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IIHS Testing of Tractor Trailer Rear Underride Guard Systems

In 2011, the Insurance Institute for Highway Safety (IIHS) tested the rear underride guard systems of tractor trailers.  Rear underride guards are metal bumpers that hang down from the back of a tractor trailer. Their purpose is to prevent a smaller vehicle from sliding underneath the tractor-trailer which can result in the vehicle’s roof shearing off.  The 2011 tests from IIHS found that having a strong, supportive underride guard on the rear of a tractor trailer was effective in keeping a smaller vehicle from sliding underneath in a rear-end crash.   

Currently, federal law requires large trucks to have rear underride guards.  Despite this mandate, IIHS studies have shown that rear guards that meet the federal safety standards could still buckle or break off in a crash.  After the IIHS conducted its first tests of rear underride guards in 2011 with 3 semis, the president of IIHS stated, “[i]f there had been real-world crashes, there would be no survivors.”

In 2013, the IIHS tested rear underride guards of 8 manufacturers which represented 80% of the heavy truck market. Only 1 passed all 3 IIHS rear underride tests.

In 2015, 292 passenger vehicle occupants were killed when their vehicle struck the rear of a tractor-trailer.  The IIHS estimates that roughly half of these incidents involved underride.

In 2017, the same IIHS rear underride guard tests from 2013 were conducted and 5 of the 8 largest manufacturers now passed all 3 IIHS tests.

While several manufacturers have demonstrated improved safety performance of their rear underride guard systems, federal safety standards governing underride guards have stayed the same.  Without federal safety laws taking the underride guard issue seriously, stringent safety standards will not be implemented across the board which jeopardizes the safety of the public.

Brian Custy