School Bus Pollution Report Card 2006

The report evaluates U.S. school bus emissions, finding that older diesel buses release significantly more soot than modern alternatives, posing health risks to children. It grades states on soot emissions, cleanup programs, and smog-forming pollution, noting wide performance gaps. The authors recommend a strategy of 'the five Rs'—retrofitting, refueling, replacement, repair, and reduced idling—and call for strengthened federal standards and increased funding to modernize fleets.

• School buses are among the oldest vehicles on U.S. roads, with an average age of nine years. They emit nearly twice as much pollution per mile as a tractor-trailer truck, and 37% of the fleet is over a decade old, with 1 in 12 buses not subject to any soot pollution standards.
• Pollution levels vary significantly by state. South Carolina and South Dakota have the dirtiest fleets, emitting nearly three times more soot than Delaware, which has the cleanest fleet. Only five states—Alaska, Connecticut, Maine, Nevada, and New York—scored above the national average across all three evaluated categories.
• While national soot pollution from school buses has decreased by more than 2% due to local, state, and federal actions, many states remain inactive. Nine states and the District of Columbia took no cleanup action in 2005, and 13 states have programs achieving less than a 1% reduction in soot.
• California and Washington lead the U.S. in cleanup efforts, reducing soot by more than 7% through retrofits and cleaner fuels. California's Lower-Emission School Bus Program has installed particulate traps on over 10% of its fleet and retired hundreds of buses, while Washington's Clean Buses, Healthy Kids Retrofit Project has retrofitted 38% of its fleet with diesel oxidation catalysts.
• Substantial investment is required to modernize the fleet. Retrofitting all buses built after 1993 with particulate traps and closed crankcase filtration would cost approximately $2.6 billion, while replacing all buses built before 1994 with new low-emission models would cost approximately $13.4 billion.
• Available technologies can drastically reduce emissions: a new natural gas bus releases over 90% less soot than a 2005 conventional diesel bus, and replacing a 1988 bus with a trap-equipped diesel bus can reduce soot by 95%. B20 biodiesel blends reduce soot by about 10%.

APA

Union of Concerned Scientists (2006). School Bus Pollution Report Card 2006. https://www.ucs.org/sites/default/files/2019-10/pollution-report-card-2006_exsum.pdf

Chicago

Union of Concerned Scientists. School Bus Pollution Report Card 2006. 2006. https://www.ucs.org/sites/default/files/2019-10/pollution-report-card-2006_exsum.pdf.

Wikipedia

{{cite report |author=Union of Concerned Scientists |title=School Bus Pollution Report Card 2006 |date=2006 |url=https://www.ucs.org/sites/default/files/2019-10/pollution-report-card-2006_exsum.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{unionofconcernedscientists2006school, author = {{Union of Concerned Scientists}}, title = {{School Bus Pollution Report Card 2006}}, institution = {Union of Concerned Scientists}, year = {2006}, url = {https://www.ucs.org/sites/default/files/2019-10/pollution-report-card-2006_exsum.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }