Symposiums & Conferences

Abstract:The goal of this research is to develop a dynamic rollover test rating system similar to the star-rating system of frontal Federal Motor Vehicle Safety Standard (FMVSS) 208 and side FMVSS 214 compliance, New Car Assessment Program (NCAP) and Insurance Institute for Highway Safety (IIHS) tests. Until now, the requirement for vehicle and occupant crashworthiness in rollovers has been a structural measure only, the vehicle’s strength-to-weight ratio (SWR), in a static roof crush test.

The short-term objective of this paper is to develop a quasi-dynamic rating system based on predictions derived from the Jordan Rollover System (JRS) dynamic rollover tests, IIHS static tests and finite element parameter sensitivity studies, verified by dynamic test sampling. The rating for the protocol is based on the National Accident Sampling System (NASS) and Crash Injury Research Engineering Network (CIREN) injury risk probability functions.

One method of predicting performance is to adjust the results of a dynamically-tested vehicle, similar to the vehicle whose performance is to be predicted, by the parameter sensitivity relationships correlated to a larger number of dynamically-tested vehicles. Another method is to formulate and then apply a multivariate equation based on the correlated parameters of a larger number of dynamically-tested vehicles.

This paper presents the prediction procedure based on a limited number of vehicles with a wide range of SWRs. The intent is to apply the procedure to vehicles compliant with 2009 FMVSS 216 and, as such, the illustrations herein are examples. In this paper, the procedure is illustrated by a calculation of two parameters, SWR and major radius (MR). Normalization procedures have also been developed to estimate real-world dynamic test protocol performance, as well as the injury measures for 5th, 50th and 95th percentile dummies. This prediction procedure is an interim solution, not a substitute, for compliance or NCAP dynamic rollover testing.

A more detailed summary of the research basis for this effort is in a companion paper 11-0090 “Predicting and Verifying Dynamic Rollover Occupant Protection.” In Press...

Abstract: The objective of this paper is to describe the developments that provide the basis for predicting new car occupant protection in real-world rollovers.

An analytical technique has been developed for predicting a vehicle’s dynamic occupant protection performance at any severity from a Jordan Rollover System (JRS) 50-vehicle rollover test database; static test roof strength, stiffness and elasticity data; inertial-influenced impact pitch orientation; size, roll moment and geometry dimensions; and occupant protection features. Only sampling, updating and verification of the JRS database will be necessary to reflect innovative construction and protection techniques until dynamic testing is implemented.

A noteworthy finding of this study was that reducing a vehicle’s major radius (i.e., its shape at the windshield) was more effective in reducing rollover deaths and injuries than increasing roof strength-to-weight ratio (SWR) above 3.0. In Press...

Abstract: 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.

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Abstract: Rollover crashworthiness for passenger vehicles is currently evaluated by the Federal Motor Vehicle Safety Standard (FMVSS) 216 static roof strength compliance test. However, research clearly shows that the static test is inadequate in evaluating a vehicle's injury potential performance in a real-world rollover event. Studies previously conducted by the Insurance Institute for Highway Safety (IIHS) show a general relationship between a vehicle's Strength-to-Weight-Ratio (SWR) and its real world injury potential. Although this general relationship is fairly accurate for most vehicles, there are many individual vehicle anomalies. The real world injury performance of the vehicles which make up these anomalies depends much less on the static roof strength (as measured in a FMVSS 216 test) and more on the dynamic performance of the roof and occupant protection systems during a real world rollover (as simulated on the Jordan Rollover System [JRS]). Repeatable dynamic crash tests are used by IIHS, National Highway Traffic Safety Administration (NHTSA), and the New Car Assessment Program (NCAP) to evaluate the performance of a vehicle in every major crash mode except rollovers. Dynamic tests represent the real world effect of vehicle dynamics, orientation, geometry, roof strength, occupant position and kinematics, restraint and other safety system effectiveness while directly measuring comparative dummy injury criteria. Because National Accident Sampling System (NASS) investigations can only measure the cumulative effect of post crash roof crush, NHTSA has established an empirical relationship that a vehicle with post crash negative headroom (PCNH) is five times more likely to injure the occupant. However, data indicates that the anomalies in head, neck, and spinal cord injury are related to the momentum exchange of dynamic head impact speed and the duration of neck loading in each roll, not the cumulative amount of residual roof crush. This paper suggests a means of comparatively evaluating a vehicle's dynamic rollover occupant injury potential performance.

