The Chicago City Council passed an ordinance modifying Illinois' 10-minute idle time limit to three minutes in the city for diesel-powered vehicles
. Vehicle operators who idle engines more than three minutes at a time will face a $250 fine.

The move is an effort to curb air pollution in the city. Cities such as New York, Philadelphia and Washington, D.C. have diesel engine idling limits of three minutes or less.

The ordinance does not apply to emergency vehicles; vehicles used as airport support equipment; vehicles that are running auxiliary equipment that requires the use of the vehicle; vehicles in traffic; vehicles standing for the purpose of service, repair or government inspection; vehicles standing to supply air conditioning when outdoor temperature is greater than 80 degrees; the operation of an auxiliary power unit or generator set as an alternative to running the main engine of a motor vehicle operating on diesel fuel; vehicles with mechanical requirements; and vehicles standing due to the automatic regeneration of diesel particulate filters or pre-shutdown cooling required by the engine manufacture.

For a full list of exemptions, click here.