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.     

The effects of seat belts on injury severity of front and rear seat occupants in the same frontal crash

Data on passenger cars in frontal crashes were reviewed using NASS 1980–1991. Only crashes with one or more rear seat passengers were included. Combinations (pairs) were made based on restraint use: lap-shoulder belts in the front seat (or no belts worn) and lap belts, (or belts worn) in the rear seat. Passive belts or child restrained occupants were not included. The AIS was used for injury severity. The data indicate the rear seat to be a safer environment. Lap belted rear seat occupants always fared better than their front seat counterparts.     

Method to evaluate the effect of safety belt use by rear seat passengers on the injury severity of front seat occupants

Although the effectiveness of seat belts for reducing injury to rear seat passengers in traffic accidents has been well documented, the ratio of rear-seat passengers restrained by seatbelts remains lower than that of drivers or passengers in front seats. If passengers in rear seats do not wear seat belts, they may sustain unexpected injury to themselves when involved in accidents, and also endanger front occupants (drivers or front seat passengers). This paper focuses on the tendency of front seat occupants to sustain severer injuries due to forward movement of passengers in rear seats at the moment of frontal collisions, and evaluates the effectiveness of rear passengers' wearing seat belts in reducing injuries of front seat occupants. Since the occurrence of occupant injuries depends considerably on the crash severity, we proposed to use pseudo-delta V in regression analysis to represent velocity change during a collision when analyzing statistical accident data. As the crash severity can be estimated from pseudo-delta V, it becomes possible to make appropriate estimations even when the crash severity differs in data. The binary model derived from the ordered response model was used to evaluate the influence on the injury level based on pseudo-delta V, belted or unbelted status, gender and age. Occupants in cars with a hood in the case of car-to-car frontal collisions were extracted from the statistical data on accidents in Japan. Among 81,817 cars, where at least one passenger was present, a total of 6847 cars in which all passengers sustained injuries and which had at least one rear seat passenger aboard were analyzed. The number of killed or seriously injured drivers is estimated to decrease by around 25% if rear seat occupants come to wear seat belts. Also, the number of killed or seriously injured passengers in front seats is estimated to decrease by 28% if unbelted rear seat occupants come to wear seat belts. Thus, wearing of seat belts by previously unbelted rear seat passengers is considered effective in reducing not only injuries to the rear seat passengers themselves but also injuries to front seat occupants.     

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 1000 N/mm) to 24.2% in a modified model (with a stiffness of 2356 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.     

How would increasing seat belt use affect the number of killed or seriously injured light vehicle occupants?

The expected effects of increasing seat belt use on the number of killed or seriously injured (KSI) light vehicle occupants have been estimated for three scenarios of increased seat belt use in Norway, taking into account current seat belt use, the effects of seat belts and differences in crash risk between belted and unbelted drivers. The effects of seat belts on fatality and injury risk were investigated in a meta-analysis that is based on 24 studies from 2000 or later. The results indicate that seat belts reduce both fatal and non-fatal injuries by 60% among front seat occupants and by 44% among rear seat occupants. Both results are statistically significant. Seat belt use among rear seat occupants was additionally found to about halve fatality risk among belted front seat occupants in a meta-analysis that is based on six studies. Based on an analysis of seat belt wearing rates among crash involved and non-crash involved drivers in Norway it is estimated that unbelted drivers have 8.3 times the fatal crash risk and 5.2 times the serious injury crash risk of belted drivers. The large differences in crash risk are likely to be due to other risk factors that are common among unbelted drivers such as drunk driving and speeding. Without taking into account differences in crash risk between belted and unbelted drivers, the estimated effects of increasing seat belt use are likely to be biased. When differences in crash risk are taken into account, it is estimated that the annual numbers of KSI front seat occupants in light vehicles in Norway could be reduced by 11.3% if all vehicles had seat belt reminders (assumed seat belt wearing rate 98.9%), by 17.5% if all light vehicles had seat belt interlocks (assumed seat belt wearing rate 99.7%) and by 19.9% if all front seat occupants of light vehicles were belted. Currently 96.6% of all (non-crash involved) front seat occupants are belted. The effect on KSI per percentage increase of seat belt use increases with increasing initial levels of seat belt use. Had all rear seat occupants been belted, the number of KSI front seat occupants could additionally be reduced by about 0.6%. The reduction of the number of KSI rear seat occupants would be about the same in terms of numbers of prevented KSI.     

