Rollover injury: effects of near- and far-seating position, belt use, and number of quarter rolls

Investigating factors affecting injury severity of single-vehicle run-off-road crashes

This study aimed to identify and investigate the contributing factors influencing injury severity in single-vehicle run-off-road (ROR) crashes, which are known for their high severity. The primary objective was to analyze and compare the impact of these factors across three distinct vehicle classes: passenger cars, sport utility vehicles (SUVs), and pickups. A mixed logit model with heterogeneity in mean and variance was developed to analyze the injury severity outcomes in ROR crashes for the three vehicle classes. The model accounted for the potential variations in the impact of contributing factors across different vehicle types. The study revealed several significant variables consistently influencing injury severity across all three vehicle classes. These included driver age, alcohol or drug usage, seatbelt utilization, airbag deployment, higher travel speeds, and the vehicle model year post-2010. Notably, as driver age increased, the impact on changes in injury severity outcomes was more pronounced for pickup drivers compared to those operating passenger cars and SUVs. Among the common findings was the highly effective role of seatbelt usage in mitigating injury severity in ROR crashes. Additionally, passenger cars were associated with increased injury severity, particularly at relatively higher travel speeds exceeding 75 mph when contrasted with SUVs and pickups traveling between 61 and 75 mph. The study highlights the importance of considering vehicle class-specific factors in analyzing injury severity in ROR crashes. Recommendations include further in-depth investigations into distinct factors contributing to injury severity within each vehicle class and utilizing more extensive crash datasets to gain additional insights for enhancing road safety.

Effect of ESC (electronic stability control) on tree and pole impacts with focus on rear impacts

Objective

The effect of ESC (Electronic Stability Control) was investigated for the rate of crash exposure, serious injury and fatality in pole and tree impacts. Field data was analyzed by crash type (front, side, rear and rollover) and model year (MY) before, during and after the implementation of ESC.

Methods

The number of pole and tree impacts was determined for four groups of vehicle model years (MY): 1981-1989 MY and 1990-2002 MY before the introduction of ESC, 2003-2009 during the phase-in of ESC and 2010-2020 MY after essentially all vehicles were equipped with ESC. Collisions were grouped by front, side, rear and rollover. Three databases were analyzed: 1990-2020 FARS, 1990-2015 NASS-CDS and 2017-2020 CISS. Vehicle registration was obtained from IHS Markit to determine the rate of pole and tree impacts per 100,000 registered vehicles. The same vehicle selection criteria was used for vehicle registration and crash data.

Results

Fatalities dropped 65.2 % (95 % CI, 63.0-67.4 %), z = 43.7, p < 0.001 into poles and 60.3 % (95 % CI, 59.0-61.5 %), z = 72.4, p < 0.001 into trees in vehicles equipped with ESC comparing 1990-2002 MY to 2010-2020 MY vehicles. Seriously injured occupants in crashes with poles dropped 75.9 % (95 % CI, 75.0-76.9 %), z = 116, p < 0.001 between 1990 and 2002 MY and 2010-2020 MY vehicles. There was a 65.2 % (95 % CI, 64.4-65.9 %), z = 141, p < 0.001 reduction in tree impacts. The crash exposure to pole impacts dropped 36.0 % (95 % CI, 35.8-36.3 %), z = 252, p < 0.001 from 80.77/100,000 registered vehicles in 1990-2002 MY vehicles to 51.69/100,000 in 2010-2020 MY vehicles. There was a 61.0 % (95 % CI, 60.8-61.2 %), z = 434, p < 0.001 reduction in tree impacts. For rear impacts, fatalities dropped 82.9 % (95 % CI, 71.3-94.4 %), z = 9.37, p < 0.001 into poles and 74.8 % (95 % CI, 67.8-81.9 %), z = 14.8, p < 0.001 into trees. Serious-injury in rear impacts with poles and trees were essentially eliminated in 2010-2020 MY vehicle crashes. There were significant drops in fatalities in side and frontals impacts and rollovers in vehicles equipped with ESC.

Conclusion

ESC helps the driver maintain vehicle heading and significantly reduced the rate of serious injury and fatality in off-road impacts with poles and trees. The benefits of ESC may not be realized with impairments when the driver does not appropriately steer the vehicle.

