On her honeymoon to Paris in 2007, Alison Cohen found a new love: a citywide bike-sharing program. Now, she's helping to bring a similar concept to several big cities around the United States and the world.

Alta Bicycle Share, Cohen's Portland, Oregon-based company, already operates bike-sharing programs in four cities. This month, the company is launching its largest initiative to date, which will eventually put 10,000 new bicycles on the streets of New York City. Customers will be able to rent them from automated, solar-powered stations installed along the streets of Manhattan.

Here's how it works: You insert a keycard at a docking station to unlock one of the almost comically safe bell- and light-equipped bikes made by PBSC Urban Solutions of Quebec. You ride it. When you are done, you redock it at another station. The pricing structure is similar to that of Zipcar. A subscription costs from $75 to $100 per year, depending on the city. (Tourists can also rent the bikes, for $7 to $10 a day.) Then customers pay usage fees, based on how long they ride. Typically, the first 30 minutes is free, and then the cost ranges from $2 to $12 per half-hour.

To launch the program in New York City, Alta had to allay several concerns, including the issue of security. In the early days of the Paris bike-sharing program, equipment thefts and station vandalism made headlines. After that, bike-sharing initiatives stalled out for a while, and the industry focused on creating vandalproof systems, says Cohen. Today, someone would have a hard time pulling a bike from its dock. "The engineering has come a long way," she says.

Another issue that initially worried city officials was bike maintenance and safety. But Cohen says Alta's insurance contracts require the company to check the bikes at every station at least once every two weeks. And if there's an immediate problem, riders can report it using a button at the station.

Bike-sharing initiatives have proved very popular with urbanites. About a year after Alta launched a program in Washington, D.C., the city celebrated its one-millionth shared-bike ride, far exceeding expectations and prompting calls for more bikes and more stations. Later this year, Alta will launch a program in Chicago with 3,000 bikes and 300 stations. The company, which has annual revenue of $6 million, is also bidding on upcoming bike-sharing programs in San Francisco; Portland, Oregon; Vancouver, British Columbia; and Copenhagen.

Each city structures its bike-sharing systems differently. Boston and Washington, D.C., for example, use a mix of federal, state, and city money to fund their programs, while New York City's bike-sharing initiative is financed entirely by private means. To cover the cost of equipment and Alta's services, the company helped New York City land a $41 million sponsorship from Citibank, whose logo will appear on bikes and stations. MasterCard, which will provide payment processing, kicked in another $6.5 million.

Though bike sharing is gaining speed, there are still a few bumps in the road. One persistent problem is simply running out of bikes or open docks at rush hour. Some bike-share users have already coined a term to describe seeing someone else swoop in and grab the last available bike or open slot. "We call it getting 'dock-blocked,' " says Phil Lepanto, a Washington, D.C., resident. In those cases, riders must try their luck at the next station.

To alleviate that problem, Alta deploys a fleet of vehicles to redistribute bikes to the stations where they are most needed. Cohen acknowledges that this is a less-than-elegant solution for a company dedicated to getting cars off the road, but she says the company is working with its partners to develop different pricing plans that could help solve the problem. "A lot of smart people are thinking about this," she says.

Pedal Pushers

Alta hopes to have nearly 16,000 bikes on the road by the end of this year.

Melbourne, Australia
Launched in May 2010 with 600 bicycles

Washington, D.C.
Launched in September 2010 with 1,340 bicycles

Boston
Launched in July 2011 with 600 bicycles

Chattanooga, Tennessee
Launched in April 2012 with 300 bicycles

New York City
Launching in summer 2012 with 10,000 bicycles

Chicago
Launching in fall 2012 with 3,000 bicycles