The unnecessary idling of vehicles, particularly those with diesel engines, contributes significantly to dangerous air pollutants, including polycyclic aromatic hydrocarbons (PAHs) and fine particulate matter. Vehicle exhaust contains many known carcinogens, asthmagens, endocrine disruptors and neurotoxins. These toxins affect everyone, especially children, pregnant women, the elderly or those with compromised health.
As a result, "No-Idling" ordinances are popping up all over the country as local municipalities seek to improve air quality. Many are also adopting zero-tolerance idling policies for town-owned vehicles.
A No-Idling sign in Burlington, VT
Here is a sample policy:
"No vehicle owned by or operated for the benefit of the town (village, city) of _____, other than an authorized emergency motor vehicle, shall be permitted to idle unless the engine is used to operate a loading, unloading or processing device, or when the ambient temperature is below freezing, or when federal, state or local agency regulations require the maintenance of a specific temperature for passenger comfort."
As part of its master plan, the City of Lebanon, NH has posted signs throughout the city to alert drivers to New Hampshire’s law regarding the idling of vehicles.
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 Sarwar, H. S., et al. (2017). Engine Idling: A Major Cause of CO Emissions & Increased Fuel Cost. International Journal of Operations and Logistics Management, 6(2), 44-55
 Huang, L., et al. (2015). Effects of fuels, engine load and exhaust after-treatment on diesel engine SVOC emissions and development of SVOC profiles for receptor modeling. Atmospheric Environment, 102, 228-238.
 Beland, F. A., et al. (2012). Nitroarenes: Occurrence, metabolism, and biological impact. New York, NY: Springer Science & Business Media.
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 Gonzalez, E., et al. (2009). Idling cars, buses damage environment, violate law (Rep.). Princeton, NJ: Princeton University, 1-3.
To encourage residents of Colorado to reduce vehicle idling, Engines Off! was created as a collaborative effort by multiple governments.
Here is a very simple brochure from the city of Fort Collins, CO regarding the health effects of engine idling.