Lord Richard Rogers, a British architect and long-time advisor on urban issues, suggested last year that London should become "a people space rather than the car space it currently is."
But the website CarFree.com cautions that simply banning automobiles won't be a quick fix. "The challenge is to remove cars and trucks from cities while at the same time improving mobility and reducing its total costs," it says.
Urban planners have an array of alternatives they can draw from as they try to make cities at least less dependent upon automobiles. They include congestion charges and more limited car-free zones, such as the popular Third Street Promenade in Santa Monica, Calif. Several British communities are exploring the creation of similar restricted spaces.
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Other cities, such as Paris, have raised the idea of banning some, but not all, automobiles. One approach would put a restriction on the use of vehicles powered by internal combustion engines, while electric- or hydrogen-powered automobiles would still have free rein. In some instances, such vehicles are already exempt from urban congestion charges.
The auto industry sees restrictions as increasingly unavoidable and is trying to adapt by, among other things, having more battery-car offerings. Some of the latest plug-in hybrid models, such as the new Porsche Panamera Plug-In, allow drivers to stick to gas power on highways coming into a city then switch solely to electric propulsion to gain access and avoid toll charges.
While pressure to push cars out of urban centers has become most intensive in older European and some American cities, urban planners in some emerging markets are also beginning to consider the challenges posed by the automobile.
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Beijing, Shanghai and some other Chinese cities, for example, have been enacting rules to reduce the number of new vehicles that can be sold and registered. And with some of those cities already reaching gridlock, it's a question of whether more radical solutions might follow.
How the public reacts remains to be seen. A number of efforts to create pedestrian malls in the U.S. have failed, and motorists—and the businesses that support them—make up a powerful lobbying force. The concept of carless cities is likely to generate a loud global debate in the years ahead.
—By CNBC Contributor Paul A. Eisenstein. Follow him on Twitter @DetroitBureau or at thedetroitbureau.com. With contributions from CNBC's Phil LeBeau. Follow him on Twitter @LeBeauCarNews.