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Abstract: Rollover crashes cause more than 10,000 fatalities and nearly 30,000 serious injuries per year in the U.S. alone. This is due to the fact that the vast majority of vehicles, including commercial, police, and military, lack the roof strength to preserve occupant survival space and protect their occupants in a rollover. Recent statistical and epidemiological studies have shown a significant relationship between roof crush and injury. This rollover occupant protection problem is well known to industries with large vehicle fleets; until now, this problem has eluded solution. Within these various industries a wide variety of rollover occupant protection systems (ROPS), both internal and external, have been designed, purchased, manufactured, installed, and maintained locally with little expert consultation. A wide variety of designs have emerged with an alarming variance in "assumed" crashworthiness. Couple this alarming trend with the risk of rendering the existing occupant protection features (e.g., airbags) ineffective, which has resulted in vehicles with inadequate crashworthiness. This paper describes how rollover damage to a vehicle with a weak roof and the resulting reduction of occupant headroom can beminimized to an inconsequential amount using an innovative externally retrofitted rollover load distribution device. This system was based on an understanding of road crash data, empirical evidence, and innovative state of the art testing and analysis to provide effective external ROPS structures for the commercial, police and military fleets.

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Abstract:In the U.S., more than 27,000 catastrophic and fatal injuries occur annually in rollover crashes. This study is part of an ongoing research program aimed at mitigating these injuries. Recent papers introduced a prototype “soft” low-durometer Hybrid III neck design and presented results of matched-pair tests, comparing production and prototype Hybrid III neck responses. This paper
• discusses neck injury criteria, and
• proposes preliminary rollover injury criteria for the prototype “soft” low-durometer neck.
Then, peak neck injury measures are used to calibrate the dynamic relationship for flexion bending between the tensed production Hybrid III neck IARV and:
• the prototype “soft” low-durometer neck, which is representative of 1/3 tensed, and
• the untensed cadaveric logistic regression curves for major flexion injury risk by Pintar et al.

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Abstract:In the U.S., about 40,000 catastrophic and fatal injuries occur annually in rollover crashes. A strategy for injury mitigation is dynamic compliance testing with dummy-occupied vehicles and occupant protection requirements, similar to that required for frontal and side impacts. Presently, the CRIS and JRS dynamic vehicle rollover test devices realistically simulate the ballistic phase of real-world rollover crashes. A search for a typical serious injury test protocol is in progress.

Over 300 rolls and more than 50 two-roll JRS tests of mostly low severity ballistic trajectory protocols have been performed with the belted production Hybrid III dummy. These dynamic tests (as compared to static tests) identified significant roof strength, construction and crush effects of vehicle geometry, buckling structure, yaw and pitch impact angle, window breakage and their relationship to occupant injury and protection. A companion paper at this conference “Characterizing the Injury Potential of a Real World Rollover” details these effects.

It was also found that with roof crush, serious neck bending injuries predominated while head injuries and partial ejections did not occur, except with the very weakest roofs. Since the bending stiffness of the joint muscles of the human body during a rollover are unknowable, a Hybrid III dummy with a modified lumbar joint and reduced musculature neck has been developed as the best available surrogate for dynamic rollover tests. The Hybrid III neck is about 3 times stiffer in bending than a normal relaxed human neck and about one third as stiff as the tensed neck of a young soldier on which the production Hybrid III neck was based. Recent results with a yaw and trip derived initial out-of-position of this dummy indicated a 8 to 11 kph (5 to 7 mph) centrifugal erection rate. In combination with roof intrusion speeds of 11 to 21 kph (7 to 13 mph) more head injuries and partial ejections, consistent with crash statistics are predicted.

