Reported in Local Transport Today

Phil Goodwin is commenting.

This is about cyclist and pedestrian. Some of you may have seen the Velib bicycle rental scheme launched in Paris in July.

“The scheme started with 10,648 bike (Paris within the inner orbital has 2 millions inhabitants) in 750 locations. By the end of 2007 there will be 20,600 bikes in 1,451 locations. The bikes have already travelled 4 millions km, 100 times round the world.

Paris city is 87km2, so 750 stations is about nine ranks per square kilometre, or think of one rank in each square with a 333m side. By the end of the year it will be a rank in each square with a 240m side. Thinking of this as circle (and remembering as you will, that the average distance from a random point in a circle to a rank will be about 90 m. One of the English langage websites says it will be 90 feet but I can’t see how they get that – maybe because the location is better than random, concentrating on popular destinations?

By comparison Paris has 368 metro stations which is about double the density of tube stations in central London. So the density of provision of cycle ranks over the whole of Paris will be eight time higher than the density of tube stations in central London.

Occasionally there is no free bike, or empty space, at the first rank you try, and you need to know to a second. Like luggage trolleys in airports, there is a tendency to congregate and you see lorries restoring entropy by redistributing bikes.”

Are these numbers meaningful at all? A city is not an open field so the urban grid will impact on distance. Urban grid and pedestrian and cyclist route choice preference interaction will impact on the likely hood of finding a rank that is full or empty? Can this predicted and how?

Is a city like an airport? Does this have anything to do with entropy?

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Alain