Roof Crush in Rollovers

We pride ourselves on being the most knowledgeable about roof crush in rollovers. Our experts have reviewed more than 1500 cases and have seen many different types of accidents and injuries. We have done numerous studies and much research on what causes roof crush and how alternative designs could be used to prevent catastrophic injuries. We have also done extensive analysis on GM's Malibu testing and Ford's CRIS fixture as well as developed our own roof crush test, the Jordan Rollover System.

 

Related Papers and Presentations

Roof Collapse and Risk of Severe Head and Neck Injury, 13th ESV Conference

ABSTRACT

A survey of accident statistics and harm to the head and neck from side impact and rollovers, suggest that vehicle upper structure should be the next high priority goal in reducing severe casualties. Contrary to contentions that roof strength has little influence on these injuries, these results from a multiplicity of studies, indicate that roof collapse should be eliminated, passive interior padding improved, laminated and retained glazing be installed and restraints improved by pretensioning retractors.
A statistical analysis of the 1982 and 1983 NASS files of rollover accidents indicates a greatly increased risk of severe injury to occupants under a collapsing roof section.
The increased risk was also demonstrated by detailed investigation and analysis of 15 rollover accidents using the protocol of SAE #890382 (Live Subject Safety Research). The instrumented data from sixteen nearly identical, rollover tests conducted by General Motors with conventional and roll caged roofs and unrestrained and belted Hybrid III dummies were analyzed and confirmed the increased risk. Limiting the deformation extent of vehicle roofs by lightweight structural changes and simple and inexpensive force limiting, energy absorbing interior surface modifications were demonstrated to reduce the risk of severe injuries by a factor of at least four. Further reductions can result from maintaining the vehicle's directional stability by Anti-Lock Braking systems, limiting an occupant's contact velocity by emergency tensioning retractors on restraints and by minimizing partial ejection potential by laminated and retained glazing.

Head and Neck Injuries in LTV Rollovers and What to Do About It, 20th International Workshop on Human Subjects and Biomechanical Research

ABSTRACT

This is a follow-up to our paper "Roof Collapse and The Risk of Severe Head and Neck Injury.
"The focus here will be to deal more broadly with the types, causes and countermeasures to injuries in rollovers, and also to describe some differences between Light Truck and Van (LTV) vs. Auto rollover. We will briefly cover:
1. Accident Statistics,
2. Real World Case Studies,
3. Example Case Summary Analysis
4 .Experimental and Real World Rollover Differences,
5. Countermeasures or What to do about rollovers

Upper Interior Head, Face and Neck Injury Experiments, International Enhanced Vehicle Safety Conference

ABSTRACT

Head, face and neck (HFN) injuries associate with upper interior contacts account for a large percentage of all serious to fatal injuries annually. In the past, many of these injuries were the result of unrestrained occupants in rollovers and side impacts. Mandatory belt use laws have helped keep the head and torso inside the vehicle, but HFN injuries in side and rollover accidents persist. Regulatory actions for side and rollover protection deal with torso injuries but head injuries have been addressed only by upper interior padding.

Roof Crush Versus Occupant Injury from 1988 to 1992 NASS, Society of Automotive Engineers (SAE) International Congress

ABSTRACT

Rollover accidents account for a large number of serious to fatal injuries annually. In the past, these injuries were often the result of unrestrained occupant ejection. Subsequent to mandatory belt use laws, a larger percentage of these injuries occur inside the vehicle, and the head and neck areas sustain a substantial number of these injuries.

An analytical effort to understand rollover injuries, using the field accident data of the NASS file and residual headroom as an indicator, was reported by the authors at the 1996 ESV conference in Melbourne, Australia. This paper describes the relationship between roof crush and restrained occupant injury in rollover accidents as derived from the analysis of 1988-1992 NASS files. It extends the residual headroom parameter to the entire population of head, face and neck occupants injured inside the compartment.

Contradictions in the Risk of Head and Neck Injury in Front, Side, Rear and Rollover Accidents, Third World Congress of Biomechanics

Forensic biomechanics analysis in the United States supports far more injury research than is sponsored by the U.S. National Highway Traffic Safety Administration. The insight obtained from the forensic biomechanical analyses has the potential to improve the safety of vehicles yet to be built. However, this can occur only if the engineers conceptualizing, designing, testing and manufacturing the vehicles are informed about, and have an understanding of, the contradictions present in discussions of the risk of head and neck injury accidents. Understanding the apparent contradictions would then allow for greater insight as to what is necessary for the prevention of significant head and neck injuries in foreseeable real world accidents.

