Relative risk of spinal cord injury in road crashes involving seriously injured occupants of light passenger vehicles

Road crashes involving occupants of light passenger vehicles are the leading cause of traumatic spinal cord injury (SCI). Confirming the results of an earlier study, this study showed that: in single vehicle car crashes in the country, the odds of SCI were nearly five times higher (4.7) for occupants of non-sedan type light passenger vehicles compared with sedans; in single vehicle rollover crashes in the country, the odds of SCI were nearly three times higher (2.8) in non-sedans compared with sedans; the odds of SCI were nearly five times higher (4.8) for sports utility vehicles (SUVs) compared with sedans. When the data from the earlier study was included in order to increase statistical power, it was found that when compared to sedans that did not roll, occupants of all types of light passenger vehicles had a statistically significant substantially higher likelihood of SCI when involved in rollover (sedans 7.5 times, SUVs 5.9 times and others 8.4 times). In addition, SUVs had a higher likelihood of SCI even when not involved in rollover (5.4 times). Vehicle designers and regulators need to give more attention to the prevention of vehicle rollover and the means to improve occupant protection in the event of rollover. This study should be extended nationally to gain a larger case series so that the SCI risk of particular vehicle configurations, considering other crash factors, can be more precisely quantified and characteristics for low occurrence of SCI identified.     

Factors associated with the likelihood of injury resulting from collisions between four-wheel drive vehicles and passenger cars

The specific effects of vehicular type on the likelihood of an injury occurring are relatively unexplored. This study sought to assess the relative risk of injury to occupants of four-wheel drive vehicles and their counterparts in passenger cars.Data for 1143 occupants from all of the 454 crashes in Oklahoma, in 1995 that involved a four-wheel drive vehicle were used. Multiple logistic regression analysis determined the association between potential predictive factors and vehicular injury. Odds ratios revealed occupancy in a passenger car to be a major predictor of the likelihood of injury. Other factors include the driver being female, driving too fast, travel on curved or level roadways, and being hit laterally or from the rear.     

Rollover crashes: predicting serious injury based on occupant, vehicle, and crash characteristics

The purpose of this research was to determine occupant, vehicle, and crash characteristics predicting serious injury during rollover crashes. We compared 27 case occupants with serious or greater severity injuries with 606 control occupants without injury or with only minor or moderate injury. Odds ratios (OR) for individual variables and logistic regression were used to identify predictive variables for serious injury associated with rollovers. Cases more often had thorax, spine, or head injury compared to controls that more often had extremity injuries. Intrusion (especially roof rail or B-pillar intrusion) at the occupant's position, the vehicle interior side and roof as sources of injury, and improper safety belt use were significantly associated with serious injury. Even when safety belt use or proper use was controlled for, occupants with greater magnitude of intrusion at their seat position were about 10 times more likely to receive serious injury. Although prevention of rollover crashes is the ultimate goal, it is important to develop safer vehicles and safety systems to better protect occupants who are involved in rollover crashes. This also requires improvement in data collection systems documenting these types of crashes.     

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

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

Cervical and thoracic spine injury from interactions with vehicle roofs in pure rollover crashes

Around one third of serious injuries sustained by belted, non-ejected occupants in pure rollover crashes occur to the spine. Dynamic rollover crash test methodologies have been established in Australia and the United States, with the aims of understanding injury potential in rollovers and establishing the basis of an occupant rollover protection crashworthiness test protocol that could be adopted by consumer new car assessment programmes and government regulators internationally. However, for any proposed test protocol to be effective in reducing the high trauma burden resulting from rollover crashes, appropriate anthropomorphic devices that replicate real-world injury mechanisms and biomechanical loads are required. To date, consensus regarding the combination of anthropomorphic device and neck injury criteria for rollover crash tests has not been reached. The aim of the present study is to provide new information pertaining to the nature and mechanisms of spine injury in pure rollover crashes, and to assist in the assessment of spine injury potential in rollover crash tests. Real-world spine injury cases that resulted from pure rollover crashes in the United States between 2000 and 2009 are identified, and compared with cadaver experiments under vertical load by other authors. The analysis is restricted to contained, restrained occupants that were injured from contact with the vehicle roof structure during a pure rollover, and the role of roof intrusion in creating potential for spine injury is assessed. Recommendations for assessing the potential for spine injury in rollover occupant protection crash test protocols are made.     

