Secretary Duffy,
The Department of Transportation (DOT) engaged Elemance LLC in 2022 to evaluate three current designs of rear impact guards. Unfortunately, Elemance conducted Finite Element analysis of two obsolete rear underride guards that were not current designs at the time of the contract. In fact, both of those designs had been proven a decade earlier to be crash-deficient. The two manufacturers — Great Dane and Wabash — have developed designs with safer, stronger rear-guard designs. Elemance compounded that error by employing an erroneous definition of Passenger Compartment Intrusion. Elemance’s research findings, Heavy-Truck Rear-Impact-Guard Finite Element Simulation and Analysis, are flawed and backwards-looking rather than helpful to the Department and Congress in evaluating current and future rear underride guard performance and regulatory standards.
Please find attached a detailed critique by engineers who are well-acquainted with the underride problem and solutions. This is what the engineers concluded about the NHTSA-contracted research:
In view of the defects in the Elemance report, a follow up study should be commissioned to evaluate examples of current state of the art rear impact guards that have been in service since 2016 and 2017 respectively. The study should utilize the correct definition of PCI and more accurately assess injury risk.
The Department should act promptly to address the flaws in this federal research in order to fulfill its mission to reduce roadway injuries and deaths.
Jerry and Marianne Karth
Note: This critique was submitted as a Public Comment on September 3, 2025, to the U.S. Department of Transportation in response to their Request for Comments on priorities for the 2026 Surface Transportation Reauthorization.
This video created by the Insurance Institute for Highway Safety twelve years ago explains their Rear Impact Guard crash testing research and how the federal standard is failing to protect road users:
This video is a compilation of IIHS Rear Impact Guard crash tests with old and new guard designs for many of the major trailer manufacturers:
This video demonstrates the night & day difference between old and new designs by one manufacturer:
