Back in 2008, the California Air Resources Board (CARB) passed a law that made it illegal to idle your new diesel powered truck, if it had a gross vehicle weight rating of more than 14,000 lbs, for more than five minutes.
This basically means most chassis cabs and trucks with more than a 1 ton capacity, think Ram chassis cabs (like the one shown above), Ford’s F-450 Super Duty, as well as class 6 and 7 rigs, vehicles most often used in delivery and construction.
Traditionally, most trucks used for such tasks were often found idling for extended periods, primarily for convenience, such as frequent stop/start driving or powering accessories, such as refrigerators and heavy equipment.
However, an engine tends to be at it’s least efficient when idling, as well as producing the greatest amount of oxides of nitrogen (smog). The CARB ruling required that in order to certify diesel trucks for California, automakers had to meet an idle emissions standard of 30 grams of NOx per hour.
One way of doing this is by injecting urea into the exhaust stream and employing a special catalytic converter, to convert it into nitrogen and water vapor, as employed on Dodge’s 4500 and 5500 chassis cabs. As a result, these trucks and others that meet the idle test standard, receive special Exemption Stickers, meaning they can now idle indefinitely.