Cervical vertebral and spinal cord injuries in rollover occupants

BACKGROUND

Rollover crashes continue to be a substantial public health issue in North America. Previous research has shown that the cervical spine is the most injured spine segment in rollovers, but much of the past research has focused on risk factors rather than the actual cervical spine injuries. We sought to examine how different types of cervical spine injuries (vertebral and/or cord injury) vary with different occupant-related factors in rollovers and to compare these with non-rollovers.

METHODS

We obtained crash and injury information from the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) for 2005-2015 and Crash Investigation Sampling System (CISS) for 2017-2022. Based on weighted data, we calculated relative risks to assess how occupant sex, seat belt use, ejection status, and fatal outcome relate to the rate of different cervical spine injuries in rollovers and non-rollovers.

RESULTS

In NASS-CDS occupants with cervical spine injuries (N = 111,040 weighted cases), about 91.5% experienced at least one vertebral injury whereas only 11.3% experienced a spinal cord injury (most of which had a concomitant vertebral fracture). All types of cervical spine injuries we examined were 3.4-5.2 times more likely to occur in rollovers compared to non-rollovers. These relative risks were similar for both sexes, belted and unbelted, non-ejected, and non-fatal occupants. The number of weighted CISS occupants with cervical spine injuries (N = 42,003) was smaller than in the NASS analysis, but cervical spine injuries remained 6.25 to 6.36 times more likely in rollovers compared to non-rollovers despite a more modern vehicle fleet.

CONCLUSIONS

These findings underscore the continued need for rollover-specific safety countermeasures, especially those focused on cervical spine injury prevention, and elucidate the frequency, severity and other characteristics of the specific vertebral and spinal cord injuries being sustained in rollovers. Our findings suggest that countermeasures focused on preventing cervical vertebral fractures will also effectively prevent most cervical spinal cord injuries.

Contributory factors to the severity of single-vehicle rollover crashes on a mountainous area, generalized additive model

The purpose of this study was to identify contributory factors to severity of rollover crashes in the mountainous state of Wyoming. These crashes account for more than half of all roadway fatalities in Wyoming, compared with the average of the U.S. rollover-related fatality crashes, which stands at 33%. In this study, the standard generalized linear model (GLM) was extended to the method of generalized additive model (GAM) to determine if giving more flexibility provides more realistic point estimates of the factors to the rollover crash severity. The results highlighted the superiority of the GAM compared with the GLM in terms of confusion matrix accuracy and Akaike Information Criterion (AIC). The results of the GAM highlighted that the majority of important factors that contribute to rollover crash severity are related to drivers' characteristics such as driving while under influence of drugs, being under an emotional condition, driving with no valid driver license, and driving with suspended drivers' license. Also, it was found that the impact of passenger vehicles on the severity of rollover crashes is not stable and varies based on the gender of drivers. Only two predictors were considered based on the smooth functions including posted speed limit and drivers' age. We accounted for non-linearity of those two predictors by means of cubic spline smooth function.

Evaluation of the effectiveness of vehicle roll stability control (RSC) for high center of gravity light passenger vehicles in Australasia

OBJECTIVE

Rollover crashes, which occur when the vehicle's side or roof makes impact with the ground, present particularly serious injury risk. Higher rollover risk has been found for high riding vehicles - those with a relatively high center of gravity compared to the width of the wheel track. Electronic Stability Control (ESC), which automatically applies brakes to individual wheels and reduces engine power to help drivers regain control when traction is lost, has been shown to be effective in preventing a proportion of rollovers. A newer safety technology, Roll Stability Control (RSC), uses similar technology aimed specifically to reduce rollover risk. This study sought to estimate rollover crash rates associated with the fitment of RSC compared to non-fitment for high center of gravity (CG) light passenger vehicles using an induced exposure analysis.

METHODS

Police-recorded Australasian crash data were studied for the years 2008-2017. A quasi-induced exposure analysis was restricted to vehicles already equipped with ESC as vehicles fitted with RSC always have ESC fitted. Rollover risk associated with RSC fitment was assessed, controlling for year of crash, speed limit at crash location, year of vehicle manufacture, vehicle market group, driver age, driver gender and jurisdiction identifier.

