Does unbelted safety requirement affect protection for belted occupants?

Area of Science:

• Automotive safety engineering
• Biomechanics
• Vehicle restraint systems

Background:

• Current US federal regulations mandate occupant performance testing with unbelted dummies.
• Eliminating unbelted occupant requirements could shift focus to optimizing restraints for belted occupants, potentially enabling seat belt interlocks.

Purpose of the Study:

• To compare the performance of vehicle restraint systems optimized for belted occupants only versus those optimized for both belted and unbelted occupants.
• To evaluate the impact of removing unbelted occupant test requirements on overall occupant safety.

Main Methods:

• Utilized two validated finite element (FE) vehicle/occupant models (midsize sedan and SUV).
• Conducted restraint design optimizations using Hybrid III anthropomorphic test devices (ATDs) under standardized crash conditions (U.S.-NCAP, FMVSS 208).
• Performed 1,760 FE simulations for field performance evaluation across 55 frontal crash conditions and analyzed NASS-CDS data (2002-2012) for injury risk assessment.

Main Results:

• Optimal restraint design parameters were largely unaffected by unbelted requirements, except for the SUV passenger side.
• Restraints optimized without unbelted requirements showed similar or lower total injury risks for belted occupants.
• However, removing unbelted requirements could potentially increase injury risks for unbelted occupants.

Conclusions:

• Eliminating unbelted occupant test requirements shows potential for reducing injury risks among belted occupants.
• Further research is needed to validate these findings and fully understand the implications for overall vehicle safety.