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

Frontal-Crash Occupant Protection in the Rear Seat: Submarining and Abdomen/Pelvis Response in Midsized Male Surrogates

Frontal-crash sled tests were conducted to assess submarining protection and abdominal injury risk for midsized male occupants in the rear seat of modern vehicles. Twelve sled tests were conducted in four rear-seat vehicle-bucks with twelve post-mortem human surrogates (PMHS). Select kinematic responses and submarining incidence were compared to previously observed performance of the Hybrid III 50th-percentile male and THOR-50M ATDs (Anthropomorphic Test Devices) in matched sled tests conducted as part of a previous study. Abdominal pressure was measured in the PMHS near each ASIS (Anterior Superior Iliac Spine), in the inferior vena cava, and in the abdominal aorta. Damage to the abdomen, pelvis, and lumbar spine of the PMHS was also identified. In total, five PMHS underwent submarining. Four PMHS, none of which submarined, sustained pelvis fractures and represented the heaviest of the PMHS tested. Submarining of the PMHS occurred in two out of four vehicles. In the matched tests, the Hybrid III never underwent submarining while the THOR-50M submarined in three out of four vehicles. Submarining occurred in vehicles having both conventional and advanced (pretensioner and load limiter) restraints. The dominant factors associated with submarining were related to seat pan geometry. While the THOR-50M was not always an accurate tool for predicting submarining in the PMHS, the Hybrid III could not predict submarining at all. The results of this study identify substantive gaps in frontal-crash occupant protection in the rear seat for midsized males and elucidates the need for additional research for rear-seat occupant protection for all occupants.

Risk and Protective Factors for Injury in Adult Front- and Rear-Seated Motor Vehicle Occupants in New York State

Although seatbelt use is known to reduce motor vehicle occupant crash injury and death, rear-seated adult occupants are less likely to use restraints. This study examines risk and protective factors associated with injury severity in front- and rear-seated adults involved in a motor vehicle crash in New York State. The Crash Outcome Data Evaluation System (CODES) (2016-2017) was used to examine injury severity in front- and rear-seated occupants aged 18 years or older (N = 958,704) involved in a motor vehicle crash. CODES uses probabilistic linkage of New York State hospitalization, emergency department, and police and motorist crash reports. Multivariable logistic regression models with MI analyze employed SAS 9.4. Odds ratios are reported as OR with 95% CI. The mortality rate was approximately 1.5 times higher for rear-seated than front-seated occupants (136.60 vs. 92.45 per 100,000), with rear-seated occupants more frequently unrestrained than front-seated occupants (15.28% vs. 1.70%, p < 0.0001). In adjusted analyses that did not include restraint status, serious injury/death was higher in rear-seated compared to front-seated occupants (OR:1.272, 1.146-1.412), but lower once restraint use was added (OR: 0.851, 0.771-0.939). Unrestrained rear-seated occupants exhibited higher serious injury/death than restrained front-seated occupants. Unrestrained teens aged 18-19 years old exhibit mortality per 100,000 occupants that is more similar to that of the oldest two age groups than to other young and middle-aged adults. Speeding, a drinking driver, and older vehicles were among the independent predictors of serious injury/death. Unrestrained rear-seated adult occupants exhibit higher severe injury/death than restrained front-seated occupants. When restrained, rear-seated occupants are less likely to be seriously injured than restrained front-seated occupants.

Predictive modeling of submarining risk in car occupants based on pelvis angle and lap belt positioning

OBJECTIVE

The engagement of the lap belt with the pelvis is critical for occupant safety during vehicle frontal crashes to prevent occupant submarining. This study aims to develop a predictive model for submarining risk based on anthropometric parameters and lap belt positioning using finite element (FE) analyses.

METHODS

FE analyses were conducted using human body models representing various body shapes (a 50th percentile male, low and high BMI males, and a 5th percentile female) in three seated postures (standard, reclined, and slouched). The lap belt-ASIS overlap and the belt-pelvis angle were used as key parameters for predicting submarining risk. A logistic regression analysis was utilized to correlate submarining occurrence with the initial values of these two parameters at the beginning of impact. Subsequently, this submarining prediction model was applied to computer tomography (CT) measurements of human subjects in different seated postures (upright, reclined, and slouched), and submarining risks were calculated based on the developed model.

RESULTS

FE simulations indicated that submarining was more likely to occur as the initial belt-pelvis angle approached zero and there was a smaller initial belt-ASIS overlap. The logistic regression analysis demonstrated that the initial belt-pelvis angle and belt-ASIS overlap were statistically significant for predicting submarining risk. The derived model effectively distinguished submarining occurrence based on the initial values of these two parameters. The application of the submarining model to CT measurements of human subjects showed that submarining risk was lower in the order of upright, slouched, and reclined postures. In the reclined posture, the high submarining risk was attributed to a small belt-ASIS overlap and a rearward-tilted pelvis angle; whereas in the slouched posture, the risk was mostly associated with a rearward-tilted pelvis angle.

CONCLUSIONS

The submarining prediction model was developed based on the belt-pelvis angle and the belt-ASIS overlap. This predictive model may help to design restraint systems for various body types and seated postures of occupants.

Injury comparisons between paired drivers and front-seat passengers in frontal collisions using publicly available crash and injury data

Forensic engineers and crash safety researchers sometimes use the injuries of a seatbelted occupant to infer the injury risk of an unbelted occupant in the same crash, had they instead been wearing a seatbelt. It is unclear, however, whether this inference is valid or how often two occupants in the same collision have similar injuries. Here, we sought to compare the injury outcomes between drivers and front-seat passengers in frontal collisions using real-world collision data. We compared the injury severity, quantified using the Abbreviated Injury Scale (AIS), of 22 injury categories between front-seat occupants with matching seatbelt use and airbag deployment in single-event frontal collisions recorded in the publicly available National Automotive Sampling System, Crashworthiness Data System (years 1993-2015) database to assess whether they had similar severity injuries. We analyzed the four combinations of seatbelt use and airbag deployment and all seatbelt/airbag conditions combined. In only 3 of 88 combinations of injuries and seatbelt/airbag conditions did more than 50% of occupant pairs have the same AIS score, although the related confidence intervals showed these proportions were not significantly greater than 50%. In contrast, we found 19 combinations of injuries and seatbelt/airbag conditions where one occupant was consistently injured more severely than the other. Our findings show that injury outcome is not similar for both front-seat occupants in the same frontal collision with similar seatbelt and airbag conditions; however, one may be able to predict that one occupant would be more severely injured than their fellow occupant.