RESULTS

The analysis found a statistically significant rollover risk ratio of 0.76 (95% CI 0.62-0.93), representing a 24% reduction in rollover risk, associated with RSC fitment for vehicles manufactured between 2008 and 2017. Analysis by particular market groups found significant risk ratio reductions for commercial utilities and large SUVs, but not for the other high CG market groups individually.

CONCLUSIONS

These results suggest that RSC is a highly effective safety feature for high CG vehicles. Fleet data from Australia and New Zealand showed declining rates of RSC fitment over recent years for SUVs, meaning the potential road safety benefits of the technology are not being fully realized.

Quantitative evaluation of the occupant kinematic response of the THUMS 50th-percentile male model relative to PMHS laboratory rollover tests

OBJECTIVE

The objective of the current study was to evaluate the whole-body kinematic response of the Total Human Model for Safety (THUMS) occupant model in controlled laboratory rollover tests by comparing the model response to postmortem human surrogate (PMHS) kinematic response targets published in 2014.

METHODS

A computational model of the parametric vehicle buck environment was developed and the AM50 THUMS occupant model (Ver 4.01) was subjected to a pure dynamic roll at 360°/s in trailing-side front-row seating position. A baseline configuration was defined by a baseline posture representing the average of all PMHS postures, with a friction coefficient of 0.4 for the belt and 0.6 for the seat. To encompass challenges in controlling boundary conditions from the PMHS tests and ensure the robustness of the model evaluation, a total of 12 simulations were performed to investigate the following: 1. The effect of initial posture by adding 3 additional postures representing PMHS extremes. 2. The effect of belt tension by varying tension from the nominal vehicle retractor belt tension of 5 N to the 35 N belt tension used in the PMHS tests. 3. The effect of friction between the environment (belt, seat) and THUMS. Trajectories (head, T1, T4, T10, L1, and sacrum), spinal segment rotations (head-to-T1, T1-to-T4, T4-to-T10, T10-to-L1, and L1-to-sacrum) relative to the rollover buck and spinal segment elongation/compression calculated from the simulations were compared to PMHS corridors using a correlation method (CORA).

RESULTS

THUMS baseline response showed lower correlation (overall CORA score = 0.63) with the PMHS response in rollover compared to other crash modes. THUMS and PMHS demonstrated similar kinematic responses in the longitudinal axis and vertical axis but significantly different lateral excursion relative to the seat. In addition, no spinal elongation was observed for THUMS compared to the PMHS. The posture, pretension, and belt frictions were found to alter model kinematics, especially on THUMS lateral axis motion. The posture was judged to be the most sensitive parameter evaluated because a change of 30 mm in the lateral axis results in up to an 80 mm of change in observed displacement.

CONCLUSIONS

Though the model response in the lateral axis is significantly different than that of the PMHS, it is unclear whether this difference is the result of extrinsic factors (posture, pretension, and friction), where exact values in experiment are unknown or by model intrinsic factors (e.g., spine stiffness). These differences in occupant kinematics could potentially subject the PMHS and THUMS to very different loading conditions under roof impact in rollover crashes: different occupant posture and different roof impact location. Therefore, different injury mechanisms and severity might be predicted by the current model relative to the PMHS. Consequently, though the information provided in the current study could be useful for improving model biofidelity for rollover crashes, additional studies are required to properly solve this issue.

Integrating engineering principles into the medico-legal investigation of a rare fatal rollover car accident involving complex dynamics

Rollover car accidents can be the result of forceful steering or hitting an obstacle that acts like a ramp. Mortality from this type of car accident is particularly high, especially when occupants are thrown out of the vehicle. We report a case of a 67-year-old man who died after a rollover accident that occurred when he was driving a car equipped with a glass moonroof. He was found inside his car with his safety belt correctly fastened and the roof shattered. At autopsy, a wide avulsion injury of the head was observed, which was associated with an atlanto-axial dislocation and full-thickness fracture of the cervical body and posterior facet joints of the seventh cervical vertebra. The data collected at the scene of the accident were integrated with the autopsy results to yield a forensic engineering reconstruction. This reconstruction elucidated the dynamics of the event and correctly ascribed the lesions observed at autopsy to the phases of the rollover. Afterward, an analysis of the scientific literature concerning rollover crash tests was conducted to understand why the driver sustained fatal injuries even though his seatbelt was properly fastened.

