A few years ago, many cities throughout the world participated in the "Day Without Cars." That day, it was impossible for motorists to access city centers. It was an initiative set up to promote the use of mass transit systems and raise voices against pollution from private transit. In some cities, such as San Francisco, the Day Without Cars means free access to public transport.
However, recently these initiatives are losing momentum and some environmentalists are raising their voice against the "deccaffeination" of this day. Criticism against this was so strong in certain cities that cities are no longer banning traffic but only shutting down a few streets for pedestrians.
The fact is that despite all thees efforts, it's impossible for many citizens to depend on mass transit. Lack of subway, streetcars and bus lines are very common problems, not only in the US, but also in many European countries.
Nevertheless, setting a day aside to not use our cars is probably a good idea to raise awareness about the impact of private transport. Long-lasting measures such as improving the alternatives, though, will surely have a better impact.
[Source: Ecologistas en Acción]