Human Inverted Drop Studies, 7th Annual Rachidian Society Meeting

Vertical drop studies of intact cadavers were conducted by Sances and Yoganandan with restrained and unrestrained upper cervical columns. Cervical injuries occurred between 0 .91 and 1.5 m of direct vertical drop upon the head with cervical compression of 2 to 4 cm. Similar drop studies were conducted by Nusholtz and Huelke who dropped intact cadavers both restrained and unrestrained from drop heights up to 1.8 m. Cervical fractures were produced at drop heights of 1.1 to 1.8 m. ln contrast, McElhaney extrapolated cervical injuries from histories and simulations in swimming pool accidents with cervical injury ranging from 3.3 m/s to 7 m/s for edge of pool dives. Pintar and his Medical College of Wisconsin colleagues produced clinical type cervical injuries in the vertically oriented human cadaver head/neck preparation with the head stabilized with the spring in the posterior area and dead weights in the anterior area at 3 to 8 m/s.'

Methods and Results: Recent studies with two males and one female were conducted by the Friedmans to evaluate the potential for neck injury when restrained inverted living humans were dropped vertically in a non-crushable production vehicle compartment or with a specially designed drop fixture. Three studies were done. One in a 1993 Chevrolet Sunbird designed to prevent roof intrusion. Another in a drop tower with an inverted seat arrangement with comparative studies using a Hybrid III 50th percentile dummy and a volunteer. The third study was conducted in a 1981Chevroet Malibu four-door compartment with a roof stiffened to prevent intrusion. The tests indicate that a restrained living human need not suffer neck injury at drop heights up to 91 cm. Head forces up to 1400N were measured.

An Investigation of Hybrid III and Living Human Drop Tests, Critical Reviews in Biomedical Engineering

ABSTRACT

The effect of roof crush on restrained occupants has often been discussed without regard to the headroom available, effectiveness of belts, and location of roof crush. In this article, the question of the ability to protect a simply restrained occupant in an environment in which the roof does not crush is addressed. The subjects were inverted and dropped vertically in no crushable production vehicle compartments and a specially designed drop fixture. Data collected includes head accelerations, vehicle accelerations, head displacements, belt angles, anchor point location, seat position, and belt tension for a variety of occupant sizes.

To our knowledge, these are the first inverted living human vertical studies to be scientifically documented and reported. It was found that no head or neck injuries resulted from drops of up to 91
cm and velocities up to 4.2 m/sec for restrained occupants in the absence of roof crush.

Finite Element Analysis of Vehicle Roof Intrusion Velocity in Rollovers, Mathematical Modeling and Scientific Computing

ABSTRACT

The present study determines the effect of roof strength on roof intrusion velocity during a rollover vehicular accident.  The response of a finite element model of a production roof  during  an  example  rollover  condition  was  compared  with that  of  a  modified  roof structure.·  It is shown that in the production  vehicle, a high change  in velocity,  substantial intrusion  displacement  and  substantial  intrusion  velocity  of  a  component   part  can  occur during the impact of the portion of the roof that  is initially  trailing.   In the modified roof structure it was found that strengthening the roof may avoid the trailing impact altogether. When the same rollover impact condition is forced to occur on the trailing side of the two roof structures, it was found that a strengthened roof can substantially reduce the intrusion and reduce the risk to occupants under these conditions.

A Study of the Effects of Roof and Restraint Characteristics on Injury Potential from Roof Impacts During Rollover, Fifth International Symposium on Computer Methods in Biomechanics and Biomedical Engineering

ABSTRACT

The effects of roof structure intrusion velocity, occupant size and location and restraint effectiveness then become important in design solutions that minimize the likelihood of injury. In the present study, previously developed finite element models of a baseline and modified roof structure are utilized with a finite element model representing a restrained occupant to evaluate the effect of the roof structure intrusion velocity envelope on restrained occupant neck loads.