Epidemiology of moderate-to-severe injury patterns observed in rollover crashes

BACKGROUND

Previous epidemiological studies have highlighted the high risk of injury to the head, thorax, and cervical spine in rollover crashes. However, such results provide limited information on whole-body injury distribution and multiple region injury patterns necessary for the improvement and prioritization of rollover-focused injury countermeasures.

METHODS

Sampled cases representing approximately 133,000 U.S. adult occupants involved in rollover crashes (between 1995 and 2013) sustaining moderate-to-severe injuries were selected from the National Automotive Sampling System Crashworthiness Data System database. A retrospective cohort study, based on a survey of population-based data, was used to identify relevant whole body injury patterns.

RESULTS

Among belted occupants injured in rollover crashes, 79.2% sustained injuries to only one body region. The three most frequently injured (AIS2+) body regions were head (42.1%), upper extremity (28.0%), and thorax (27.1%). The most frequent multi-region injury pattern involved the head and upper extremity, but this pattern only accounted for 2.3% of all of occupants with moderate or worse injuries.

CONCLUSIONS

The results indicated that for rollover-dominated crashes, the frequently observed injury patterns involved isolated body regions. In contrast, multi-region injury patterns are more frequently observed in rollovers with significant planar impacts. Identification of region-specific injury patterns in pure rollover crashes is essential for clarifying injury mitigation targets and developing whole-body injury metrics specifically applicable to rollovers.

An Injury Severity-, Time Sensitivity-, and Predictability-Based Advanced Automatic Crash Notification Algorithm Improves Motor Vehicle Crash Occupant Triage

BACKGROUND

Advanced Automatic Crash Notification algorithms use vehicle telemetry measurements to predict risk of serious motor vehicle crash injury. The objective of the study was to develop an Advanced Automatic Crash Notification algorithm to reduce response time, increase triage efficiency, and improve patient outcomes by minimizing undertriage (<5%) and overtriage (<50%), as recommended by the American College of Surgeons.

STUDY DESIGN

A list of injuries associated with a patient's need for Level I/II trauma center treatment known as the Target Injury List was determined using an approach based on 3 facets of injury: severity, time sensitivity, and predictability. Multivariable logistic regression was used to predict an occupant's risk of sustaining an injury on the Target Injury List based on crash severity and restraint factors for occupants in the National Automotive Sampling System - Crashworthiness Data System 2000-2011. The Advanced Automatic Crash Notification algorithm was optimized and evaluated to minimize triage rates, per American College of Surgeons recommendations.

RESULTS

The following rates were achieved: <50% overtriage and <5% undertriage in side impacts and 6% to 16% undertriage in other crash modes. Nationwide implementation of our algorithm is estimated to improve triage decisions for 44% of undertriaged and 38% of overtriaged occupants. Annually, this translates to more appropriate care for >2,700 seriously injured occupants and reduces unnecessary use of trauma center resources for >162,000 minimally injured occupants.

CONCLUSIONS

The algorithm could be incorporated into vehicles to inform emergency personnel of recommended motor vehicle crash triage decisions. Lower under- and overtriage was achieved, and nationwide implementation of the algorithm would yield improved triage decision making for an estimated 165,000 occupants annually.

Occupant injury in rollover crashes - Contribution of planar impacts with objects and other vehicles

