Vehicle inspection is the most effective program to reduce air pollution from vehicles.
Emissions from motor vehicles are the major cause of air pollution in the Portland area. Every city in the U.S. with a serious carbon monoxide or smog problem has an vehicle inspection program. On average, vehicles that fail vehicle inspection tests produce up to four times as much pollution as those that pass. Air pollution in the Portland and Medford areas has been dramatically reduced because of the vehicle inspection programs. Since population and traffic are predicted to grow steadily in both regions, vehicle inspection and other air pollution prevention programs will still be needed to keep the air healthy.