Injuries to belted older children in motor vehicle crashes

Context

The American Academy of Pediatrics and the National Highway Traffic Safety Administration currently recommend that, unless they are under 57 in. in height, 8–12-year-old children use seat belts and all should ride in the rear seats of vehicles. These recommendations assume that the vehicle seat belt should provide adequate protection for these older children in the event of a crash.

Objectives

To describe characteristics of older children in the rear seat using seat belts in crashes, to estimate their risk and body region distribution of injury, and to identify risk factors for injury.

Methods

A representative sample of 6680 seat belt-restrained occupants, 8–12 years of age, seated in the rear seat during crashes involving insured vehicles in 16 US states between December 1998 and December 2007. A telephone interview was conducted with the driver of each vehicle. The main outcome was the parent-reported injury defined as Abbreviated Injury Scale (AIS) 2 or greater injuries.

Results

The risk of injury for belted 8–12 year olds in the rear seat was 1.3%. Head injury was the most common injury (60%), followed by injuries to the face (9%), upper extremity (9%) and abdomen (9%). One out of five (21%) 8–12 year olds either did not use the shoulder portion of the vehicle seat belt or placed it incorrectly behind their back or under their arm. Bivariate analyses indicated a higher risk of injury for these children (1.8%) as compared to children using both the lap and shoulder portions of the seat belt (1.1%). However, this difference was not statistically significant when other risk factors such as crash severity and characteristics of the driver were considered.

Conclusions

Injuries to the head, face, abdomen and upper extremity are the most common injuries to target for improved protection among 8–12 year olds in seat belts. Driver and crash characteristics are important risk factors for injury. A recent federal motor vehicle safety standard requiring lap and shoulder belts in all rear seat positions has the potential to further decrease the risk of injury to older children using seat belts.     

Effectiveness of the revision to FMVSS 301: FARS and NASS-CDS analysis of fatalities and severe injuries in rear impacts

PurposeThis study investigated the change in the fatality and severe injury risks in rear impacts with vehicle model years (MY) grouped prior to, during the phase-in and after the revision to FMVSS 301.MethodsFARS and NASS-CDS data were used to determine the injury risks of non-ejected occupants in light vehicles involving non-rollover, rear impacts. The data were analyzed by MY groups: 1996–2001, 2002–2007 and 2008+ to represent the years prior to, during the phase-in and post-revision phase-in of FMVSS 301. The 1996–2013 FARS data were analyzed for rear crashes defined by the initial crash direction (IMPACT1) and direction with most damage (IMPACT2) to the rear. Fatality risk was determined by the number of fatally injured occupants per all occupants with known injury status.The 1994–2013 NASS-CDS was analyzed for rear crashes defined by the damage area variable. The risk of severe injury (MAIS 4+F) was determined as the number of occupants with MAIS 4+F injury per all occupants with known injury status. The distribution of rear crashes was determined by impact location and crash severity. NASS-CDS electronic cases with 2008+ MY vehicles were analyzed to evaluate the vehicle and occupant performance.ResultsThe fatality risk was 20.6% in the 1996–2001, 17.3% in the 2002–2007 and 15.0% in the 2008+ MY vehicles using FARS with the initial crash direction variable (IMPACT1) to the rear. There was a 27.1% reduction in risk with post-FMVSS 301 vehicles 2008+ MY. The risk was 19.0%, 15.4% and 12.8% with the most damage variable (IMPACT2) to the rear. There was 32.8% reduction in risk with 2008+ MY vehicles.The NASS-CDS analysis showed that the risk of severe injury (MAIS 4+F) was 0.27 ± 0.05% for 1996–2001, 0.30 ± 0.13% for 2002–2007 and 0.08 ± 0.04% for 2008+ MY year vehicles. There was a 70.2% reduction in the risk for severe injury with 2008+ MY vehicles.The NASS-CDS case review of MAIS 4+F injury in rear impacts of 2008+ MY vehicles that comply with the revised FMVSS 301 indicated that the crashes were very severe and generally involved significant 2nd row intrusion.ConclusionsThe revision to FMVSS 301 has effectively reduced the risks for fatal and severe injury in vehicles compliant with the revision (2008+ MY). The reduction was 27.1–32.8% in fatality risk using FARS data and 70.2% in severe injury risk using the NASS-CDS when compared to vehicles prior to the phase-in of the revised FMVSS 301 (1996–2001 MY vehicles). It is not possible to parse the effects of other design changes in seats and restraint systems that also increased safety over the study years.     

