Stephen A. Batzer, Ph.D, PE ::::
Case Synopsis: A young man, while driving his sedan to work, in the dark, lost control of his vehicle which then exited the curvy roadway. The vehicle impacted the sloped shoulder with its front bumper and rolled a single revolution, passenger’s side leading. The intrusion into the vehicle, by the roof, crushed the driver’s spine. He survived, but has been confined to a wheelchair.
Expert Analysis: An analysis of the roof structure showed that while the vehicle’s design was legal, its roof strength was weak and the greenhouse structure was unable to support the vehicle’s dynamic weight and preserve the occupant’s survival space. Total residual crush was measured to be 7.3” over the driver’s position, while the dynamic crush during roof inversion added 2 – 4” more. Vehicles endure strikes of magnitude two to three times their curb weight when rolling over: however, the US federal government, until recently, in no way required roofs to be strong enough to resist such impacts without hazardous deformation.
Result: The analysis showed that to be a robustly designed roof, it would have required an additional 22 lbs of steel at a cost of $37.65, which was a trivial investment in the safety of the occupants of the vehicle.
Stephen A. Batzer, Ph.D., PE, is a consultant with DJS Associates and can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.