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

PURPOSE: Vehicle and occupant responses in rollovers are complex since many factors influence both. This study analyzes the following factors: 1) belt use, 2) seated position with respect to the lead side in the rollover, 3) another front occupant in the crash, and 4) number of quarter rolls. The aim was to improve our understanding of rollover injury mechanisms. METHOD: Rollover accidents were analyzed using 1992-2004 NASS-CDS data. The sample included adult drivers and right-front passengers. All occupants were evaluated and then a subset of non-ejected occupants was analyzed. Using roll direction and seating position, the sample was divided into near- and far-seated occupants. Injury and fatality risks were determined by seatbelt use, occupancy, rollover direction, and number of quarter rolls. Risk was defined as the number of injured (e.g., MAIS 3+) divided by the number of exposed occupants (MAIS 0-6). Significance in differences was determined. A matched-pair analysis was used to determine the risk of serious injury for near- and far-seated occupants who were either belted or unbelted in the same crash. RESULTS: For all occupants, serious injury risks were highest for far-seated, unbelted occupants at 18.1% +/- 4.8%, followed by near-seated unbelted occupants at 12.0% +/- 3.5%. However, the difference was not statistically significant. Belted near- and far-seated occupants had a similar injury risk of 4.3% +/- 1.2% and 4.0% +/- 1.2%, respectively. For non-ejected occupants, serious injury risk was 9.5% +/- 3.2% for far-seated unbelted occupants and 4.9% +/- 2.1% for near-seated unbelted occupants, not a statistically significant difference. Serious injury risk was similar for belted near- and far-seated non-ejected occupants, at 3.6% +/- 1.1%. Seatbelts were 64.2%-77.9% effective in preventing serious injury for all occupants and 62.1%-26.5% for far- and near-seated, non-ejected occupants, respectively. Based on the matched pairs, seatbelts were less effective for near-seated (5.0%) compared to far-seated (2.8%) occupant MAIS 3+F risks. This was similar for non-ejected occupants. An unbelted near-seated occupant increased the risk for a belted far-seated occupant by 2.2 times, whereas an unbelted far-seated occupant increased the risk for a belted near-seated occupant by 10.2 times. For all occupants, the risk of serious injury increased with the number of quarter rolls, irrespective of seated position. For near-seated occupants, seatbelt effectiveness was higher in < or =1 roll than 1+ roll, at 72.3% compared to 28.3%. For far-seated occupants, seatbelt effectiveness was similar in < or =1 and 1+ roll samples at 78.3% and 76.8%, respectively. Near-seated occupants had the lowest serious injury risk when they were the sole occupant in the vehicle. This was also true for non-ejected occupants. However, far-seated occupants had a lower injury risk when another occupant was involved in the crash. CONCLUSIONS: The effect of carrying another occupant appears to reduce the risk of serious injury to far-seated occupants. However, near-seated occupants are better off being the sole occupant in the vehicle. Seatbelt effectiveness was lowest at 28.3% for non-ejected, near-seated occupants in 1+ rolls. This finding deserves further evaluation in an effort to improve seatbelt effectiveness in rollovers. For belted drivers alone in a rollover, fatality risks are 2.24 times higher for the far- versus near-seated position. Analysis of rollovers by quarter turns indicates that occupants are both far-side and near-side in rollovers. The extent to which this confounds the relationship between roll direction, seating position, and injury risk is unknown.     

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

Abstract

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.     

Driver and front passenger injury in frontal crashes: Update on the effect of unbelted rear occupants

Purpose: This is a study of the influence of an unbelted rear occupant on the risk of severe injury to the front seat occupant ahead of them in frontal crashes. It provides an update to earlier studies.

Methods: 1997–2015 NASS-CDS data were used to investigate the risk for severe injury (Maximum Abbreviated Injury Score [MAIS] 4+F) to belted drivers and front passengers in frontal crashes by the presence of a belted or unbelted passenger seated directly behind them or without a rear passenger. Frontal crashes were identified with GAD1 = F without rollover (rollover ≤ 0). Front and rear outboard occupants were included without ejection (ejection = 0). Injury severity was defined by MAIS and fatality (F) by TREATMNT = 1 or INJSEV = 4. Weighted data were determined. The risk for MAIS 4+F was determined using the number of occupants with known injury status MAIS 0+F. Standard errors were determined.