Injury risks between first- and second-generation airbags in frontal motor vehicle collisions

BACKGROUND: Airbags in vehicles manufactured after 1997 were depowered to decrease injury risks for infants/children and small adults. It is possible that compared to earlier airbags second-generation airbags provide less injury protection due to their depowered nature. METHODS: A cohort study was conducted using 1995-2004 national data. Risk ratios (RRs) and 95% confidence intervals (CIs) compared injury risks for occupants involved in frontal collisions in vehicles wherein a first- or second-generation airbag deployed by body region and injury severity using the Abbreviated Injury Scale (AIS). Associations were adjusted for crash severity, seatbelt use, seat position, occupant location, and vehicle curb weight. RESULTS: For upper extremity injuries reduced RRs were observed for AIS 1 or greater (RR=0.76, CI 0.67-0.86), AIS 2 or greater (RR=0.76, CI 0.58-1.00) and AIS 3 (RR=0.81, CI 0.64-1.03). Elevated risks were observed for AIS 5 thoracic injuries (RR=1.46, CI 1.04-2.07) but were made null when differences in age and gender were adjusted for. CONCLUSIONS: Vehicles equipped with first- and second-generation airbags appear to offer similar protection for front-seated occupants. The observed decreased risks for upper extremity injury and increased risks for severe thoracic injuries warrant further attention.     

Rear seat restraint system effectiveness in preventing fatalities

Restraint system effectiveness for rear seat adult (16 years or older) car occupants is estimated by applying the double pair comparison method to Fatal Accident Reporting System (FARS) data for 1975 through 1985. As this data set contains information on fatal crashes only, the results apply exclusively to fatalities, and should not be generalized to other levels of injury. Rear seat occupants coded as using any restraint system are assumed to be using the lap belt only. Occupants in all four outboard seating positions (that is, driver and right front passenger, right and left rear passengers) serve as "other" occupants. Disaggregating the "other" occupant by restraint use generates six estimates of restraint system effectiveness for each of the two rear outboard positions. Insufficient data precluded estimating effectiveness for the center rear (or center front) positions, and also use of these occupants as "other" occupants. Average restraint system effectiveness for the two outboard rear seating positions is estimated as (18 +/- 9)%, where the error limit indicates one standard error. These estimates suggest that there is a 39 in 40 chance that rear lap belts reduce fatality likelihood, but a less than 1 in 10 chance that the reduction exceeds 30%.     

Aortic injuries in newer vehicles

The occurrence of AI was studied in relation to vehicle model year (MY) among front seat vehicular occupants, age ≥ 16 in vehicles MY ≥ 1994, entered in the National Automotive Sampling System Crashworthiness Data System between 1997 and 2010 to determine whether newer vehicles, due to their crashworthiness improvements, are linked to a lower risk of aortic injuries (AI). MY was categorized as 1994–1997, 1998–2004, or 2005–2010 reflecting the introduction of newer occupant protection technology. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals for the association between AI and MY independent of possible confounders. Analysis was repeated, stratified by frontal and near lateral impacts. AI occurred in 19,187 (0.06%) of the 31,221,007 (weighted) cases, and contributed to 11% of all deaths. AIs were associated with advanced age, male gender, high BMI, near-side impact, rollover, ejection, collision against a fixed object, high ΔV, vehicle mismatch, unrestrained status, and forward track position. Among frontal crashes, MY 98–04 and MY 05–10 showed increased adjusted odds of AI when compared to MY 94–97 [OR 1.84 (1.02–3.32) and 1.99 (0.93–4.26), respectively]. In contrast, among near-side impact crashes, MY 98–04 and MY 05–10 showed decreased adjusted odds of AI [OR 0.50 (0.25–0.99) and 0.27 (0.06–1.31), respectively]. While occupants of newer vehicles experience lower odds of AI in near side impact crashes, a higher AI risk is present in frontal crashes.     

