Reducing Rollover Occupant Injuries: How and How Soon

Public release of previously confidential Malibu test data and film [1] provides the basis for this review. These are sixteen well-instrumented, definitive 32 mph dolly rollover tests of production Chevrolet Malibu sedans with unbelted Hybrid III dummies and eight with belted dummies (half of the cars in each group had roll cages to simulate strong roofs). This paper analyzes and reinterprets this material to resolve the principal motivating research question: does a strong roof reduce the potential for rollover head and neck injuries? Our findings are: (1) a rolling vehicle’s center of gravity rises and falls only about 10 cm during a rollover so that its vertical velocity at roof impact is never more than 2.5 m/sec; (2) the six dummies showing the highest head and neck forces were all seated on the far side of Malibus without roll cages; (3) these high head and neck loads occurred after onset of roof intrusion from rapid roof collapse and buckling, not from occupant diving; (4) average roof impact neck forces measured by near side dummies and by far side dummies seated under roofs that did not contact the ground all averaged 3,300 to 3,600 N, and none was sufficient to cause serious injury; (5) the unrestrained Hybrid III dummy drop tests showed that neck loads of 7,000 N correspond to a 2.4 m/sec roof intrusion velocity while 3,500 N neck loads corresponds to a 1.1 m/sec intrusion velocity; (6) the windshields of the production vehicles broke early leaving weakened roof structures that deformed back and forth with subsequent roof impacts; and (7) the tempered side glazing of production Malibus broke far more frequently than in rollcaged vehicles facilitating partial or complete ejection. The Malibu tests provide considerable insight into the potential countermeasures that could reduce rollover injuries