Addressing a plaza full of reporters at Madison Square this afternoon, Transportation Commissioner Janette Sadik-Khan announced that the city is entering the next phase of its initiative to launch a public bike system stretching from the Upper West Side to Bedford Stuyvesant. The system will be run by Alta Bike Share and consist of about 600 stations with 10,000 bicycles, creating a network of comparable size and density to bike-share systems in cities like London and Paris.

Station density is perhaps the single greatest key to success in a modern bike-share system. The less searching you have to do for a station, and the closer you are to your destination when you dock your bike, the better. As Minneapolis Mayor R.T. Rybak told Streetfilms earlier this year, the underlying principle is “go big or go home.” With this announcement, NYC DOT and Alta have clearly signaled that they are going big. Once bike-share launches, it will change the way New Yorkers get around the city, extending the range of the transit system and adding point-to-point convenience for short trips.

Sadik-Khan said the selection of the bike-share operator also marks the beginning of an extensive public outreach campaign, which will seek ideas from local residents, community boards, and civic leaders to determine where bike-share stations should go. “This is just the start,” she said. “We really want your help in planning the system.” Public workshops will be held throughout the fall, and the bike-share system is on track to launch in 2012, potentially by the summer.

Leaders from NYC’s business community and progressive political landscape hailed the bike-share program as a way to give New Yorkers more transportation options and attract a skilled workforce. Both Kathy Wylde, the CEO of the city’s biggest business lobbying group, the Partnership for NYC, and Dan Cantor, leader of the labor-affiliated Working Families Party, were on hand to back the initiative. Wylde called bike-share “an important contribution to the next generation of what will make New York attractive to talent,” and Cantor said it is “one of those things that we’re going to look back at in a few years and say, ‘What took so long?'”

Asked specifically why cycling and bike-share is progressive, Cantor said: “This is so obvious. This is good for human beings. It’s good for the planet. It reduces greenhouse gas emissions. It burns calories. It makes you a happy person when you ride a bike.”

Three City Council members who represent districts within the bike-share service area also endorsed the plan: Gale Brewer, Brad Lander, and Tish James. The precise borders of the service area have yet to be finalized, but its general contours will run from the Upper West Side and the Upper East Side to Bed Stuy and Greenpoint. The city is considering ways to expand service to other areas after the first phase of the system is up and running, said Sadik-Khan.

One of the defining aspects of the contract is that the system must operate without public subsidy. Alta is assuming all the financial risk of running the system, which is projected to cost about $50 million per year to operate. They expect to turn a profit, a portion of which will be shared with the city. Some revenue will come from memberships, which will be priced at less than $100 for an annual pass and give users access to an unlimited number of trips under 30 minutes, after which additional fees kick in. Daily, weekly and monthly passes will also be available (specific prices have not yet been set, but you can read about the general structure of how membership will work).

Another major source of revenue will be corporate sponsorship, and Alta is now seeking a single sponsor whose brand will go everywhere the bike-share system goes — 600 kiosks and 10,000 bikes.

Judging by the Q&A after the presser, NYC’s bike-share plans will face an uphill battle in the media. A good chunk of NYC’s press corps seems to think the bike-share story is about what might happen once people who don’t normally ride in New York are using public bikes. Will they wear helmets? Will they follow the rules of the road? (Experience in other cities suggests that bike-share users are safer on the streets than cyclists riding their own bikes.) As for providing a new transit option and overcoming the barriers to bike riding posed by theft and walk-up apartments without much storage space — don’t count on a wave of coverage about that.

We’re at the very beginning of the process to bring a world-class public bike system to NYC. This fall will come dozens of public workshops to discuss where hundreds of stations should go. The NIMBYs are already staking out their position, and the press corps is as hungry for conflict as ever. If you want bike-share in NYC to be as good as it should be, get ready to make your case.

Noah Kazis contributed reporting to this post.