Volunteers pedaled rickshaws along the cobbled streets, charging passengers $1.20 an hour; bikes were available for free; and city workers encouraged children to walk to school along routes supervised by adults acting as Pied Pipers and picking up kids at arranged stops.
Some critics dismissed the idea as a gimmick. "We live in a society that is organized, like it or not, in such a way that we cannot do without cars," Christian Gerondeau, president of the French Federation of Auto Clubs, told French radio. "Stigmatizing the car is the wrong battle."
Authorities in Nantes, though, are trying to show that there might be another way.
The centerpiece of their efforts is a state-of-the-art tramway providing service to much of the town, and a network of free, multistory parking lots to encourage commuters to "park and ride."
Rene Vincendo, a retired hospital worker waiting at one such parking lot for his wife to return from the city center, is sold. "To go into town, this is brilliant," he says. "I never take my car in now."
Indeed, a poll in April by the tramway authority found that 95 percent of users were satisfied with the service.
It is not cheap, though. Beyond the construction costs, city hall subsidizes fares to the tune of 60 million euros ($72 million) a year, making passengers pay only 40 percent of operating costs.
That is the only way to draw people onto trams and buses, says Mr. de Rugy, since Nantes, like many European cities, is expanding, and commuters find themselves with ever-longer distances to travel.
It's a chicken-and-egg problem, says John Adams, a professor of geography at University College in London. There is no longer room in European cities for cars to park, so drivers must live farther from work, and the traffic increase obliges urban planners to devote more room to roads and parking, which worsens urban sprawl.
The danger, he warns, is that "the further you go down the route of car dependence, the harder it is to return, because so many shops, schools, and other services are built beyond the reach of any financially feasible public transport network."