California’s Diesel Risk Reduction Plan, adopted in 2000, calls for an 85% reduction in diesel particulate matter (PM) emissions by 2020. To achieve this goal, certification emissions standards for new heavy-duty (HD) engines have been tightened, and in-use regulations such as the Truck and Bus Rule have required existing HD trucks to be retrofit to meet these standards. To monitor the effectiveness of these efforts, CARB has supported field campaigns that measure real-world emissions from heavy-duty vehicles.
Real-world HD emissions were measured at the Port of Los Angeles and Cottonwood Weigh Station by the University of Denver. Field campaigns were conducted at each site in 2013, 2015, and 2017. Emissions were reported as fuel-based emission factors (e.g., mass pollutant per mass of fuel burned).
Main results derived
Emission factors for NO, NOX, black carbon (BC), particulate matter (PM), hydrocarbons (HC), and CO were recorded for over 7,000 trucks total during these six campaigns. These results verify that regulations aimed at reducing emissions of diesel PM from trucks have been successful in the real world. However, they also indicate that real-world emissions of NOX are greater than expected based on certification standards and other laboratory-based measurements.
Impact on CARB programs
These results will allow CARB to monitor the continued real-world performance of HD aftertreatment components such as diesel particulate filters (DPFs) and selective catalytic reduction (SCR), including any deterioration in their performance. They will also help inform CARB’s inventories of vehicular emissions, and guide enforcement activities.
Some of the data derived from these studies helped to identify gliders (i.e., new heavy-duty chassis outfitted with pre-existing engines) and quantify their emissions.