Fatalities to occupants of cargo areas of pickup trucks

We sought to describe the fatalities to occupants of pickup truck cargo areas and to compare the mortality of cargo area occupants to passengers in the cab. From the Fatality Analysis Reporting System (FARS) files for 1987-1996, we identified occupants of pickup trucks with at least one fatality and at least one passenger in the cargo area. Outcomes of cargo area occupants and passengers in the cab were compared using estimating equations conditional on the crash and vehicle. Thirty-four percent of deaths to cargo occupants were in noncrash events without vehicle deformation. Fifty-five percent of those who died were age 15-29 years and 79% were male. The fatality risk ratio (FRR) comparing cargo area occupants to front seat occupants was 3.0 (95% Confidence Interval [CI] = 2.7-3.4). The risk was 7.9 (95% CI = 6.2-10.1) times that of restrained front seat occupants. The FRR ranged from 92 (95% CI = 47-179) in noncrash events to 1.7 (95% CI = 1.5-1.9) in crashes with severe vehicle deformation. The FRR was 1.8 (95% CI = 1.4-2.3) for occupants of enclosed cargo areas and 3.5 (95% CI = 3.1-4.0) for occupants of open cargo areas. We conclude that passengers in cargo areas of pickup trucks have a higher risk of death than front seat occupants, especially in noncrash events, and that camper shells offer only limited protection for cargo area occupants.     

Rear seat safer: seating position, restraint use and injuries in children in traffic crashes in Victoria, Australia

Car crashes are a major cause of death and serious injury to children but most analyses of risk are based on US data. The Australian context is different in at least three ways: (1) the proportion of passenger-side airbags, a potential risk to children in front seats, is much lower; (2) unlike in the US, Australian airbags are designed to work with restrained passengers; (3) restraint use for children 0-12 years is high (>90%). Official data drawn from Victorian crash records (n=30,631) were used to calculate relative risks of death or serious injury for children (0-3 years, 4-7 years; 8-12 years) traveling in passenger cars during 1993-1998 and 1999-2004. Over 90% were reportedly wearing a restraint, and 20% were traveling in the front seat. For children under 4 years traveling in the front seat, the relative risk of death was twice as great as when traveling in the rear, and that of serious injury was 60% greater. The relative risk of death whilst traveling in the front seat was almost four times greater for children aged under 1 year. We suggest that serious consideration should be given to mandating rear seating for children, particularly those aged 4 and under.     

A review of research on the protection afforded to occupants of cars by seat belts which provide upper torso restraint

The paper presents a critical review and summary of research on the protection afforded to car occupants by seat belts which provide upper torso restraint. The nature and causes of the injuries which occur even when seat belts are worn are then considered, and methods of reducing injuries still further are suggested.

Summaries are given of 8 selected European and American papers on seat belts in accidents. The estimated reductions in serious injuries varied from 45 to 70%, and reasons are suggested for the occurrence of these differences. Evidence of the reduction in deaths, as opposed to serious injuries, when seat belts are worn is scanty, but Australian experience of the results of compulsory seat belt wearing suggest that the wearing of seat belts with upper torso restraint reduces deaths of car occupants by at least 40%.

In non-fatal accidents to belted occupants, head, chest and leg injuries give rise to the largest numbers of severe injuries (AIS >3). In fatalities to belted occupants, however, while head injury retains its premier position, abdominal injury is at least as important as chest injury.

Modifications to the design of lap and diagonal seat belts are suggested, (a) to restrict loads on the abdomen and chest to levels which will not result in serious injury, and (b) to reduce forward movement of the head so as to lessen the risk of head injury.     

China belting up or down? Seat belt wearing trends in Nanjing and Zhoushan

National seat belt wearing legislation became effective in China May 2004 and associated provincial and city regulations followed. Despite rapid motorisation seat belt studies in China have been scarce. Patterns and trends in urban seat belt wearing were observed for all driver, front and rear seating positions over the years 2005–2007 in two eastern cities Nanjing (Jiangsu Province) and Zhoushan (Zhejiang Province). There were 35,256 vehicles observed in Nanjing, 20,939 in Zhoushan and 95,933 occupants overall. Males dominated all seating positions, especially drivers. Seat belt wearing overall was significantly higher for drivers (49.9% Nanjing, 47.4% Zhoushan) than for front seat passengers (9.1% Nanjing, 1.0% Zhoushan) and virtually nonexistent for rear passengers (0.5% Nanjing, 0.2% Zhoushan). Generally levels declined significantly from year to year (drivers Nanjing 66.7%, 47.7%, 38.6%; Zhoushan 57.4%, 57.9%, 30.6%; front passengers Nanjing 19.2%, 6.6%, 3.2%). Zhoushan wearing did not initially decline, 2006 observations coinciding with anticipation of provincial regulations (July 2006). Observations revealed an absence of child restraints. Pretend wearing/belt tampering was observed almost exclusively in taxi drivers (14.2% of Nanjing taxi drivers, 11.3% of Zhoushan’s). Awareness of and attitudes to urban seat belt laws should be investigated, appropriate countermeasures developed and enforcement reassessed.     