The JRS roof crush results of 40 production vehicles roughly normalized to a proposed real world severity test protocol has been matched to NHTSA’s post crash negative headroom criteria and to a CDC serious injury risk to various body part analysis. A dynamic rollover crashworthiness compliance test based on a roof crush injury risk criteria with reported injury measures from an instrumented, belted, initially out-of-position dummy is available now.

In 2010, with resolving epidemiology and protocol parameter sensitivity data, our goal is a representative injury risk compliance pilot test series with occupant protection injury measure data demonstrated in 2011 and confirmed for an NPRM by VRTC in 2012. We firmly believe that a dynamic test will be ready for implementation long before the NHTSA plan.

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Abstract:There are approximately 270,000 rollover crashes annually in the U.S., causing about 10,000 deaths and 30,000 serious injuries. The objective of a 5-year multivariate NHTSA project is to define the global issue: to characterize a real-world rollover. CfIR seeks, more specifically, to identify the rollover segment with the greatest serious injury potential for FMVSS 216 compliant vehicles that would be consistent with a compliance or comparative evaluation dynamic rollover test. This process requires evaluating the injury potential sensitivity of each segment and its influence on the following segment.

Ten segments of a 2-roll event were considered, because it has been shown that 95% of single vehicle rollovers and serious-to-fatal injuries occur within 8 quarter turns. A description of the preliminary segment-by-segment evaluation and the sensitivity to injury potential is characterized by analysis, experiments and illustrations. Parameters were derived and validated with JRS dynamic rollover tests. The test parameters were then applied and normalized to approximately 40 other JRS tests for a comparative pilot injury risk evaluation to the NHTSA post-crash negative headroom criteria.

Since many of the JRS tests included dummies, injury performance was also evaluated based on dummy injury measures from head and neck data collected during the tests. Tests were conducted with production and prototype Hybrid III necks and lumbar spines representing tensed and partially-relaxed human musculature. The results were also compared and correlated with Injury Assessment Reference Values (IARV), consensus impact speed injury criteria and dummy positioning. The results indicate that while the injury risk evaluation generally supports static compliance test criteria, dynamic tests identify vehicle geometry, structural design deficiencies and dummy injury measure results that roughly account for the substantial variation in injury rate identified by IIHS from the SWR static test norm. Examples of the data for some of these “anomalies” and failures are provided.

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Abstract:This study is part of an ongoing research project aimed at mitigating catastrophic human neck injuries, predominantly due to neck bending, in rollover crashes. Presently, the Hybrid III dummy is considered to be the best available human surrogate for dynamic rollover tests. However, there are known biofidelity and instrumentation limitations associated with its use to predict catastrophic neck injuries in real-world rollover crashes.

A previous study investigated the use of the non-biofidelic Hybrid III dummy in a dynamic rollover test to accurately predict the predominant human neck bending injury sustained in real-world rollover crashes. An empirical relationship between upper and lower Hybrid III neck loading was derived. The effects of neck preflexion angle, roof impact speed, roof crush, onset-to-peak neck axial forces and moments, and impact duration on neck bending injury were identified. Peak neck injury measures were rejected.

For this study, the 67-durometer Hybrid III production neck was fabricated with more compliant 35-durometer butyl rubber in order improve the dummy biofidelity in rollover tests. The tests in the previous study were repeated. Correlations were established between the prototype and production necks. Parametric studies of the prototype neck revealed similar trends as observed with the Hybrid III production neck.

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Abstract:In the U.S., more than 27,000 catastrophic and fatal injuries occur annually in rollover crashes. Due to the incidence and severity of injuries in rollover crashes, a strategy for injury mitigation is dynamic compliance testing with dummy-occupied vehicles and occupant protection requirements, similar to that required for frontal and side impacts. Presently, there are dynamic vehicle rollover test devices like the Controlled Rollover Impact System and the Jordan Rollover System that realistically recreate real-world rollover crash scenarios. However, the Hybrid III dummy, which is considered to be the best available human surrogate for dynamic rollover tests, has a very stiff neck with limited biofidelity in rollover crashes; the Hybrid III neck is much stiffer than the human neck. Catastrophic human head or neck injuries resulting from roof interaction and partial ejection in real-world rollover crashes are poorly replicated by dynamic rollover tests with the non-biofidelic Hybrid III dummy neck. Only with a more biofidelic dummy can effective testing result in injury mitigation in rollover crashes.

