finite element analysis | AnnaLeah & Mary

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:

Well, on the way home from DC on Amtrak, I read Computer Modeling & Evaluation Of Side Underride Protective Device Designs — the 90-page side underride research report published in April 2018 by the Texas A&M Transportation Institute from a study they did through a NHTSA contract. Here are my preliminary thoughts. . .

From the report’s Introduction:

Use of side underride protection devices (SUPDs) has been suggested to mitigate passenger car underride during impacts with the side of a trailer. SUPDs attach to the frame of the trailer and act as a guard or a barrier to prevent the impacting passenger car from underriding the truck. However, attachment of additional weight to the truck is viewed unfavorably by some due to the related increase in fuel consumption and reduction in cargo capacity.

Past studies have looked at designing SUPDs for 90-degree impacts with passenger cars at speeds up to 50 mph (Bodapati, 2006; Galipeau-Belair, 2014). Different design impacts may result in different SUPD characteristics and weight. If the design impact conditions are
changed from 90-degree impacts to oblique impacts, it may be possible to further reduce the weight of the SUPDs, thus making them more favorable for use on heavy trucks.

[Besides hoping to get the trucking industry to agree to a lighter weight side guard — and assuming that they would get resistance to a rulemaking with a heavier guard], why would the Department of Transportation (NHTSA) commission a study of guards to prevent only oblique angle (less than 90 degrees) side impacts? Especially when there is talk of a weight exemption (with the legislation) for the underride safety equipment.

Presumably, these lighter weight guards would not stop cars impacting a truck at 90 degree angles. Yet, we know that many people have died and are dying from both 90 degree or T-bone crashes as well, like these two cases:

July 2017, First photos of I-81 crash of milk truck, 2 vehicles that killed 4
April 2018, ‘It’s tragic’: Vacationing Grosse Pointe family dies

Are we going to issue a rule that will protect people from some side underride crashes but not others — even though it is technologically and practically feasible? Really?!

What was the point of designing the study that way — as directed by NHTSA? In my opinion, that research money could have been better spent — since we already have proof that cars can be stopped in a T-bone crash at 40 mph. Like on research to prevent front underride/override or to find the outer limits of rear underride protection (are the updated rear guards as strong as they could be?) — as called for in the STOP Underrides! Bill.

In 1969, DOT planned on adding side guards to trucks after technical studies had been completed. Well, they’ve been completed. We’ve been waiting almost 50 years. Will they act now?

Let’s get the Committee On Underride Protection (COUP) established immediately — as called for in the STOP Underrides! Bill. Let’s get engineers, along with an interdisciplinary team, talking together and collaboratively communicating to inform effective actions. Daylight’s burning!