Motor Vehicle Crash and Hospital Charges in Front- and Rear-Seated Restrained and Unrestrained Adult Motor Vehicle Occupants

There are reports that historically higher mortality observed for front- compared to rear-seated adult motor vehicle (MV) occupants has narrowed. Vast improvements have been made in strengthening laws and restraint use in front-, but not rear-seated occupants suggesting there may be value in expanding the science on rear-seat safety.

METHODS

A linked 2016-2017 hospital and MV crash data set, the Crash Outcomes Data Evaluation System (CODES), was used to compare characteristics of front-seated (n = 115,939) and rear-seated (n = 5729) adults aged 18 years and older involved in a MV crash in New York State (NYS). A primary enforced seat belt law existed for front-seated, but not rear-seated occupants. Statistical analysis employed SAS 9.4.

RESULTS

Compared to front-seated occupants, those rear-seated were more likely to be unrestrained (21.2% vs. 4.3%, p < 0.0001) and to have more moderate-to-severe injury/death (11.9% vs. 11.3%, p < 0.0001). Compared to restrained rear-seated occupants, unrestrained rear-seated occupants had higher moderate-to-severe injury/death (21.5% vs. 7.5%, p < 0.0001) and 4-fold higher hospitalization. More than 95% of ejections were unrestrained and had 7-fold higher medical charges. Unrestrained occupants' hospital stays were longer, charges and societal financial costs higher.

CONCLUSIONS

These findings extend the science of rear-seat safety in seriously injured rear-seated occupants, document increased medical charges and support the need to educate consumers and policy makers on the health and financial risks of adults riding unrestrained in the rear seat. The lack of restraint use in adult rear-seated motor vehicle occupants consumes scarce health care dollars for treatment of this serious, but largely preventable injury.

Crash characteristics and injury risk of adult car occupants in near-side impacts

OBJECTIVE

In the US, 27% of car occupant fatalities occur in side-impacts. Near-side impacts cause more serious injuries than far-side impacts. Car occupant safety overall has improved, but rear-seat occupant protection lags behind front-seat protection. The current study had two aims: first, to describe crash characteristics and injury outcomes for near-side rear-seated restrained occupants before and after side-impact regulations (FMVSS-214) were mandated; and secondly, to estimate injury risks in near-side impact depending on seating position, delta-v, and other predictors.

METHODS

The National Automotive Sampling System - Crashworthiness Data System (NASS - CDS) database for 1995 to 2015 was analyzed. The descriptive statistics focused on rear-seated restrained adults, comparing old (<1997) and new (≥1997) vehicles exposed to near-side impacts. Weighted logistic regression models including all front and rear-seat occupants were used to predict the occurrence of at least moderate injury in near-side impacts.

RESULTS

Rear-seated restrained adults in new vehicles were exposed to higher delta-v and intrusion levels compared to old vehicles. Moreover, injuries to rear-seat occupants in new vehicles were more distributed across body regions, compared to old vehicles (mainly thorax and head). The risk of sustaining injuries increased significantly with delta-v and occupant age, when not using a seatbelt, when seated in a passenger car and when hit in the passenger compartment. The risk increased by trend, but not significantly, when seated in a newer vehicle, when seated in the rear-seat and when the crash opponent was an SUV or van.

CONCLUSIONS

Trends and risk factors for at least moderate injuries in near-side impacts were identified to guide future directions for occupant protection in side-impacts and its assessments.

Adult occupant injury risk in rear impact and frontal impact: Effect of impact conditions and occupant-related factors

OBJECTIVES

The objectives of this study were to compare the adult occupant injury risk on specific body regions in frontal and rear impact and to investigate the effect of those crash conditions and occupant-related factors on the injury risk.

METHOD

Data from the NASS-CDS and Crash Investigation Sampling System were studied for crashes during 2000 to 2019 involving model year 2000 to 2020 motor vehicles, including frontal collisions and rear-end collisions. The injury risk by specific body regions were compared by descriptive statistics, and logistic regression models were developed to examine the effects of various factors on injury risk by specific body regions, controlling for crash type (frontal impact and rear impact), vehicle impact speed, vehicle impact location, vehicle model year, and occupant gender, age, belt use, and seating position.

RESULTS

After controlling for the confounding factors, the occupants in frontal impact had higher overall injury risk than in rear impact (at Maximum Abbreviated Injury Scale [MAIS] 3+; odds ratio [OR] = 6.23; 95% confidence interval [CI] [6.06-6.40]), except for lower neck/spine injury risk at MAIS 1+ (OR = 0.47; 95% CI [0.46-0.47]). The impact speed (at MAIS 3+; OR = 1.10; 95% CI [1.10-1.10]) and aging (at MAIS 3+; OR = 1.05; 95% CI [1.05-1.05]) increase overall injury risk, and the unbelted occupants had higher overall injury risk than belted occupants not only in frontal impact (at MAIS 3+; OR = 4.04; 95% CI [3.98-4.10]), but also in rear impact (at MAIS 3+; OR = 28.4; 95% CI [26.4-30.5]). Females had higher overall injury risk than males in frontal impact (at MAIS 3+; OR = 2.01; 95% CI [1.99-2.04]) but not in rear impact (at MAIS 3+; OR = 0.77; 95% CI [0.73-0.81]).

