enlarge Shawn Patrick Ouellette/Staff Photographer

John Rooks stands with some of the white bikes that he and other volunteers have put out in Portland for people to borrow in an effort to reduce traffic congestion and air pollution. “Environmentally, it’s something we need to do,” he said.

enlarge Shawn Patrick Ouellette/Staff Photographer

The bikes are free to use but first must be unlocked. People can look up the combination to the locks online at www.whitebike.org.

Michael Scott had seen a bike-sharing program in Houston and was excited to come across a small fleet of white bicycles near Monument Square in Portland Monday.

Minutes later, he and Amanda Potter were pedaling a pair of the bikes across Congress Street. They planned to drop off some items at their home and go for a ride before locking the bikes back up for someone else to use.

"This is great for people who don't have any transportation of their own," Potter said.

Portland is once again part of a movement of cities worldwide with bike-sharing networks that are intended to promote green transportation by reducing traffic congestion and air pollution. Although the programs vary from city to city, they generally allow people to borrow bikes from self-service racks, ride them, then leave them for the next person to borrow.

Portland first became part of the trend in 1996, when free yellow bikes were placed in downtown bike racks. Theft and vandalism ended that effort.

John Rooks thinks the time is right to try again, especially with interest in alternative transportation and concern about global warming.

"Culturally, we're ready. And environmentally, it's something we need to do," said Rooks, president of Dwell Creative, a public relations design firm in Portland that created the new White Bike program.

Rooks and other employees rolled out the first five white bikes Monday morning and locked them to a rack next to One City Center.

Three of the bikes had been borrowed and pedaled away within a few hours.

The yellow bikes distributed 12 years ago were left unlocked, while the white bikes have locks to prevent theft. However, anyone can easily look up the combination to the locks at www.whitebike.org. The Web address is printed on a small sign on each bike.

Scott, for example, saw the bikes after he and Potter left the Portland Public Library. "I went right back to the library and looked them up online," he said.

Some of the white bikes will undoubtedly be stolen or damaged, Rooks said. But he hopes the locks will keep enough bikes in circulation to have even a small effect. The whole idea, he said, is to encourage their use.

"If we can get a few more people to bike to work and create some dialogue about pedestrian-friendly cities, then I think this can be a successful program," he said. "We're trying to get the idea out there and start some dialogue, and show how inexpensive it is."

White Bikes is a simple, low-budget version of bike sharing.

Rooks said it has cost about $800 to get the program started, including building the Web site and buying locks. Bikes were donated, and businesses helped with the painting and signs. There is no fee to use the bikes.

People are encouraged to ride them anywhere in the city, then simply lock them up again in a public place. Donated helmets have been left with some of the bikes, although users are encouraged to have their own.

The idea of sharing bikes is believed to have started in Holland in the 1960s, and programs are widespread in European cities. Unlike White Bikes, which is free, more elaborate sharing networks often charge membership or use fees.

Popular programs in cities such as Paris and London involve special storage stations where users slide credit cards to unlock bikes and to lock them up. Paris is expected to have about 20,000 bikes on its streets by the end of this year.

Washington, D.C., is starting a SmartBike program, which charges users $40 a year for membership cards to unlock bikes from 10 downtown kiosks. Philadelphia is considering a different version.

Rooks and his fellow employees did not approach Portland for its support, although he said the program could grow with public and corporate support. "I just wanted to get it out there and see what happens."

The initial...