Every day, American drivers share the highways with tractor trailers.
A new report finds that while the odds of surviving a crash into the back of one of those trucks have improved, certain collisions are still more deadly than others.
So-called "underride" incidents can leave a car's occupants susceptible to severe head and neck injuries - even death - when the top of the car is crushed.
New crash tests of eight types of semitrailers by the Insurance Institute for Highway Safety found that most underride guards - those steel bars that hang from the backs of trailers - do a decent job of preventing passenger cars from sliding underneath in the event of a crash.
Still IIHS testing found that a certain type of crash -- crashes that involved the outer edge of those trailers -- could put passengers in greater danger.
The typical underride guard is suspended from two vertical components hanging relatively near the center of the truck. That means that the part of the guard that sticks out toward the ends of the truck, doesn't have a lot of support.
The good news for drivers: Many trailer manufacturers have been installing underride guards that are even stronger than US guidelines require.
The number of passengers killed in accidents where the front of a vehicle strike the rear of a truck has dropped over the last decade though data doesn't track how many of these crashes specifically involved underride.