Vehicle roof strength as it relates to contained occupant injury prevention during rollover crashes
This paper presents a theoretical estimate of the roof strength required to protect contained occupants during a rollover crash assuming an effective restraint system is implemented in the vehicle. To date a number of road safety advocates have suggested that a roof’s Strength-to-vehicle Weight Ratio (SWR) must be a minimum of 3.5, as measured according to the US Federal Motor Vehicle Safety Standard (FMVSS) 216 protocol, to protect contained occupants from severe or fatal injury. To date these conclusions have been based on real world crash data, statistics and crash test data. This study further validates the conclusions reached by these researchers using a purely mathematical approach that utilises Newtonian laws of physics, empirical values from rollover crash test data and the FMVSS 216 test protocol.
The mathematical derivation identifies what proportion of crash energy each component of the vehicle absorbs. The analysis considers both friction between the vehicle and the roadway and deformation of the vehicle. By identifying the energy that must be absorbed through deformation of the vehicle’s roof using the FMVSS 216 five inches (127 mm) of roof crush strength limit as a constraint, it was possible to calculate theoretically using some broad empirical assumptions generated from rollover crash test data, that a SWR of 3.6 is required to prevent serious and fatal injuries.