Robo Mcduff is indeed correct. And Robo don't forget the sideprotection bars to prevent bikeriders to go under the truck as well
But below is a segment of the european rules for the under-ride protection, just for reference. Not sure if the same rules applies for the US or not but I would suggest people checked to prevent a little slip from their LEO's
Protection from underriding at the rear, also referred to as under-ride bumper, requirements as stated in the detailed regulations for vehicles:
In case of a fixed bed, the general rules are:
a) to provide protection against under the rear collisions with smaller vehicles
b) shall be located no more than 0.55 m above the ground (measured from the lower edge of the curb weight with any bogie lift lowered)
c) shall be located no more than 0.40 meters from the rearmost point on the vehicle,
d) must not be wider than the rear axle, measured from the outer sides of the wheel rims (excluding the bulging of the tire just above the ground), or be more than 0.10 meters shorter on each side, and
e) must have a minimum height of 0, 10 m
It might seem as a set of stupid rules, but one of the images I added begs to differ
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
. Obviously if people would just keep the proper distance while driving and keep their eyes on the road a lot of these accidents could be prevented, but sadly I don't think that is going to happen.