UC Riverside

Brake and tire wear particulate matter (PM) represent a large fraction of road traffic pollution from vehicles. Road traffic pollution is often associated with tailpipe sources from diesel and gasoline-powered vehicles. Although this contribution has drastically decreased over the years due to the implementation of stringent regulations and technological advancements, it is not the sole source of traffic pollution. The non-tailpipe sources, brake and tire wear, generate particle emissions through abrasive wear during vehicle driving activity. These emissions are not actively regulated and are a concern to near-road communities as their contribution to traffic-related emissions has surpassed their tailpipe counterpart.This dissertation investigates the real-world characteristics of the non-tailpipe brake source during near-road environments and onboard sensing activity. Non-tailpipe sources contribute to airborne particulate matter concentrations and are reported to contain traces of heavy metals. Emitted particles that settle onto road surfaces can be mixed and resuspended with road dust. Long-term exposure to particulate air pollution is known to cause adverse health effects due to their size and chemical composition toxicity. This dissertation provides results of metal contents and size distributions of brake and tire wear particles found in ambient PM2.5 and PM10 at near-road environments for two major highways in California. Prior research efforts have focused on measurement from laboratory tests to examine non-tailpipe source emissions. Findings show that brake wear PM is dynamic and dependent on brake activity such as braking intensity, temperature, brake lining materials, vehicle weight, and vehicle vocation. Therefore, it is important to characterize brake emissions by first understanding the real-world brake activity. This dissertation investigates strategies to establish a test method and analysis for brake activity measurements of heavy-duty vehicles. The brake fluid pressure and brake pad temperature were measured for a heavy-duty vehicle using chassis dynamometer test cycles and on-road driving tests.