EcoWatch: When I worked for the City of New York, I often asked people what they felt was the worst environmental problem. Many said tailpipe pollution. Emissions from the tailpipes of cars and trucks seemed particularly insulting because--as we all walked our kids to school--the tailpipes seemed to be spewing black smoke just at the level of our kids heads.
Our cars and trucks have become a lot cleaner since then, but exhaust from vehicle tailpipes is still a major source of air pollution, responsible...