6 S% y: \# L9 K @# |: l7 o( v" o + V$ x8 n: f9 ~New crash tests: Underride guards on most big rigs leave passenger vehicle occupants at risk in certain crashes' c! q. L9 F+ \# ]; s& y0 n, N/ Z9 K
+ M( ^: n$ @! k1 v, \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.