California Air Resources Board

CARB will host a seminar on a research study measuring heavy-duty vehicle emissions at the Caldecott Tunnel in Oakland, California. The seminar will cover the emissions benefits of the Truck and Bus Regulation and examine vehicle age-related changes in the performance of exhaust after-treatment control systems.

Background

Heavy-duty (HD) diesel vehicles emit pollutants like oxides of nitrogen (NO_X) and black carbon (BC), which degrade air quality and pose health risks. Starting January 2023, California’s Truck and Bus Rule mandates that most trucks and buses must be equipped with engines from the year 2010 or newer that comply with more stringent emission standards. To meet these requirements, most HD trucks in California are outfitted with emission control technologies like Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR) systems. Monitoring truck emissions helps examine the emission reductions achieved by having more stringent standards. Monitoring at the same site every year can show how emission control systems deteriorate over time, meaning that as a truck ages, it tends to emit more.

Researchers at the University of California, Berkeley (UCB) measured emissions from HD trucks using a plume capture system at the Caldecott Tunnel in Oakland, California. This system collects part of the exhaust gas as trucks pass by and analyzes the emissions for pollutants such as NO_X, BC, nitrous oxides (N₂O), and ammonia (NH₃). It also reads trucks’ license plates to identify their engine model year and emissions control technologies.  The research team collected samples from 1,000 trucks every year over three months between 2021 to 2023. The results provide valuable insights into emission trends based on vehicle age and aftertreatment control technologies.