The influence of damage distribution on serious brain injury in occupants in frontal motor vehicle crashes

In spite of improvements in motor vehicle safety systems and crashworthiness, motor vehicle crashes remain one of the leading causes of brain injury. The purpose of this study was to determine if the damage distribution across the frontal plane affected brain injury severity of occupants in frontal impacts. Occupants in "head on" frontal impacts with a Principal Direction of Force (PDOF) equal to 11, 12, or 1o'clock who sustained serious brain injury were identified using the Crash Injury Research Engineering Network (CIREN) database. Impacts were further classified based on the damage distribution across the frontal plane as distributed, offset, and extreme offset (corner). Overall, there was no significant difference for brain injury severity (based on Glasgow Coma Scale<9, or brain injury AIS>2) comparing occupants in the different impact categories. For occupants in distributed frontal impacts, safety belt use was protective (odds ratio (OR)=0.61) and intrusion at the occupant's seat position was four times more likely to result in severe (Glasgow Coma Scale (GCS)<9) brain injury (OR=4.35). For occupants in offset frontal impacts, again safety belt use was protective against severe brain injury (OR=0.25). Possibly due to the small number of brain-injured occupants in corner impacts, safety belts did not significantly protect against increased brain injury severity during corner impacts. This study supports the importance of safety belt use to decrease brain injury severity for occupants in distributed and offset frontal crashes. It also illustrates how studying "real world" crashes may provide useful information on occupant injuries under impact circumstances not currently covered by crash testing.     

The association between sudden illness and motor vehicle crash mortality and injury among older drivers in NSW, Australia

This exploratory study aims to investigate the associations between sudden illness and the risk of motor vehicle crash-related mortalities and injuries among older drivers aged 60 or above. Information utilised in the study was obtained from police reports of all road traffic accidents that occurred on the roads between 1996 and 2000 in New South Wales, Australia. There were 409 older drivers involved in crashes after becoming ill suddenly. Among these the majority (62.1%) of crashes led to at least one occupant in the vehicle being killed or injured. There is a significant association between sudden illness and crash-related mortality and injury after adjusting for other risk factors. The risk of injury and death is increased by nearly six times (OR = 5.58, 95% CI = 4.54-6.85) for those who suffered a sudden illness while driving when compared to those non-sufferers. These results are discussed in the light of possible preventive strategies and the provision of risk assessment and safety counselling for older people.     

Calcaneal fractures in occupants involved in severe frontal motor vehicle crashes

The calcaneous is the largest tarsal bone in the foot and plays an important role in walking and running. Motor vehicle crashes and falls from elevation have been associated with calcaneal fractures. Although not life-threatening, these injuries may result in permanent disability. This study used the Crash Injury Research and Engineering Network (CIREN) database to describe calcaneal fractures and concomitant lower extremity skeletal injury patterns for occupants involved in motor vehicle crashes. Sixty-three drivers and 7 front row passengers with calcaneal fractures were identified in the CIREN database during 1997-2005. Almost all these occupants were involved in severe (based on the delta V and vehicle crush) frontal or off-set frontal crashes with toe pan intrusion. Eighty-four percent of the calcaneal fractures were intra-articular or partially articular. Overall, 93% of occupants also had injury to other body regions with 84% having other lower extremity fractures. One year after the crash, most occupants had not returned to their prior level of physical functioning. Surgically managing patients with calcaneal fractures for an optimal outcome remains a challenge for orthopedic surgeons. Because lower extremity injuries, including calcaneal fractures, may cause permanent disability, it is important to prevent these injuries through structural improvements in motor vehicle design.     

The relationship between visibility aid use and motor vehicle related injuries among bicyclists presenting to emergency departments

Background

Little is known about the effectiveness of visibility aids (VAs; e.g., reflectors, lights, fluorescent clothing) in reducing the risk of a bicyclist–motor-vehicle (MV) collision.

Purpose

To determine if VAs reduce the risk of a bicyclist–MV collision.

Methods

Cases were bicyclists struck by a MV and assessed at Calgary and Edmonton, Alberta, Canada, emergency departments (EDs) from May 2008 to October 2010. Controls were bicyclists with non-MV injuries. Participants were interviewed about their personal and injury characteristics, including use of VAs. Injury information was collected from charts. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated for VAs during daylight and dark conditions, and adjusted for confounders using logistic regression. Missing values were imputed using chained equations and adjusted OR estimates from the imputed data were calculated.

