Idle (engine)

Idling refers to running a vehicle's engine when the vehicle is not in motion. This commonly occurs when drivers are stopped at a red light, waiting while parked outside a business or residence, or otherwise stationary with the engine running. When idling, the engine runs without any loads except the engine accessories.

Both running an engine and idling an engine produce several pollutants that are monitored by the Environmental Protection Agency (EPA):

These health effects are more damaging in those with preexisting heart disease, asthma, or other lung problems. Children are also more susceptible, due to their faster breathing rate and the fact that their respratory system is still developing. Idling pollutants also disproportionately affect the elderly, who have limited physiological reserve to compensate for the adverse effects of the pollutants.

Effort has been made to reduce the amount of time engines spend idling, chiefly due to fuel economy and emissions concerns, although some engines can also be damaged if kept idling for extended periods. In the United States, about a billion gallons (3.8 billion liters) of fuel is consumed by idling heavy-duty truck and locomotive engines each year. Many newer semi-trucks have small auxiliary power units (APUs) to run accessories more efficiently while the truck is parked. Hybrid vehicles typically shut down their internal combustion engines while stopped, although some conventional vehicles are also including start-stop systems to shut off the engine when it would otherwise idle.

At the macro level, governments can implement strategies to reduce reliance on motorised transport, including investing in public transport and implementing transit-oriented development.

The city of Toronto enacted the first idling bylaw (No. 673-1998 Chapter 517 in the Municipal Code) in Canada in 1996 to reduced idle time to 3 minutes for vehicles and marine vessels. There are plans by the health department to ask the bylaw to be amended to a limit of one minute and no exemptions to the city's fleet, including the Toronto Transit Commission buses.

Other Canadian municipalities have followed Toronto's lead:

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