School bus retrofits and idle reduction

Toxic chemicals and fine particles in diesel emissions can trigger asthma, lung and heart problems, and are responsible for as many as 125,000 cancer cases nationwide.

Diesel fumes can be particularly harmful to children, who face heightened exposure to diesel exhaust from the self-polluting nature of buses with their large doors opening and closing, and the tendency of buses to idle during loading and unloading periods. Research has shown that students on school buses are exposed to 5 to 15 times the levels of particulate pollution than at nearby monitoring sites.

PDF icon The Harmful Effects of Vehicle Exhaust

School bus retrofit program

The MPCA is a major partner of Clean Air Minnesota’s Project Green Fleet (PGF). Since it began in 2005, PGF has worked with school districts and school bus fleet operators to retrofit buses with Diesel Oxidation Catalysts and closed-crankcase filtration systems.

HTML icon Project Green Fleet

Project Green Fleet is a collaborative effort led by Environmental Initiative, with business, government agencies and non-profit organizations, to improve air quality and protect public health by reducing emissions from Minnesota's school buses and other diesel vehicles.


With support from the MPCA and funding including $2.4 million from the state Legislature and additional federal and private assistance, PGF has made tremendous progress retrofitting Minnesota’s "legacy fleet"—older buses that will remain on the road for many years.

  • 3,209 school buses were retrofitted through 2013 — that’s about 97% of the project's statewide goal! PGF plans to retrofit 90 more buses and declare victory.
  • Estimated lifetime emission reductions of 14 tons of particulate matter (PM), 82 tons of carbon monoxide (CO), and 163 tons of hydrocarbons (HC).
  • Thirty-seven school districts and two Head Start Programs participating by the end of 2008.
  • PDF icon Map of PGF progress through the end of 2011

School bus idling

picture of school busIn May 2002, Minnesota adopted legislation to protect the health and safety of children from harmful diesel bus emissions. This law calls for schools to reduce the unnecessary idling of school buses in front of schools, and reroute bus parking zones away from air-intake vents (or if necessary, relocate the air-intake vents).

HTML icon Minnesota state law regarding school bus idling (Minn. Stat. 123B.885)

The MPCA worked with the Sierra Club and other health-based organizations to provide resources to help your school protect students from diesel emissions. There are sample letters to help explain the idling law, posters and camera-ready signs for Clean Air Zones. While the Sierra Club effort is no longer active, Project Green Fleet, through their school bus retrofit program, continues to work with participating school districts to create and adopt idle reduction policies for their bus fleets.

Schools can begin with these simple steps to minimize children's exposure to harmful diesel emissions. By adopting a no-idling policy and redesigning bus parking zones, schools can protect the health of students.

  • Implement a no-idling policy. Post "no idling" signs and alert bus drivers, parents and administrators that engines should be turned off when a bus (or any vehicle) is waiting, or parked. Buses generally do not need to idle, except in cold weather.
  • Redesign bus parking zones. Move bus parking area away from school air intake vents and park buses at a diagonal to avoid front-to-back passing of emissions to help reduce students' exposure to emissions.

Beyond the mandate of the law, your school can reduce students' exposure to diesel emissions by good maintenance of your current bus fleet and investment in cleaner fuels and technologies, use of biodiesel, and the purchase of newer, cleaner buses, over the long term.

Resources for schools

Sample "no idling" policy

PDF icon Sample School Board Policy

Sample newsletter article

PDF icon School Idling Policy Notification: Sample Article for Parents/School Newsletters

Related links

Cleaning up diesel engines in Minnesota

HTML icon National Idling Reduction Network News

The National Idling Reduction Network brings together a broad coalition of stakeholders to identify consistent, workable solutions to the challenges of heavy-vehicle idling for the entire United States. Their newsletter archive is available online.

HTML icon Project Green Fleet

Project Green Fleet is a collaborative effort led by Environmental Initiative, with business, government agencies and non-profit organizations, to improve air quality and protect public health by reducing emissions from Minnesota's school buses and other diesel vehicles.

File Vehicle Exhaust

Research into effects of diesel exhaust on children.

HTML icon Anti-Idling Vehicle Ordinance (Minneapolis)

The city's newly amended ordinance now restricts idling of cars and other gas or diesel powered vehicles to no more than three minutes in a one hour period.

HTML icon National Clean Diesel Campaign (U.S. EPA)

Promotes clean air strategies to reduce diesel emissions by working with manufacturers, fleet operators, air quality professionals, environmental and community organizations, and state and local officials.

HTML icon Clean School Bus (U.S. EPA)

A national program designed to help communities reduce emissions from older diesel school buses.

More information and assistance

For more information about school bus retrofits or idle reduction, contact Mark Sulzbach at 651-757-2770.