Not sure anyone could answer that question as it is, or probably at all with any accuracy.
Surely it depends from which angle you get hit, whether you're talking about lap belts (which Im guessing you are?) & what speed the vehicles are travelling.
Lap belts in themselves can cause horrendous injuries & I took the bench out of my truck as soon as I bought it as I wouldn't sit anyone I cared about on one.
Any help?