Results: The risk for severe injury was 0.803 ± 0.263% for the driver with an unbelted left rear occupant and 0.100 ± 0.039% with a belted left rear occupant. The driver's risk was thus 8.01 times greater with an unbelted rear occupant than with a belted occupant (P <.001). With an unbelted right rear occupant behind the front passenger, the risk for severe injury was 0.277 ± 0.091% for the front passenger. The corresponding risk was 0.165 ± 0.075% when the right rear occupant was belted. The front passenger's risk was 1.68 times greater with an unbelted rear occupant behind them than a belted occupant (P <.001). The driver's risk for MAIS 4+F was highest when their seat was deformed forward. The risk was 9.94 times greater with an unbelted rear occupant than with a belted rear occupant when the driver's seat deformed forward. It was 13.4 ± 12.2% with an unbelted occupant behind them and 1.35 ± 0.95% with a belted occupant behind them.

Conclusions: Consistent with prior literature, seat belt use by a rear occupant significantly lowered the risk for severe injury to belted occupants seated in front of them. The reduction was greater for drivers than for front passengers. It was 87.5% for the driver and 40.6% for the front passenger. These results emphasize the need for belt reminders in all seating positions.     

Evaluation of Vehicle-Based Crash Severity Metrics

Objective: Vehicle change in velocity (delta-v) is a widely used crash severity metric used to estimate occupant injury risk. Despite its widespread use, delta-v has several limitations. Of most concern, delta-v is a vehicle-based metric which does not consider the crash pulse or the performance of occupant restraints, e.g. seatbelts and airbags. Such criticisms have prompted the search for alternative impact severity metrics based upon vehicle kinematics. The purpose of this study was to assess the ability of the occupant impact velocity (OIV), acceleration severity index (ASI), vehicle pulse index (VPI), and maximum delta-v (delta-v) to predict serious injury in real world crashes.

Methods: The study was based on the analysis of event data recorders (EDRs) downloaded from the National Automotive Sampling System / Crashworthiness Data System (NASS-CDS) 2000–2013 cases. All vehicles in the sample were GM passenger cars and light trucks involved in a frontal collision. Rollover crashes were excluded. Vehicles were restricted to single-event crashes that caused an airbag deployment. All EDR data were checked for a successful, completed recording of the event and that the crash pulse was complete. The maximum abbreviated injury scale (MAIS) was used to describe occupant injury outcome. Drivers were categorized into either non-seriously injured group (MAIS2?) or seriously injured group (MAIS3+), based on the severity of any injuries to the thorax, abdomen, and spine. ASI and OIV were calculated according to the Manual for Assessing Safety Hardware. VPI was calculated according to ISO/TR 12353-3, with vehicle-specific parameters determined from U.S. New Car Assessment Program crash tests. Using binary logistic regression, the cumulative probability of injury risk was determined for each metric and assessed for statistical significance, goodness-of-fit, and prediction accuracy.

Results: The dataset included 102,744 vehicles. A Wald chi-square test showed each vehicle-based crash severity metric estimate to be a significant predictor in the model (p < 0.05). For the belted drivers, both OIV and VPI were significantly better predictors of serious injury than delta-v (p < 0.05). For the unbelted drivers, there was no statistically significant difference between delta-v, OIV, VPI, and ASI.

Conclusions: The broad findings of this study suggest it is feasible to improve injury prediction if we consider adding restraint performance to classic measures, e.g. delta-v. Applications, such as advanced automatic crash notification, should consider the use of different metrics for belted versus unbelted occupants.     

Real-World Rib Fracture Patterns in Frontal Crashes in Different Restraint Conditions

Objective: The purpose of this study was to use the detailed medical injury information in the Crash Injury Research and Engineering Network (CIREN) to evaluate patterns of rib fractures in real-world crash occupants in both belted and unbelted restraint conditions. Fracture patterns binned into rib regional levels were examined to determine normative trends associated with belt use and other possible contributing factors.

Methods: Front row adult occupants with Abbreviated Injury Scale (AIS) 3+ rib fractures, in frontal crashes with a deployed frontal airbag, were selected from the CIREN database. The circumferential location of each rib fracture (with respect to the sternum) was documented using a previously published method (Ritchie et al. 2006) and digital computed tomography scans. Fracture patterns for different crash and occupant parameters (restraint use, involved physical component, occupant kinematics, crash principal direction of force, and occupant age) were compared qualitatively and quantitatively.

