A French Revolution: This One On Two Wheels, No Guillotine

Vélib is the brainchild of Mayor Bertrand Delanoë, a Socialist and longtime green campaigner who has set a target for the city to reduce car traffic by 40 percent by 2020. Since he took office in 2001, his administration has added about 125 miles of bicycle paths, at the expense of lanes for cars, prompting accusations from drivers that it has aggravated congestion in the city.

Still, only about 40,000 of the 2.5 million Parisians say they use their bicycles regularly. Mr. Delanoë would like to raise that number to 250,000 by the end of the year.

City Hall is hoping to draw on the experience of smaller-scale rental programs in other cities like Berlin and Stockholm to address concerns about theft and financial viability that ended an experimental program in Amsterdam in the 1960s.

The key, Mr. Aidenbaum said, is to make it easy. "What this initiative does is to take away some of the inconveniences of owning a bike in Paris," he said, "the lack of storage space in Paris buildings, the issue of theft and the hassle of maintenance."

First indications are positive. Even before the docking stations opened, 13,000 people had bought annual subscriptions online. On Sunday, some docking stations were so popular that they temporarily ran out of bikes.

Denis Bocquet, 37, an urban planner who divides his time between Paris and Berlin, had to wait in line before renting a bike with his partner, Nora Lafi. From now on, he said, he would use the Vélib to go to work during his stints in Paris.

"It used to be stressful and dangerous to cycle in Paris, but the city has changed, and this could change it even more," Mr. Bocquet said.