California Air Resources Board

Principal Investigator/Author: Georgios Karavalakis

Contractor: University of California, Riverside

Contract number: 23RD008

Project Status: Active

Relevant CARB programs: Mobile Source Emissions

Topic areas: Non-Exhaust Emissions

Research Summary:

As stricter regulations have substantially reduced exhaust emissions over time, there has been a shift in the significance of non-exhaust emissions (brake-wear, tire-wear, road dust resuspension) on near-road exposure and regional air quality. Tire rubber contains diverse mixtures of organic compounds, making tire-wear emissions particularly complex. These emissions are currently not well characterized compared to other non-exhaust emissions. Additionally, existing tire-wear research has focused on particulate matter (PM) emissions, leaving gaseous emissions less understood. This project will characterize gaseous emissions from tire wear of on-road vehicles, estimate their secondary PM formation potentials, and understand their impact on air quality and nearby communities. Real-world measurements of tire-wear gases from on-road vehicles will be conducted and offline chemical analysis will be performed to establish the emission factors and chemical profiles of tire-wear gaseous emissions. Results from this project can be used to inform emission inventories, air quality planning, and assess the potential health impacts on nearby communities. 

The University of California, Riverside (UCR) team will design an on-road test method to measure real-time tire-wear gaseous emissions from a California representative light-duty vehicle (LDV) equipped with California representative tires. They will aim to use a high-sales volume light-duty truck (such as a Ford F150 or a Chevrolet Silverado) or a special utility vehicle (SUV), which will provide ample space to install sampling media and instrumentation. The test vehicle will be operated on different routes in the South Coast Air Basin with different characteristics, including topology, road and pavement conditions, and traffic. For this project, two sets of tires (i.e., new tires vs. old tires) will be tested for gaseous tire-wear emissions.

Keywords: non-exhaust emissions, brake wear emissions, tire wear emissions, road exposure, particulate matter (PM), PM emissions, on-road vehicles, secondary PM formation, nearby communities, emission factor, emission inventories, real-world emissions, light-duty truck, SUV, South Coast Air Basin