"Traffic congestion experts have long warned that pollution caused by idling vehicles on crowded roads was harming Americans' health.

Now, for the first time, researchers at Harvard University have quantified the damage: They say that congestion in the USA's 83 largest urban areas last year led to more than 2,200 premature deaths and a related public health cost of at least $18 billion."

Larry Copeland reports for USA TODAY May 25, 2011. [2]