A new study published by the Insurance Institute for Highway Safety found that while most semitrailers are doing their part in trying to keep cars from sliding underneath them during a crash, most of them fail to prevent deadly underride.
Underride crashes occur when a vehicle collides with the rear or side of a semi-truck trailer. The force of impact during the crash as well as the weight of the trailer have the capability to crush or shear off the roof of a car. When the occupant compartment is crushed, safety apparatuses like airbags and seat belts tend to fail. Individuals involved in these types of accidents usually suffer serious and often fatal head and torso injuries, as well as decapitation.
Most modern semitrailers are required to have underride guards (steel bars that hang below the back of trailers) to prevent vehicles from sliding beneath them. Their purpose is to ultimately decrease the amount of vehicular damage and increase the chances of survival during an accident. Many tractor trailer manufacturers now produce trailers with underride guards that are stronger and larger than what is required by law, to maximize their effectiveness in the event of an accident.