Results: There were 158 belted and 44 unbelted occupants included in this study. For belted occupants, fractures were mainly located near the path of the shoulder belt, with the majority of fractures occurring on the inboard (with respect to the vehicle) side of the thorax. For unbelted occupants, fractures were approximately symmetric and distributed across both sides of the thorax. There were negligible differences in fracture patterns between occupants with frontal (0°) and near side (330° to 350° for drivers; 10° to 30° for passengers) crash principal directions of force but substantial differences between groups when occupant kinematics (and contacts within the vehicle) were considered. Age also affected fracture pattern, with fractures tending to occur more anteriorly in older occupants and more laterally in younger occupants (both belted and unbelted).

Conclusions: Results of this study confirmed with real-world data that rib fracture patterns in unbelted occupants were more distributed and symmetric across the thorax compared to belted occupants in crashes with a deployed frontal airbag. Other factors, such as occupant kinematics and occupant age, also produced differing patterns of fractures. Normative data on rib fracture patterns in real-world occupants can contribute to understanding injury mechanisms and the role of different causation factors, which can ultimately help prevent fractures and improve vehicle safety.     

Driver injury in near- and far-side impacts: Update on the effect of front passenger belt use

Purpose: This is a study that updates earlier research on the influence of a front passenger on the risk for severe driver injury in near-side and far-side impacts. It includes the effects of belt use by the driver and passenger, identifies body regions involved in driver injury, and identifies the sources for severe driver head injury.

Methods: 1997–2015 NASS-CDS data were used to investigate the risk for Maximum Abbreviated Injury Scale (MAIS) 4 + F driver injury in near-side and far-side impacts by front passenger belt use and as a sole occupant in the driver seat. Side impacts were identified with GAD1 = L or R without rollover (rollover ≤ 0). Front-outboard occupants were included without ejection (ejection = 0). Injury severity was defined by MAIS and fatality (F) by TREATMNT = 1 or INJSEV = 4. Weighted data were determined. The risk for MAIS 4 + F was determined using the number of occupants with known injury status MAIS 0 + F. Standard errors were determined.

Results: Overall, belted drivers had greater risks for severe injury in near-side than far-side impacts. As a sole driver, the risk was 0.969 ± 0.212% for near-side and 0.313 ± 0.069% for far-side impacts (P < .005). The driver's risk was 0.933 ± 0.430% with an unbelted passenger and 0.596 ± 0.144% with a belted passenger in near-side impacts. The risk was 2.17 times greater with an unbelted passenger (NS). The driver's risk was 0.782 ± 0.431% with an unbelted passenger and 0.361% ± 0.114% with a belted passenger in far-side impacts. The risk was 1.57 times greater with an unbelted passenger (P < .10). Seat belt use was 66 to 95% effective in preventing MAIS 4 + F injury in the driver. For belted drivers, the head and thorax were the leading body regions for Abbreviated Injury Scale (AIS) 4+ injury. For near-side impacts, the leading sources for AIS 4+ head injury were the left B-pillar, roof, and other vehicle. For far-side impacts, the leading sources were the other occupant, right interior, and roof (8.5%).

Conclusions: Seat belt use by a passenger lowered the risk of severe driver injury in side impacts. The reduction was 54% in near-side impacts and 36% in far-side impacts. Belted drivers experienced mostly head and thoracic AIS 4+ injuries. Head injuries in the belted drivers were from contact with the side interior and the other occupant, even with a belted passenger.     

Census Study of Real-Life Near-Side Crashes with Modern Side Airbag-Equipped Vehicles in the United States

Objective: This study aimed to investigate the crash characteristics, injury distribution, and injury mechanisms for Maximum Abbreviated Injury Score (MAIS) 2+ injured belted, near-side occupants in airbag-equipped modern vehicles. Furthermore, differences in injury distribution for senior occupants compared to non-senior occupants was investigated, as well as whether the near-side occupant injury risk to the head and thorax increases or decreases with a neighboring occupant.

