National Center for Sustainable Transportation

Studies have shown that long-term exposure to ambient air pollution endangers human health. Regulations targeting internal combustion engines have proven effective in reducing their particulate matter (PM) emissions over the years. However, PM from non-tailpipe sources such as brake and tire wear are not currently regulated and are expected to eventually become the dominant source of traffic-related PM emissions. Although studies have produced a greater understanding of brake wear, laboratory tests are an imperfect substitute for real-world activity. Therefore, it is necessary to investigate brake activity for diverse vehicle classes and sizes under in-use conditions.

Researchers at the University of California, Riverside aimed to establish a test method to determine brake activity of a heavy-duty vehicle under both dynamometer tests and on-road tests. The results advance the research methodology, ultimately contributing to a more accurate determination of brake activity and informing efforts to improve non-tailpipe PM emissions inventories. This policy brief summarizes the key findings from that research.

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