Results

There were 2403 injured bicyclists including 278 cases. After adjusting for age, sex, type of bicycling (commuting vs. recreational) and bicyclist speed, white compared with black (OR 0.52; 95% CI 0.28, 0.95), and bicyclist self-reported light compared with dark coloured (OR 0.67; 95% CI 0.49, 0.92) upper body clothing reduced the odds of a MV collision during daylight. After imputing missing values, white compared with black (OR 0.57; 95% CI: 0.32, 0.99) and bicyclist self-reported light compared with dark coloured (OR 0.71; 95% CI 0.52, 0.97) upper body clothing remained protective against MV collision in daylight conditions. During dark conditions, crude estimates indicated that reflective clothing or other items, red/orange/yellow front upper body clothing compared with black, fluorescent clothing, headlights and tail lights were estimated to increase the odds of a MV collision. An imputed adjusted analysis revealed that red/orange/yellow front upper body clothing colour (OR 4.11; 95% CI 1.06, 15.99) and tail lights (OR 2.54; 95% CI: 1.06, 6.07) remained the only significant risk factors for MV collisions. One or more visibility aids reduced the odds of a bicyclist MV collision resulting in hospitalization.

Conclusions

Bicyclist clothing choice may be important in reducing the risk of MV collision. The protective effect of visibility aids varies based on light conditions, and non-bicyclist risk factors also need to be considered.     

Effect of population density on mortality after motor vehicle collisions

The objective of this study was to evaluate the effect of population density on mortality after traffic crashes. Subjects were the drivers of vehicles requiring towing after collisions, sampled by NASS-GES during 1994–1998. Cases were classified by population of crash location (greater or lesser than 25,000) and by population density of the driver’s county of residence (using ZIP code and Census data). Cases were also categorized by age, belt use and vehicle speed. Analytic methods for weighted, stratified survey data were used to estimate effects on mortality. A total of 190,721 cases with a specified crash location were identified in the sample, of which 93.7% had a specified population at the crash location, and 94.1% could be linked to the driver’s county data. Mortality was higher in locations with populations less than 25,000 and was inversely proportional to the driver’s county population density. Age, belt use, and vehicle speed also affected mortality significantly, but the effect of rural location remained after controlling for these factors (O.R. 2.10, 95% C.I. 1.62–2.73). The excess risk for residents of rural areas to die in traffic crashes can be attributed in part to post-crash factors.     

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.     

Traumatic brain injury,driver aggression and motor vehicle collisions in Canadian adults

ObjectiveThis study examines the associations between lifetime traumatic brain injury (TBI), driver aggression, and motor vehicle collisions among a population sample of adults who reside in the province of Ontario, Canada.MethodA cross-sectional sample of 3993 Ontario adults, aged 18–97 were surveyed by telephone in 2011 and 2012 as part of Center for Addiction and Mental Health’s ongoing representative survey of adult mental health and substance use in Canada. TBI was defined as trauma to the head that resulted in loss of consciousness for at least five minutes or overnight hospitalization.ResultsAn estimated 91% (95% CI: 90.0, 91.9) of individuals in this sample held a valid Ontario driver’s license at the time of testing. Among those, 16.7% reported a history of lifetime TBI and 83.3% reported no TBI. The prevalence of TBI was higher among men than women. Relative to licensed adults without TBI, adults with a history of TBI had significantly higher odds of engaging in serious driver aggression in the past 12 months, such as making threats to hurt another driver, passenger or their vehicle (AOR = 4.39). These individuals also reported significantly higher odds (AOR = 1.74) of being involved in a motor vehicle collision that resulted in hurting themselves, their passenger(s) or their vehicle.ConclusionThis is the first population-based study to demonstrate a relationship between a history of TBI and higher rates of serious driver aggression and collision involvement. Given the large proportion of adult drivers with a history of TBI, these individuals may account for a disproportion burden of all traffic safety problems. Whether the increased road safety risk of adults with a history of TBI is reflective of neurocognitive deficits or is merely evidence of a cluster of unsafe activities produced by a higher risk lifestyles requires further research attention.     

