Although carbon dioxide emissions from industry are declining on both continents, those from transportation account for almost one-third of all greenhouse-gas emissions in the United States and 22 percent in European Union countries. Across the globe, but especially in Europe, where European Union countries have pledged to reduce greenhouse gas production by 2012 under the United Nations’ Kyoto protocol, there is great pressure to reduce car emissions.

Image About 450 students walk the routes each morning in Lecco. Credit... The New York Times

Last year the European Environmental Agency warned that car trips to school  along with food importing and low-cost air travel  were growing phenomena with serious implications for greenhouse gases.

In the United States and in Europe, “multiple threads are warping traditional school travel and making it harder for kids to walk,” said Elizabeth Wilson, a transportation researcher at the Humphrey Institute of Public Affairs at the University of Minnesota. Among those factors are a rise in car ownership; one-child families, often leery of sending students off to school on their own; cuts in school-bus service or charges for it as a result of school-budget cutbacks and fuel-price gyrations; and the decline of neighborhood schools and the rise of school choice, meaning that students often live farther from where they learn.

Worse still, said Roger L. Mackett, professor at the Center for Transport Studies at University College in London, there is growing evidence that children whose parents drive a lot will become car-dependent adults. “You’re getting children into a lifelong habit,” he said.

In Lecco, car use has proved a tenacious habit even though the piedibus has caught on. “Cars rule,” said Augosto Piazza, the founder of the city’s program, an elfin man with shining blue eyes, a bouncing gait and a yellow vest. As he “drove” along a bus route on a recent morning, store owners waved fondly to the familiar packs of jabbering children.

Yet as they pulled up to Carducci School, dozens of private cars were parked helter-skelter for dropoffs in the small plaza outside as gaggles of mothers chatted on the sidewalk nearby. “I have two kids who go to different schools, plus their backpacks are so heavy,” said Manuela Corbetta, a mother in a black jacket and sunglasses, twirling her car keys as she explained why her children do not make the 15-minute trek. “Sometimes they have 10 notebooks, so walking really isn’t practical.”