Assessing the relative risk of severe injury in automotive crashes for older female occupants

A logistic regression model was used in the prediction of injury severity for individuals who are involved in a vehicular crash. The model identified females and older occupants (segmented by age 55-74, and 75 and older) as having a significantly higher risk of severe injuries in a crash. Further, interactions of older females with other factors, such as occupant seat position, crash type, and environmental factors were also shown to significantly impact the relative risk of a severe injury. This study revealed that females 75 years and older had the lowest odds of injury among all female occupants studied (OR=1.16) while females between 55 and 74 years old have higher risk of severe injuries (OR=1.74). All older females (55 and older) were at greater risk for head-on, side-impact and rear-end collisions. Seatbelt use reduced severe injuries for females in this age group, but not to the same extent as the rest of the population studied. Additionally, crashes in severe weather, which were less likely to result in severe injuries for the general population, increased the risk of severe injuries to females that were 55 and older. Among occupants of light trucks, sport utility vehicles and vans, older females were less likely than others to be severely injured. In this case, older females appear better off in vehicles which are larger and protect better in severe crashes. This research demonstrates that circumstances surrounding a crash greatly impact the severity of injuries sustained by older female occupants.     

The actual threat posed by unrestrained rear seat car passengers

A statistical analysis of the threat posed by unrestrained rear seat car passengers to restrained drivers and front seat passengers was published in 2002. This was based on Japanese accident data from 1995 to 1999, and the conclusions have been checked using corresponding accident data from Great Britain. The law in respect of the use of seat belts and other restraint systems was less strict in Japan than in Great Britain between 1995 and 1999, so an earlier period had to be studied. The results suggest that the risk of death to a front seat car occupant is increased by about three-quarters by the presence of an unrestrained rear seat passenger behind them, a much smaller increase than was claimed by the Japanese researchers.     

Neck injuries in frontal impacts: influence of crash pulse characteristics on injury risk

AIS1 neck injuries are the most frequent disabling injuries among car occupants in road traffic accidents. Although neck injury is mostly regarded as resulting from rear end collisions, almost one third of all neck injuries occur in frontal impacts. The injury mechanisms in both rear-end and frontal impacts are still not known, although different hypotheses exist. Since 1992, approx. 100,000 vehicles on the Swedish market have been equipped with crash recorders to measuring frontal impacts. This paper analyses the influence of different characteristics derived from the acceleration time history on the risk of short- and long-term disability to the neck in frontal impacts. The study includes injury outcomes from 187 restrained front seat occupants in 143 frontal collisions with an overlap exceeding 25%, where the crash pulses have been recorded using crash pulse recorders. The results show that the shape of the crash pulse influences the risk of long-term disability to the neck. The vehicle accelerations in the mid and last third of the crash pulse seem to be important. It is also shown how change of velocity and mean and peak accelerations influence the neck-injury risk. It is suggested that the risk of sustaining an AIS1 neck injury in frontal impacts could be reduced by using more effective pretensioners and more advanced belt-load limiters. These results may also have implications for neck injury mechanisms in rear-end impacts.     

Effect of weight,height and BMI on injury outcome in side impact crashes without airbag deployment