Identification of vehicle components associated with severe thoracic injury in motor vehicle crashes: a CIREN and NASS analysis

INTRODUCTION: Thoracic trauma secondary to motor vehicle crashes (MVC) continues to be a major cause of morbidity and mortality. Specific vehicle features may increase the risk of severe thoracic injury when striking the occupant. We sought to determine which vehicle contact points were associated with an increased risk of severe thoracic injury in MVC to focus subsequent design modifications necessary to reduce thoracic injury. METHODS: The National Automotive Sampling System (NASS) databases from 1993 to 2001 and the Crash Injury Research and Engineering Network (CIREN) databases from 1996 to 2004 were analyzed separately using univariate and multivariate logistic regression stratified by restraint use and crash direction. The risk of driver thoracic injury, defined as an abbreviated injury scale (AIS) of score > or =3, was determined as it related to specific points of contact between the vehicle and the driver. RESULTS: The incidence of severe chest injury in NASS and CIREN were 5.5% and 33%, respectively. The steering wheel, door panel, armrest, and seat were identified as contact points associated with an increased risk of severe chest injury. The door panel and arm rest were consistently a frequent cause of severe injury in both the NASS and CIREN data. CONCLUSIONS: Several vehicle contact points, including the steering wheel, door panel, armrest and seat are associated with an increased risk of severe thoracic injury when striking the occupant. These elements need to be further investigated to determine which characteristics need to be manipulated in order to reduce thoracic trauma during a crash.     

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.     

Regional mortality from motor vehicle traffic injury: relationships among place-of-occurrence, place-of-death, and place-of-residence

Regional mortality data, which are compiled according to place-of-residence of the decedent, are an important reference for regional health planning and resource allocation. However, it would be inappropriate to apply these data to studies of environmental risk factors if a large proportion of fatal motor vehicle traffic injuries (MVTI) in fact occur outside the resident county. The aim of this study was to determine the proportion and characteristics of residents of a rural area of Taiwan who died from MVTIs that occurred outside the county of residence. We also explored the relationships among the place-of-occurrence, place-of-death, and place-of-residence of these decedents. The families or neighbors of residents of Huatung Area (eastern Taiwan) who died from MVTIs in 1994 or 1995 were interviewed to identify the place-of-occurrence of the MVTI. Of the 882 Huatung Area residents who died as a result of an MVTI during the study period and for whom relevant data were available, the MVTI occurred outside the resident county in 207 (23%) cases. Residents whose MVTI occurred outside the county of residence were more likely to be youths (aged 15-24) or young adults (aged 25-44) and driving automobiles or trucks. Of the 866 cases in which the exact place was known, the place-of-occurrence and the place-of-death (recorded on the death certificate) were in the same county in 849 (98%). Because a high proportion of fatal MVTIs occurred outside the resident county, the mortality rate calculated according to place-of-residence does not accurately reflect the environmental risk factors in this area. The finding that the characteristics of those whose MVTI occurred outside the county differed from those decedents whose MVTI occurred within the county indicates that there are two target groups for prevention programs. In addition, at least in Huatung Area, the place-of-death recorded on the death certificate could serve as a surrogate for the place-of-occurrence in epidemiologic studies.     

Knee injuries in motor vehicle collisions: a study of the National Accident Sampling System database for the years 1979-1995

A detailed study of knee injuries recorded in the 1979–1995 National Accident Sampling System database maintained by the National Highway Traffic Safety Administration was conducted. Injuries to other body regions were also considered in order to illustrate the relative frequency of knee injuries. This study demonstrated that knee injuries constitute ≈10% of all injuries recorded every year. However, the majority of these injuries were of low severity (i.e. contusions, abrasions, lacerations) with an abbreviated injury score (AIS) of 1. Most knee injuries occurred following a frontal collision with no intrusion. The study also indicated most knee fractures occur in crashes where the vehicle velocity differences (ΔVs) were less than 45 kmph, with some occurring at ΔVs as low as 10 kmph. Serious non-fracture knee injuries (i.e. ligament tears) rated AIS 2 accounted for 20 out of every 1000 injuries and predominantly occurred at ΔVs below 25 kmph. In this study it was noted that women were more likely to experience a knee contusion than men. This study further suggests that knee impact scenarios have remained relatively constant over the years as the knee injury rates showed little variation. The rate of lap and shoulder belt use was lower in occupants who experienced a knee injury vs. the rate in the overall database and airbags were present in only a small number of cases. As this study largely included only vehicles without airbags it provides a good baseline for analysis of the influence of the airbag on knee injury trends in the future.     

