Muenster road space poster — check the numbers!

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 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…