CONCLUSIONS

Occupants in rear impact had lower injury risk than in frontal impact at MAIS 1+ to MAIS 3+, except for neck/spine at MAIS 1+. The belt restraint was effective not only in frontal impact but also in rear impact. This study provided injury risk references for current vehicles that may provide insight to the potential injury risk of rear-facing occupants in future vehicle configurations.

Autopsy findings in drivers and passengers from fatal motor vehicle collisions: limited differences in injury patterns and toxicological test results

We performed a retrospective study of the injuries and characteristics of occupant fatalities in motor vehicle collisions in southeast Norway. The goal was to provide updated knowledge of injuries sustained in modern vehicles and detect possible differences in injury pattern between drivers and passengers. Forensic autopsy reports, police, and collision investigation reports from 2000 to 2014 were studied, data extracted and analyzed.

A total of 284 drivers, 80 front-seat passengers, and 37 rear-seat passengers were included, of which 67.3% died in front collisions, 13.7% in near-side impacts, 13.5% in rollovers and 5.5% in other/combined collisions. Overall, 80.5% died within one hour after the crash. The presence of fatal injuries to the head, neck, thorax and abdomen were observed in 63.6%, 10.7%, 61.6% and 27.4% respectively. All occupants with severe injuries to the head or neck had signs of direct impact with contact point injuries to the skin or skull. Injuries to the heart and spleen were less common in front-seat passengers compared to drivers. Seat belt abrasions were more common and lower extremity fractures less common in both front-seat and rear-seat passengers compared to drivers. Blood alcohol and/or drug concentrations suggestive of impairment were present in 30% of all occupants, with alcohol more often detected among front-seat passengers compared to drivers.

Few driver-specific and passenger-specific patterns of injury could be identified. When attempting to assess an occupant’s seating position within a vehicle, autopsy findings should be interpreted with caution and only in conjunction with documentation from the crash scene.

Is the front passenger seat always the "death seat"? An application of a hierarchical ordered probit model for occupant injury severity

Although many studies have investigated the correlations between injury severities and seat positions, few researchers explored the correlates of injury severities (e.g., seat positions) within a crash that results in multiple occupant injuries. Therefore, we examine the injury correlates within and between crashes, and study the correlations between seat positions and occupant injury severity by constructing a hierarchical ordered probit model. A total of 20,327 occupant injuries in 16,405 motor vehicle crashes in South Australia (2012 - 2016) are used. The results of this study indicate that the rear left passenger seat is associated with a 7.66% higher chance of getting injured (including moderate and severe injury), and the front left passenger seat is associated with a 2.94% higher chance of getting injured compared with the driver seat. Besides, the higher injury chances for other passenger seats including the rear right and rear middle seats are 4.97% and 4.74%, respectively, compared with the driver seat. Thus, this study offers passengers insightful suggestions about how to protect themselves by choosing the right passenger seat in a vehicle.

Investigating traffic fatality trends and restraint use among rear-seat passengers in the United States, 2000-2016

INTRODUCTION

Motor-vehicle crash is one of the leading causes of unintentional injury death in the United States. Previous studies focused on fatalities among drivers and front-seat passengers, with a limited number of studies examining rear-seat passenger fatalities. The objectives of this study were to assess trends in rear-seat passenger motor-vehicle fatalities in the United States from 2000 to 2016 and to identify demographic factors associated with being unrestrained among fatally injured rear-seat passengers.

METHODS

Rear-seat passenger fatality data were obtained from the Fatality Analysis Reporting System (FARS) database. The fatality rate ratios for overall rear-seat passengers and for different age and sex groups were determined by comparing fatality rates in 2000 and 2016 using random effects models. Risk ratios of being unrestrained for age and sex groups were obtained using general estimating equations.

RESULTS

Compared to 2000, the overall rear-seat passenger fatality rate in 2016 decreased by 44% (95% confidence interval [CI]: 39-49%). In particular, the fatality rate among rear-seat passengers decreased more in males than females, and passengers aged 14-19 years experienced a larger decline than all other age groups. Fatally injured male rear-seat passengers had a higher risk of being unrestrained (adjusted risk ratio: 1.06, 95% CI: 1.04-1.07) than their female counterparts, and both youngest (≤13 years) and oldest (65-85 years) passengers were less likely to be unrestrained than those aged 20-64 years.

CONCLUSIONS

Overall, fatality rates among rear-seat passengers have declined, with differential degrees of improvement by age and sex. Practical Applications: Continued restraint use enforcement campaigns targeted at teenagers and males would further preserve them from fatal injuries and improve traffic safety for the overall population.

Rear seating position is associated with a higher risk of mortality in motor vehicle crashes: analysis of Japanese Trauma Data Bank

Aim

The study examined the association of vehicle seating positions with the risk of death in serious motor vehicle crashes (MVCs) in Japan.

Methods

Data from the Japan Trauma Data Bank between 2004 and 2015 were analyzed. All MVC drivers with the legal age for driving and all copassengers were enrolled (n = 23,040). The cases were divided into three groups based on their seating position during the crash: the driver seat, front passenger seat, and rear passenger seats. The primary outcome variable was in‐hospital mortality. Multivariable logistic regression analysis was used to assess the association between the seating position and in‐hospital mortality. Potential factors associated with each seating position and in‐hospital mortality were also assessed.

Results

The odds ratios (ORs) for deaths were estimated for front and rear passengers compared to those for the driver in MVCs. The adjusted ORs (95% confidence interval [CI]) for death were 0.96 (0.84–1.11) and 1.22 (1.04–1.42) for front and rear passengers, respectively. Factors significantly associated with MVC deaths were age over 71 years (OR = 3.38; 95% CI, 2.58–4.41), male gender (OR = 1.54; 95% CI, 1.39–1.71), and night driving (OR = 1.17; 95% CI, 1.06–1.29).

Conclusions

This hospital‐based study suggested that rear seating increased the risk of MVC‐related death. Further studies are needed in order to find mechanisms of the increase in mortality by the seating position.