Comparison of injury mortality risk in motor vehicle crash versus other etiologies

The mortality risk ratio (MRR), a measure of the proportion of people who died that sustained a given injury, is reported to be among the most powerful discriminators of mortality following trauma. The primary aim was to determine whether mechanistic differences exist and are quantifiable when comparing MRR-based injury severity across two broadly defined etiologies (motor vehicle crash (MVC) versus non-MVC) for the clarification of important injury types that have some room for improvement by emergency treatment and vehicle design. All International Classification of Diseases, 9th revision (ICD-9) coded injuries in the National Trauma Data Bank (NTDB) database were stratified into MVC and non-MVC groups and the MRR for each injury was computed within each group. Injuries were classified as 11 different types for MRR comparison between etiologies. Overall, MRRs for specific injuries were 10–18% lower for MVC compared to non-MVC etiologies. MVCs however produced much higher mean MRRs for crushing injuries (0.184 versus 0.072) and internal injuries to the thorax, abdomen, and pelvis (0.200 versus 0.169). Non-MVCs produced much higher MRRs for intracranial injuries (0.199 versus 0.250). Analysis of the top 95% most frequent MVC injuries revealed higher MVC MRR values for 78% of the injuries with MRR ratios indicating an average 50% increase in a given injury's MRR when MVC was the etiology. Addressing the large differences in MRR in between etiologies for identical injuries could provide a reduction in fatalities and may be important to patient triage and vehicle safety design.     

Motorcycle helmet type and the risk of head injury and neck injury during motorcycle collisions in California

The use of novelty motorcycle helmets is often prompted by beliefs that wearing a standard helmet can contribute to neck injury during traffic collisions. The goal of this analysis was to examine the association between helmet type and neck injury risk and the association between helmet type and head injury. Data were collected during the investigation of motorcycle collisions of any injury severity by the California Highway Patrol (CHP) and 83 local law enforcement agencies in California between June 2012 and July 2013. We estimated head injury and neck injury risk ratios from data on 7051 collision-involved motorcyclists using log-binomial regression. Helmet type was strongly associated with head injury occurrence but was not associated with the occurrence of neck injury. Rider age, rider alcohol use, and motorcycle speed were strong, positive predictors of both head and neck injury. Interventions to improve motorcycle helmet choice and to counteract misplaced concerns surrounding neck injury risk are likely to lead to reductions in head injury, brain injury, and death.     

Urban-rural differences in motor vehicle crash fatality and hospitalization rates among children and youth

This population-based study examined motor vehicle crash hospitalization rates and death rates among children and youth in rural and urban areas of the province of Alberta, Canada. Using police report data (1997-2002, inclusive), average annual motor vehicle crash hospitalization and death rates among those 0-19 years of age were calculated for rural and urban regions. Across all age and sex strata examined, both the hospitalization and the fatality rates were significantly higher in rural compared with urban regions. After adjusting for age, sex and calendar year, the relative risk of a motor vehicle crash hospitalization (rural versus urban) was 3.0 (95% CI: 2.8, 3.2). After adjusting for age, sex and calendar year, the relative risk of a motor vehicle crash fatality was 5.4 (95% CI: 4.2, 6.9). Motor vehicle crash injury hospitalization and fatality rates among children and youth in the province of Alberta are considerably higher in rural areas compared with urban areas. There is a need to identify social, demographic and environmental driving hazards associated with the rural environment.     

Predictors of injury among younger and older adults in fatal motor vehicle crashes

With 2003 Fatality Analysis Reporting System data, we examined relationships among predictors of motor vehicle injury/fatality outcomes for younger (35–54 years) and older (65 years and older) drivers. Using the Precede-Proceed Model of Health Promotion as an organizing framework, we classified variables into person, vehicle and environment domains and conducted a multinomial logistic regression.Significant risk factors for older driver injuries were impact crashes at 1–3 o’clock (OR = 1.65; CI: 1.05–2.59), 7–9 o’clock angles (OR = 2.59; CI = 1.45–4.63), and driving with one passenger (OR = 2.25; CI: 1.58–3.20). Previous other motor vehicle convictions were significantly associated with reduced risk of injury (OR = 0.55; CI = 0.34–0.90). The 7–9 o’clock angle (OR = 3.06; CI: 1.83–5.12), and driving in daylight hours were risk factors for fatality among older drivers.Many risk factors (e.g., female gender, non-seatbelt use, rollover crashes, and vehicle body type), and protective factors (e.g., number of lanes and non-airbag deployment) were relevant for younger and older drivers. Findings showed relevant factors for drivers from both age groups, with some pointing to older adults, and set the stage for further research to develop injury and fatality prevention programs.     