This study is part of an ongoing research project aimed at mitigating catastrophic human neck injuries in real-world rollover crashes. The goal was to develop a biofidelic neck assembly for the Hybrid III dummy in rollover crash environments. The design goals of this prototype neck included decreased stiffness and a mechanism that represents the unknowable human muscle tension in rollover crash environments.

This paper and its companion paper in this conference introduce the new neck design, present results of matched-pair tests that compare the responses of the new neck with the production Hybrid III neck, and propose preliminary rollover injury criteria for this neck. The neck demonstrates repeatability, improved biofidelity, which results in more realistic occupant kinematics, dynamics, injury prediction, and evaluation of various countermeasures.

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Abstract:The US, European and Australian New Car Assessment Program (NCAP) and the Insurance Institute for Highway

Safety (IIHS) produce ratings of new vehicle performance based on dynamic crash tests in frontal, side and rear crashes; and vehicle handling tests. No dynamic based crashworthiness ratings exist to date in relation to rollover crashes. This study fills that gap and proposes a rating system for new vehicle performance in rollover crashes. Combined with existing rating systems, consumers will then have a complete and balanced picture of occupant protection performance.

A database of more than 40 Jordan Rollover System (JRS) dynamic rollover tests, assessing injury potential by roof crush and crush speed has generically validated NHTSA and IIHS statistical data as a function of FMVSS 216 quasi-static, strength to weight ratio (SWR). There is however a wide disparity between the performance of individual vehicles at the same or similar SWR between the IIHS statistical and JRS dynamic test data. That disparity has been partially investigated in a companion paper in this conference (Vehicle Roof Geometry and its Effect on Rollover Roof Performance.

IIHS data indicated a 50% reduction in incapacitating and fatal injury risk with a fleet average SWR = 4. However, the use of a SWR-based rollover criterion does not provide sufficient crashworthiness fidelity essential for consumers, nor does such a criterion provide industry the opportunity to design cost-efficient rollover crashworthy vehicles based on occupant injury performance. Only a dynamic rollover testing protocol based on injury criteria would provide this information.

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Abstract:Nearly a half century ago, the General Motors Research Laboratories, developed the high performance Electrovair, with an induction motor drive and solid state controller; the Lunar Rover, GM’s Mark on the Moon; passive occupant protection; separation cruise control; optical lane following; and an electrochemical rechargeable Lithium Iodine engine.

In 1968, a new company called Minicars grew out of this earlier work. This group developed prototype electric, gas and hybrid electric powered versions of a small car for the U.S. government. In 1970, Minicars was a subcontractor to AMF for the development of its Experimental Safety Vehicle.

The Minicars’ Research Safety Vehicle (RSV) was conceived in 1975 as a 1985 prototype. It was to be an S3E vehicle: Safe, Environmental, Efficient and Economical. It was built with foam filled, thin wall sheet metal sections and a polyurethane skin. This car passively protected occupants in 80 kph (50 mph) full frontal, 129 kph (80 mph) half car offset frontal, 64 kph (40 mph) angled side, rear and 48 kph (30 mph) rollover dynamic tests. An electronic version incorporated antilock brakes, radar separation cruise control, and emergency braking when a crash was unavoidable. A production version was to weigh 2,200 pounds, carry four people, and get 32 mpg. It also had 16 kph (10 mph) frontal and rear no damage bumpers and 80 km (50 mile) run flat tires.

Only years later have advanced air bags – as featured in the RSV – become standard in all light vehicles. In the decades since the ESV program and dynamic regulatory testing began, National Highway Traffic Safety Administration (NHTSA) now estimates that airbags save 2,500 lives annually, but we still lose about 12,000 people in frontal, 9,000 in side and over 10,000 in rollover crashes. We can do better by simply looking back to what the RSV program achieved.