Planar impacts with objects and other vehicles may increase the risk and severity of injury in rollover crashes. The current study compares the frequency of injury measures (MAIS 2+, 3+, and 4+; fatal; AIS 2+ head and cervical spine; and AIS 3+ head and thorax) as well as vehicle type distribution (passenger car, SUV, van, and light truck), crash kinematics, and occupant demographics between single vehicle single event rollovers (SV Pure) and multiple event rollovers to determine which types of multiple event rollovers can be pooled with SV Pure to study rollover induced occupant injury. Four different types of multiple event rollovers were defined: single and multi-vehicle crashes for which the rollover is the most severe event (SV Prim and MV Prim) and single and multi-vehicle crashes for which the rollover is not the most severe event (SV Non-Prim and MV Non-Prim). Information from real world crashes was obtained from the National Automotive Sampling System - Crashworthiness Data System (NASS-CDS) for the period from 1995 through 2011. Belted, contained or partially ejected, adult occupants in vehicles that completed 1-16 lateral quarter turns were assigned to one of the five rollover categories. The results showed that the frequency of injury in non-primary rollovers (SV Non-Prim and MV Non-Prim) involving no more than one roof inversion is substantially greater than in SV Pure, but that this disparity diminishes for crashes involving multiple inversions. It can further be concluded that for a given number of roof inversions, the distribution of injuries and crash characteristics in SV Pure and SV Prim crashes are sufficiently similar for these categories to be considered collectively for purposes of understanding etiologies and developing strategies for prevention.

Effect of cargo loading on occupant injury and seat deformation in motor-vehicle crashes

PURPOSE

NHTSA studied interior loose objects in the 2000-04 NASS-CDS as part of rulemaking on cargo retention testing in FMVSS 208. This study extends the investigation of cargo and loose interior object loading on occupant injury and seat deformation by cargo in motor-vehicles crashes using NASS-CDS data.

METHODS

1996-2011 NASS-CDS was used to investigate the effects of loose interior objects and seat responses on occupant injury in motor vehicle crashes. Crashes were grouped by front, side, rear and rollover. Light vehicles were included with model year 1994+. NASS-CDS added new variables for cargo loading as an injury source and cause for seat deformation in 2007. NASS-CDS electronic cases were analyzed for rear occupants with moderate to severe injury (AIS 2+) from loose objects and MAIS 4+F injury with cargo deforming seats in frontal crashes.

RESULTS

There were no AIS 2+ injuries due to cargo loading in the 16 years of NASS-CDS, including specific coding from 2007-11 and by case evaluation in earlier years. In frontal crashes, loose or other interior objects accounted for 250 AIS 2+ injuries in drivers, 32 in front passengers and 206 in 2nd row occupants. The overall rate of AIS 2+ injury was 1.000% for 2nd row occupants due to loose or other interior objects. The individual cases of AIS 2+ injury from loose or other interior objects in 2nd row occupants involved 16 occupants with 44 injuries in frontal crashes. Two cases involved police vehicles and one, an ambulance. In two other cases, the loose interior object was a bike placed in the 3rd row of a station wagon and an unsecured fan in the 2nd row. Each year, there were 540 driver seats deformed by cargo, 438 front-passenger seats and 889 in 2nd row seats. Most cargo deformation of front seats occurred in frontal crashes. Annually, there were 462 driver seats deformed by cargo in frontal crashes, 143 front-passenger seats and 660 in 2nd row seats.

CONCLUSIONS

This analysis supports NHTSA's earlier conclusion that cargo is not a major source of injury in frontal crashes. While anecdotal cases have been presented in the literature, there were no cases in NASS-CDS. NASS-CDS also showed that when untethered cargo deforms rear seats, it was not related to severe injury to 2nd row occupants.

Spinal fracture-dislocations and spinal cord injuries in motor vehicle crashes

PURPOSE

This study estimated the annual count of spinal cord injuries (SCIs) in motor vehicles crashes by type and seat belt use using 18 years of NASS-CDS data. It determined the rate for SCI and fracture-dislocation of the spine.

METHODS

1994-2011 NASS-CDS was used to estimate the annual occurrence of spinal injuries in front seat occupants involved in motor vehicle crashes. Crashes were grouped by front, side, rear, and rollovers, and the effects of belt use were investigated. Light vehicles were included with model year 1994+. Spinal injuries were classified as minor (Abbreviated Injury Scale [AIS] 1), moderate (AIS 2), serious (AIS 3), fracture-dislocations, and SCI (AIS 4+). The annual count and rate for different types of spinal injury were estimated along with standard errors. The results were compared to estimates of head injuries. NASS-CDS electronic cases of SCIs in rear impacts were investigated.

