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Rear Seat Occupant Packaging &

Restraint Design & Analysis


Rear Seat Occupant Protection has been neglected throughout the regulated history of Automotive Safety in the United States, as emphasized by the recent United States Supreme Court in the Williamson v Mazda, U.S. Sup. Ct. 08-1314 [Oct. 2010 Term] Decision. This is also emphasized by the fact that not until 2007 did the FMVSS even require upper torso restraint for all rear designated seating positions. The lack of a dynamic crash test requirement for rear seat restraint systems for most of the 45 years of regulation by the Federal Motor Vehicle Safety Standards also relegated rear occupant protection to a third-tier priority David J. Biss has been a principle researcher and advocate for safer rear seat occupant protection with notable examples as follows:


David J. Biss Systems Analysis Engineer for Rear Seat Occupant Packaging/Protection and Seat Design


David J. Biss was the primary Occupant Kinematics/Dynamics and Engineering Design Expert in the three-occupant rear seat case presented at the left for which he identified the failure modes; the injury causations; defects; and alternative designs which lead to a very successful resolution of the case. The animation at left demonstrates the Systems Engineering Methods Mr. Biss used to contribute to a very satisfactory settlement.



Head vs. Crash Speed - Lap-Only Belt

(click to enlarge)

During the Regulatory Battles regarding rear seat occupant protection, Mr. Biss published the seminal work that quantified the violent physics and kinematics which explained the long history of broken bodies and the complex of injuries called the “Seat-Belt Syndrome.” These injuries consist of spinal Chance fractures; broken necks; massive intestinal ruptures; massive head injuries and others. Figure 4 from Reference 8 in his CV shows that fundamental physics dictates that in a frontal crash the head speed of a lap only belted occupant will likely BE GREATER THAN the Delta-V of the vehicle’s crash!


Nils Bohlin of Sweden identified in 1959 the hazards of lap-only belts shown by his patent for the three-point belt (http://multivu.prnewswire.com/mnr/volvo/37521/), and also shown in the left-hand panel. In the 1960's Roy Haeusler of Chrysler showed the absolutely predictable physics of lap-only belt kinematics with his “You Bought Them – Wear Them” video, shown below. While both Bohlin and Haeusler use the front seat as examples, because that was the subject at the time, the physics and injuries they predicted are absolutely and equally applicable to the rear seating positions. Even when three-point belts are installed in rear seats, many times the principle that “The seat is a fundamental part of the restraint system” is still ignored, with consequences like those shown in the three-occupant rear seat case video above.


(click to enlarge)


Nils Bohlin

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(click to enlarge)


Chrysler Film Showing Hazards of Lap-Only Belts



While some commentators may say that “this is old stuff,” the fundamental occupant protection principles laid down by the pioneers such as DeHaven, Stapp, Bohlin, and others, are invariant and, like basic physics, are eternal. If all car manufacturers had stayed true to these basic occupant protection principles they would have faced vastly fewer occupant deaths and injuries resulting in vastly fewer product liability claims.




(The full SAE papers can be ordered at http://papers.sae.org/)


  • A Study Of The Rear Seat Occupant In NCAP - SAE2008-01-0511- pdf
  • Consumer Information Testing to Improve Rear Seat Safety - NCAC-2008 - pdf
  • Ford Introduces Inflatable Seat Belts - EN 11-17-09 - pdf
  • Passenger Seating Position & The Risk Of Passenger Death - IP2006 - pdf
  • Rear Seat Occupant Protection In Frontal Crashes - ESV-07-0386-O - pdf
  • Seat Belt History - Wikipedia - pdf
  • Small Occupant Dynamics In Rear Seat - SAE2005-01-1708 - pdf
  • Williamson v Mazda, Supreme Court 08-1314 (pub. opinion) - pdf