Investigation of injury potential through matched pair drop testing.

The National Highway Traffic Safety Administration has concluded that there is a relationship between roof intrusion and the risk of injury to belted occupants in rollovers events. Previous testing on many different production vehicle types indicates that damage consistent with field rollover accidents can be achieved through inverted drop testing from small drop heights. It has been shown in previous drop test pairs with Hybrid III dummies, that the amount of roof intrusion is related to occupant neck injury. This paper analyzes inverted drop testing performed on Ford F250 Crew Cab production and reinforced pickups. Each of these pickup tests used Hybrid III test dummies in order to evaluate the occupant injury potential in relation to roof intrusion. The reinforced truck's residual crush was an order of magnitude less than the production truck crush. These tests indicated that the reduction of roof crush resulted in a direct reduction in neck loading and therefore an increase in occupant protection. In addition, it was found that the restraint loading was inversely related to the neck loading of the dummies.

Design of rapid medical evacuation system for trauma patients resulting from biological and chemical terrorist attacks.

In the event of a large scale, biological or chemical terrorist attack it is unlikely that local emergency response organizations will have sufficient quantities of dedicated ambulances to evacuate all of the affected victims. As a potential solution to this problem, we have developed a device that can be retrofitted to a variety of government or civilian utility vehicles in order to convert them for emergency medical transport (US Pat. 7,028,351). Each installed device allows the host vehicle to safely transport either a single patient on a stretcher or multiple ambulatory patients. Additionally, each device provides a means for temporary or permanent attachment of emergency medical equipment. When not in use, the device can be collapsed to improve ease and efficiency of storage. Preliminary analyses of certain highly loaded structures on the device were carried out using known principles of solid mechanics. The analyses were carried out assuming the highest reasonable loading condition. This condition was determined to occur when the device is configured for the transport three 95(th) percentile males and 20 kg of medical equipment. This loading condition was assumed to be more severe than any that might occur due to an attendant performing CPR, or any other medical procedures, on a single supine patient. The base sections of the load bearing stretcher supports were then modeled using 3D CAD software and run through a finite element analysis (FEA) as a means to more accurately simulate the stresses that are likely to occur in the actual parts. As the device must be highly mobile, these analyses were used to confirm that the load bearing structures can be manufactured from low cost materials and still be light enough to be easily transported. Future work will include sizing and installation studies to ensure that the production version of the device can be rapidly implemented in a wide variety of private, commercial, and government utility vehicles.

Biomechanics of side impact injuries: evaluation of seat belt restraint system, occupant kinematics and injury potential.

Side impact crashes are the second most severe motor vehicle accidents resulting in serious and fatal injuries. One of the occupant restraint systems in the vehicle is the three point lap/shoulder harness. However, the lap/shoulder restraint is not effective in a far-side crash (impact is opposite to the occupant location) since the occupant may slip out of the shoulder harness. The present comprehensive study was designed to delineate the biomechanics of far-side planar crashes. The first part of the study involves a car-to-car crash to study the crash dynamics and occupant kinematics; the second part involves an epidemiological analysis of NASS/CDS 1988-2003 database to study the distribution of serious injury; the third part includes the mathematical MADYMO analysis to study the occupant kinematics in detail; and the fourth part includes an in-depth analysis of a real world far-side accident to delineate the injury mechanism and occupant kinematics. Results indicate that the shoulder harness is ineffective in far-side crashes. The upper torso of the belted driver dummy slips out of the shoulder harness and interacted with the opposite vehicle interior such as the door panel. The unbelted occupants had a similar head injury severity pattern compared to belted occupants. The present study is another step to advance towards better understanding of the prevention, treatment and rehabilitation of side impact injuries.

The effect of roof strength on reducing occupant injury in rollovers.

Roof crush occurs and potentially contributes to serious or fatal occupant injury in 26% of rollovers. It is likely that glazing retention is related to the degree of roof crush experienced in rollover accidents. Occupant ejection (including partial ejection) is the leading cause of death and injury in rollover accidents. In fatal passenger car accidents involving ejection, 34% were ejected through the side windows. Side window glass retention during a rollover is likely to significantly reduce occupant ejections. The inverted drop test methodology is a test procedure to evaluate the structural integrity of roofs under loadings similar to those seen in real world rollovers. Recent testing on many different vehicle types indicates that damage consistent with field rollover accidents can be achieved through inverted drop testing at very small drop heights. Drop test comparisons were performed on 16 pairs of vehicles representing a large spectrum of vehicle types. Each vehicle pair includes a production vehicle and a vehicle with a reinforced roof structure dropped under the same test conditions. This paper offers several examples of post-production reinforcements to roof structures that significantly increase the crush resistance of the roof as measured by inverted drop tests. These modifications were implemented with minimal impact on vehicle styling, interior space and visual clearances. The results of these modifications indicate that roof crush can be mitigated by nearly an order of magnitude, as roof crush was reduced by 44-91% with only a 1-2.3% increase in vehicle weight. Additionally, this paper analyzes the glazing breakage patterns in the moveable tempered side windows on the side adjacent to the vehicle impact point in the inverted drop tests. A comparison is made between the production vehicles and the reinforced vehicles in order to determine if the amount roof crush is related to glazing integrity in the side windows. Lastly, two drop test pairs, performed with Hybrid III test dummies, indicates that the reduction of roof crush resulted in a direct reduction in neck loading and therefore an increase in occupant protection.

Biomechanical analysis of occupant kinematics in rollover motor vehicle accidents: dynamic spit test.

A better understanding of occupant kinematics in rollover accidents helps to advance biomechanical knowledge and to enhance the safety features of motor vehicles. While many rollover accident simulation studies have adopted the static approach to delineate the occupant kinematics in rollover accidents, very few studies have attempted the dynamic approach. The present work was designed to study the biomechanics of restrained occupants during rollover accidents using the steady-state dynamic spit test and to address the importance of keeping the lap belt fastened. Experimental tests were conducted using an anthropometric 50% Hybrid III dummy in a vehicle. The vehicle was rotated at 180 degrees/second and the dummy was restrained using a standard three-point restraint system. The lap belt of the dummy was fastened either by using the cinching latch plate or by locking the retractor. Three configurations of shoulder belt harness were simulated: shoulder belt loose on chest with cinch plate, shoulder belt under the left arm and shoulder belt behind the chest. In all tests, the dummy stayed within the confinement of the vehicle indicating that the securely fastened lap belt holds the dummy with dynamic movement of 3 1/2" to 4". The results show that occupant movement in rollover accidents is least affected by various shoulder harness positions with a securely fastened lap belt. The present study forms a first step in delineating the biomechanics of occupants in rollover accidents.

Biomechanics of seat belt restraint system.

Seat belt system restrains and protects occupants in motor vehicle crashes and any slack in seat belt system induces additional loading on occupant. Signs of belt loading are more obvious in high-speed frontal collisions with heavy occupants. However subtle changes may occur at low speeds or with low forces from occupants during rollovers. In certain cases, the seat belt webbing is twisted and loaded by the occupant. The loading of webbing induces an observable fold/crimp on the seat belt. The purpose of the study is to biomechanically evaluate the force required to produce such marks using an anthropometric physical test dummy. Two tests were conducted to determine the amount of force required to put an observable fold/crimp in a shoulder belt. A head form designed by Voight Hodgson was used to represent the neck which interacted with the belt. The force was applied with a pneumatic pull ram (central hydraulic 89182 N) and the force was measured with a 44,000 N transducer load cell (DSM-10K). Results indicate that the force of over 1,000 N produced a fold or crimp in the belt.

Multivariate head injury threshold measures for various sized children seated behind vehicle seats in rear impacts.

Government recommendations to place children into the rear areas of motor vehicles to avoid airbag induced injuries have been complicated by the fact that most adult occupied front seats will collapse into the rear area during rear-impacts, and thus pose another potentially serious injury hazard to rear-seated children. Many variables affect whether or not a front seat occupant will collapse into the rear child, and whether that interaction could be injurious to the child. For instance, the severity of rear impact, coupled with front and rear occupant sizes (mass and stature), and the level of front seat strength, all interrelate to influence whether or not a rear seated child is likely to be impacted and possibly injured. The most common types of child injuries in these instances are head and chest injuries. In this study, a "high-low" experimental method was employed with a multi-level "factorial analysis" technique to study "multivariate" biomechanics of child head injury potential determined from rear-seated 3 and 6 year-old child surrogates in different types of vehicle bodies mounted to a sled system. The sled-buck systems were towed rearward into crushable barriers that matched the crash pulses of the vehicle types being tested. Various sizes of adult surrogates (i.e. 50 kg up to 110 kg), seated in both the "typical" low strength "single recliner" collapsing type front seat (i.e. 3.2 kN) and a much stronger "belt-integrated" seat design (i.e. up to 14.5 kN), were tested in the two different "sled body-buck" set-ups at various impact levels (i.e. 22.5 to 50 kph). One set-up used a popular minivan vehicle body with "built-in booster" seats for the 3 year-old. The other used a 4-door family sedan vehicle body with the 6 year-old in a standard rear bench seat. The parameters of the tests enabled the experimental data to be combined into polynomial "head injury" functions of the independent variables so the "likelihood" of rear child head-injury potential could be "mapped" over ranges of the key parameters. Accident cases were compared with predictions to verify the methodology.

Testing and injury potential analysis of rollovers with narrow object impacts.

Recent statistics highlight the significant risk of serious and fatal injuries to occupants involved in rollover collisions due to excessive roof crush. The government has reported that in 2002. Sports Utility Vehicle rollover related fatalities increased by 14% to more than 2400 annually. 61% of all SUV fatalities included rollovers [1]. Rollover crashes rely primarily upon the roof structures to maintain occupant survival space. Frequently these crashes occur off the travel lanes of the roadway and, therefore, can include impacts with various types of narrow objects such as light poles, utility poles and/or trees. A test device and methodology is presented which facilitates dynamic, repeatable rollover impact evaluation of complete vehicle roof structures with such narrow objects. These tests allow for the incorporation of Anthropomorphic Test Dummies (ATDs) which can be instrumented to measure accelerations, forces and moments to evaluate injury potential. High-speed video permits for detailed analysis of occupant kinematics and evaluation of injury causation. Criteria such as restraint performance, injury potential, survival space and the effect of roof crush associated with various types of design alternatives, countermeasures and impact circumstances can also be evaluated. In addition to presentation of the methodology, two representative vehicle crash tests are also reported. Results indicated that the reinforced roof structure significantly reduced the roof deformation compared to the production roof structure.

Biomechanical analysis of motor vehicle seat belt buckles.

Various studies have reported that inertially sensitive buckles are susceptible to impact unlatching. The present work synthesizes the results from various experimental studies conducted over the years to study the mechanical behavior of buckles and subsequent injuries to occupants. First, the side press button seat buckle due to impact a lateral impact from an adjacent child restraint seat component indicated that the side button RCF-67 buckle released at a speed of 2.2 m/sec with a force range of 264 to 440 N and acceleration range of 100 to 175 G. In contrast, the top button Autoliv Lockarm buckles did not release up to 1300 vertical G's. Second, side release RCF-67 buckles when loaded with the webbing required approximately three times more force to open than top press buckles. Inverted occupants in a three-point belt could not release the RCF-67 buckle. Third, a side sled impact on the drivers side of a production vehicle buck with a three-point belt and a RCF-67 buckle was done at 7 m/s to 8 m/s. A convertible child seat with a dummy in the passenger seat moved inboard toward the buckle and unlatched it. Fourth, an intact vehicle drop study at 0.3 m showed that the accelerations on a JDC buckle on a metal stalk are large compared to acceleration of the floor pan. The present study provides comprehensive data to evaluate the mechanical behavior of seat buckles under various motor vehicle crash conditions.

Motor vehicle seat belt restraint system analysis during rollover.

The multi-planar and multiple impact long duration accident sequence of a real world rollover results in multidirectional vehicle acceleration pulses and multiplanar occupant motions not typically seen in a planar crash sequence. Various researchers have documented that, while contemporary production emergency locking seatbelt retractors (ELRs) have been found to be extremely effective in the planar crashes in which they are extensively evaluated, when subjected to multi-planar acceleration environments their response may be different than expected. Specifically, accelerations in the vertical plane have been shown to substantially affect the timeliness of the retractors inertial sensor moving out of its neutral position and locking the seat belt. An analysis of the vehicle occupant motions relative to the acceleration pulses sensed at the retractor location indicates a time phase shift that, under certain circumstances, can result in unexpected seat belt spool out and occupant excursions in these multi-planar, multiple impact crash sequences. This paper will review the various previous studies focusing on the retractors response to these multidirectional, including vertical, acceleration environments and review statistical studies based upon U.S. government collected data indicating a significant difference in belt usage rates in rollover accidents as compared to all other planar accident modes. A significant number of real world accident case studies will be reviewed wherein the performance of ELR equipped seatbelt systems spooled out. Finally, the typical occupant injury and the associated mechanism due to belt spool out in real world accidents will be delineated.

Biomechanical injury evaluation of laminated side door windows and sunroof during rollover accidents.

Significantly more fatalities and serious injuries occur due to ejection in roll over 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 roll over 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 16 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 and 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.

Inverted drop testing and neck injury potential.

Inverted drop testing of vehicles is a methodology that has long been used by the automotive industry and researchers to test roof integrity and is currently being considered by the National Highway Traffic Safety Administration as a roof strength test. In 1990 a study was reported which involved 8 dolly rollover tests and 5 inverted drop tests. These studies were conducted with restrained Hybrid III instrumented Anthropometric Test Devices (ATD) in production and rollcaged vehicles to investigate the relationship between roof strength and occupant injury potential. The 5 inverted drop tests included in the study provided a methodology producing "repeatable roof impacts" exposing the ATDs to the similar impact environment as those seen in the dolly rollover tests. Authors have conducted two inverted drop test sets as part of an investigation of two real world rollover accidents. Hybrid-III ATD's were used in each test with instrumented head and necks. Both test sets confirm that reduction of roof intrusion and increased headroom can significantly enhance occupant protection. In both test pairs, the neck force of the dummy in the vehicle with less crush and more survival space was significantly lower. Reduced roof crush and dynamic preservation of the occupant survival space resulted in only minor occupant contact and minimal occupant loading, establishing a clear causal relationship between roof crush and neck injuries.

Experimental injury study of children seated behind collapsing front seats in rear impacts.

In the mid 1990's the U.S. Department of Transportation made recommendations to place children and infants into the rear seating areas of motor vehicles to avoid front seat airbag induced injuries and fatalities. In most rear-impacts, however, the adult occupied front seats will collapse into the rear occupant area and pose another potentially serious injury hazard to the rear-seated children. Since rear-impacts involve a wide range of speeds, impact severity, and various sizes of adults in collapsing front seats, a multi-variable experimental method was employed in conjunction with a multi-level "factorial analysis" technique to study injury potential of rear-seated children. Various sizes of Hybrid III adult surrogates, seated in a "typical" average strength collapsing type of front seat, and a three-year-old Hybrid III child surrogate, seated on a built-in booster seat located directly behind the front adult occupant, were tested at various impact severity levels in a popular "minivan" sled-buck test set up. A total of five test configurations were utilized in this study. Three levels of velocity changes ranging from 22.5 to 42.5 kph were used. The average of peak accelerations on the sled-buck tests ranged from approximately 8.2 G's up to about 11.1 G's, with absolute peak values of just over 14 G's at the higher velocity change. The parameters of the test configuration enabled the experimental data to be combined into a polynomial "injury" function of the two primary independent variables (i.e. front seat adult occupant weight and velocity change) so that the "likelihood" of rear child "injury potential" could be determined over a wide range of the key parameters. The experimentally derived head injury data was used to obtain a preliminary HIC (Head Injury Criteria) polynomial fit at the 900 level for the rear-seated child. Several actual accident cases were compared with the preliminary polynomial fit. This study provides a test efficient, multi-variable, method to compare the injury biomechanical data with actual accident cases.

Biomechanical analysis of padding in child seats and head injury.

Head injury is a common finding for infants and young children involved in automobile accidents. Although the child restraint seats have increased the level of safety for the pediatric population, skull fracture and/or brain injury occur during the interaction between the child's head and interior of the car seats with no padding. The introduction of effective and sufficient padding may significantly reduce the head injury. The present study was designed to evaluate the biomechanical effects of padding in child seats to reduce the potential for head injury. A head drop test of a six-month old anthropomorphic dummy was conducted. The side of the dummy head impacted the interior wing of child car seats of relatively soft and stiff materials, and a rigid metal plate at velocities of 2.2, 4.5 and 6.7 m/s. In all tests, three types of padding environments were used (no padding, comfort foam, 16 to 19 mm polypropylene padding). All data were collected at 10 kHz and filtered. A total of 39 tests were conducted. The head injury criteria (HIC), and head acceleration, and head angular acceleration were obtained. The HIC was calculated over a 36 ms interval from the resultant tri-axial acceleration. The angular accelerations were derived from the angular velocity data. The head injury biomechanical parameters decreased with the addition of padding. The HIC, peak acceleration, and angular acceleration were reduced up to 91%, 80%, and 61% respectively. The present results emphasize the importance of energy absorbing padding to provide an improved safety environment in child car seats.

Biomechanical analysis of head-neck force in hybrid III dummy during inverted vertical drops.

The hybrid III dummy has been used extensively for crash testing. The comparison between the cadaver and dummy data provides the biofidelic nature of dummy head-neck system to predict cervical spine injury as a function of applied force. The existing dummy data are limited to a lower drop height up to 0.5 m. The present study quantified the head-neck biomechanical response of the dummy up to a drop height of 1.20 m. At 0.15 m, the head force was 5740 N and 5695 N at the upper neck and 4231 N at the lower neck. At 0.6 m, the head force was 13,000 N and 12,000 N at the upper neck and 8900 N at the lower neck. At 1.2 m, the calculated head force was 19,500 N and 18,600 N at the upper neck and 13,500 N at the lower neck. The present results closely match with data of previous studies. The data indicated that the hybrid III system transmits about 70 to 75% of the applied force from the head or upper neck to the lower neck area. In contrast, the cadaver studies showed for drops from 0.9 to 1.5 m, about 20 to 30% of the applied force was transmitted from the head to the lower neck. The comparison demonstrates the capability of the Hybrid III dummy head-neck force response to realistically predict injury and also the need for comparing the dummy's response to the human head neck force data for injury.

Restraints and occupant kinematics in vehicular rollovers.

Occupant kinematics and the potential for injury in vehicular rollover crashes are dramatically affected by various restraint system characteristics. This study reviews previous research that utilized various methodologies and test fixtures to evaluate restrained occupant motions, primarily in the vertical direction, during both inverted and quasi-static simulated rollover environments. Additional laboratory tests were conducted in order to understand the static and dynamic excursion of restrained humans and surrogates in typical production motor vehicles under inverted circumstances. These tests indicated that volunteer occupants restrained within a complete vehicle by typical production 3 point seat belts will move vertically towards the vehicle roof structure by approximately 50-150 mm in production vehicles, depending on occupant size and belt configuration, when inverted and subjected to a static 1 g acceleration. Dynamic inverted vehicle drop testing in 3-point belt production vehicles, resulting in 4 to 11 g impacts, resulted in surrogates moving only about an additional 23 to 55 mm beyond the static inverted 1 g excursions.

Biomedical engineering analysis of glass impact injuries.

This article outlines the history, development, and safety aspects of glass and its use in motor vehicles. It traces the manufacture and describes the characteristics of laminated and tempered glass. It further compares the differences in injuries caused by impact with laminated and tempered glass. The development, use, and results of high penetration resistance (HPR) laminated glass for windshields are examined. Head and neck injuries from impact with glass and glazing structures are delineated. Results of studies with laminated and tempered glass are presented. The probability and severity of injuries occurring secondary to partial or full ejection of vehicle occupants are discussed, and the differences between the performance of laminated and tempered glass are highlighted. Current research to quantify head and neck injury parameters caused by glass impact during rollover is described. The biomechanics of head and neck injury assessment and the development of injury prediction parameters and reference values, respectively, are reviewed.