An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »


School Bus Idle Reduction

The Clean School Bus National Idle Reduction Campaign helps you take action toward a cleaner, healthier environment. You are the key to reducing idling!

Why Idle Reduction Matters

Unnecessary school bus idling affects human health, pollutes the air, wastes fuel, and causes excess engine wear.

Human Health Impacts

Diesel exhaust is designated “carcinogenic to humans” by the International Agency for Research on Cancer (IARC). It contains significant levels of particulate matter (PM). These particles can lodge deep into the lungs and heart and are linked to premature death, aggravated asthma, and decreased lung function. Children are more susceptible than healthy adults because their respiratory systems are still developing and they have faster breathing rates. 

Air Pollution

Not only can diesel exhaust from idling pollute the air in and around the bus, it can also enter school buildings through air intakes, doors, and open windows. Diesel exhaust pollutants contribute to ozone pollutionacid rain, and climate change.

Myth: It’s better to leave the engine idling because restarting it produces more pollution.
Fact: Continuous idling for more than three minutes emits more PM than a restart. Emissions after a restart contain less carbon monoxide, nitrogen oxides, and other pollutants than if the school bus idled continuously over a 10-minute period.

Wasted Fue​l

Idling buses waste fuel and money.  School districts that eliminate unnecessary idling can save significantly on fuel costs each year. You can use the Diesel Emissions Quantifier (DEQ) to calculate how reducing idling will reduce your fuel costs!

Engine Wear-and-Tear

Idling does not protect the engine or help it run better.  In fact, idling a bus may cause unnecessary wear.

Myth: It's better for an engine to run at low speed (idling) than to run at regular speed.
Fact: Running an engine at low speed causes twice the wear on internal parts as driving at regular speeds.

Myth: It's important to warm up the engine with a long idle period, especially in cold weather.
Fact: School bus engines do not need to idle more than a few minutes to warm up. Engine manufacturers generally recommend no more than three to five minutes of idling.

Top of Page

What You Can Do

Everyone has a role in reducing emissions from school buses.

School Officials

One way to reduce emissions from school buses is to establish an idle reduction policy. Here is a sample School Bus Idling Policy(1 pg, 16 K) you can use as a model.

At a minimum, the policy should include the following:

  • Buses should typically be moving whenever the engine is on.
  • Engines should be turned off quickly after arriving at loading or unloading areas.
  • Buses should not be restarted until they are ready to depart.
  • Morning warm-up idling time should be limited to manufacturers' recommendations.
  • When possible, shorten commute times for children.

To MAXIMIZE the success of your idling reduction policy:

  • Review state or local idling laws to ensure your school buses are in compliance.
  • Effectively train bus drivers on idle reduction policies.
  • Spot-check bus depots, loading, unloading, and delivery areas for idling compliance.
  • Use idle reduction technologies to save fuel and help with cabin comfort and equipment operation.
  • Recognize and celebrate drivers who successfully reduce idling.
  • Work with bus companies to ensure idle reduction policies are implemented.
  • Post no-idling signs on school grounds.
  • Develop educational programs(1 pg, 18 K, March 2018) for students about air pollution.
  • Urge community leaders to issue a local Idle Reduction Proclamation(1 pg, 14 K) .
  • Share your success with other school districts, the media, and the general public by issuing a press release about your program.

School Transportation Providers

  • Implement idle reduction policies(1 pg, 21 K, March 2018) .
  • Educate drivers and give recognition to drivers who reduce idling times.
  • Discourage drivers from following directly behind other school buses or large vehicles, especially if they are emitting visible smoke.
  • Replace the oldest buses with newer, cleaner buses.
  • Take steps to retrofit existing buses with pollution controls and idle reduction devices.
  • Turn off the school bus engine while waiting for pick-up.
  • Keep buses well maintained.

Parents and Students

  • Talk with school officials and transportation providers about establishing idle reduction programs.
  • Do not idle your personal vehicle.
  • Help school officials make and post no-idling signs.

Top of Page

Idling Reduction Technologies

Idle reduction technologies reduce emissions by minimizing the amount of time an engine operates.  To learn more about these technologies, visit our Idle Reduction Technologies page.

Myth: Idling is necessary to keep the cabin comfortable.
Fact: Many buses maintain a comfortable interior temperature for a while without idling.  Fuel-Operated Heaters, also known as  Direct Fired Heaters, can be purchased and installed to keep the cabin comfortable.

Fuel-Operated Heaters can be used to warm engines and passenger compartments in colder climates.  Each block pre-heater uses only half a cup of diesel per hour compared to half a gallon or more per hour while idling. These heaters run off diesel fuel or electric outlets and include a programmable timer to automatically start or stop the heating function. Benefits of these heaters are fuel savings, lower emissions, longer oil life, less wear-and-tear on the engine, and relatively easy installation and maintenance. 

Top of Page