Colorado

Idle Reduction Requirement - Denver

Idling of any vehicle for more than 10 minutes in any one-hour period is prohibited within the city and county of Denver. Exemptions apply for the following: when ambient outside air temperatures have been less than 20 degrees Fahrenheit for the previous 24 hours; current ambient outside air temperature are less than 10 degrees Fahrenheit. This requirement does not apply to emergency vehicles, vehicles engaged in traffic operations, vehicles being serviced, vehicles that must idle to operate auxiliary equipment, and vehicles that are idle due to traffic congestion. (Reference Revised Municipal Code, City and County of Denver, Section 4-43)

Idle Reduction Requirement - Aspen

Idling of any vehicle for more than five minutes within any one-hour period is prohibited in the City of Aspen. Exemptions apply for safety reasons and to maintain specified engine temperatures. Violators are subject to a penalty of up to $1,000 and/or one year imprisonment. (Reference City of Aspen Municipal Code 13.08.110)