text: Silly me - when I first starting seeing the side guards a few years ago, I thought they were for aerodynamic purposes ...
  A good idea, mandating them, but they don't look as if they are substantial enough to stop a car moving at highway speeds from going under a jack-knifed truck - I thought they were designed to push cars away from the rear trailer wheels in the event of an accident where both vehicles are traveling roughly in the same direction ...