Injury patterns in frontal crashes: The association between knee-thigh-hip (KTH) and serious intra-abdominal injury

Safety belts protect occupants in frontal impacts by reducing occupant deceleration and preventing the occupant from hitting interior vehicle components likely to cause injury. However, occupants moving forward during the impact may contact the safety belt webbing across their chest and abdomen. We hypothesized that if the occupant loaded their knee-thigh-hip (KTH) region with enough force to result in injury to this region—it might prevent compression (and injury) of their abdomen by the safety belt. Crash Injury Research and Engineering Network (CIREN) data were used to test the association between KTH and intra-abdominal injury related to safety belts. Odds ratios with 95% confidence limits (CL) and logistic regression models were used to assess statistical significance. Analyses were based on 706 CIREN adult, front seat occupants using their safety belt and injured in frontal crashes. Occupants with KTH injury were four times less likely (adjusted odds ratio = 0.25, 95% CL 0.10, 0.62) to have concomitant serious intra-abdominal injury caused by the safety belt. Although safety belts save lives and prevent serious injury, some occupants may sustain serious intra-abdominal injury when the abdomen is loaded by the safety belt during a frontal impact. These results may be useful to motor vehicle manufacturers and others who design and test motor vehicle safety systems.     

The association of age, sex and helmet use with the risk of death for occupants of two-wheeled motor vehicles involved in traffic crashes in Spain

Background

This study was designed to separate the association of age, sex and helmet use with the risk of death for occupants of two-wheeled motor vehicles (TWMV) involved in crashes into its two theoretical components: severity of the crash and occupant resilience.

Methods

We analyzed the retrospective cohort comprising all 48 016 pairs of drivers and passengers aged 14 years or more in TWMV involved in crashes with victims in Spain from 1993 to 2007 recorded in the Spanish traffic crash registry. The outcome (death or survival), age, sex and helmet use was known for both occupants. Adjusted relative risks (RR) for the association of age, sex and helmet with the risk of death were calculated with Poisson regression models.

Results

Each 1-year increase in age was related with a 3% increase in the risk of death related with lower resilience. The severity-dependent RR of death was 1.84 for male sex and 0.86 for non-helmet use, and the resilience-dependent RR was 0.72 and 2.53, respectively.

Conclusions

The direction and magnitude of the association between age, sex and helmet use and the risk of death of an occupant of a TWMV involved in a crash changed depending on which component of risk was considered: crash severity or occupant resilience. Specifically, female sex and non-helmet use seemed to be associated with crashes of lower severity, but together with increased age they were also related with lower resilience to the energy released in the crash, and therefore with a higher risk of death after adjustment for crash severity. This should be taken into account when assessing the association of individual factors with the risk of death after a crash.     

The relationship between body weight and risk of death and serious injury in motor vehicle crashes

We sought to investigate the effect of increased body weight on the risk of death and serious injury to occupants in motor vehicle crashes. We employed a retrospective cohort study design utilizing data from the National Automotive Sampling System, Crashworthiness Data System (CDS), 1993-1996. Subjects in the study included occupants involved in tow-away crashes of passenger cars, light trucks, vans and sport utility vehicles. Two outcomes were analyzed: death within 30 days of the crash and injury severity score (ISS). Two exposures were considered: occupant body weight and body mass index (BMI; kg/m2). Occupant weight was available on 27263 subjects (76%) in the CDS database. Mortality was 0.67%. Increased body weight was associated with increased risk of mortality and increased risk of severe injury. The odds ratio for death was 1.013 (95% CI: 1.007, 1.018) for each kilogram increase in body weight. The odds ratio for sustaining an injury with ISS > or = 9 was 1.008 (95% CI: 1.004, 1.011) for each kilogram increase in body weight. After adjustment for potentially confounding variables (age, gender, seatbelt use, seat position and vehicle curbweight), the significant relationship between occupant weight and mortality persisted. After adjustment, the relationship between occupant weight and ISS was present, although less marked. Similar trends were found when BMI was analyzed as the exposure. In conclusion, increased occupant body weight is associated with increased mortality in automobile crashes. This is probably due in part to increased co-morbid factors in the more overweight occupants. However, it is possibly also due to an increased severity of injury in these occupants. These findings may have implications for vehicle safety design, as well as for transport safety policy.     

Comparison of the binary logistic and skewed logistic (Scobit) models of injury severity in motor vehicle collisions

The binary logistic model has been extensively used to analyze traffic collision and injury data where the outcome of interest has two categories. However, the assumption of a symmetric distribution may not be a desirable property in some cases, especially when there is a significant imbalance in the two categories of outcome. This study compares the standard binary logistic model with the skewed logistic model in two cases in which the symmetry assumption is violated in one but not the other case. The differences in the estimates, and thus the marginal effects obtained, are significant when the assumption of symmetry is violated.