In many U.S. cities, the personal automobile is the single greatest polluter, as emissions from millions of vehicles on the road add up. In fact, vehicles account for more than 25 percent of all air pollution nationwide. Traffic congestion is no longer just a big-city problem: the time commuters spend stalled in traffic in small and medium-sized cities has more than quadrupled since 1982, costing hours of delay, billions of gallons of wasted fuel, and billions of dollars in time and fuel costs.

What each individual does - or chooses not to do - as it regards their driving behavior can make a big difference.

It All Adds Up to Cleaner Air is a unique public education and partnership-building initiative developed collaboratively by several federal agencies to help regional, state and community efforts to reduce traffic congestion and air pollution. It All Adds Up seeks to inform the public about the connection between their transportation choices, traffic congestion and air pollution, and emphasizes simple, convenient actions people can take to improve air quality and reduce congestion.