“IT JUST MAKES people really happy,” says Parry Burnap, executive director of Denver Bike Sharing, describing her city’s new program. “You see someone you don’t even know and they ding their bell,” a colleague told her recently. City-sponsored bike-share programs are popping up across North America from Washington, DC, to Montreal. The concept: Rent a bike from any public docking station and drop it off at any other station when you’re done.

The benefits: healthier citizens, more interactive urban environments, fewer cars on the road.

So why doesn’t Seattle—which Bicycling magazine calls the fourth most bike-friendly city in the country—have a similar setup? “Weather, topography, helmet laws, and funding,” explains King County Metro transportation planner Ref Lindmark.

But Chris Holben of Capital Bikeshare in DC says foul weather isn’t a problem. It’s a publicity opportunity. “We had Winter Warrior contests where we gave prizes to people who rode every day between January and February.” Membership numbers climbed.

Unlike that city, though, Seattle has a mandatory bike-helmet law (see: No-Brainer ), which could require more innovative solutions, such as Melbourne, Australia’s street-side vending machines that sell $5 helmets.

Still, none of these obstacles have killed King County Metro’s yen for pedal-powered commutes. Lindmark says they’re researching designs for a bike-share program right now. “Our hope is that it’s no more than two years away.”