In 2006, the MPCA began retrofitting school buses with diesel oxidation catalyst mufflers, working in a close partnership with Clean Air Minnesota and the Minnesota Environmental Initiative to help launch Project Green Fleet.
In 2008, the Minnesota Legislature gave the MPCA $2.4 million for this important work.
About 1,500 school buses were retrofit with pollution reducing exhaust systems through state grant funding. As of June 30, 2011, 2,751 Minnesota school buses had been retrofit overall from state and federal grants and some private funding. These reduce fine-particle emissions by 20-25 percent.
According to the EPA, for every dollar spent on reducing diesel emissions there is up to $13 in health benefits.
More information is available about the school bus retrofit idle reduction effort.