Bus Study Finds Idling Worse Than Re-starting Engines

An EPA study of school buses finds idling for more than three minutes generates more pollution than stopping and re-starting the engine -- debunking a widely held belief of some drivers, officials said on May 21. Turning the engine off cuts carbon monoxide, fine particles, nitrogen oxide, and carbon dioxide, a greenhouse gas.

EPA studied school bus exhaust levels when the buses were parked but engines kept running and calculated the benefits from turning them off for various periods and then restarting them.

"Pollution from school buses has health implications for everyone, especially asthmatic children," said Alan J. Steinberg, EPA Region 2 administrator. "This study shows in no uncertain terms that allowing a bus to idle exposes children to more pollution and shows that a very simple step -- shutting off that engine -- can really make a difference."

EPA measured the pollution from six buses owned and operated by the Katonah-Lewisboro School District of New York. The level of pollution from buses that idled for more than three minutes was 66 percent higher in fine particulate matter than pollution generated from shutting off the buses and then re-starting them.

Diesel exhaust particulate matter can penetrate deep into the lungs and pose serious health risks, including aggravating the symptoms of asthma and other respiratory problems in healthy individuals. The Northeast has some of the highest asthma rates in the nation, including childhood asthma rates near 12 percent in areas of New York City.

In the United States, 24 million children ride the school bus every day. On average, students spend an hour and a half each weekday in a school bus. Nationally, school buses drive more than 4 billion miles each year.

Due to the longevity of diesel engines, it is estimated that about one-third of all diesel school buses now in service were built before 1990. Older buses are not equipped with today's pollution controls or safety features and are estimated to emit as much as six times more pollution as the new buses that were built starting in 2004, and as much as sixty times more pollution as buses that meet the 2007 diesel standards. There are steps that school bus operators can take now to reduce pollution levels including idling reduction programs, anti-caravanning practices, ensuring proper maintenance of engines and replacing and retrofitting older buses.

EPA will continue to work with states and local agencies, including school districts, to promote idling reduction efforts and reduce air pollution. These and other projects are possible due to collaborative efforts like the Northeast Diesel Collaborative, a partnership of EPA and private, non-profit and government groups in New York, New Jersey, Puerto Rico and the six New England states working together to fight air pollution.

For more information about reducing pollution from school buses, visit EPA's Clean School Bus USA Web site at http://www.epa.gov/region02/cleanschoolbus.

This article originally appeared in the 05/01/2007 issue of Environmental Protection.

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