RESULTS

There were 5,592 ± 1,170 fracture-dislocations of the spine and 1,046 ± 193 AIS 4+ SCI per year in motor vehicle crashes. Most of the injuries occurred in rollovers and frontal crashes and the least occurred in rear impacts. The rate of SCI was 0.054 ± 0.010%. The highest rate was 0.220 ± 0.056% in rollover crashes and the lowest rate was 0.032 ± 0.009% in frontal crashes. The highest rate for spinal fracture-dislocation was 1.552 ± 0.455% in rollovers and the lowest was 0.065 ± 0.021% in rear impacts. The rate for SCI was 0.027 ± 0.005% in belted and 0.145 ± 0.028% in unbelted occupants giving 81% effectiveness of belt use in reducing SCI. The cervical spine was associated with 66.3 ± 11.3% of the AIS 4+ SCI with 30.5 ± 7.4% in the thoracic spine and 3.2 ± 1.3% in the lumbar spine. Severe head injuries occurred 13.3 times more often than SCIs.

CONCLUSIONS

Spinal cord injury occurred in one out of 1,860 front seat occupants in tow-away crashes. The rate was highest in rollover crashes and was reduced by seat belt use. Fracture-dislocation of the spine occurred about 5.3 times more often than SCIs and was also prevented by seat belt use.

Comparison of risk factors for cervical spine, head, serious, and fatal injury in rollover crashes

Previous epidemiological studies of rollover crashes have focused primarily on serious and fatal injuries in general, while rollover crash testing has focused almost exclusively on cervical spine injury. The purpose of this study was to examine and compare the risk factors for cervical spine, head, serious, and fatal injury in real world rollover crashes. Rollover crashes from 1995-2008 in the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) were investigated. A large data set of 6015 raw cases (2.5 million weighted) was generated. Nonparametric univariate analyses, univariate logistic regression, and multivariate logistic regression were conducted. Complete or partial ejection, a lack of seatbelt use, a greater number of roof inversions, and older occupant age significantly increased the risk of all types of injuries studied (p<0.05). Far side seating position increased the risk of fatal, head, and cervical spine injury (p<0.05), but not serious injury in general. Higher BMI was associated with an increased risk of fatal, serious, and cervical spine injury (p<0.05), but not head injury. Greater roof crush was associated with a higher rate of fatal and cervical spine injury (p<0.05). Vehicle type, occupant height, and occupant gender had inconsistent and generally non-significant effects on injury. This study demonstrates both common and unique risk factors for different types of injuries in rollover crashes.

Preventing motor vehicle crashes related spine injuries in children

BACKGROUND

Spinal cord injury (SCI) is a devastating event that results in permanent disability for injured children. Among all etiologies of SCI, motor vehicle crashes (MVCs) are the leading cause and account for 29% of all traumatic SCIs in children. We tried to evaluate types and mechanisms of MVC-related spinal column and spinal cord injuries, risk factors, safety issues and legislation.

DATA SOURCES

A literature review was performed using PubMed from 1966 to 12th April 2010 with the following key words: children OR pediatric, spine, injury OR trauma, restraint, seat belt, motor vehicle, road OR traffic, collision OR crash, safety. Cross referencing of discovered articles was also performed.

RESULTS

Risk factors for MVC-related SCI include single vehicle crashes, vehicle rollover, and ejection of the passenger from the vehicle. Any anatomic region of the spinal cord may be injured as a result of MVC and may vary according to the type of accident and restraint system usage. Increasing use of three-point seat belts, which are more protective than isolated lap seat belts, has decreased the incidence of MVC-related SCI. There is evidence that airbag use without seatbelt use is associated with an increased risk of cervical spine fractures with or without SCI. Vehicle designers need to give more attention to the prevention of vehicle rollover and to improve occupant protection when rollover occurs.

CONCLUSIONS

MVC is a common cause of SCI in children; therefore, paying attention to risk factors and modes of prevention is important. As MVC-related SCI can lead to permanent disability, prevention and education play an important role in decreasing childrens' morbidity and mortality. Making behavior, roads and vehicles safer can significantly reduce MVC-related SCI in children.

