Unnecessary engine idling can be a significant source of air pollution, particularly for people near the source. MGL Chapter 90, Section 16A states that:

No person shall cause, suffer, allow or permit the unnecessary operation of the engine of a motor vehicle while said vehicle is stopped for a foreseeable period of time in excess of five minutes.

In Boston, the Air Pollution Control Commission (APCC) has responsibility for enforcing this law. Violators are liable for $100 tickets per offense.

The APCC engages in many efforts to educate drivers and institutions about the costs of excessive idling (air pollution, engine wear, fuel waste) and the benefits of idling reduction. The City is conducting direct outreach and education to idling drivers, partnering with neighborhood and non-profit groups, and responding to citizen complaints about problem areas. (For more information, see EPA: Idling.) The City of Boston is itself engaged in an intensive effort to reduce idling in the City fleet.