Method: National Automotive Sampling System's Crashworthiness Data System (NASS-CDS) data from 2000 to 2012 were searched for all side impacts (GAD L&R, all principal direction of force) for belted occupants in modern vehicles (model year > 1999). Rollovers were excluded, and only front seat occupants over the age of 10 were included. Twelve thousand three hundred fifty-four MAIS 2+ injured occupants seated adjacent to the intruding structure (near-side) and protected by at least one deployed side airbag were studied. To evaluate the injury risk influenced by the neighboring occupant, odds ratio with an induced exposure approach was used.

Result: The most typical crash occurred either at an intersection or in a left turn where the striking vehicle impacted the target vehicle at a 60 to 70° angle, resulting in a moderate change of velocity (delta-V) and intrusion at the B-pillar. The head, thorax, and pelvis were the most frequent body regions with rib fracture the most frequent specific injury. A majority of the head injuries included brain injuries without skull fracture, and non-senior rather than senior occupants had a higher frequency of head injuries on the whole. In approximately 50% of the cases there was a neighboring occupant influencing injury outcome.

Conclusion: Compared to non-senior occupants, the senior occupants sustained a considerably higher rate of thoracic and pelvis injuries, which should be addressed by improved thorax side airbag protection. The influence on near-side occupant injury risk by the neighboring occupant should also be further evaluated. Furthermore, side airbag performance and injury assessments in intersection crashes, especially those involving senior occupants in lower severities, should be further investigated and side impact dummy biofidelity and injury criteria must be determined for these crash scenarios.     

The effects of airbags and seatbelts on occupant injury in longitudinal barrier crashes

Introduction

Longitudinal barriers, such as guardrails, are designed to prevent a vehicle that leaves the roadway from impacting a more dangerous object while minimizing the risk of injury to the vehicle occupants. Current full-scale test procedures for these devices do not consider the effect of occupant restraints such as seatbelts and airbags. The purpose of this study was to determine the extent to which restraints are used or deployed in longitudinal barrier collisions and their subsequent effect on occupant injury.

Methods

Binary logistic regression models were generated to predict occupant injury risk using data from the National Automotive Sampling System / Crashworthiness Data System from 1997 through 2007.

Results

In tow-away longitudinal barrier crashes, airbag deployment rates were 70% for airbag-equipped vehicles. Compared with unbelted occupants without an airbag available, seat belt restrained occupants with an airbag available had a dramatically decreased risk of receiving a serious (MAIS 3+) injury (odds-ratio (OR) = 0.03; 95% CI: 0.004-0.24). A similar decrease was observed among those restrained by seat belts, but without an airbag available (OR = 0.03; 95% CI: 0.001- 0.79). No significant differences in risk of serious injuries were observed between unbelted occupants with an airbag available compared with unbelted occupants without an airbag available (OR = 0.53; 95% CI = 0.10-2.68).

Impact on Industry

This study refutes the perception in the roadside safety community that airbags rarely deploy in frontal barrier crashes, and suggests that current longitudinal barrier occupant risk criteria may over-estimate injury potential for restrained occupants involved in a longitudinal barrier crash.     

Age Dependence of Female to Male Fatality Risk in the Same Crash: An Independent Reexamination

A 1988 study reported that females are more likely than males to be killed by the same physical insult. This was determined by analyzing 1975–1983 data. The present study revisits this question using 123,678 fatalities from 1984–1996 data. As none of these data contributed to the earlier study, the present investigation is therefore independent of the earlier one. Female to male fatality risk ratios are calculated for 14 categories of vehicle occupants, including six light truck occupants (belted and unbelted drivers and right front passengers, and unbelted left and right rear passengers). The earlier study did not include light trucks. Close agreement is found between the results of the present and prior studies, thus solidifying the interpretation that findings are of a general nature and not dependent on specific data sets. Except at ages less than about 10 years, or older than about 55, females are more likely to be killed than males. While obtained using traffic data, the results are interpreted to reflect fundamental differences in human physiological response to blunt trauma in general, and are expected to apply to blunt trauma from falls, being struck by objects, etc.     

Forward collision warning system impact

Abstract

Objective: The objective of this research is to use historical crash data to evaluate the potential benefits of both high- and low-speed automatic emergency braking (AEB) with forward collision warning (FCW) systems.

Methods: Crash data from the NHTSA’s NASS–General Estimates System (GES) and Fatality Analysis Reporting System (FARS) databases were categorized to classify crashes by the speed environment, as well as to identify cases where FCW systems would be applicable.

