California Air Resources Board

CARB staff estimated Truck and Bus regulation compliance rates for all heavy vehicles with a gross vehicle weight rating (GVWR) greater than 26,000 pounds and lighter vehicles with a GVWR of 14,001 to 26,000 pounds. To calculate the compliance rate for heavy and light trucks, staff first looked at three types of vehicle registration: (1) vehicles registered with DMV, (2) vehicles registered with the International Registration Plan (IRP) that are based in California, and (3) vehicles registered with IRP that are based in all other states. IRP is a registration reciprocity agreement between the contiguous United States and Canadian provinces, which provides apportioned payments of registration fees based on the total distance operated in participating jurisdictions to them. CARB obtains data on vehicles registered with California DMV quarterly, and on vehicles registered with IRP every month. The vehicle registration data includes the make and model of the vehicle, the vehicle model year, and information about the registered owner of each vehicle.

For vehicles registered with California DMV, staff used Accuzip software to standardize the address of each registered owner. Standardized addresses allows for the grouping of vehicles by registration address in order to determine fleet size. Once vehicles were grouped by address, fleet size was determined by counting the number of vehicles registered to a particular address.

Within each fleet, staff identified all heavy and light vehicles based on the schedule below. In general, vehicles are equipped with an engine that is one year older than the chassis model year. For example, a 2007 model year chassis is most likely equipped with a 2006 model year engine. All heavy vehicles must be equipped with a diesel particulate filter per the schedule below, or be reported into CARB’s Truck Regulation Upload, Compliance and Reporting System (TRUCRS) to use a flexibility option or exemption. All light vehicles must be replaced with newer trucks per the schedule below, or be reported in TRUCRS to use a flexibility option or exemption. The vehicle identification numbers (VIN) of any potentially noncompliant vehicles were cross-referenced with TRUCRS to determine whether that vehicle was reported compliant. For vehicles registered with IRP that are based in a state other than California, staff also identified all potentially noncompliant heavy and light vehicles and cross-referenced their VINs with TRUCRS to determine whether that vehicle was reported compliant. By January 1, 2023 all trucks and buses must have 2010 model year engines, with few exceptions.  For more information, visit CARB's Truck and Bus Regulation website.

The tables below summarize, by vehicle registration type, vehicle counts per engine model year group corresponding to the Engine Model Year Compliance Schedule. Once the noncompliant vehicles were identified, staff compared these numbers with the overall population of vehicles to arrive at various compliance rates depending on fleet size and registration type. These results are also summarized below and show a range of compliance from 71 to 100%.