Factors contributing to serious and fatal injuries in belted rear seat occupants in frontal crashes

Objectives: Earlier research has shown that the rear row is safer for occupants in crashes than the front row, but there is evidence that improvements in front seat occupant protection in more recent vehicle model years have reduced the safety advantage of the rear seat versus the front seat. The study objective was to identify factors that contribute to serious and fatal injuries in belted rear seat occupants in frontal crashes in newer model year vehicles. Methods: A case series review of belted rear seat occupants who were seriously injured or killed in frontal crashes was conducted. Occupants in frontal crashes were eligible for inclusion if they were 6 years old or older and belted in the rear of a 2000 or newer model year passenger vehicle within 10 model years of the crash year. Crashes were identified using the 2004-2015 National Automotive Sampling System Crashworthiness Data System (NASS-CDS) and included all eligible occupants with at least one Abbreviated Injury Scale (AIS) 3 or greater injury. Using these same inclusion criteria but split into younger (6 to 12 years) and older (55+ years) cohorts, fatal crashes were identified in the 2014-2015 Fatality Analysis Reporting System (FARS) and then local police jurisdictions were contacted for complete crash records. Results: Detailed case series review was completed for 117 rear seat occupants: 36 with Maximum Abbreviated Injury Scale (MAIS) 3+ injuries in NASS-CDS and 81 fatalities identified in FARS. More than half of the injured and killed rear occupants were more severely injured than front seat occupants in the same crash. Serious chest injury, primarily caused by seat belt loading, was present in 22 of the injured occupants and 17 of the 37 fatalities with documented injuries. Nine injured occupants and 18 fatalities sustained serious head injury, primarily from contact with the vehicle interior or severe intrusion. For fatal cases, 12 crashes were considered unsurvivable due to a complete loss of occupant space. For cases considered survivable, intrusion was not a large contributor to fatality. Discussion: Rear seat occupants sustained serious and fatal injuries due to belt loading in crashes in which front seat occupants survived, suggesting a discrepancy in restraint performance between the front and rear rows. Restraint strategies that reduce loading to the chest should be considered, but there may be potential tradeoffs with increased head excursion, particularly in the absence of rear seat airbags. Any new restraint designs should consider the unique needs of the rear seat environment.

Evaluation of differences in injury patterns according to seat position in trauma victims survived traffic accidents

PURPOSE

Investigation of injury patterns epidemiology among car occupants may help to develop different therapeutic approach according to the seat position. The aim of the study was to evaluate and compare differences in the incidence of serious injuries, between occupants in different locations in private cars.

METHODS

A retrospective study including trauma patients who were involved in motor vehicle accidents and admitted alive to 20 hospitals (6 level Ⅰ trauma centers and 14 level Ⅱ trauma centers). We examined the incidence of injures with abbreviated injury score 3 and more, and compared their occurrence between seat locations.

RESULTS

The study included 28,653 trauma patients, drivers account for 60.8% (17,417). Front passenger mortality was 0.47% higher than in drivers. Rear seat passengers were at greater risk (10.26%) for traumatic brain injuries than front seat passengers (7.48%) and drivers (7.01%). Drivers are less likely to suffer from serious abdominal injuries (3.84%) compared to the passengers (front passengers - 5.91%, rear passengers - 5.46%).

CONCLUSION

Out of victims who arrived alive to the hospital, highest mortality was found in front seat passengers. The rate of serious chest injuries was higher as well. Rear seat passengers are at greater risk for serious traumatic brain injuries. All passengers have a greater incidence of abdominal injuries. These findings need to be addressed in order to develop "customized" therapeutic policy in trauma victims.

Hip dislocations and concurrent injuries in motor vehicle collisions

INTRODUCTION

Motor Vehicle Collisions (MVC) can cause high energy hip dislocations associated with serious injury profiles impacting triage. Changes in safety and regulation of restraint devices have likely lowered serious injuries from what was previously reported in the 1990s. This study aims to describe modern-day injury profile of patients with traumatic hip dislocations, with special attention to aortic injury.

METHODS

Retrospective review of a prospectively maintained trauma database at an urban level 1 trauma center was conducted. Patients with hip dislocation following MVC between January 2005 and December 2015 were grouped based on seatbelt use and airbag deployment. Patients with unknown restraint use were excluded. Multiple logistic regression was used to identify risk of injury profile between groups.

RESULTS

Of 204 patients with hip dislocation after MVC, nearly 57% were unrestrained. Seatbelt alone was used in 36 (17.7%), airbag deployed in 14 (6.9%), and 38 (18.6%) with both. Gender and number of injuries were similar between groups. The most common concomitant injury was acetabular fracture (53.92%) and the abdominopelvic region was the most injured. Use of a seatbelt with airbag deployment was protective of concomitant pelvic ring injury (OR = 0.22). Airbag deployment was significantly protective of lumbar fracture (OR = 0.15) while increasing the likelihood of radial and ulnar fracture or dislocation (OR = 3.27), acetabular fracture (OR = 5.19), and abdominopelvic injury (OR = 5.07). The no restraint group had one patient (0.80%) with an intimal tear of the thoracic aorta identified on CT chest that was successfully medically managed.

DISCUSSION AND CONCLUSION

Hip dislocations are high energy injuries with severe associated injuries despite upgrades in restraint devices. These patients require careful examination and heightened awareness when evaluating for concomitant injuries.

Passenger use of and attitudes toward rear seat belts

OBJECTIVES

This study sought to identify attitudes toward belt use in the rear seat and to gain insight into the experiences of rear-seat passengers.

METHOD

A telephone survey conducted between June and August 2016 targeted adult passengers who had recently ridden in the rear and who did not always wear their seat belt when doing so. Respondents were questioned regarding their reasons for not buckling up and possible conditions under which they would be more likely to buckle up during rear-seat travel.

RESULTS

Of 1163 recent rear-seat passengers, 72% reported always using their seat belt in the rear. Full-time belt use was lower among passengers who primarily travel in the rear of hired vehicles compared with personal vehicles. The most common explanation for not buckling up was that the back seat is safer than the front. Four out of five agreed they do not buckle up because of type of trip; two-thirds forget or do not see the need; and two-thirds agreed with reasons related to design, comfort, or usability issues. Nearly 40% agreed that they sometimes do not buckle up in the rear because there is no law requiring it.

CONCLUSION

Many reasons for not using belts in the rear are similar to reasons in the front, such as forgetfulness, inconvenience, or discomfort. One difference is that many rear-seat passengers perceive using the belt is unnecessary because the back seat is safer than the front. More than half of part-time belt users and nonusers reported interventions such as rear seat belt reminders, stronger belt-use laws, and more comfortable belts would make them more likely to use their seat belt in the rear seat. Practical applications: This study identifies barriers to rear seat belt use that point to the need for a multi-faceted approach to increase belt use.

Optimizing Seat Belt and Airbag Designs for Rear Seat Occupant Protection in Frontal Crashes

Recent field data have shown that the occupant protection in vehicle rear seats failed to keep pace with advances in the front seats likely due to the lack of advanced safety technologies. The objective of this study was to optimize advanced restraint systems for protecting rear seat occupants with a range of body sizes under different frontal crash pulses. Three series of sled tests (baseline tests, advanced restraint trial tests, and final tests), MADYMO model validations against a subset of the sled tests, and design optimizations using the validated models were conducted to investigate rear seat occupant protection with 4 Anthropomorphic Test Devices (ATDs) and 2 crash pulses. The sled tests and computer simulations were conducted with a variety of restraint systems including the baseline rear-seat 3-point belt, 3-point belts with a pre-tensioner, load limiter, dynamic locking tongue, 4-point belts, inflatable belts, Bag in Roof (BiR) concept, and Self Conforming Rear seat Air Bag (SCaRAB) concept. The results of the first two sled series demonstrated that the baseline 3-point belt system are associated with many injury measures exceeding injury assessment reference values (IARVs); showed the significance of crash pulse and occupant size in predicting injury risks; and verified the potential need of advanced restraint features for better protecting the rear-seat occupants. Good correlations between the tests and simulations were achieved through a combination of optimization and manual fine-tuning, as determined by a correlation method. Parametric simulations showed that optimized belt-only designs (3-point belt with pre-tensioner and load limiter) met all of the IARVs under the soft crash pulse but not the severe crash pulse, while the optimized belt and SCaRAB design met all the IARVs under both the soft and severe crash pulses. Two physical prototype restraint systems, namely an "advanced-belt only" design and an "advanced-belt and SCaRAB" design, were then tested in the final sled series. With the soft crash pulse, both advanced restraint systems were able to reduce all the injury measures below the IARVs for all four ATDs. Both advanced restraint systems also effectively reduced almost all the injury measures for all ATDs under the severe crash pulse, except for the THOR. The design with the advanced-belt and SCaRAB generally provided lower injury measures than those using the advanced belt-only design. This study highlighted the potential benefit of using advanced seatbelt and airbag systems for rear-seat occupant protection in frontal crashes.

Paired vehicle occupant analysis indicates age and crash severity moderate likelihood of higher severity injury in second row seated adults in frontal crashes

The majority of advances in occupant protection systems for motor vehicle occupants have focused on occupants seated in the front row of the vehicle. Recent studies suggest that these systems have resulted in lower injury risk for front row occupants as compared to those in the second row. However, these findings are not universal. In addition, some of these findings result from analyses that compare groups of front and second row occupants exposed to dissimilar crash conditions, raising questions regarding whether they might reflect differences in the crash rather than the front and second row restraint systems. The current study examines factors associated with injury risk for pairs of right front seat and second row occupants in frontal crashes in the United States using paired data analysis techniques. These data indicate that the occupant seated in the front row frequently experiences the more severe injury in the pair, however there were no significant differences in the rate of occurrence of these events and events where the more severe injury occurs in the second row occupant of the pair. A logistic regression indicated that the likelihood of the more severe injury occurring in the second row seated occupant of the pair increased as crash severity increased, consistent with data from anatomic test dummy (ATD) tests. It also indicated that the second row occupant was more likely to have the more severe injury in the pair if that occupant was the older occupant of the pair. These findings suggest that occupant protection systems which focus on providing protection specifically for injuries experienced by older occupants in the second row in higher severity crash conditions might provide the greatest benefit.

Injury risk for matched front and rear seat car passengers by injury severity and crash type: An exploratory study

BACKGROUND

The risk of serious injury or death has been found to be reduced for some front compared to rear seat car passengers in newer vehicles. However, differences in injury severity between car occupants by seating position has not been examined. This study examines the injury severity risk for rear compared to front seat car passengers.

METHOD

A retrospective matched-cohort analysis was conducted of vehicle crashes involving injured rear vs front seat car passengers identified in linked police-reported, hospitalisation and emergency department (ED) presentation records during 2001-2011 in New South Wales (NSW), Australia. Odds ratios were estimated using an ordinal logistic mixed model and logistic mixed models.

RESULTS

There were 5419 front and 4588 rear seat passengers in 3681 vehicles. There was a higher odds of sustaining a higher injury severity as a rear-compared to a front seat car passenger, with a higher odds of rear seat passengers sustaining serious injuries compared to minimal injuries. Where the vehicle occupant was older, travelling in a vehicle manufactured between 1990 and 1996 or after 1997, where the airbag deployed, and where the vehicle was driven where the speed limit was ≥70km/h there was a higher odds of the rear passenger sustaining a higher injury severity then a front seated occupant.

CONCLUSION

Rear seat car passengers are sustaining injuries of a higher severity compared to front seat passengers travelling in the same vehicle, as well as when travelling in newer vehicles and where the front seat occupant is shielded by an airbag deployed in the crash. Rear seat occupant protective mechanisms should be examined. Pre-hospital trauma management policies could influence whether an individual is transported to a hospital ED, thus it would be beneficial to have an objective measure of injury severity routinely available in ED records. Further examination of injury severity between rear and front seat passengers is warranted to examine less severe non-fatal injuries by car seating position and vehicle intrusion.

Rear seat safety: Variation in protection by occupant, crash and vehicle characteristics

OBJECTIVES

Current information on the safety of rear row occupants of all ages is needed to inform further advances in rear seat restraint system design and testing. The objectives of this study were to describe characteristics of occupants in the front and rear rows of model year 2000 and newer vehicles involved in crashes and determine the risk of serious injury for restrained crash-involved rear row occupants and the relative risk of fatal injury for restrained rear row vs. front passenger seat occupants by age group, impact direction, and vehicle model year.

METHOD

Data from the National Automotive Sampling System Crashworthiness Data System (NASS-CDS) and Fatality Analysis Reporting System (FARS) were queried for all crashes during 2007-2012 involving model year 2000 and newer passenger vehicles. Data from NASS-CDS were used to describe characteristics of occupants in the front and rear rows and to determine the risk of serious injury (AIS 3+) for restrained rear row occupants by occupant age, vehicle model year, and impact direction. Using a combined data set containing data on fatalities from FARS and estimates of the total population of occupants in crashes from NASS-CDS, logistic regression modeling was used to compute the relative risk (RR) of death for restrained occupants in the rear vs. front passenger seat by occupant age, impact direction, and vehicle model year.

RESULTS

Among all vehicle occupants in tow-away crashes during 2007-2012, 12.3% were in the rear row where the overall risk of serious injury was 1.3%. Among restrained rear row occupants, the risk of serious injury varied by occupant age, with older adults at the highest risk of serious injury (2.9%); by impact direction, with rollover crashes associated with the highest risk (1.5%); and by vehicle model year, with model year 2007 and newer vehicles having the lowest risk of serious injury (0.3%). Relative risk of death was lower for restrained children up to age 8 in the rear compared with passengers in the right front seat (RR=0.27, 95% CI 0.12-0.58 for 0-3 years, RR=0.55, 95% CI 0.30-0.98 for 4-8 years) but was higher for restrained 9-12-year-old children (RR=1.83, 95% CI 1.18-2.84). There was no evidence for a difference in risk of death in the rear vs. front seat for occupants ages 13-54, but there was some evidence for an increased relative risk of death for adults age 55 and older in the rear vs. passengers in the right front seat (RR=1.41, 95% CI 0.94-2.13), though we could not exclude the possibility of no difference. After controlling for occupant age and gender, the relative risk of death for restrained rear row occupants was significantly higher than that of front seat occupants in model year 2007 and newer vehicles and significantly higher in rear and right side impact crashes.

CONCLUSIONS

Results of this study extend prior research on the relative safety of the rear seat compared with the front by examining a more contemporary fleet of vehicles. The rear row is primarily occupied by children and adolescents, but the variable relative risk of death in the rear compared with the front seat for occupants of different age groups highlights the challenges in providing optimal protection to a wide range of rear seat occupants. Findings of an elevated risk of death for rear row occupants, as compared with front row passengers, in the newest model year vehicles provides further evidence that rear seat safety is not keeping pace with advances in the front seat.

Predictors of rear seat belt use among U.S. adults, 2012

INTRODUCTION

Seat belt use reduces the risk of injuries and fatalities among motor vehicle occupants in a crash, but belt use in rear seating positions is consistently lower than front seating positions. Knowledge is limited concerning factors associated with seat belt use among adult rear seat passengers.

METHODS

Data from the 2012 ConsumerStyles survey were used to calculate weighted percentages of self-reported rear seat belt use by demographic characteristics and type of rear seat belt use enforcement. Multivariable regression was used to calculate prevalence ratios for rear seat belt use, adjusting for person-, household- and geographic-level demographic variables as well as for type of seat belt law in place in the state.

RESULTS

Rear seat belt use varied by age, race, geographic region, metropolitan status, and type of enforcement. Multivariable regression showed that respondents living in states with primary (Adjusted Prevalence Ratio (APR): 1.23) and secondary (APR: 1.11) rear seat belt use enforcement laws were significantly more likely to report always wearing a seat belt in the rear seat compared with those living in a state with no rear seat belt use enforcement law.

CONCLUSIONS AND PRACTICAL APPLICATIONS

Several factors were associated with self-reported seat belt use in rear seating positions. Evidence suggests that primary enforcement covering all seating positions is an effective intervention that can be employed to increase seat belt use and in turn prevent motor vehicle injuries to rear-seated occupants.

Factors associated with mortality in rear-seated adult passengers involved in fatal motor vehicle crashes on US roadways

BACKGROUND

Recent efforts to pass rear seat belt laws for adults have been hampered by large gaps in the scientific literature. This study examines driver, vehicle, crash, and passenger characteristics associated with mortality in rear-seated adult passengers.

METHODS

The Fatality Analysis Reporting System (FARS) 2010 to 2011 was used to examine motor vehicle occupant mortality in rear-seated adult passengers 18 years and older. Side crash vehicle safety ratings were assessed in a subset analysis of vehicles struck on the same side as the rear-seated passenger. Multilevel logistic regression models used SAS GLIMMIX.

RESULTS

Of the 7,229 rear-seated adult passengers, 2,091 (28.9%) died. Multivariable predictors of increased mortality were advancing passenger age, younger driver age, excessive speed, ejection, being unbelted, rear impact, and same-side crash. Belt use was associated with a 67.0% reduction in total mortality. Despite this, belt wearing was low (48.1%) and differed by seating position, with less than one third of middle-seated passengers belted. Multivariable analysis showed mortality to be nearly three times higher in same-side crashes than other impact locations (odds ratio (OR) = 2.76, 2.22, 3.44). In a multivariable subpopulation analysis of same-side crashes, right-seated passengers had an increased mortality (52.7% vs. 43.2%, p < 0.01) compared to left-seated passengers (OR = 1.55, 1.02, 2.36). Vehicle side crash safety ratings, available for 27.7% (n = 172) of same-side crashes, were not predictive of mortality.

CONCLUSIONS

Except for same-side crashes, seat belts were associated with significantly lowered mortality. Despite this, seat belt wearing was low and represents one of several areas where further improvements in mortality might be realized.

A simulation study on the efficacy of advanced belt restraints to mitigate the effects of obesity for rear-seat occupant protection in frontal crashes

OBJECTIVE

Recent field data analyses have shown that the safety advantages of rear seats relative to the front seats have decreased in newer vehicles. Separately, the risks of certain injuries have been found to be higher for obese occupants. The objective of this study is to investigate the effects of advanced belt features on the protection of rear-seat occupants with a range of body mass index (BMI) in frontal crashes.

METHODS

Whole-body finite element human models with 4 BMI levels (25, 30, 35, and 40 kg/m2) developed previously were used in this study. A total of 52 frontal crash simulations were conducted, including 4 simulations with a standard rear-seat, 3-point belt and 48 simulations with advanced belt features. The parameters varied in the simulations included BMI, load limit, anchor pretensioner, and lap belt routing relative to the pelvis. The injury measurements analyzed in this study included head and hip excursions, normalized chest deflection, and torso angle (defined as the angle between the hip-shoulder line and the vertical direction). Analyses of covariance were used to test the significance (P <.05) of the results.

RESULTS

Higher BMI was associated with greater head and hip excursions and larger normalized chest deflection. Higher belt routing increased the hip excursion and torso angle, which indicates a higher submarining risk, whereas the anchor pretensioner reduced hip excursion and torso angle. Lower load limits decreased the normalized chest deflection but increased the head excursion. Normalized chest deflection had a positive correlation with maximum torso angle. Occupants with higher BMI have to use higher load limits to reach head excursions similar to those in lower BMI occupants.

DISCUSSION AND CONCLUSION

The simulation results suggest that optimizing load limiter and adding pretensioner(s) can reduce injury risks associated with obesity, but conflicting effects on head and chest injuries were observed. This study demonstrated the feasibility and importance of using human models to investigate protection for occupants with various BMI levels. A seat belt system capable of adapting to occupant size and body shape will improve protection for obese occupants in rear seats.

High strength steels, stiffness of vehicle front-end structure, and risk of injury to rear seat occupants

Previous research has shown that rear seat occupant protection has decreased over model years, and front-end stiffness is a possible factor causing this trend. In this research, the effects of a change in stiffness on protection of rear seat occupants in frontal crashes were investigated. The stiffness was adjusted by using higher strength steels (DP and TRIP), or thicker metal sheets. Finite element simulations were performed, using an LS Dyna vehicle model coupled with a MADYMO dummy. Simulation results showed that an increase in stiffness, to the extent it happened in recent model years, can increase the risk of AIS3+ head injuries from 4.8% in the original model (with a stiffness of 1,000 N/mm) to 24.2% in a modified model (with a stiffness of 2,356 N/mm). The simulations also showed an increased risk of chest injury from 9.1% in the original model to 11.8% in the modified model. Distribution of injuries from real world accident data confirms the findings of the simulations.

Assessment of vehicle and restraint design changes for mitigating rear seat occupant injuries

OBJECTIVE

Investigate the combined effects of belt geometry, seat substructure, and seat belt pretensioners and load limiters on rear seat occupant injury risk.

METHODS

An instrumented Hybrid III 5th percentile adult female dummy was subjected to simulated frontal impacts (Δv = 45.8 km/h, peak acceleration = 27.1 g). Testing was conducted on a rear seat of a typical family sedan with modifications allowing for adjustment in upper anchorage position, mounting of an antisubmarining seat pan, and the use of seat belt pretensioners with load limiters.

RESULTS

Dummy seated posture had the strongest effect on submarining. Seat belt pretensioners with load limiters reduced head and femur excursion and decreased chest injury measurements but did not prevent submarining. The antisubmarining seat pan, on the other hand, prevented submarining in one case but could not prevent submarining with the dummy in a slouched posture. Upper anchorage position resulting in poor belt geometry was shown to increase both chest injury measures and submarining.

CONCLUSIONS

The results from this study demonstrate the importance of an upright seated posture and the potential benefits of including adjustable upper anchorages to allow good sash belt fit, antisubmarining seat pans, belt buckles positioned near the seat bight, and seat belts with pretensioners and load limiters for rear seat occupants. These data can be used to inform the design of a system of restraints to reduce injuries to rear seat occupants.

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.

Long-term medical consequences for child occupants 0 to 12 years injured in car crashes

OBJECTIVE

There is limited knowledge of the long-term medical consequences for children injured in car crashes. Thus, in the event of injury, the aim of the study was to specify patterns and risks of injuries resulting in permanent medical impairment of children (0-12 years) for different body regions and injury severity levels, according to Abbreviated Injury Scale (AIS). The aim was also to compare the impairment outcome with adults.

METHODS

Data were obtained from the Folksam insurance company, including reported car crashes from 1998 to 2010 with at least one injured child 0-12 years of age. In all, 2619 injured children with 3704 reported medical diagnoses were identified. All injuries were classified according to the AIS 2005 revision. If the child had not recovered within 1 year postinjury an assessment of permanent medical impairment (PMI) was made by one or several medical specialists.

RESULTS

In all, 55 children sustained 59 injuries resulting in PMI of which 75 percent were at AIS 1 or AIS 2. The head and cervical spine were the body regions sustaining the most injuries resulting in PMI. Sixty-eight percent of all injuries resulting in PMI were AIS 1 injuries to the cervical spine, with the majority occurring in frontal or rear impacts. Given an injury to the cervical spine, the risk of injuries resulting in PMI was 3 percent, and older children (≥6 years) had a significantly higher risk (3% versus 1%) than younger children. The head was the second most commonly injured body region with injuries resulting in PMI (12/59), which were predominantly AIS 2+. In addition, mild traumatic brain injuries at AIS 1 were found to lead to PMI. Whereas for children the injuries leading to PMI were primarily limited to the head and cervical spine, adults sustained injuries that led to PMI from a more diverse distribution of body regions.