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Abstract:The Jordan Rollover System (JRS) provides a realistic, highly controlled, repeatable dynamic test of vehicle roof crush performance under typical rollover conditions. The principal use thus far has been in comparing vehicles’ roof crush and injury potential performance in one and two roll events. Because the JRS directly measures the force between the roof and the ground during touchdown, it can be used to measure, assess and optimize occupant protection by adjusting roof geometry, roof structural design and material strength and elasticity, for the least cost and weight.

This study demonstrates that the peak force (load) between the initial leading side roof rail (near side) and the road is roughly four times the vehicle weight (the load-to-weight ratio or LWR) when a vehicle first touches down at around 150º of roll. The force then drops substantially as the vehicle continues to roll over the flat of the roof, in most instances dropping to zero because the vehicle is momentarily airborne. When the vehicle rolls beyond 180º and comes into contact with the side rail opposite to the leading side of roll (far side), the force rapidly rises again. The roof then either collapses or lifts the vehicle center of gravity (COG). The far side rail of a weak roof vehicle that cannot lift the COG may then halt the vehicle’s downward fall, imposing even larger forces on the road segment when the vehicle’s door and main body structure interact with the roadway. To deal with such forces, a long standing and natural presumption has been to substantially increase the roof strength to weight ratio (SWR), which can result in weight efficiency cost penalties. However, one production vehicle that was tested minimized roof crush without substantially increasing its SWR.

Analysis of the results has found that far side roof crush is strongly related to the difference between the major radius (the maximum distance from the principal axis of rotation to the roof rail) and minor radius (distance from that axis to the center of the roof). Three to four inches, as between cars and LTV’s has a significant effect on injury potential. The typical difference in a light truck vehicle LTV is around 15 cm to 25 cm (6” to 10”) while in an passenger car it is around 8 cm to 15 cm (3” to 6”).

These observations were confirmed by physical tests of strong and weak roofed vehicles. These tests led to the conclusion that a geometry change in the roof to minimize the difference in radius across the roof would reduce the degree to which the far side of a less strong roof had to lift the vehicle as it rolled beyond 180º. A finite element analysis confirmed that for a vehicle of modest roof strength, a structurally strong, rounded roof panel will reduce the far side deformation and intrusion speed by about two-thirds without increasing underlying roof strength. These results were confirmed in JRS testing of current production passenger cars and SUV vehicles and with a “HALO” TM – High Attenuation Load Offset (U.S. and International Patent Pending Rollover Damage Minimization Device) retrofit kit for SUVs.

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Abstract:In the U.S., more than 27,000 catastrophic and fatal injuries occur annually in rollovers. This study is part of an ongoing research project aimed at mitigating the likelihood and severity of such injuries.

Last year, the authors developed a dynamic rollover test methodology for replicating, predicting, and differentiating between types of real-world neck injuries using the non-biofidelic Hybrid III dummy as the human surrogate. Based on platen drop and pendulum test results, dummy positioning for flexion injury was determined and peak neck injury measures were rejected. A new neck injury criteria, the integrated bending moment (IBM), was proposed that related human neck flexion injury to Hybrid III lower neck moment-time histories. The IBM was validated by dynamic rollover tests performed with the Jordan Rollover System (JRS) with roofs of different strength-to-weight ratios (SWR's). The measured lateral and flexion neck moments were then roughly correlated with human neck flexion injury measures proposed by Pintar, et al., in 1998.

To date, real-world head injuries resulting from roof interaction and partial ejection could not be replicated in dynamic rollover tests with the non-biofidelic Hybrid III dummy because of stiffness differences between the Hybrid III and human neck.

Findings thus far suggest that improved correlations with human injury measures could be achieved with the development of a dummy neck that is biofidelic in the rollover crash mode. In this paper, the production Hybrid III neck was modified with lower durometer butyl rubber discs and nodding blocks for improved biofidelity. Pendulum tests were repeated to correlate the production and modified Hybrid III neck responses. JRS tests were performed with an increased far-side impact angle to evaluate the capability of the modified preflexed neck to replicate and predict head, neck, thoracic spine, and ejection injury potential in real-world rollovers.

Results of this study indicate the following:

Matched-pair platen pendulum tests with the low-durometer neck were found to be repeatable.

