The Insurance Institute for Highway Safety (IIHS) recently published results of crash tests with and without semitrailer side underride guards.  According to the IIHS, strong underride guards on the rear of tractor-trailers have proven effective in preventing underride in crash tests. The new IIHS tests show how a well-built guard can prevent a passenger vehicle from sliding beneath the side of a semitrailer.

The Institute ran identical cars into the sides of semi-trailers both with and without side underride guards. The car hitting the trailer equipped with the guards stopped before the trailer floor could intrude into the passenger compartment. The car hitting the trailer having just an aerodynamic skirt beneath its side slid under the trailer, peeling back the roof to a point over the rear door.

The Institute has been testing rear underride guards for several years and the latest tests illustrate the importance of countermeasures to prevent side underride crashes.  IIHS reported that the car hitting the underride guard-equipped trailer was able to properly restrain and protect the driver dummy with its safety systems. Any occupants of the car that slid under the trailer without a side underride guard would likely have sustained fatal injuries, according to IIHS.

Over the years, the Institute has successfully been encouraging trailer manufacturers to improve underride guards. IIHS recently announced the first winners of the new TOUGHGUARD award, recognizing rear underride guards designed to prevent underride in a range of crashes into the backs of tractor-trailers.

IIHS has been tracking passenger vehicle occupant deaths in crashes with tractor-trailers over an 11-year period. Side underride deaths has estimated that side underride accidents occur in about half of the fatal crashes between large trucks and passenger vehicles.

“Our tests and research show that side underride guards have the potential to save lives,” says David Zuby, the Institute’s Executive Vice President and Chief Research Officer. “We think a mandate for side underride guards on large trucks has merit, especially as crash deaths continue to rise on our roads.”

In 2014, the National Transportation Safety Board recommended that: “The NTSB concludes that passenger vehicle occupant deaths and injuries resulting from side underride collisions with tractor-trailers could be reduced by side underride protection systems. The NTSB recommends that NHTSA require that newly manufactured trailers with GVWRs over 10,000 pounds be equipped with side underride protection systems that will reduce underride and injuries to passenger vehicle occupants.”


Insurance Institute for Highway Safety (IIHS)

AngelWing Side Underride Protection System

National Transportation Safety Board Recommendations

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