A New "Tragedy of the Commons".

The tale I hear from almost all of my City & Regional Planning professors goes something like this.

Back in the day, cities used to have wide open commons with plenty of grass so you could bring your sheep for a brief stay and not worry about them while away from your farm. However, because of this free resource, it was in each sheep herder's self-interest to crowd the common with as many sheep as possible, since it was a free resource. With the commons overrun by sheep, the once beautiful meadows would eventually reach destruction. The moral of the story is that because of the self-interest of a few, the majority would have to suffer the loss.

In Paris, a new tragedy of the commons has been found: The tragedy of Bike Sharing.

A popular bicycle rental scheme in Paris that has transformed travel in the city has run into problems just 18 months after its successful launch.

Over half the original fleet of 15,000 specially made bicycles have disappeared, presumed stolen.

They have been used 42 million times since their introduction but vandalism and theft are taking their toll.

The company which runs the scheme, JCDecaux, says it can no longer afford to operate the city-wide network.

Championed by Paris Mayor Bertrand Delanoe, the bikes were part of an attempt to "green" the capital.

Parisians took to them enthusiastically. But the bikes have suffered more than anticipated, company officials have said.

Hung from lamp posts, dumped in the River Seine, torched and broken into pieces, maintaining the network is proving expensive. Some have turned up in eastern Europe and Africa, according to press reports.

Since the scheme's launch, nearly all the original bicycles have been replaced at a cost of 400 euros ($519) each.

The Velib bikes - the name is a contraction of velo (cycle) and liberte (freedom) - have also fallen victim to a craze known as "velib extreme".

Various videos have appeared on YouTube showing riders taking the bikes down the steps in Montmartre, into metro stations and being tested on BMX courses.

Remi Pheulpin, JCDecaux's director general, says the current contract is unsustainable. "It's simple. All the receipts go to the city. All the expenses are ours," he said.

The costs, he said, were "so high that a private business cannot handle it alone, especially as it's a problem of public order. If we want the velib set-up to keep going, we'll have to change the business model," he told Le Parisien newspaper.

As much as I love the bike sharing program, I'm surprised no one thought this aspect of the program through. Why not require a credit card in order to rent the bike in the first place? If it is not returned within a long amount of time--say, a month--your credit card is charged for the amount of the bike? Maybe it's not a perfect suggestion, but it certainly beats how the program is running now.