A comprehensive analysis is performed to evaluate the effect of weight, height and body mass index (BMI) of occupants on side impact injuries at different body regions. The accident dataset for this study is based on the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) for accident year 2000–08. The mean BMI values for driver and front passenger are estimated from all types of crashes using NASS database, which clearly indicates that mean BMI has been increasing over the years in the USA. To study the effect of BMI in side impact injuries, BMI was split into three groups namely (1) thin (BMI < 21), (2) normal (BMI 24–27), (3) obese (BMI > 30). For more clear identification of the effect of BMI in side impact injuries, a minimum gap of three BMI is set in between each adjacent BMI groups. Car model years from MY1995–1999 to MY2000–2008 are chosen in order to identify the degree of influence of older and newer generation of cars in side impact injuries. Impact locations particularly side-front (F), side-center (P) and side-distributed (Y) are chosen for this analysis. Direction of force (DOF) considered for both near side and far side occupants are 8 o’clock, 9 o’clock, 10 o’clock and 2 o’clock, 3 o’clock and 4 o’clock respectively. Age <60 years is also one of the constraints imposed on data selection to minimize the effect of bone strength on the occurrence of occupant injuries. AIS2+ and AIS3+ injury risk in all body regions have been plotted for the selected three BMI groups of occupant, delta-V 0–60 kmph, two sets (old and new) of car model years. The analysis is carried with three approaches: (a) injury risk percentage based on simple graphical method with respect to a single variable, (b) injury distribution method where the injuries are marked on the respective anatomical locations and (c) logistic regression, a statistical method, considers all the related variables together. Lower extremity injury risk appears to be high for thin BMI group. It is found that BMI does not have much influence on head injuries but it is influenced more by the height of the occupant. Results of logistic analysis suggest that BMI, height and weight may have significant contribution towards side impact injuries across different body regions.     

Identification and validation of a logistic regression model for predicting serious injuries associated with motor vehicle crashes

A multivariate logistic regression model, based upon National Automotive Sampling System Crashworthiness Data System (NASS-CDS) data for calendar years 1999–2008, was developed to predict the probability that a crash-involved vehicle will contain one or more occupants with serious or incapacitating injuries. These vehicles were defined as containing at least one occupant coded with an Injury Severity Score (ISS) of greater than or equal to 15, in planar, non-rollover crash events involving Model Year 2000 and newer cars, light trucks, and vans. The target injury outcome measure was developed by the Centers for Disease Control and Prevention (CDC)-led National Expert Panel on Field Triage in their recent revision of the Field Triage Decision Scheme (American College of Surgeons, 2006). The parameters to be used for crash injury prediction were subsequently specified by the National Expert Panel. Model input parameters included: crash direction (front, left, right, and rear), change in velocity (delta-V), multiple vs. single impacts, belt use, presence of at least one older occupant (≥55 years old), presence of at least one female in the vehicle, and vehicle type (car, pickup truck, van, and sport utility). The model was developed using predictor variables that may be readily available, post-crash, from OnStar^®-like telematics systems. Model sensitivity and specificity were 40% and 98%, respectively, using a probability cutpoint of 0.20. The area under the receiver operator characteristic (ROC) curve for the final model was 0.84. Delta-V (mph), seat belt use and crash direction were the most important predictors of serious injury. Due to the complexity of factors associated with rollover-related injuries, a separate screening algorithm is needed to model injuries associated with this crash mode.     

Comparison of pregnant and non-pregnant occupant crash and injury characteristics based on national crash data

The objective of this study was to provide specific characteristics of injuries and crash characteristics for pregnant occupants from the National Automotive Sampling System/Crashworthiness Data System (NASS/CDS) database for pregnant women as a group, broken down by trimester, and compared to non-pregnant women. Using all NASS/CDS cases collected between the years 2000 and 2012 with at least one pregnant occupant, the entire pregnant data set included 321,820 vehicles, 324,535 occupants, and 640,804 injuries. The pregnant occupant data were compared to the characteristics of NASS/CDS cases for 14,719,533 non-pregnant females 13–44 years old in vehicle crashes from 2000 to 2012. Sixty five percent of pregnant women were located in the front left seat position and roughly the same percentage of pregnant women was wearing a lap and shoulder belt. The average change in velocity was 11.6 mph for pregnant women and over 50% of crashes for pregnant women were frontal collisions. From these collisions, less than seven percent of pregnant women sustained MAIS 2+ injuries. Minor differences between the pregnant and non-pregnant occupants were identified in the body region and source of injuries sustained. However, the data indicated no large differences in injury or crash characteristics based on trimester of pregnancy. Moreover, the risk of an MAIS 2+ level injury for pregnant occupants is similar to the risk of injury for non-pregnant occupants based on the total vehicle change in velocity. Overall this study provides useful data for researchers to focus future efforts in pregnant occupant research. Additionally, this study reinforces that more detailed and complete data on pregnant crashes needs to be collected to understand the risk for pregnant occupants.