There was once something just a little romantic, in the early years of trucking, about the roar of a diesel engine starting up, the cloud of black smoke pumping out of the chromed exhaust stack, and the steady rumble as the engine settled in to work. Those days are gone, however, disappearing with the tree-lined country roads along which such trucks used to travel.

Now, most people see red, not stars, when they look at an idling diesel truck — and a regulatory mood is stealing over the congested landscape.

Vehicle noise is already regulated almost everywhere as a public nuisance. Eleven states and two Canadian provinces also have smoke emissions statutes on the books, and three more states have smoke regulations under development. Statewide anti-idling laws are generally spreading east to west, with ten states limiting idling statewide and another eight with local idling limits also in place.

Federal clean air guidelines underpin these state and local restrictions, putting nonattainment states at risk of losing federal funding if they don't, literally, clean up their acts — and soon.

“What we are finding is that, in order to meet EPA requirements, states are searching for overlooked opportunities to reduce emissions,” says Terry Levinson, environmental systems scientist for the Energy Systems Division, Center for Transportation Research, Argonne National Laboratory.

“This means attention is finally falling on mobile sources of pollution, such as commercial trucks,” she adds. It is clear that trucks will bear a greater part of the clean air burden in the future.”

Here's a brief summary of the idling and smoke emissions regulations already in place. Virtually every state and municipality regulates vehicle noise, so noise limits are not listed here.

Alabama — Prohibits the emission of “visible air contaminants from diesel-powered motor vehicles or other movable sources” of a shade or density greater than 20% opacity for longer than five consecutive seconds.

Arizona — Regulates smoke emissions.

California — Regulates idling and smoke emissions statewide. Idling limit is five minutes.

Colorado — Regulates smoke emissions statewide. Idling restrictions are also in place within Denver, Aspen and Colorado Springs.

Connecticut — Restricts visible air pollution from vehicles, effectively limiting truck idling to five minutes per hour. There are certain allowances for PTOs and for engine heating at temperatures below 20 deg. F.

District of Columbia — Limits truck idling to three minutes, unless vehicle is powering PTO or ambient temperature is below 32 deg. F.

Hawaii — Idling is prohibited statewide, including for powering A/C. There are some specific exemptions.

Georgia — Idling restrictions are in place for Atlanta.

Illinois — Idling is prohibited on business streets statewide for longer periods than are necessary to load/unload.

Maryland — Idling is generally limited statewide to five minutes, with exemptions for operation of heating or cooling equipment or other specific purposes.

Massachusetts — Idling is limited statewide to three minutes, with some exceptions. There is a $100 fine for the first offense and a $500 fine for each subsequent offense. Noise and smoke emissions are also regulated statewide. The City of Boston actively enforces the anti-idling restrictions with a dedicated enforcement team.

Minnesota — The City of Owatonna limits idling on residential streets.

Missouri — The City of St. Louis limits truck idling to ten minutes. There is a $500 fine for violations and the possibility of imprisonment.

Montana — The City of Helena limits idling to two hours.

New Hampshire — Idling is limited statewide to five minutes if the ambient temperature is above 32 deg. F. Limits are extended to 15 minutes when the ambient temperature is between -10 deg. and +32 deg. F. Unlimited idling is permitted if the temperature is below -10 deg. F. “where no nuisance is created.”

Nevada — Limits idling statewide to 15 minutes except for emergency vehicles, for vehicles in traffic congestion, while vehicles are being repaired or for operation of certain specified equipment. Regulates smoke emissions statewide.

New Jersey — Idling of diesel- or gasoline-powered trucks is limited statewide to three minutes unless the vehicle is at the operator's place of business. If a vehicle has been stopped for more than three consecutive hours, idling is limited to 15 consecutive minutes. There are specific exemptions, including for the operation of refrigerator units and PTOs and for truck sleepers in non-residential areas if the driver is sleeping or resting.

New Mexico — Regulates smoke emissions statewide, specifically including emissions during idling. Smoke opacity is limited to 30% for no more than ten seconds at altitudes of less than 8,000 ft., or 40% when vehicle is being started.

New York — Limits diesel truck idling statewide to five minutes, with exemptions for powering certain auxiliary equipment such as PTOs or cranes or if a truck is motionless for more than two hours and the ambient temperature is below 25 deg. F. Within New York City, idling is limited to three minutes, and anti-idling laws are enforced.

Pennsylvania — Limits diesel truck idling within the City of Philadelphia to two minutes. Trucks may idle for up to five minutes when the ambient temperature is below 32 deg. F. and for up to 20 minutes when the temperature is less than 20 deg. F.

Rhode Island — Regulates smoke emissions statewide.

Texas — Has local idling limits for diesel trucks in several cities, including Houston and Dallas. Idling is also prohibited for more than five minutes during the months of April through October in eight counties in the Houston-Galveston area. There are some exemptions, but not for truck idling to provide heating or cooling to the cab/sleeper.

Utah — Regulates smoke emissions statewide.

Virginia — Limits idling to three minutes in commercial and residential areas, unless it is to provide power for devices other than for heating or cooling the driver. Diesels may idle up to ten minutes to minimize restart problems.

Washington — Regulates smoke emissions statewide.

British Columbia — Regulates smoke emissions province-wide.

Ontario — Regulates smoke emissions province-wide.