The influence of occupant anthropometry and seat position on ejection risk in a rollover

PURPOSE

During rollover crashes, ejection increases an occupant's risk of severe to fatal injury as compared to risks for those retained in the vehicle. The current study examined whether occupant anthropometry might influence ejection risk. Factors such as restraint use/disuse, seating position, vehicle type, and roll direction were also considered in the analysis.

METHODS

The current study examined occupant ejections in 10 years of National Automotive Sampling System (NASS) single-event rollovers of passenger vehicles and light trucks. Statistical analysis of unweighted and weighted ejection data was carried out.

RESULTS

No statistically significant differences in ejection rates were found based on occupant height, age, or body mass index. Drivers were ejected significantly more frequently than other occupants: 62 percent of unrestrained drivers were ejected vs. 51 percent unrestrained right front occupants. Second row unrestrained occupants were ejected at rates similar to right front-seated occupants. There were no significant differences in ejection rates for near- vs. far-side occupants.

CONCLUSIONS

These data suggest that assessment of ejection prevention systems using either a 50th or 5th percentile adult anthropomorphic test dummy (ATD) might provide a reasonable measure of system function for a broad range of occupants. They also support the development of ejection mitigation technologies that extend beyond the first row to protect occupants in rear seat positions. Future studies should consider potential interaction effects (i.e., occupant size and vehicle dimensions) and the influence of occupant size on ejection risk in non-single-event rollovers.

Mortality and injury patterns associated with roof crush in rollover crashes

BACKGROUND

In the United States, a significant number of spine injuries, traumatic brain injuries (TBI), and deaths result from motor vehicle rollover crashes each year though they make up a small percentage of total crashes. We sought to explore the relationship between these injuries and the degree of roof crush.

METHODS

We searched the NASS CDS database for belted, adult (> or =16), non-middle seat passengers involved in rollover crashes from 1993 to 2006. We also searched the CIREN database for illustrative cases. Logistic regression was used to evaluate the relationship between different levels of roof crush and mortality, severe injury (AIS > or = 3) to the spine, spinal cord, and head injury.

RESULTS

The risk of mortality, TBI, and spine injury all increased as the degree of roof crush increased. For mortality increased risk occurred at >15 cm [15-30 cm: OR 2.089 (95% CI: 1.461-2.987); >30 cm: OR 6.301 (95% CI: 4.369-9.087)]. For TBI, increased risk was seen above 15 cm crush [15-30 cm: OR 1.52 (95% CI: 1.045-2.21); >30 cm: OR 3.672 (95% CI: 2.456-5.490)]. For spine injury increased risk was seen above 8 cm crush [8-15 cm: OR 1.968 (95% CI 1.273-3.043); 15-30 cm: OR 2.530 (95% CI 1.634-3.917); > or =30 cm OR 2.682 (95% CI 1.474, 4.877). Results were similar across the different statistical models.

CONCLUSION

There is an association between the degree of roof crush and mortality, spine injury, and head injury in rollover crashes.

Severe-to-fatal injury risks in crashes with two front-seat occupants by seat belt use

PURPOSE

This study investigates the risk of severe-to-fatal injury (Maximum Abbreviated Injury Score, MAIS 4+F) in crashes with two front-seat occupants. It determines the relative risk of injury in the same crash by belt use and seating position.

METHODS

1993-2008 NASS-CDS was analyzed for crashes with occupants in both front-outboard seats. The effect of belt use was investigated for the driver and passenger. Light vehicles were included with model year 1990+. Injury severity was subdivided into MAIS 0-2 and 4+F in NASS-CDS to compare no-to-moderate injury with severe-to-fatal injury. Standard errors were calculated in SAS and the z-test was used to determine the significance of differences in risk. Relative risks were determined by seat belt use and seating position; odds ratios were determined for one or both occupants being severely injured.