Results: Though only about 19% of reported crashes occur in environments with speeds greater than 45?mph, approximately 32% of all serious or fatal crashes occur in environments with speeds greater than 45?mph. The percentage of crashes where FCW systems would be relevant has remained remarkably constant, varying between about 21 and 26% from 2002 to 2015. In 2-vehicle fatal crashes where one rear-ends the other, the fatality rates are actually higher in the struck vehicle (33%) than the striking vehicle (26%). The disparity is even greater when considering size–class differences, such as when a light truck rear-ends a passenger car (15 vs. 42% fatality rates, respectively).

Conclusions: NHTSA and the Insurance Institute for Highway Safety (IIHS) proposed the Automatic Emergency Braking Initiative in 2015, which is intended to make AEB (also called crash-imminent braking) with FCW systems standard on nearly all new cars by September 2022. Twenty automakers representing 99% of the U.S. auto market voluntarily committed to the initiative. Though the commitment to safety is laudable, the AEB component of the agreement only covers low-speed AEB systems, with the test requirements set to 24?mph or optionally as low as 12?mph. The test requirements for the FCW component of the agreement include 2 tests that begin at 45?mph. Only 21% of relevant serious injury or fatal accidents occur in environments at speeds under 24?mph, whereas about 22% of serious or fatal crashes occur in environments with speeds greater than 45?mph. This means that the AEB with FCW systems as agreed upon will cover only 21% of serious or fatal crashes and will not cover 22% of serious or fatal crashes. Because these systems are protective not only for the occupants of the vehicle where they are installed but also other vehicles on the roads, the data indicate that these systems should be a standard feature on all cars for high-speed as well as low-speed environments for the greatest social benefit.     

The safety implications of vehicle seat adjustments

INTRODUCTION: The goal of this study was to gather information on the preferred front seat position of vehicle occupants and to determine the impact of variation in seat position on safety during crashes. METHOD: The study evaluated the relationship between seat position and occupant size using the chi-square test and compared the risk of severe injury for small females and large males with regard to forward and rearward seat position using logistic regression. RESULTS: While smaller drivers sat closer to the steering wheel than larger drivers, front passengers of all sizes used similar seat positions. Additionally, the risk of injury was higher for small, unbelted females in rearward seat positions and large males (belted and unbelted) in forward seat positions. CONCLUSIONS: Occupants who adjust their seats to positions that are not consistent with required federal tests are at a greater risk for severe injury in a crash.     

Safety belt effectiveness in preventing driver fatalities versus a number of vehicular, accident, roadway, and environmental factors

Safety belt effectiveness in preventing fatalities to drivers is examined versus a number factors (vehicle, accident, and environmental) by applying the double-pair comparison method to appropriate subsets of the Fatal Accident Reporting System (FARS) data. For each of 13 factors studied, safety belt effectiveness (the percent of fatally injured unbelted drivers who would not have been killed if they had been wearing safety belts) is estimated, as is an associated standard error of the estimate. The results, which are presented graphically, provide no evidence that safety belt effectiveness is systematically influenced by most of the factors investigated, including car mass and model year. The absence of any systematic relationship with car mass is in agreement with an earlier finding based on the pedestrian fatality exposure method; this agreement adds plausibility to the assumptions used for both the earlier and the present methods. Safety belt effectiveness is greater for single-car crashes (62 ± 5) % than for crashes involving two cars (30 ± 8) % , this difference being statistically significant at p<.02. The results suggest weakly that safety belt effectiveness is greater for two-door (48 ± 6) % than for four-door (38 ± 10) % cars, and is greater for striking (44 ± 6) % cars than for struck (27 ± 12)% cars. The above differences probably reflect higher effectiveness in frontal (or rollover) crashes than in side impacts.     

An application of a conditional logistic regression to study the effects of safety belts, principal impact points, and car weights on drivers' fatalities

In addition to experimental trials in automotive factories, there is a fundamental need to monitor real people involved in real motor vehicle collisions to determine the impact of automotive design characteristics on injury mortality. To aid in designing future safety features for drivers' seats, data from the Fatal Accident Reporting System (FARS) were used to assess the effects of safety belts, directions of crash impacts, age, sex, and car weights on motor vehicle injury fatalities. Furthermore, because the FARS includes only accidents in which there was at least one fatality, this paper introduces a multivariate approach — a logistic regression conditioned on each accident —to avoid the sampling biases inherent in the FARS. The resulting model is used to quantify the relations among the safety belts, the directions of crash impacts, and vehicle weights and their effects on fatalities. Recause the proposed approach allows researchers to study many important variables simultaneously and eliminates the biases resulting from many possible confounders, the estimates presented in this paper are considered to be more precise and more firmly established than earlier estimates. The new approach to analyzing the FARS data will also be useful for investigating the effects of other risk factors or automotive characteristics on crash fatalities.     

