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Reducing Emissions from School Buses

More than 24 million children nationwide ride a bus to and from school every day, and the majority of those buses are running on diesel. The exhaust dirties the air inside and outside of the bus. Diesel exhaust from school buses idling in line seeps into the buses through open windows and doors, exposing the children on the buses and children waiting to board. Engines are designed to vent some crankcase emissions to the air, which means the driver, and then 

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the passengers, get hit with the pollution. Diesel exhaust can also get into school ventilation systems and through open school windows, causing poor indoor air quality.


Emissions from school buses and other sources are a health concern for everyone, but children are more susceptible to air pollution problems because they breathe 50 percent more air per pound of body weight than do adults. There is no known safe exposure to diesel exhaust. According to a study of diesel exhaust inside school buses, done by NRDC and U.C. Berkeley School of Public Health, a student sitting in the back of a school bus with the windows closed receives an average exposure to diesel exhaust that is up to 4 times greater than a child riding in a passenger car immediately ahead of the same bus.


In order to prevent emissions, Pennsylvania passed a law known as the Pennsylvania Diesel Powered Motor Vehicle Idling Act (effective 2009), which prohibits the unnecessary idling of school buses and other on-road diesel vehicles for more than five minutes in an hour. Buses can idle for up to 15 minutes during a 60-minute period, but only when passengers are aboard. Owners and operators of locations where these vehicles load or unload are also required to erect and maintain idling restriction signs.


The law also mandates that schools where these vehicles operate post signs reminding drivers about the law. Many districts were unaware of the law and the requirement to post signage.

In 2014, in collaboration with a number of other local environmental and health-based organizations, GASP conducted school bus idling observations at Pittsburgh Public Schools. In general, we found about one in four school buses was idling beyond the allotted five minutes in an hour. We also observed that the mandated “no idling” signage was not present. This all suggested that there was room for improvement and a need for more education of parents, school personnel, and drivers.


In the following months, GASP worked with Green Building Alliance to hold presentations for bus drivers, school nurses, and interested faculty. We also supplied around 120 “No Idling” signs to the Pittsburgh Public School District and the various charter, parochial, and private schools for which they are required to provide transportation at no charge. Funding for this effort was provided by the Heinz Endowments.


In addition to pushing for better enforcement of Pennsylvania’s diesel No Idling law, we have also worked to get Pittsburgh Public Schools to use cleaner, less polluting school buses.  Check out these posts about it:

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