If you've been to Paris, or Rio, or Barcelona, you might have noticed denizens swiping cards, getting bikes, and tooling merrily through the streets until they leave their bike where they're going. A Zipcar, but for bikes, and no reservation necessary. Such systems have long been the apple of Transportation Commissioner Janette-Sadik-Kahn's eye. Now, she'll bring a prototype to New York in her Summer Streets program, when much of Park Avenue will be closed to cars. On August 8, 15, and 22, until 1 pm there will be several stations on Park Avenue below 47th street, where New Yorkers can see the racks, swipe a card (the bikes are free, the card is only to make sure they're returned), and ride on to the next station. There will only be about 30 bikes available, but in a fully-built out system there would be hundreds or thousands of bikes, available as a real alternative to walking, transit, or driving. The city DOT has sent out a "request for expressions of interest," but as to when there might be an actual bike-share, umm, 2010 anyone?