Many motor vehicle occupants are at increased risk of injury due to physical differences that affect their interaction with the vehicle interior and restraints as well as their response and tolerance to crash loading. Older occupants may sustain more severe injuries due to weaker bones and calcified tissues. Occupant shape, which is associated with body mass index, can lead to suboptimal restraint fit. Vulnerable occupant research is underway to identify the unique challenges of protecting all motor vehicle occupants: