Rear Occupants Research Articles

Research on the Safety of Rear Seat Occupants in the Frontal Collision

To study the injury values rear seat occupants sustain in the frontal collision, this paper constructed the simulation model of the rear occupant restraint system of a vehicle model using MADYMO software. The influence of the rear 3-point seatbelt stiffness and retractor locking feature, the rear seat cushion stiffness and angle with the vehicle floor on head injury criterion HIC36, thorax 3ms resultant acceleration T3MS, thorax performance criterion THPC, left and right femur force of rear occupants were analysed through the simulation model. The conclusion shows that HIC36 drops when the seatbelt stiffness increases and retractor locking feature decreases compared to the original values; HIC36, T3MS, left and right femur force become less when the seat cushion stiffness decreases and angle increases compared to the original values.

Head Impact Contact Points for Restrained Child Occupants

Objective: Head injuries are the most common injuries sustained by children in motor vehicle crashes regardless of age, restraint, and crash direction. For rear seat occupants, the interaction of the subject with the seat back and the vehicle side interior structures has been previously highlighted. In order to advance this knowledge to the development of countermeasures, a summary of vehicle components that contributed to these injuries is needed. Therefore, the objective of this study was to create a contact map of the vehicle interior for head and face injuries to rear-seated restrained children in front crashes. Methods: The Crash Injury Research and Engineering Network (CIREN) was queried for rear-seated, restrained child occupants (age 0–15 years) in forward-facing child restraints, booster seats, or lap and shoulder belts who sustained an AIS2+ head and/or face injury in a frontal motor vehicle crash. Cases were analyzed to describe injury patterns and injury causation scenarios. A contact point map was developed to summarize the vehicle components related to injury causation of the head/face injury. Results: Twenty-one cases met the combined inclusion and exclusion criteria. Seven of the child occupants were restrained in forward-facing child restraints, 2 in belt-positioning booster seats, and 12 in lap and shoulder belts. There were 28 head and 17 facial injuries. For left rear occupants, the most common contact point was the pillar in front of the occupant's seat row; that is, B-pillar for second-row occupants, indicating a leftward kinematics. For right rear occupants, due to differences in crash dynamics, the most common contact point location was the passenger's seat back, suggesting that these occupants moved predominantly forward. Conclusions: Contact points associated with head/face injury for restrained children 0 to 15 years in frontal crashes have been delineated. In a majority of the cases, the head/face injury was the most severe injury and severe injuries to other body regions were uncommon, suggesting that efforts to mitigate head injuries for these occupants would greatly improve their overall safety. The majority of the head/face contact points were to the first row seat back and B-pillar. In these frontal crashes, the importance of head/face contact with the vehicle side structure suggests that deploying a curtain air bag in frontal impacts may help manage the energy of impact. These data advance the current understanding of injury patterns and causation in frontal crashes involving restrained rear-row occupants and can be used to develop solutions to mitigate the injuries sustained.

Case study of a frontal car accident involving three fatally injured children

Rear occupants are generally considered to sustain less severe injuries in frontal car impacts compared with front occupants. Contrary to this thesis, in 2009, in a serious accident involving two passenger cars took place in Austria in which three children seated in the rear were fatally injured in a frontal collision. Based on this car accident, the present study was performed to gain a better understanding of rear occupants’ injury mechanisms and potential improvements to rear-seat restraint system. The study employed a validated numerical model that shows that loads and injury criteria can be reduced by up to 70%. Also, national accident databases have been analysed. The accidentology indicates that children restrained by the vehicle rear belt are fatally injured only approximately two times more frequently than children using a child restraint system. The investigation indicates that the protection level offered to children aged 6–14 does not match the high protection level available for adults and for children up to six.

Front-to-Rear Crashes Involving Two Vehicles With Severe Driver Injury

Purpose: This study investigates the risk for severe-to-fatal injury (Maximum Abbreviated Injury Scale [MAIS] 4+F) to drivers in two-vehicle crashes involving front impacts into the rear of another vehicle. Methods: 1995–2009 National Automotive Sampling System–Crashworthiness Data System (NASS-CDS) was analyzed for driver injuries in front-to-rear crashes without rear occupants in either vehicle. The study involved 13+-year-old front outboard occupants in model year (MY) 1995+ light vehicles. Injury severity was subdivided into MAIS 0+6 and MAIS 4+F to assess the risk of severe-to-fatal injury (MAIS 4+F/MAIS 0+6). Injury risks were determined using weighted data for the drivers by impact type. Standard errors were calculated in SAS to determine ±95 percent confidence intervals. An in-depth analysis was made of individual cases with severely injured drivers in the front and rear impacts. Results: There were 215,163 drivers in the 15 years of NASS-CDS with known injuries in front-to-rear two-vehicle collisions; 624 were severely injured (MAIS 4+F) in the rear impacts and 124 in the front impacts. The risk for severe-to-fatal driver injury was 0.290 ± 0.241 percent in rear impacts and 0.058 ± 0.057 percent in front impacts. The difference was not statistically significant (P > .05). There were 13 unweighted cases with MAIS 4+F driver injury in rear impacts. Most (77%) involved intrusion in the vicinity of the driver's seating area with the seat supported upright or deformed forward. There were 5 unweighted cases with severely injured drivers in frontal impacts. Three (60%) involved intrusion due to offset frontal loading. There was only one crash where both drivers were severely injured. Conclusions: In front-to-rear crashes with two vehicles, typically one driver was severely injured, not both. The risk of severe injury was not significantly different for drivers in the front or rear impacts. The risk was higher in rear impacts due to intrusion into the driver's seating area that supported or pushed the driver's seat forward. The risk for drivers in frontal crashes was also often related to intrusion due to offset loading and occupant compartment deformation.

Investigation of Rear Occupant Head Restraint Interaction in High-Severity Rear Impact using BioRID and HIII

Investigation of Rear Occupant Head Restraint Interaction in High-Severity Rear Impact using BioRID and HIII

A matched-cohort analysis of belted front and rear seat occupants in newer and older model vehicles shows that gains in front occupant safety have outpaced gains for rear seat occupants

Previous studies have suggested that rear seat occupants are at lower risk of serious injury and death in crashes. However, over the last 10–15 years there have been significant changes in front seat safety systems. The aim of this study was to determine whether there is still a benefit for rear seated occupants compared to front seat occupants. A matched-cohort approach, using data on restrained occupants from the US National Automotive Sampling System (data years 1993–2007), was adopted. Conditional poisson regression modeling was used to evaluate the relative risk of AIS3+ injury in front (passenger and driver) and rear seat occupants, in vehicles of model year 1990–1996 compared to newer vehicles. Occupant age, belt type, and intrusion were additional variables in the model. The relative risk of AIS3+ injury for front and rear occupants was influenced by age and model year. For those aged 16–50 years in older vehicles, the front and rear seat offered similar levels of protection (RR = 1.14, CI = 1.09–1.19), however in newer model vehicles (1997–2007), the rear seat carried a higher risk of injury (RR = 1.98, CI = 1.90–2.06). For adults over 50 years, the rear seat carried a higher risk in both older and newer vehicles, and for 9–15 year olds, the rear seat carried a lower risk. These findings suggest that safety for front seat occupants has improved over the last decade, to the point where, for occupants over 15 years of age, the front seat is safer than the rear seat. While the benefit of rear seating for children aged 9–15 years has decreased over time, they are still at lower risk in the rear seat.

Transportation Safety Standards for Wheelchair Users: A Review of Voluntary Standards for Improved Safety, Usability, and Independence of Wheelchair-Seated Travelers

Safe transportation for wheelchair users who do not transfer to the vehicle seat when traveling in motor vehicles requires after-market wheelchair tiedown and occupant restraint systems (WTORS) to secure the wheelchair and provide crashworthy restraint for the wheelchair-seated occupant. In the absence of adequate government safety standards, voluntary standards for the design and performance of WTORS, and for wheelchairs used as seats in motor vehicles, have been developed. The initial versions of these standards qualify equipment for use in all types and sizes of motor vehicles using a 30-mph (48-kph), 20-g frontal sled-impact test. The wheelchair standard requires four accessible, crash-tested securement points on wheelchairs so they can be more easily and effectively secured using a four-point strap-type tie-down system. Future voluntary standards are aimed at reducing injury risk for wheelchair-seated occupants in rear impacts and at providing a method for evaluating the crashworthiness of wheelchair seating systems independent of wheelchair base-frames. They also address improved usability and independence for wheelchair-seated travelers using public transportation by specifying universal docking interface geometry for wheelchairs and design and performance requirements for rear-facing wheelchair passenger stations for use in the very low-g environments of large fixed-route transit buses.

Research Study on Neck Injury Lessening with Active Head Restraint Using Human Body FE Model

Objectives: The objective of this study is to examine the effectiveness of the active head restraint system in reducing neck injury risk of car occupants in low-speed rear impacts. Methods: A human body FE model “THUMS” was used to simulate head and neck kinematics of the occupant and to evaluate loading to the neck. Joint capsule strain was calculated to predict neck injury risk as well as NIC. The validity of the model was confirmed comparing its mechanical responses to those in human subjects in the literatures. Seat FE models were also prepared representing one with a fixed head restraint and the other one with an active head restraint system. The active head restraint system was designed to move the head restraint forward and upward when the lower unit was lower unit was loaded by the pelvis. Rear impact simulations were performed assuming a triangular acceleration pulse at a delta-V of 25 km/h. Results : The model reproduced similar head and neck motions to those measured in the human volunteer test, except for active muscular responses. The calculated joint capsule strain also showed a good match with those of PMHS tests in the literature. A rear-impact simulation was conducted using the model with the fixed head restraint. The result revealed that NIC was strongly correlated with the relative acceleration between the head and the torso and that its maximum peak appeared when the head contacted the head restraint. It was also found that joint capsule strain grew in later timing synchronizing with the relative displacement. Another simulation with the active head restraint system showed that both NIC and joint capsule strain were lowered owing to the forward and upward motion of the head restraint. A close investigation of the vertebral motion indicated that the active head restraint reduced the magnitude of shear deformation in the facet joint, which contributed to the strain growth in the fixed head restraint case. Conclusions: Rear-impact simulations were conducted using a human body FE model, THUMS, representing an average-size male occupant. The cervical system including the facet joint capsules was incorporated to the model. The validity of the model was examined comparing its mechanical responses to those in the literature such as the whole body motion of the volunteer subject and the vertebral motion in the PMHS tests. Rear-impact simulations were conducted using the validated THUMS model and two prototype seat models; one had a fixed head restraint and the other one was equipped with an active head restraint system. The active head restraint system works moving the head restraint forward and upward when the lower unit is loaded by the pelvis. The head and neck kinematics and responses were analyzed from the simulation results. The force and acceleration rose at the pelvis first, followed by T1 and the head. The early timing of force rise and its magnitude indicated that the pelvis force was a good trigger for the active head restraint system. The results showed that the head was supported earlier in a case with the active head restraint system, and both NIC and joint capsule strain were lowered. The study also analyzed the mechanism of strain growth in the joint capsules. Relatively greater strain was observed in the direction of the facet joint surface, which was around 45 degrees inclined to the spinal column. The forward and upward motion of the active head restraint were aligned with the direction of the joint deformation and contributed to lower strain in the joint capsules. The results indicated that the active head restraint could help reduce the neck injury risk not only by supporting the head at an early timing but also through its trajectory stopping the joint deformation.

Pattern of seat belt wearing in Nanjing, China

Objective:To describe the patterns of seat belt wearing in Nanjing, China for drivers, front seat passengers, and rear occupants of motor vehicles.Design:Roadside observational study.Setting:Four sites in central and northern Nanjing...

Association of rear seat safety belt use with death in a traffic crash: a matched cohort study

Objective: To estimate the association of rear seat safety belt use with death in a traffic crash. Design: Matched cohort study. Setting: The US during 2000 through 2004. Subjects: Drivers...

Relative risk of injury and death in ambulances and other emergency vehicles

This study addresses of the impacts of emergency vehicle (ambulances, police cars and fire trucks) occupant seating position, restraint use and vehicle response status on injuries and fatalities. Multi-way frequency and ordinal logistic regression analyses were performed on two large national databases, the National Highway Traffic Safety Administration’s Fatality Analysis Reporting System (FARS) and the General Estimates System (GES). One model estimated the relative risk ratios for different levels of injury severity to occupants traveling in ambulances. Restrained ambulance occupants involved in a crash were significantly less likely to be killed or seriously injured than unrestrained occupants. Ambulance rear occupants were significantly more likely to be killed than front-seat occupants. Ambulance occupants traveling non-emergency were more likely than occupants traveling emergency to be killed or severely injured. Unrestrained ambulance occupants, occupants riding in the patient compartment and especially unrestrained occupants riding in the patient compartment were at substantially increased risk of injury and death when involved in a crash. A second model incorporated police cars and fire trucks. In the combined ambulance–fire truck–police car model, the likelihood of an occupant fatality for those involved in a crash was higher for routine responses. Relative to police cars and fire trucks, ambulances experienced the highest percentage of fatal crashes where occupants are killed and the highest percentage of crashes where occupants are injured. Lack of restraint use and/or responding with ‘lights and siren’ characterized the vast majority of fatalities among fire truck occupants. A third model incorporated non-special use van and passenger car occupants, which otherwise replicated the second model. Our findings suggest that ambulance crewmembers riding in the back and firefighters in any seating position, should be restrained whenever feasible. Family members accompanying ambulance patients should ride in the front-seat of the ambulance.

Suggestions for Evaluation Criteria of Neck Injury Protection in Rear-End Car Impacts

Rear-end impact sled tests were performed with the aim of developing evaluation criteria for neck injury protection, using the Biofidelic Rear Impact Dummy (BioRID I). Based on accident experience, occupants in rear seats and occupants with increased distance to head restraints are at a lower and higher risk, respectively, as compared to a front-seat occupant in a regular sitting posture. The occupant situations that were simulated and compared were front-seat occupant and rear-seat occupant in a regular sitting posture and front-seat occupant with increased head to head restraint distance. The evaluation measurements chosen for testing were based on three guidelines concerning body acceleration, relative movements of the spine, and rebound motion. This study suggests several evaluation criteria, which concur with Whiplash Protection Study (WHIPS) guidelines using the BioRID I.

Risk of injury to child passengers in compact extended-cab pickup trucks.

An increasing number of compact pickup trucks can accommodate restrained rear occupants. Rear seats in these pickup trucks are exempt from regulatory safety testing though their relative safety has not been determined. To evaluate the risk of injury to children in compact extended-cab pickup trucks compared with children in other vehicles and to determine if any unique hazards exist. Cross-sectional study of children aged 15 years or younger in crashes of insured vehicles, with data collected via insurance claim records and a telephone survey. Probability sample of 7192 multirow vehicles involved in crashes, with 11 335 child occupants, in 3 large US regions from December 1, 1998, to November 30, 2000. Relative risk of injury, defined as concussions and more serious brain injuries, spinal cord injuries, internal organ injuries, extremity fractures, and facial lacerations, estimated by odds ratios (ORs) adjusting for age, restraint use, point of impact, vehicle weight, and crash severity. Injuries were reported for 1356 children, representing 1.6% of the population. Children in compact extended-cab pickup trucks were at greater risk of injury than children in other vehicles (adjusted OR, 2.96; 95% confidence interval [CI], 1.68-5.21). Children in the rear seats of compact pickup trucks were at substantially greater risk of injury than rear-seated children in other vehicles (adjusted OR, 4.75; 95% CI, 2.39-9.43). Children seated in the front seat of compact extended-cab pickup trucks were at greater risk of injury than children in the front seats of other vehicles, but this risk was not statistically significant (adjusted OR, 1.70; 95% CI, 0.78-3.69). Children in compact extended-cab pickup trucks are not as safe as children in other vehicles, primarily due to the increased relative risk of injury in the back seat. For families with another choice of vehicle, clinicians should advise parents against transporting children in compact pickup trucks. The current exemption for regulatory testing for occupant protection in the rear seats of compact pickup trucks should be reconsidered.

Relationships between seat properties and human subject kinematics in rear impact tests

The mitigation of whiplash associated disorders (WAD) has received increased priority in the last 10 years. Although the exact mechanism(s) for WAD causation have not been established, several have been proposed and it is likely the mechanism(s) are associated with the kinematics of the head relative to the torso. It follows that automotive seat designs that address reductions in certain head–torso kinematics may lead to a reduction in WAD potential. Seat properties that may have an effect on head–neck kinematics include geometry, stiffness and energy absorption. This study evaluated the performance of five seats with varying properties, including the new Volvo ‘WHIPS’ seat. Seat properties such as geometry relative to the occupant's head, dynamic and static stiffness, and energy absorption were determined via component testing. A new prototype dynamic seat test, which used a pendulum and seat back pan, was evaluated. Human subject impact tests were conducted using three occupants in rear impacts with velocity changes of 4 and 8 km/h. Potentially relevant occupant kinematic parameters were identified, and then correlated with seat properties in an attempt to determine any relative influence of seat properties on potential WAD mechanisms. Two higher velocity human subject tests using the Volvo Whiplash Injury Protection System (WHIPS) seat were also conducted. Vertical and horizontal head to head restraint distances were found to be most influential on occupant head–neck kinematics. Horizontal and vertical head to head restraint offsets were significantly correlated with rearward translational motion of the head center of gravity relative to the upper torso across all occupants. Rearward offset was also significantly correlated with rearward rotation of the head relative to upper torso, while vertical offset was significantly correlated with head acceleration relative to the upper torso during the flexion phase of the impact. Seat constitutive properties such as stiffness and energy absorption were not significantly correlated with occupant head–neck kinematics. The new dynamic seat test posed problems in data interpretation, and suggestions for improvement are made. The Volvo ‘WHIPS’ seat proved to be very effective in reducing many potential WAD associated head–neck kinematics. The two increased severity impacts activated the additional protective energy absorption elements in the seat, and no injuries were sustained by the occupants.

Effectiveness of cargo barriers to protect front seat occupants in rear impacts - crash test evaluation

although cargo barriers have been well developed for providing cargo restraint in frontal impacts, the effect of load and restraint systems subjected to rear impacts has not been subjected to the same performance evaluation. This paper examines this issue and presents the results from a rear impact crash test carried out on a telecommunication service vehicle fitted with storage shelving and items typically carried out for service calls. Published research on injury risk to vehicle occupants in rear impacts has focused primarily on fuel tank integrity; whiplash and seat design/headrest issues; and seatback strength. However injury outcomes in rear impacts can also be significantly influenced by cargo, fitted shelving or other items carried in the rear of the vehicle. The test results clearly identified the increased injury risks to front seat occupants that can arise in rear impacts due to items carried in the rear storage space of vehicles. Modifications to the vehicle shelving and the avoidance of direct load paths are required to avoid transferring high impact loads into the cargo barrier and directly through to the occupants. The development of a suitable rear impact test protocol is also presented.

C HARACTERISTICS OF F ATAL A MBULANCE C RASHES IN THE U NITED S TATES : A N 11- YEAR R ETROSPECTIVE A NALYSIS

Background. Ambulance crashes have become an increasing source of public concern. Emergency medical services directors have little data to develop ambulance operation and risk management policies. Objective. To describe fatal ambulance crash characteristics, identifying those that differentiate emergency and nonemergency use crashes. Methods. This was a retrospective analysis of all fatal ambulance crashes on U.S. public roadways reported to the Fatality Analysis Reporting System (FARS) database from 1987 to 1997. Main outcome measures were 42 variables describing crash demographics, crash configuration, vehicle description, crash severity, and ambulance operator and vehicle occupant attributes. Results. Three hundred thirty-nine ambulance crashes caused 405 fatalities and 838 injuries. These crashes occurred more often between noon and 6 PM (39%), on improved (99%), straight (86%), dry roads (69%) during clear weather (77%), while going straight (80%), through an intersection (53%), and striking (81%) another vehicle (80%) at an angle (56%). Most crashes (202/339) and fatalities (233/405) occurred during emergency use. These crashes occurred significantly more often at intersections (p < 0.001), at an angle (p < 0.001), with another vehicle (p < 0.001). Most crashes resulted in one fatality, not in the ambulance. Thirty pedestrians and one bicyclist comprised 9% of all fatalities. In the ambulance, most serious and fatal injuries occurred in the rear (OR 2.7 vs front) and to improperly restrained occupants (OR 2.5 vs restrained). Sixteen percent of ambulance operators were cited; 41% had poor driving records. Conclusions. Most crashes and fatalities occurred during emergency use and at intersections. The greater burden of injury fell upon persons not in the ambulance. Rear compartment occupants were more likely to be injured than those in the front. Crash and injury reduction programs should address improved intersection control, screening to identify high-risk drivers, appropriate restraint use, and design modifications to the rear compartment of the ambulance.

Foot-ankle injuries: Influence of crash location, seating position and age

Foot-ankle injuries have increased in relative importance in recent years. As a basis for future countermeasures, an epidemiology study has been undertaken using Swedish accident data from Folksam Insurance. The database consists of 805 foot-ankle injuries out of 57,949 car occupant injuries reported from 1985 to 1991. The influence of crash location, seating position and occupant age is determined for the frequency, incidence and rate of foot-ankle injury in car crashes. Frontal car crashes produce 76% of the AIS 2–3 foot-ankle injuries with 13% in side impacts and 8% in roll-overs. The rate of AIS 2–3 foot-ankle injury is 24.7 per 1000 occupants injured in all crash locations and is similar irrespective of seating positions. Ankle fractures and sprains both occur at an incidence of 3.7 per 1000 injuries, followed by malleolus fractures at 2.7 and midtarsal fractures at 2.4. The foot-ankle injury incidence and rate are significantly greater ( p<0.01) in near oblique-frontal crashes than for 12 o'clock frontals. For drivers in 11 o'clock and front passengers in 1 o'clock, the incidence is 27.8 per 1000 injuries as compared to 17.5 for drivers and front passengers in 12 o'clock crashes. Occupant age is not as significant as seating position and crash location; however, there are higher incidences for rear occupants ⩾60 years old in oblique frontal crashes. Using the new AAAM Impairment Injury Scale (IIS), 48% of the foot-ankle injuries are rated with residual impairment IIS 1–2. The incidence in near-seated occupants is 1.5 times greater in oblique frontal crashes than in frontals. The incidence for IIS 1–2 impairment in near oblique-frontal crashes is 12.8 per 1000 occupant injuries as compared to 8.3 in frontal crashes.