California Air Resources Board

Principal Investigator/Author: Thomas Kirchstetter

Contractor: University of California, Berkeley

Contract number: 20RD004

Project Status: Active

Relevant CARB programs: Diesel Vehicles, Heavy-Duty Low NOx, Mobile Source Emissions Research Program  

Topic areas: Air Pollution, On-Road Heavy-Duty Vehicles, Research

Research Summary:

Measurements of real-world emissions from heavy-duty vehicles (HDVs) are needed to inform the development of emissions inventories, estimate the emissions benefits of policies that target the on-road heavy-duty fleet, better characterize the relatively small percentage of HDV "high-emitters", and to evaluate the deterioration and failure rates of HD aftertreatment, specifically diesel particulate filters and Selective Catalytic Reduction. This project will involve three field campaigns at the Caldecott tunnel in 2021, 2022, and 2023, each of which will measure fuel-based emission factors from at least 1,000 HDVs and match these to license plates. Results will include fuel-specific emission factors for black carbon (BC), nitric oxide (NO), nitrogen dioxide (NO2), ammonia (NH3), and nitrous oxide (N2O) for each vehicle. They will also include analysis of the impact of vehicle attributes (age, aftertreatment, etc.), new regulations, and other variables on these emissions. This project will allow estimation of the benefits of the full Truck and Bus Rule and inform both emissions inventories and the development of a Heavy-Duty Inspection and Maintenance program.

Keywords: high emitters; diesel particulate filters; selective catalytic reduction; deterioration and failure rates of aftertreatment system; heavy-duty vehicles; long-term trends in NOx and BC emissions; plume capture measurements.