Muenster road space poster — check the numbers!

Posted on January 4, 2008 by jsallen

Here’s a poster produced by the city of Muenster, Germany, which has been described as one of Germany’s most bicycle-friendly cities. Click on the image to see a larger version.

The Muenster traffic poster

The Muenster traffic poster

The claim is made that the poster shows the space needed to transport the same number of people by car, bus or bicycle. What it actually shows, though is the much smaller amount of space to park the cars, bus and bicycles.

Nonetheless, the poster appears in many postings on the Internet and in planning documents, for example this one from the United Nations (since deleted).

In case the poster’s message isn’t clear enough, the sky is cloudy in the picture with the cars. The sun is peeking out in the picture with the bus and shines brightly in the one with the bicycles. And the image at the left with the cars is zoomed in more than the other two images, so the cars appear to occupy more space.

A document published by US Federal Highway Administration expands on the caption. I have copied the US document onto my Web site with a link directly to the quote, which reads as follows:

  • Bicycle: 72 people are transported on 72 bikes, which requires 90 square meters.
  • Car: Based on an average occupancy of 1.2 people per car, 60 cars are needed to transport 72 people, which takes 1,000 square meters.
  • Bus: 72 people can be transported on 1 bus, which only requires 30 square meters of space and no permanent parking space, since it can be parked elsewhere.

I have no question myself that overuse of private motor vehicles is a problem in cities. But good design requires a good understanding of the problem. Let’s take a more sophisticated look in to space requirements.

  • 72 bicycles in 90 square meters — that’s 1 1/4 square meter per bicycle. If we allow 2 meters (6 1/2 feet) of length for each bicycle — giving about 25 cm (10 inches) of following distance between each one and the next — acceptable only among experienced road racers — then they have only 1/2 meter of width in which to ride — about 19 inches, less than the width of many bicycle handlebars.
  • 60 cars in 1000 square meters is one car in 16.7 square meters. Let’s assume that cars have 3 meter (10 foot)  lanes in which to drive. Then each car is allowed 5.6 meters of length. As a typical car is 4 meters long, the following distance here is about 1.5 meters, or 5 feet — safe only if the cars are stopped or creeping forward very slowly.
  • The space described for the bus is only the size of the bus itself, typically 2.5 meters from side mirror to side mirror, and 12 meters from front to rear bumper.

Ludicrous, isn’t it?

Someone in Germany generated these numbers, and the US authors swallowed them. The US document  has been quoted again and again. To be sure, the document includes a disclaimer — part of which is especially to the point:

The metric units reported are those used in common practice by the persons interviewed. They have not been converted to pure SI units since, in some cases, the level of precision implied would have been changed.

Level of precision, indeed. Units, shmunits. Garbage in, garbage out.

How much space do vehicles actually need? There are several important concerns, different for different vehicles.

  • Speed: this determines the number of different destinations accessible within a given travel time. The bicycle wins if streets are congested. The private car wins if they are not. The number of destinations reachable within a given time increases approximately as the square of speed, and so higher-speed travel modes are even more essential than it might seem when destinations are sparse — where population density is low, and for specialized services such as home repair and pickup/delivery of packages. That’s why urban couriers ride bicycles and suburban couriers use cars or vans.
  • Throughput — the number of people transported past a given point within a given time — depends on speed as well as efficiency of road use. It increases with speed up to a point, and then decreases as following distance becomes greater. If passenger cars travel twice as fast as bicycles, then only half as many passenger cars in the same length of street achieve the same throughput, even assuming only one person per car. A single bus may carry as many passengers as the cars in the picture, but it achieves less throughput with its repeated stops; also, buses run only once every few minutes at best. The throughput of a bus is impressive; the throughput of a bus line is meager.
  • Bicyclists generally take up three or four times as much space as the parked bicycles shown. If, as is common, bicyclists are riding to the right of other traffic in a single line, the ones shown would extend for more than the length of the block. There would be about half as many passenger cars as shown, for the same throughput as with the bicycles, as long as traffic isn’t congested; or the one bus.
  • Performance — throughput times speed — measures how many people a transportation mode can serve, times the number of destinations any one person can reach.
  • Street space may be used for special purposes. Buses need special reserved space for bus stops and sometimes for bus lanes. Cars take up street space when parked or stopped to load/unload, bicycles don’t but sometimes are given special bike lanes. The comparison doesn’t address these issues at all.
  • Waiting time and walking time affect speed and performance. Bicycles generally can be parked near trip endpoints; a private motor vehicle often requires a longer walk to/from a parking place, and a motorist may also spend time looking for a parking sapce. Bus passengers must walk to/from the bus stop; also wait there and possibly also at a transfer location.
  • The ability to travel with baggage or passengers is different for each mode. The private motor vehicle is most convenient (unless the driver has to make a two-way trip just to take a passenger or parcel somewhere); the bus is convenient for travel with other people but only with as much baggage as a passenger can carry; the bicycle is least convenient/flexible with passengers and baggage.
  • The cost of the space used by each mode is different and is borne in different ways.
  • The ability of people to use different modes is different. Young children must be accompanied by an adult no matter how they travel. Older children, elderly people or people with disabilities might not be able to ride a bicycle or drive a private motor vehicle, but could take the bus. Only adults can get driver’s licenses.