CONCLUSION

The pattern of injuries resulting in permanent medical impairment is different for children and adults; therefore, safety priorities for children need to be based on child data. The majority of those injuries leading to PMI were at lower AIS levels. Furthermore, AIS 1 cervical spine and AIS 1+ head injuries should be given priority concerning mitigation of long-term consequences for children.

The scope and nature of injuries to rear seat passengers in NSW using linked hospital admission and police data

OBJECTIVE

To compare the pattern of injuries to front and rear seat occupants and test the hypothesis that rear seat passengers of different ages sustain different patterns of injury.

METHOD

Patients admitted to a hospital following involvement in a crash in New South Wales (NSW) Australia between 2005 and 2007 were identified using International Classification of Diseases (10th edition [ICD10]) codes. Hospital admissions data were linked with NSW police crash data using probabilistic techniques. The profiles and patterns of injury of front and rear seat passengers were compared. Logistic regression was used to examine how age influenced the pattern of injury among rear seat passengers.

RESULTS

Sixty-three percent of hospital admissions were linked with police records. One in 5 passengers were rear seat passengers. There were more unrestrained occupants in the rear (7%) compared to drivers (3%) and front seat passengers (2%). Younger (9-15 years) injured passengers were seated in the rear more often than in the front passenger position and older injured passengers (>50 years) were seated more often in the front passenger position than in the rear (15% rear compared to 5% front aged 9-15 years; 22% rear compared to 37% front aged >50 years; χ(2), P < .001). There were proportionally more fatal injuries among rear seat passengers (10%) than among drivers (5%) and front seat passengers (6%), and the pattern of injury between front and rear passengers also varied. Rear seat passengers had more head and abdominal injuries and fewer thoracic and knee/lower leg injuries than front seat passengers. After adjusting for vehicle age, restraint status, travel speed, and whether or not a fatality occurred in the crash, older (>50 years) rear passengers had 6.3 times the odds of sustaining thoracic injuries (95% confidence interval [CI], 2.6-15.0) and lower odds (odds ratio [OR] = 0.4, 95% CI, 0.2-0.9) of sustaining abdominal/lumbar injuries than the youngest occupants (9-15 years).The odds of sustaining a head injury did not vary with age, and the odds of sustaining thoracic, abdominal, or lower extremity injuries did not differ significantly between rear seat passengers aged 16-50 years and 9-15 years.

CONCLUSIONS

The findings suggest that there is a need for enhanced protection for rear seat passengers, because they have proportionally more fatal injuries than front-seated occupants. The frequency of abdominal injury and the differences between injury patterns observed in front seat passengers suggests a potential benefit from adding abdominal injury risk assessment to rear seat occupant protection test protocols. There is also scope to improve chest protection for older rear seat passengers.

Biomechanical assessment of a rear-seat inflatable seatbelt in frontal impacts

This study evaluated the biomechanical performance of a rear-seat inflatable seatbelt system and compared it to that of a 3-point seatbelt system, which has a long history of good real-world performance. Frontal-impact sled tests were conducted with Hybrid III anthropomorphic test devices (ATDs) and with post mortem human subjects (PMHS) using both restraint systems and a generic rear-seat configuration. Results from these tests demonstrated: a) reduction in forward head excursion with the inflatable seatbelt system when compared to that of a 3-point seatbelt and; b) a reduction in ATD and PMHS peak chest deflections and the number of PMHS rib fractures with the inflatable seatbelt system and c) a reduction in PMHS cervical-spine injuries, due to the interaction of the chin with the inflated shoulder belt. These results suggest that an inflatable seatbelt system will offer additional benefits to some occupants in the rear seats. Further research is needed to assess the field effectiveness, customer comfort and acceptance and change in the belt usage rate with the inflatable seatbelt system.

In-depth evaluation of real-world car collisions: fatal and severe injuries in children are predominantly caused by restraint errors and unstrapped cargo

OBJECTIVE

Major improvements have taken place in the development of child restraint systems and in-car safety in general, but motor vehicle accidents remain the leading cause of death and disability in children. An interdisciplinary study was therefore performed to investigate the injury mechanisms in car collisions involving children.

METHODS

Motor vehicle collisions (MVCs) resulting in death or serious injuries to the drivers or their passengers in the southeastern part of Norway in the period 2007-2009 were included in the study if children less than 16 years of age were passengers. An investigation team examined the crash scene within 24 h of the accident. The internal and external environment of the vehicle was investigated, with particular focus on safety equipment and registration of child occupant contact points. Information was collected from witnesses, crash victims, the police, road authority reports, and medical records. Clinical or postmortem examinations were performed on the child occupants.

RESULTS

Fifteen high-impact car crashes involving 27 child occupants were investigated: 7 children died (median [range] age 8 (0-15) years), 8 were severely injured (8 [5-13] years), and 12 sustained minor or no injuries (3.5 [0-14] years). Fourteen out of 15 fatalities or severe injuries (MAIS ≥3) were found to be due to various safety errors: harness straps or seat belts incorrectly routed (5/15) or poorly adjusted (4/15), unstrapped luggage (4/15), or technical errors (1/15). All 7 of the fatally injured children died at the crash scene, and 6 died due to head/upper neck trauma. No safety errors were found among the 12 children with either minor or no injuries. No association was found between the instantaneous change in velocity (ΔV) and the injury severity.

CONCLUSION

The risk of child passengers being severely or fatally injured in MVCs is significantly higher when they are incorrectly restrained or exposed to unsecured heavy luggage. Appropriate crash investigations may provide important information regarding the injury mechanisms, which will be necessary for the implementation of preventive measures to reduce future fatalities.