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 I think that the what the world, and americans in particular, needs is an attitude adjustment.  Today's society is very much about me, with few people really siting back and thinking about the bigger picture, and how their day to day activities are affecting the rest of us, both in the present, and in the future.  Such an adjustment will not happen over time, and we will never achieve an ideal situation when it comes to vehicle exhaust, or the lack there of.  However, society has made great strides towards making our world a better one for everyone.  Many states now have no-smoking policies in restaurants, and many other public places.  Hummers are no longer quite the status symbol that they used to be, and hybrids are becoming more and more popular.  Unfortunately, such changes are still more about the individual than they are about society, as non smokers don't want to eat dinner next to someone who is smoking, etc.  While such steps are certainly better than none, I find it highly unlikely that any significant progress will be made until society as a whole stops thinking about their own individual needs, and instead thinks about the needs of everyone, and how taking public transportation, or carpooling, could make an impact, and forget about their own personal inconveniences.