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New crash tests: Underride guards on most big rigs leave passenger vehicle occupants at risk in certain crashes ' L: G4 o' o1 P$ ?( r9 ]8 i" S6 G9 e4 |1 a, L2 d" Y
Modern semitrailers for the most part do a good job of keeping passenger vehicles from sliding underneath them, greatly increasing the chances of surviving a crash into the back of a large truck, recent tests by the Insurance Institute for Highway Safety (IIHS) show. But in crashes involving only a small portion of the truck's rear, most trailers fail to prevent potentially deadly underride.