Development of brake activity measurement method for heavy-duty vehicles

ABSTRACT

Tailpipe PM (particulate matter) emissions have been reduced due to decades of tightening regulations, however non-tailpipe PM emissions are not regulated and are expected to become a significant source of traffic-related PM emissions. Previous studies have focused on emission measurement from laboratory and track tests. Their findings suggest brake wear PM emission rates are dependent on brake activity. Therefore, it is important to characterize brake emissions by first understanding the real-world brake activity from many different vehicle vocations and driving conditions. The goal of the current study is to establish a test method and analysis for brake activity measurements of heavy-duty vehicles. In this study, brake fluid pressure and brake pad temperature were measured for a heavy-duty vehicle during chassis and on-road driving tests. The chassis tests consisted of the Central Business District (CBD) cycle representative of a repetitive stop-and-go driving pattern of a bus, and the Urban Dynamometer Driving Schedule (UDDS) cycle representative of urban driving conditions of heavy-duty vehicles. The on-road tests consisted of a local Riverside City route focused on urban roads at low vehicle speeds with frequent braking, while the second route from Riverside City to Victorville focused on highway driving and downhill braking. The brake pad temperature of the triplicate CBD cycle gradually increased linearly with a slope of 2.3°C/min and the temperature per kinetic energy lost during braking increased by 2.3 × 10⁻⁵°C/J for the CBD cycle. The UDDS cycles had the largest kinetic energy loss between 3.2 × 10³ to 3.0 × 10⁵ J in the histogram. The local Riverside city route brake temperature increased by 2.0°C/min. The kinetic energy loss for the on-road tests were one order of magnitude larger than that of the dynamometer tests due to brake events occurring under higher speeds.

Implications: The non-tailpipe source contributions to traffic related particulate matter (PM) emissions have surpassed that of tailpipe emissions. The results of this work provide a measurement method to obtain brake activity information for a heavy-duty vehicle, which is critical estimating emission inventory accurately.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data used in this study is available and can be downloaded at the following repository: https://doi.org/10.6086/D14H5C

Author contribution

Jung and Johnson designed the test. Lopez conducted test and all authors contributed to the manuscript. We are grateful to John Koupal sharing data from the final report of their brake emission testing project.

Supplementary material

Supplemental data for this paper can be accessed online at https://doi.org/10.1080/10962247.2023.2205367

Additional information

Funding

National Center for Sustainable Transportation supported the study.

Notes on contributors

Brenda Lopez

Brenda Lopez is a graduate at the University of California Riverside.

Kent Johnson

Kent Johnson is a research faculty at the University of California Riverside.

Heejung Jung

Heejung Jung is a professor at the University of California Riverside.