The problem of truck underride is generally not very well understood. That may be partly due to the fact that we expect a disastrous outcome from a collision between a large truck and a much smaller passenger vehicle.
In fact, one of the biggest problems in a crash between a large truck and a passenger vehicle is that the two vehicles are geometrically mismatched, i.e., the bottom of the truck is higher up than the hood of the passenger vehicle. So the first point of impact is not between the truck and the crush/crumple zone of the car but between the truck and the windshield of the car along with the head and upper body of the occupants of the car. This is called Passenger Compartment Intrusion (PCI) and results in horrific deaths and debilitating injuries for those who might survive.
This holds true all around the truck. Although there is currently a federal standard for rear underride guards at the back of tractor-trailers, it has been proven by the IIHS to be too weak. There is no federal standard for side guards. And there is no federal standard for protection at the front of trucks, although Europe has had a requirement for Front Underride Protection (FUP) for years. Not to mention that single unit trucks (also known as box trucks) are exempt from federal underride standards. . . and that, although there is a requirement to keep rear guards in like new condition, that is not enforced for the millions of trailers on the road today — so maintenance has not been made a priority.
Hundreds of people die each year in the U.S. because of underride which results in Passenger Compartment Intrusion. If we could prevent underride, many truck crashes would become more survivable. And technology does exist to prevent underride. We just don’t require it to be installed on trucks. As a result, hundreds of people continue to die each year — who could have survived.
These cars collided with the sides of trailers which did not have side guards:
This car collided with the side of a trailer which was equipped with an AngelWing side guard:
Big difference. Night & day. Life & death.
This car collided with the back of a trailer with a weak, ineffective rear underride guard. AnnaLeah and Mary Karth died as a result of PCI:
In contrast, in March 2017. the car below collided with the back of a trailer equipped with an improved, stronger rear guard (provided by Stoughton Trailers as standard on their new trailers at no added weight or cost penalty to their customers). The car is totaled, but there is no PCI; the driver and passenger walked away with no debilitating injuries: