I wear my seatbelt in back whenever it's possible. Just take a minute or two and look at the pictures of EMS crashes. It's common for the medic in back to die, often because of non-existent or ineffective restraints.
The chances of an EMT being injured in a car accident far exceed the chances of an injury from an assault. I even read one article in JEMS that suggested EMTs wear light body armor (bullet resistant vests) not only for protection from an assault, but even more importantly as protection from a crash.
We can develop a vest that will be bullet proof and work for MVC's.
If you look at the vests that bullriders wear, they are designed to diffuse the force upon impact. Trust me they do work and have saved many of serious injuries.
We just have to make a hybrid of the two!