To summarize: The poster, and the caption “amount of space needed to transport the same number of people by bus, bicycle or car” are misleading, because the vehicles are parked, not moving. All in all, the Muenster poster and the US government publication that quotes it make an apples vs grapefruit vs. cranberries comparison – of dried fruit. Each mode — bus, bicycle or private motor vehicle, is preferable for some trips, but the comparison doesn’t get at why a person will choose one or another mode, and it seriously misrepresents the space requirements it purports to illustrate.

Better luck next time…

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

Diversion fall

Posted on September 29, 2007 by jsallen

Was it the strength workouts at a gym, a new routine for me at age 60?

Was it the judo class I took so long ago, in high school — my father’s hopeful but feckless plan for me to fend off a pair of bus-stop bullies? I had little talent for judo, my father never gave me the needed lecture on persistence, and I quit after a few weeks. I did learn how to break a fall by slapping my hands on the mat.

Was it the bicycling gloves? That part is for sure.

So, last night, I was following my bicycle’s headlamp beam out to the street at my church. The front wheel went off the edge of a narrow sidewalk, slid along and wouldn’t climb back up. Faster than thought, I toppled over. The technical term is “diversion fall.”

But also faster than thought, my hands flew off handlebars and the palms of both gloves judo-slapped the pavement.

I slowly picked myself up.

In 1975 I broke a collarbone in a fall like this. Now I must be hurt somehow too. There often isn’t pain right away.

Knee, hip, shoulder, elbow, wrists, hands? No, no, no no, no and no. Not a single scratch or bruise or scrape.

I picked up the bicycle and slid the bicycle computer back into its bracket on the handlebar. I popped the front fender stay clips back into place. I spun the wheel and the computer still worked. I started for home slowly in case the bicycle might have other complaints. The gear shifting was a little bit odd but I wasn’t going to try to fix it in the dark.

Today I take the bike out of the garage to adjust the gears.

This time I was lucky, but it wasn’t only luck.

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Review of New York Times article of June 5, 2007

Posted on June 11, 2007 by jsallen

This is a review of the article Cars and Bikes Can Mix, When the Rules of the Road Are Clear, which appeared in the New York Times on June 5, 2007 and is available online.

That’s a good headline, except that the problem is usually with behavior, not the rules of the road. The author is an all-too-typical bicyclist who has not learned or been taught good information, and the article has a number of significant errors. It isn’t up to the Times’s standards.

The article mentions the League of American Bicyclists “Share the Road” campaign but without identifying it. The author would do well to attend a League Bike-Ed class.

The article leads with what bleeds, descriptions of fatal crashes. Fear factor is clearly at work here.

Pictures of crash types show them but not how to avoid them — useless information.

And now, I’ll comment on some specific statements in the article.