Biomechanical Injury Evaluation of Laminated Side Door Windows and Sunroof During Rollover Accidents, Rocky Mountain Bioengineering Symposium Spring Conference

ABSTRACT

Significantly more fatalities and serious injuries occur due to ejection in rollover accidents. The present study was conducted to determine the occupant retention and head-neck injury potential aspects of laminated glass in side door windows and sunroofs during rollover accidents. The test protocol for this study was based on National Highway Traffic Safety Administration ['NHTSA) studies for advanced glazing. The impact study of 18 kg with head-neck form was conducted on laminated glass of side doors and sunroofs from production vehicles. The drop speed was varied from 11 to I6 kph. The Hybrid III 50% male dummy head-neck form was impacted on the approximately center of the glass portion of the windows. The head injury criteria, head resultant acceleration, and neck loads and moments were quantified. A series of drop tests were conducted on roll down side windows with laminated glass. The head-neck biomechanical parameters were well below the critical value injury tolerance limits. Results indicated that the glass contained the dummy assembly anti the head-neck biomechanical parameters were below the critical value injury tolerance limits in simulated rollover accidents. The present study demonstrates that head-neck injury is unlikely due to laminated glass side windows and sunroof laminated glass used in production vehicles during rollover accidents and that the dummy is contained by the laminated glazing.

Biomechanics of Occupant Ejection During Rollover Accidents, Southern Biomedical Engineering Conference
 
A major crash modality resulting in occupant ejection is rollover. Rollover accidents are most the dangerous crashes measured by the highest fatality or serious injuries to number of occupants in light vehicles [I]. Malliaris reported that rollovers accounted for over 50% of ejection and over 55% of the harm to ejectees, although it represented only about 8% of the crash modes [2]. Summers indicated that the majority of the rolls over fatalities come from 10% of the roll over involved occupants who are ejected, or partially ejected, from the vehicle [3]. Terhune also found ejection rates were substantially higher in roll over than in non-roll over crashes [4]. Clark found that almost a third of the occupants in crashes with roll over and ejection will have serious or greater injuries [5]. A roll over study by Orlowski indicated that it is generally more desirable to remain in the car than to be ejected in a roll over collision [6].The ejection during rollovers is more serious for light trucks and vans (LTVs) than for passenger cars [7]. Terhune concluded that light trucks differed from passenger cars in more frequently exposing their occupants to risk through single vehicle rollovers and noted that the rollover tendencies were most pronounced in LTVs [4]. Winniki reported an analysis by vehicle type and showed benefits of ejection prevention in tight trucks. For drivers of light trucks in ejection crashes the relative risk of fatality was 5.62 and for passengers it was 4.66 (compared with the non-ejected occupant). The fractional reduction in fatalities was estimated as 82 percent for drivers and 78.5 percent for passengers when ejection was eliminated from these vehicles [8]. By reducing the opportunity for ejection the probability of severe injury or fatality associated with ejection would be correspondingly reduced. Therefore, the purpose of this study is to examine the occupant retention capability and head-neck injury aspects of laminated glass in side windows and sunroof in vehicles. The present study is a continuation of our previous studies on laminated glass [9-12].

Biomechanics of Thoracic Spine Injuries in Motor Vehicle Rollover Accidents, International Symposium of Biomechanical Engineering

 ABSTRACT

The purpose of this study is to present a detailed biomechanical analysis of thoracic spine injuries sustained by occupants involved in rollover accidents due to roof crush. Three real world case studies, experimental biomechanical data and accident database (National Automotive Sampling System) statistical analysis are presented. In three real world cases, the occupants sustained sever thoracic spinal neurological injuries due to roof headliner by the occupant. Given the nature of thoracic injuries and substantial roof crush in the occupant’s (area, it is logical to conclude that shoulder loading is a potential injury mechanism. Experimental laboratory testing of intact cadavers shows that the thoracic spiral injuries occurred at quasistatic forces ranging from 1110 N to 2750 N with a mean value of 1737 N and standard error of 274 N. The failure level in thoracolumbar level varied from T7 to L2. However, thoracic spine injuries (1110 to 1735 N). A preliminary query of NASS database (1993-2002) notes serious thoracic spinal injuries (AIS>3) of approximately 750 cases due to significant roof contact corroborating the present hypothesis.

