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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

CMVRTC: Continued Analysis of PBBT Brake Performance Evaluation Data


To continue gathering Level 1 brake performance stroke measurements and correlate those stroke measurements with performance-based brake tester (PBBT) brake force measurements on each wheel end and for the total vehicle.


Currently the PBBT device can be used to determine the overall vehicle brake performance of commercial motor vehicles (CMVs). States currently utilizing a PBBT have expressed concern that some cargo-carrying CMVs when tested on the PBBT can barely pass the minimum overall vehicle performance criteria of 43.5 percent brake efficiency, and many times have several individual wheel-ends with values significantly below the 43.5 percent brake efficiency value. CMV stopping distance testing conducted by the Oak Ridge National Laboratory (ORNL) has shown that the effect on stopping distance is significant when specific wheel ends have very low or no measurable brake performance.


In this project, researchers will continue to collect Level 1 brake performance stroke measurements and correlate those stroke measurements with PBBT brake force measurements on each wheel end, and for the total vehicle. ORNL will continue to analyze data to correlate brake stroke length measurements with PBBT wheel-end brake force values. These data will be used to support future rulemaking efforts to develop a CMV PBBT brake performance individual wheel end criteria and a revised overall vehicle brake performance measurement.


Analysis of brake inspection data; identification of additional data/data analysis needs; briefing for the Commercial Vehicle Safety Alliance (CVSA) PBBT Users Group Meeting; letter report on findings.



October 2017: Kick-off meeting.
January 2018: Literature review of PBBT and CMV brake performance testing complete.
February 2019: Draft guidance document complete.
April 2019: Final briefing.
May 2019: Final report complete.


FY17 Funding: $75,000

Project Manager:

For more information, contact Chris Flanigan of the Technology Division at 202-385-2384 or


Oak Ridge National Laboratory
Last updated: Friday, May 31, 2019