In JRS tests performed with an increased far-side impact angle, the low-durometer preflexed Hybrid III neck reasonably replicated head, neck, thoracic spine, and ejection injuries and kinematics of weak-roofed vehicles.

The low-durometer neck allowed a more direct correlation with human neck flexion injury measures.

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Abstract:Rollover accidents have the highest serious to fatal injury rates of any accident mode. Research and development on rollover occupant protection has been frustrated by the lack of a low cost, controlled, repeatable, dynamic test. The most widely used tests, dolly and CRIS system rollovers, do not meet all of these conditions, but the Jordan Rollover System (JRS) does. This study demonstrates JRS repeatability using three identical production vehicles with anthropomorphic test dummies. The first test of each vehicle used string potentiometers to measure roof performance. The second used both string potentiometers and an instrumented test dummy. The JRS test parameters, roof structural performance, and Hybrid III dummy injury measures were all shown to be highly repeatable with variation generally not more than 10 percent. The dummy and vehicle repeatability was on par with the repeatability shown in similar crash test studies conducted by IIHS and NHTSA.

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Abstract: World renowned expert engineers will meet to debate the cause of injury in a rollover (Diving vs. Roof Intrusion) and to expose the weak U.S. government standard that has led to more than three decades of unnecessary fatalities and catastrophic injuries in rollover accidents. Although the experts supporting the “Diving Theory” have declined to participate, the debate will go on with their testimony under oath on this issue. Other topics of discussion will be Ejection, Severity, Testing, Regulation, Injury Measures, Disabled Living & Spinal Cord Injuries, Societal Costs, Defense and Plaintiff Strategies, Public Information, NCAP, and International Cooperation. Engineers who have studied the issue of Roof Crush in depth will present scientific papers and videos of roof drop test comparisons and vehicle rollover comparisons of strong roofs vs. weak roofs. Survivors of Roof Crush will tell their stories.

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Abstract:In an attempt to find a test protocol that characterizes the rollover occupant protection capability of a passenger vehicle better than the test used in Federal Motor Vehicle Safety Standard 216, we developed equipment and protocols for a modified, quasi-static roof crush test (M216, a test conducted sequentially on both sides of the roof over the A pillars at a pitch angle of 10º and roll angles of 25° and 40° respectively) and for a repeatable, dynamic rollover test called the Jordan Rollover System (JRS).

We have conducted M216 and JRS tests on 17 production vehicles to determine roof crush and crush velocities at a number of points in the interior. These tests included complete production vehicles, body bucks at reduced weight to increase the effective roof strength-to-weight ratio, and pairs of identical vehicles where one has had the roof reinforced in a manner that is entirely hidden by the vehicle’s sheet metal and upholstery. Data from the JRS tests and the M216 tests are compared with the results of FMVSS 216 tests.

Analyses of the data highlight the relative value and validity of each test methodology, its ability to predict roof performance in actual rollovers, its use in vehicle roof structure design, and its potential contribution to regulation or consumer information. Based on the roof crush and crush speed in the vicinity of front seat occupants’ heads, we propose a rollover crashworthiness ranking system. While static tests measure the force and deformation of the roof on the outside, the dynamic tests measure the crush on the inside during the sequence of rollover roof impacts, where it is directly related to the occupant’s survival space and injury potential.

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Abstract:In an attempt to understand the relationship between quasi-static and dynamic test results, repeatable, dynamic rollover tests were conducted on production vehicles to determine intrusion and intrusion velocities using the Jordan Rollover System (JRS). These tests included complete production vehicles and body bucks at reduced weight, to vary the roof strength-to-weight ratio. Data from these tests are compared with the results of quasi-static roof strength tests measured at greater roll and pitch angles than are used in FMVSS 216. Biomechanical data indicates that serious head, face, neck or thoracic spine injury are a consequence of rapid impacts with significant amplitude. The test data suggests a correlation between quasi-static roof strength and dynamic roof intrusion velocity. Localized failures (buckling and collapse of structural elements that often translate into the roof panel) are a more critical aspect of roof performance than its strength as measured in FMVSS 216.

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Abstract: 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.

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