Biomechanical Simulation for Evaluation of Alternative Rollover Occupant Protection Systems Designs, IASTED Biomedical Engineering

ABSTRACT

The evaluation of the biomechanical performance that can be expected from alternative designs for restrained occupant rollover protection was approached through the use of finite element modeling. Finite element models o vehicle designs and the Hybrid III dummy were used to evaluate elements of alternative rollover occupant protection system designs. Results from rollover crash tests of a production vehicle were used to validate the baseline models. The alternative designs were then incorporated into the vehicle designs and comparisons of various biomechanical injury measurements of the neck were made.

Effects of Buckling on Intrusion Velocity Behavior, Sixth European Conference on Structural Dynamics

ABSTRACT

This study examines the effect of automotive roof buckling on the intrusion velocity in the vertical direction under rollover conditions. A finite element model of a vehicle structure was created and provided with conditions representative of an automotive rollover event. The model was validated based on test and observational data. The impact conditions of the roof structure in the vertical direction were compared with the intrusion velocity with and without the presence of a buckle. It was found that the vertical velocity amplification (intrusion amplification) could be in the range of 2 to 3 times the corresponding vertical impact velocity in the area of a buckle.

Biomechanical Effects of Buckling Induced increases in intrusion Velocity Behavior, ASME Summer Bioengineering Conference

ABSTRACT

This study examines the effect{ of automotive roof buckling on the intrusion velocity in the vertical direction under rollover conditions and the consequences on biomechanical response finite element model of a vehicle structure was created and provided with conditions representative of an automotive rollover event. The model was validated based on test and observational data. The impact conditions of the roof structure in the vertical direction were compared with the intrusion velocity with and without the presence of a buckle. lt was found that the vertical velocity amplification (intrusion amplification) could be in the range of 2 to 3 times the corresponding vertical impact velocity in the area of a buckle. Such an additional amplification compromises the occupant compartment and increases the injury potential.

Vehicle Roof Structure Design Evaluation Under Rollover Impact Conditions, 6th IASTED International Conference on Modeling, Simulation, and Optimization

ABSTRACT

This study examines the ability to evaluate vehicle roof structure designs under rollover impact conditions using finite element modeling. Observed roof performance during rollover impact is evaluated and design alternatives and their effect on intrusion velocity in the vertical direction under rollover impact is analyzed. A finite element model of a vehicle structure was created: conditions creating deformation observed in a rollover impact event were analyzed. The model was validated based on test and observational data. Under the same impact conditions the intrusion velocity of the roof structure was evaluated for the baseline and alternative designs. It was found that a low cost alternative design could reduce the observed intrusion velocities.

Finite Element Modeling of Rollover Crash Tests with Hybrid III Dummies, ASME 2007 Summer Bioengineering Conference

ABSTRACT

This paper reports on the finite element modeling of rollover crash tests with Hybrid III dummies. Finite element models of a vehicle design and the Hybrid III dummy were used to evaluate the subsystem under manufacturer created rollover conditions for a production and roll caged roof structure. The objective of this study was to demonstrate the ability to reproduce the impact environment occurring in rollover crash tests. There are over 26,000 fatalities and serious injuries annually occurring in rollover accidents in the United States. Many of these are to restrained occupants and their head and spinal injuries have been associated with contact with the roof structure. To analyze the crash tests the effects of the system, finite element models were made of rollover crash tests that had been conducted using baseline and modified passenger vehicles and Hybrid III dummies using the defined impact conditions. Neck loads were utilized to validate the model against the test results. The results show that finite element modeling can reproduce the results from rollover crash tests.

Finite Element Modeling of Rollover Crash Tests with Hybrid III Dummies, 2008 SAE World Congress

ABSTRACT

The objective of this study was to demonstrate the ability to reproduce the impact environment occurring in rollover crash tests. There are over 26,000 fatalities and serious injuries annually occurring in rollover accidents in the United States [1]. Many of these are to restrained occupants and their head and spinal injuries have been associated with contact with the roof structure.  Finite element models of the Hybrid III dummy and vehicles were used to model the rollover crash tests conducted for Ford.
The rollover crash tests involved a production vehicle in a baseline form and one with a roll cage added to it.  The impact conditions were incorporated and the results compared with the published test results. The results show that finite element modeling can reproduce the results from rollover crash tests.

Xprts LLC Home Page Areas of Expertise Expert Profiles Page Testing Center Rollover Resources About Xprts LLC Contact Xprts LLC FREE Initial Case Review