Stoughton Trailers LLC is the first trailer manufacturer to earn the Insurance Institute for Highway Safety’s Toughguard award for an intermodal container chassis, IIHS reported June 12. The award applies to Stoughton’s 53-ft intermodal container chassis built after April 2025.
“We’re excited about the commitment that Stoughton has shown to preventing underride crashes,” said IIHS President David Harkey.
The Toughguard award is presented to trailers that meet the most rigorous safety standards for rear underride protection in the event of a rear-end collision. Stoughton Trailers previously earned the award for its dry van and refrigerated trailer product lines in 2017.
“The safety of the motoring public is a top priority for Stoughton,” said Scott Lubenow, senior director of product engineering and R&D at Stoughton Trailers. “We’re proud to become the first trailer manufacturer to achieve the Toughguard award on an intermodal chassis, another example of how our team remains driven to ensure that our trailer products provide superior protection against underride crashes.”
Underride guards that meet IIHS’s Toughguard criteria significantly improve safety. Until now, only dry van, refrigerated and flatbed trailers have met these more rigorous standards. However, with the growing role of shipping containers in global trade, an increasing amount of freight is being moved using these chassis.
The National Highway Traffic Safety Administration (NHTSA) updated federal regulations governing rear underride protection on large trucks in June 2022. However, the new rule remains far less stringent than the Toughguard requirements and is not expected to push manufacturers to improve, IIHS suggested.
“A major weakness of the federal regulation is that in the required test, the underride guard is bolted to a universal testing rig instead of an actual trailer,” IIHS Senior Test Coordinator Sean O’Malley said. “When we were developing the Toughguard program, we found that many underride guards that survived testing attached to NHTSA’s rig broke off when attached to the trailer they were built to be used on, either because the attachment points on the trailer failed or the bolts did.”
In contrast, IIHS evaluates underride guards on the trailers they are designed for.
In the IIHS test, a midsize car crashes into the back of the parked trailer at 35 mph in three configurations, hitting the trailer with its full width, a 50% overlap and a 30% overlap. To earn the IIHS award, the guard must prevent underride in all three configurations. The 30% overlap configuration — which was left out of the new federal requirements — is the most challenging, because only the corner of the underride guard must absorb all the force of the impact.
Design challenges
Designing an underride guard for an intermodal chassis that meets Toughguard requirements presents unique engineering challenges, the Stoughton release noted. Unlike dry van, refrigerated or flatbed trailers—whose frames run the full width to support the guard—intermodal chassis have a narrower, more limited structure.
An intermodal chassis is a ladder-like framework positioned between the trailer’s wheels to support a removable container. Because it lacks the continuous structural frame found in other trailer types, designing an underride guard required an entirely new approach. Rather than using vertical supports attached to a trailer deck, the new guard features long, angled supports that extend from the outer edges of the guard to the chassis rails, providing the necessary strength and stability.
Stoughton’s intermodal chassis product line is supported by three dedicated manufacturing lines in Stoughton and Evansville, Wisconsin, and Waco, Texas. The company is one of the largest chassis manufacturers in North America.