  • “Thanks to the proliferation of designated bike paths and the growing use of helmets, deaths among bicyclists have declined to around 600 a year from about 800. Still, 600 is 600 too many, as are the approximately 46,000 annual injuries that cyclists suffer in crashes with motor vehicles.” Bike paths don’t have a significant effect on the fatality rate; most riding is on streets. The 600 to 800 figure is about right for the USA, but the article confusingly makes several references to New York City. Cyclist fatalities per year have declined substantially since the 1970s, but largely due to a decline in cycling by children. There has been a small uptick in cyclist fatalities, along with other traffic fatalities, in the past few years.
  • “Prompted by organizations like Transportation Alternatives, the city has created hundreds of bike paths on or near city streets.” The facilities on streets are bike lanes, not bike paths. Hundreds of miles, I think, not hundreds of facilities. Paths adjacent to city streets, with few exceptions, should not be described as a safety improvement, as they have a poor safety record due to crossing and turning conflicts at intersections.
  • “Bicycles are legally entitled to use most roads, though they must ride on the shoulder when the speed limit exceeds 50 miles per hour.” Bicyclists are required to allow other traffic to overtake when safe in all states, but are required specifically to use the shoulder only in Maryland, Alaska, New York and Colorado. Each of these states has exceptions to the rule, for example to turn left or if the shoulder is not usable. See Paul Schimek’s guide to traffic laws.
  • The author advises motorists: “[w]hen turning right, signal well ahead of time, turn from the middle of the intersection rather than across the bike path, and make sure no bike is on your right before you turn. Do not pass a cyclist if you will be turning right immediately after.” Again, the author confuses bike lanes with bike paths. Her advice for motorists to turn right from the left lane is contrary to law, which requires that motorists merge into the bike lane. “[A]nd make sure no bike is on your right before you turn.” This is a problem when turning right from the left lane — the look to the rear can distract motorists from the traffic situation ahead in the intersection; and the bike lane can give bicyclists a false sense of security in moving forward into motorists’ right rear blindspot. Bicyclists best avoid this by merging left, or not advancing to the head of the bike lane when a vehicle is waiting there.
  •  “More than half of collisions occur when cyclists and drivers are on perpendicular paths,” Poorly stated, inaccurate and misleading. The expression “Perpendicular-path” collision apparently is an invention by the author. Most car-bike crashes occur due to crossing and turning movements — not necessarily perpendicular, for example if a motorist overtakes a bicyclist and turns right. What the author doesn’t say, apparently because she doesn’t understand it, it that only about 7% of car-bike crashes are the widely-feared rear-enders.
  •  “Signal all turns and stops and make full stops at stop signs.” The author gives rote advice which fails to convey the purpose of signaling. Bicyclists need to signal to indicate the desire to merge when preparing a turn, to overtake stopped vehicles and in many other situations. The law in most states exempts bicyclists from signaling when the hands must be on the handlebar for control. There is in any case no need to signal once in the position to turn — the bicyclist’s position makes the intention clear. Bicyclists can’t signal when using handbrakes. But there is generally no need to signal when slowing or stopping, as a following driver can see past the bicyclist, who is usually going slower anyway. The purpose of a bicyclist’s slow signal is generally to indicate to a following driver that it is unsafe to pass.
  •  “Never ride on the sidewalk – sidewalk crashes are 25 times as frequent than crashes that occur on major streets. Safest are streets with bike lanes.” The 25 times figure is from Moritz’s survey of adult bicyclists. Some other studies show sidewalks to be, whew, only 4 or 5 times as dangerous. The Moritz study shows streets with bike lanes to be slightly safer than others, but no study makes a valid comparison with all other things (available width, traffic volume etc.) being equal. In addition, there are certain particular hazards in bike lanes of which bicyclists should be aware — right-turn conflicts, car doors etc.
  • “Ride in a straight path. If you must pull out into the lane used by drivers, turn around first to be sure the coast is clear.” No, not “turn around” — look back, signal if necessary to get a driver’s cooperation, then look back again to be sure you have it.
  • “If you are stopped at a light or stop sign to the right of a car or truck, the driver might not see you.” Don’t go there. Stop behind the first vehicle. Stopping next to the front of a vehicle can be deadly, as the rear wheels can sweep across your path if it turns right. This is especially so with long trucks and buses.
  • “Try to make eye contact with drivers before you change lanes or turn left.” It helps to see whether the driver is looking toward you, if possible, but the real test is to make sure the driver has yielded to you.
  • “Wear brightly colored clothing in daylight (though I was wearing an electric blue running suit when I was hit and the driver still failed to see me);” She probably had positioned herself out of the driver’s view, or in a direction the driver wouldn’t normally look, or else the driver was lying.
  • “If you cycle at night, you are supposed to have a white headlight and red taillight (preferably a blinking one) so drivers can see you.” Not “supposed to” but the law, which in most states requires a rear reflector and/or steady taillight (though blinking ones work too) and in many states, requires additional reflectors. Additional reflectors are a good idea in any case.
  • “Scan the road 100 feet ahead for possible hazards.” Why 100 feet ahead? Scanning distance depends on speed, road and traffic conditions.

Whew.

Posted in Bicycling, Crashes, Laws, Reviews | Tagged , , , , , , , , , , , , , , | 1 Comment

Welcome to my blog

Posted on June 11, 2007 by jsallen

Hello — I’m John S. Allen, bicycling advocate, author and expert witness.

I am starting this blog to post timely material about bicycling concerns. My main concerns will be with bicycling advocacy, education and facilities design, with an occasional technical tip and ride report thrown in.

Enough for now — read on.

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