Characteristics of vehicle-animal crashes in which vehicle occupants are killed

During the past 10 years almost 1,500 people have been killed in motor vehicle collisions with animals. Police reports on 147 fatal vehicle-animal crashes during 2000-2002 were obtained from nine states. The goal was to determine common crash types, types of animals involved, and steps that could be taken to reduce the crashes and injuries. Seventy-seven percent of the struck animals were deer, but six other types of animals were involved including small ones such as dogs. Eighty percent of the crashes were single-vehicle events. In most of these cases a motorcycle struck an animal and the rider came off the vehicle, or a passenger vehicle struck an animal and then ran off the road; in a few cases the animal went through the windshield. Multiple-vehicle crashes included vehicles striking deer that went through the windshields of oncoming vehicles, vehicles striking animals and then colliding with other vehicles, and vehicles striking animals that subsequently were struck by other vehicles. Crashes occurred primarily in rural areas, on roads with 55 mph or higher speed limits, during evening or nighttime hours, and in darkness. Greater application of deer-vehicle collision countermeasures known to be effective is needed, but it is noteworthy that a majority of fatalities occurred from subsequent collisions with other vehicles or objects, not from animal contacts. Sixty-five percent of motorcyclists killed were not wearing helmets, and 60% of vehicle occupants killed were unbelted; many of these fatalities would not have occurred with proper protection.     

State-level seat belt use in the United States, 2011–2016: Comparison of self-reported with observed use and use by fatally injured occupants

Introduction: Despite 49 states and the District of Columbia having seat belt laws that permit either primary or secondary enforcement, nearly half of persons who die in passenger vehicle crashes in the United States are unbelted. Monitoring seat belt use is important for measuring the effectiveness of strategies to increase belt use. Objective: Document self-reported seat belt use by state seat belt enforcement type and compare 2016 self-reported belt use with observed use and use among passenger vehicle occupant (PVO) fatalities. Methods: We analyzed the Behavioral Risk Factor Surveillance System (BRFSS) self-reported seat belt use data during 2011–2016. The Pearson correlation coefficient (r) was used to compare the 2016 BRFSS state estimates with observed seat belt use from state-based surveys and with unrestrained PVO fatalities from the Fatality Analysis Reporting System. Results: During 2011–2016, national self-reported seat belt use ranged from 86–88%. In 2016, national self-reported use (87%) lagged observed use (90%) by 3 percentage points. By state, the 2016 self-reported use ranged from 64% in South Dakota to 93% in California, Hawaii, and Oregon. Seat belt use averaged 7 percentage points higher in primary enforcement states (89%) than in secondary states (82%). Self-reported state estimates were strongly positively correlated with state observational estimates (r = 0.80) and strongly negatively correlated with the proportion of unrestrained PVO fatalities (r = −0.77). Conclusion: National self-reported seat belt use remained essentially stable during 2011–2016 at around 87%, but large variations existed across states. Practical Applications: If seat belt use in secondary enforcement states matched use in primary enforcement states for 2016, an additional 3.98 million adults would have been belted. Renewed attention to increasing seat belt use will be needed to reduce motor-vehicle fatalities. Self-reported and observational seat belt data complement one another and can aid in designing targeted and multifaceted interventions.     

The field performance of frontal air bags: a review of the literature

This article presents a broad review of the literature on frontal air bag field performance, starting with the initial government and industry projections of effectiveness and concluding with the most recent assessments of depowered systems. This review includes as many relevant metrics as practicable, interprets the findings, and provides references so the interested reader can further evaluate the limitations, confounders, and utility of each metric. The evaluations presented here range from the very specific (individual case studies) to the general (statistical analyses of large databases). The metrics used to evaluate air bag performance include fatality reduction or increase; serious, moderate, and minor injury reduction or increase; harm reduction or increase; and cost analyses, including insurance costs and the cost of life years saved for various air bag systems and design philosophies. The review begins with the benefits of air bags. Fatality and injury reductions attributable to the air bag are presented. Next, the negative consequences of air bag deployment are described. Injuries to adults and children and the current trends in air bag injury rates are discussed, as are the few documented instances of inadvertent deployments or non-deployment in severe crashes. In the third section, an attempt is made to quantify the influence of the many confounding factors that affect air bag performance. The negative and positive characteristics of air bags are then put into perspective within the context of societal costs and benefits. Finally, some special topics, including risk homeostasis and the performance of face bags, are discussed.     