RESULTS

In 76.7 percent of the MAIS 4+F crashes, either the driver (32.4%) or passenger (44.3%) was severely injured, rather than both occupants (23.3%). When both were belted, one occupant was severely injured in 86.5 percent of crashes. When both were unbelted, both occupants were severely injured in 68.9 percent of the crashes. Both occupants were belted in 74.7 percent of the cases and unbelted in 18.6 percent. In 6.7 percent of crashes, either the driver (4.4%) or passenger (2.3%) was unbelted when the other was belted. The highest risk occurred with an unbelted driver and belted passenger (4.98 +/- 0.73% vs. 1.97 +/- 0.38%, z = 3.65, p < .05). When both occupants were belted, the driver and passenger injury risk was similar (0.459 +/- 0.098% vs. 0.449 +/- 0.047%, z = 0.10, ns).

CONCLUSIONS

In crashes with two front occupants, typically one occupant was severely injured, not both. Overall, the odds ratio was 3.28 for one compared to two occupants being severely injured; and, risks vary by seat belt use and seating position. The highest relative risk for unbelted versus belted occupants was 9.22 when both occupants were severely injured in the same crash.

Ejection and severe injury risks by crash type and belt use with a focus on rear impacts

PURPOSE

This study investigated the risk of severe-to-fatal injury (MAIS 4+F) with complete and partial ejection by crash type and belt use with a focus on ejection in rear impacts.

METHODS

1993-2007 NASS-CDS was analyzed for crashes with complete and partial ejection. The effect of belt use was investigated and crashes were grouped by front, side, rear, and rollovers. Light vehicles were included with model year 1994+. Injuries of severity MAIS 4+F and AIS 3-6 by body region were determined by crash type, belt use, and ejection status. NASS-CDS electronic cases of complete ejection and serious injury were evaluated to determine the circumstances in rear impacts.

RESULTS

For unbelted occupants, the highest risk for complete ejection is in rollovers (16.4 +/- 1.1%) and the risk for severe injury is 37.6 +/- 2.7%. The lowest risk for complete ejection is in frontal crashes (0.97 +/- 0.22%), but the risk for serious injury is 31.3 +/- 6.2% when ejection occurs. The risk for ejection is 2.7 +/- 1.5% in rear impacts with a 7.4 +/- 3.4% risk for severe injury. For belted occupants, the highest risk for complete ejection is in rollovers (0.068 +/- 0.022%) and the risk for severe injury is 25.9 +/- 13.3% when ejection occurs. The relative risk for ejection is 193 times greater for unbelted compared to belted occupants in all crashes with a range of 100 times in frontal crashes up to 847 times in rear impacts. Unbelted occupants have 20 times greater risk for severe injury when completely ejected and 18 times greater risk with partial ejection compared to nonejected occupants. Belted occupants have a 77 times greater risk of severe injury when completely ejected and 37 times greater risk when partially ejected.

CONCLUSIONS

Ejection involves significantly higher risks for severe injury in all crash types. The relative risk for MAIS 4+F injury is 20 times greater for unbelted and 77 times greater for belted occupants who are completely ejected compared to nonejected occupants. Ejection of occupants in rear crashes often occurs during vehicle yaw motion after the primary impact.

Induced exposure estimates of rollover risk for different types of passenger vehicles

OBJECTIVE

This study aimed to model rollover risk of New Zealand and Australian passenger vehicles to identify which driver and vehicle factors were associated with the highest risk of rollover. A further objective was to test the feasibility and reliability of the quasi-induced risk estimation approach for studying rollover risk.

METHOD

The most appropriate comparison crash type, whose counts formed the exposure measures for the induced exposure risk estimates, had been identified in a previous study to be multi-vehicle crashes in which the vehicle in question had been damaged in the rear. Statistical models were fitted to data from four Australasian jurisdictions from 1993 to 2004 for vehicles involved in rollover crashes and vehicles involved in the comparison crash type.

RESULTS

Higher rollover risk was found for those vehicle types with a relatively high center of gravity compared to the width of the wheel track, namely sport utility vehicles (SUVs) and people movers. A particularly high risk of rollover was found when teenagers drove SUVs. Within vehicle market groups, there was evidence of improving rollover safety for newer model vehicles relative to older vehicles and evidence of generally reducing rollover risk over the period studied.

CONCLUSION

The quasi-induced exposure method produced very consistent estimates of rollover risk despite large differences in the crash recording systems and crash type definitions used in the four jurisdictions studied. This provides evidence of the reliability of this approach to crash risk estimation and of the generalizability of the findings of this study.