Accidents involving large trucks are often devastating due to the size difference between passenger vehicles and the trucks. There are many different risks you have for accidents relating to these trucks that you would not have with other vehicles. One such risk is an underride accident, which according to the U.S. Government Accountability Office, is when your vehicle ends up under some part of the truck. 

Underride accidents can happen at the rear, side or, in rare cases, the front of the truck. Rear accidents can happen when you do not stop in time to avoid a rear-end collision with the truck. Since it is so high off the ground, there is room for the front part of your vehicle to go under the truck. It is possible for your whole vehicle to go under the truck in some cases, depending on speed and other factors of the accident. 

Side underride accidents are just now becoming a focus of research and concern. They can occur when your vehicle goes under the truck from either side. Again, the height of the truck means it is possible for your vehicle to slide under. 

Rear accidents were quite common, but the government put regulations in place to require bars on the rear of trucks to stop them from occurring. These regulations have helped reduce this type of accident. Side underride accidents, though, are not regulated the same. There is some movement to try to require side bars on trucks that are similar to the rear bars, but there is a need for more research before government agencies will take this step.