While many building codes in Europe cap the number of parking spaces in new buildings to discourage car ownership, American codes conversely tend to stipulate a minimum number. New apartment complexes built along the light rail line in Denver devote their bottom eight floors to parking, making it “too easy” to get in the car rather than take advantage of rail transit, Mr. Kodransky said.

While Mayor Michael R. Bloomberg has generated controversy in New York by “pedestrianizing” a few areas like Times Square, many European cities have already closed vast areas to car traffic. Store owners in Zurich had worried that the closings would mean a drop in business, but that fear has proved unfounded, Mr. Fellmann said, because pedestrian traffic increased 30 to 40 percent where cars were banned.