bell and horn requirements could possibly be invoked by a police officer with nothing better to do, to cite bicyclists who are not committing any other offenses. If I had to defend myself against this charge in court, I’d bring little ding-ding bell, give a demonstration of it and of my voice, and ask whether the court could tell me seriously that the bell was a more effective warning device.

…and hope I didn’t have laryngitis on the trial date.

If I regularly rode where a bell is required by law, I suppose that I would install one. But I’d still use my voice most of the time.

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Ciccarelli on cycle tracks

Posted on March 19, 2010 by jsallen

John Ciccarelli is a consultant on bicycling and a League of American Bicyclists-certified cycling instructor who specializes in teaching adults who have never ridden a bicycle before. His comments here are reprinted by permission, and are in response to an e-mail he cites.

Subject: Re: Making Cycling Irresistible: Lessons from the Netherlands, Denmark, and Germany
Continue reading →

Posted in Bicycle facilities, Bicycling, Cycle tracks, Laws, New York City, Sidepaths | Tagged , , , , , , , , , , , , , , , , , , , | 3 Comments

Concord Avenue dream and nightmare

Posted on March 19, 2010 by jsallen

(The links below will work better if you first click on the headline above so you are viewing only this single post).

Overview | Present Road Diet | Proposed Footprint |Crash Risks |
Operational Issues | Suggestions | Details | Summary

Overview

A Google map provides an overview of the stretch of Concord Avenue in Cambridge, Massachusetts, USA between Alewife Brook Parkway and Blanchard Road. You’ll get a better view if you close the address balloon.

View Larger Map

This article will describe an important improvement made to Concord Avenue around the year 2000, and another proposed change which I do not consider an improvement.
Continue reading →

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