Association between driver and child passenger restraint: Analysis of community-based observational survey data from 2005 to 2019

Introduction: Crash data suggest an association between driver seatbelt use and child passenger restraint. However, community-based restraint use is largely unknown. We examined the association between driver seatbelt use and child restraint using data from a state-wide observational study. Methods: Data from Iowa Child Passenger Restraint Survey, a representative state-wide survey of adult seat belt use and child passenger safety, were analyzed. A total of 44,996 child passengers age 0–17 years were observed from 2005 to 2019. Information about driver seatbelt use and child restraint was directly observed by surveyors and driver age was reported. Logistic regression was used to examine the association between driver seatbelt use and child restraint adjusting for vehicle type, community size, child seating position, child passenger age, and year. Results: Over the 15-year study period, 4,114 (9.1%) drivers were unbelted, 3,692 (8.2%) children were completely unrestrained, and another 1,601 (3.6%) children were improperly restrained (analyzed as unrestrained). About half of unbelted drivers had their child passengers unrestrained (51.8%), while nearly all belted drivers had their child passengers properly restrained (92.3%). Compared with belted drivers, unbelted drivers had an 11-fold increased odds of driving an unrestrained child passenger (OR = 11.19, 95%CI = 10.36, 12.09). The association between driver seatbelt use and child restraint was much stronger among teenage drivers. Unbelted teenage drivers were 33-fold more likely (OR = 33.34, 95%CI = 21.11, 52.64) to have an unrestrained child passenger. Conclusion: These data suggest that efforts to increase driver seatbelt use may also have the added benefit of increasing child restraint use. Practical applications: Enforcement of child passenger laws and existing education programs for new drivers could be leveraged to increase awareness of the benefits of seatbelt use for both drivers themselves and their occupants. Interventions aimed at rural parents could emphasize the importance of child safety restraints.     

Nighttime pedestrian fatalities: A comprehensive examination of infrastructure,user, vehicle,and situational factors

Introduction: Pedestrian fatalities in the United States increased 45.5% between 2009 and 2017. More than 85% of those additional pedestrian fatalities occurred at night. Method: We examine Fatality Analysis Reporting System (FARS) data for fatal pedestrian crashes that occurred in the dark between 2002 and 2017. Within-variable and before/after examinations of crashes in terms of infrastructure, user, vehicle, and situational characteristics are performed with one-way analysis of variance (ANOVA) and two-sample t-tests. We model changes in crash characteristic proportions between 2002–2009 and 2010–2017 using linear regressions and test for autocorrelation with Breusch-Godfrey tests. Results: The increase in fatal nighttime pedestrian crashes is most strongly correlated with infrastructure factors: non-intersection unmarked locations (saw 80.8% of additional fatalities); 40–45 mph roads (54.6%); five-lane roads (40.7%); urban (99.7%); and arterials (81.1%). In addition, SUVs were involved in 39.7% of additional fatalities, overrepresenting their share of the fleet. Increased pedestrian alcohol and drug involvement warrant further investigation. The age of pedestrians killed increased more (18.1%) than the national average (3.2%). Conclusions: By identifying factors related to the increase in nighttime pedestrian fatalities, this work constitutes a vital first step in making our streets safer for pedestrians. Practical Applications: More research is needed to understand the efficacy of different solutions, but this paper provides guidance for such future research. Engineering solutions such as road diets or traffic calming may be used to improve identified infrastructure issues by reducing vehicle speeds and road widths. Rethinking vehicle design, especially high front profiles, may improve vehicle issues. However, the problems giving rise to these pedestrian fatalities are likely a result of not only engineering issues but also interrelated social and political factors. Solutions may be correspondingly comprehensive, employing non-linear, systems-based approaches such as Safe Systems.