Diesel Emissions - Mobile Equipment

Diesel Trucks

Button Sky Trim

Both on-road and off-road diesel powered vehicles and equipment are regulated by California Air Resources Board (CARB). On-road trucks greater than 14,000 lbs and off-road diesel equipment are required to meet numerical emissions limits for PM10. Offering an older diesel powered vehicle for sale within the state of California also has significant restrictions as does adding one to your fleet.

If you intend to purchase or sell a diesel powered vehicle, please notify UCSF Environmental Programs.

In 2008, CARB passed regulations that significantly restrict idling times of diesel trucks and off-road diesel vehicles. Heavy duty trucks greater than 10,000 lbs and off-road diesel vehicles consisting of tractors, trenchers, street sweepers, cranes, forklifts, or other diesel powered equipment are prohibited from idling > 5 min. Idling in excess of 5 min is allowable only under the following circumstances:

  • You are stuck in traffic.
  • When idling is necessary for inspecting, testing, repairing, or servicing your vehicle.
  • You need to verify that the vehicle is in a safe operating condition.
  • You are operating a power take-off device.
  • You cannot move because of adverse weather conditions or mechanical failure.  
  • You are queuing (must be beyond 100 feet from any residential area).
  • Your truck’s engine meets the optional NOx idling emission standard and your truck is located beyond 100 feet from any residential area.
  • You need to accomplish work for which the vehicle was designed (such as operating a crane).
  • It is necessary to bring the machine system to operating temperature.
  • It is necessary to ensure safe operation of the vehicle.


A fact sheet from CARB is available here.