Matched Pair Testing of Injury Potential in Repeatable Rollover Tests with the Cris and Jrs

The availability of repeatable dynamic rollover fixtures, like the Controlled Rollover Impact System (CRIS) and Jordan Rollover System (JRS), has changed the face of rollover structural and occupant protection development and evaluation. Tests performed with these devices have demonstrated scientific principles of occupant protection and injury potential which were previously resolvable only by expert rhetoric. Matched-pair experiments with instrumentation measuring dynamic roof crush and dummy injury metrics are now possible. The effectiveness of occupant protection features such as padding, window curtain airbags, belt pretensioners and headrests are qualitatively and quantitatively measureable. The sensitivity of rollover parameters themselves and their effect on injury potential can be determined by tests with different roll rates, pitch angles, impact angles and drop heights. Simulating injury potential to humans with ultimately biofidelic dummy musculature can also be demonstrated. This paper presents two matched pair test sets performed on the CRIS and two matched pair test sets performed on the JRS. The matched pair test sets performed on the CRIS compare the dummy injury measures in reinforced and production versions of the 1998 Ford Crown Victoria and the 1996 Chevrolet Blazer. The CRIS test of the matched pair Crown Victoria vehicles has been presented previously in a paper by Moffatt et al [1]. The matched pair tests that were performed on the JRS were conducted to study the effect of a reinforced roof on dummy injury measures. These tests, performed on production and reinforced versions of the 1998 Ford Explorer and the 1999 Hyundai Sonata, included the measurements of road loads, roof crush and crush speed, dummy upper and lower neck loads, belt loads, as well as the movement of the vehicle during the test. INTRODUCTION In this study four matched pair, production vs. reinforced roof vehicle test sequences were performed and/or analyzed. Two sequences were conducted on the Controlled Rollover Impact System (CRIS) and two were conducted on the Jordan Rollover System (JRS). The sequences conducted on the CRIS consisted of tests of three matched pair 1998 Crown Victorias and tests of a matched pair of 1996 Chevrolet Blazers, all of which were conducted by Exponent [2,3]. The vehicles used in the matched pair testing conducted on the JRS were 1999 Hyundai Sonata and 1998 Ford Explorer vehicles. There is much controversy concerning the threshold dummy head and neck loads that represent an injury potential, especially in the Hybrid III dummy with the very stiff, vertically oriented neck in a rollover circumstance. The lack of consensus makes it difficult to predict injury based strictly on peak neck loads. Nusholtz et al concluded that peak force was not found to be a reasonable predictor of cervical spine damage [4]. The vehicles in this study that exhibited large amounts of roof crush clearly showed a much more severe interaction between the roof and head of the dummy which caused major neck bending. This agrees with studies done by Allen which show that bending type injuries (flexion and extension) account for more than 90% of the neck injuries that occur in vehicle accidents [5]. According to Ridella, spine injuries involving "compression combined with flexion, extension, or lateral bending" are much more prevalent (2-6 times depending on the rollover crash mode) than head injuries, as can be predicted by Head Injury Criteria (HIC) calculations [6].