Relative risk of injury and death in ambulances and other emergency vehicles

This study addresses of the impacts of emergency vehicle (ambulances, police cars and fire trucks) occupant seating position, restraint use and vehicle response status on injuries and fatalities. Multi-way frequency and ordinal logistic regression analyses were performed on two large national databases, the National Highway Traffic Safety Administration’s Fatality Analysis Reporting System (FARS) and the General Estimates System (GES). One model estimated the relative risk ratios for different levels of injury severity to occupants traveling in ambulances. Restrained ambulance occupants involved in a crash were significantly less likely to be killed or seriously injured than unrestrained occupants. Ambulance rear occupants were significantly more likely to be killed than front-seat occupants. Ambulance occupants traveling non-emergency were more likely than occupants traveling emergency to be killed or severely injured. Unrestrained ambulance occupants, occupants riding in the patient compartment and especially unrestrained occupants riding in the patient compartment were at substantially increased risk of injury and death when involved in a crash. A second model incorporated police cars and fire trucks. In the combined ambulance–fire truck–police car model, the likelihood of an occupant fatality for those involved in a crash was higher for routine responses. Relative to police cars and fire trucks, ambulances experienced the highest percentage of fatal crashes where occupants are killed and the highest percentage of crashes where occupants are injured. Lack of restraint use and/or responding with ‘lights and siren’ characterized the vast majority of fatalities among fire truck occupants. A third model incorporated non-special use van and passenger car occupants, which otherwise replicated the second model. Our findings suggest that ambulance crewmembers riding in the back and firefighters in any seating position, should be restrained whenever feasible. Family members accompanying ambulance patients should ride in the front-seat of the ambulance.     

Injuries to unrestrained occupants in small car-small car and large car-large car head-on collisions

Estimates were made of the effects of observed differences in the crash responses of small and large cars on the likelihood of injury to unrestrained occupants in small car-small car and large car-large car head-on collisions using a simple spring-mass model. Two measures of the likelihood of injury were computed: the relative velocity of an unrestrained occupant and car at the instant the occupant strikes the interior, and the approximate closing speed at which occupant compartment intrusion would be expected to begin. Model estimates of the intrusion thresholds for large ear-large car and small car-small car head-on crashes were comparable. However, unrestrained occupants were predicted to strike the interiors of their cars at a lower relative velocity in a head-on crash involving two large cars than in a similar crash involving two small cars. Head-on crashes involving a large and small car were also modelled for purposes of comparison. The estimated intrusion thresholds for small cars in such crashes were considerably lower than in small car-small car crashes. Also, calculations indicated that in a small car-large car head-on crash, an unrestrained small car occupant strikes the interior of his car with a higher relative velocity than an unrestrained large car occupant, and this velocity is higher than if his car struck another small car. However, the difference in the relative velocities with which unrestrained small and large car occupants impact the interiors of their cars in small car-large car collisions was found to diminish with increasing closing speed. These results suggest that the frontal structures of small cars should be longer and less stiff than on current models and the occupant compartment should be stiffer. Such designs would help to reduce injuries to restrained and unrestrained small car occupants in collisions with both small and large cars.     

The effects of vehicle model and driver behavior on risk

We study the dependence of risk on vehicle type and especially on vehicle model. Here, risk is measured by the number of driver fatalities per year per million vehicles registered. We analyze both the risk to the drivers of each vehicle model and the risk the vehicle model imposes on drivers of other vehicles with which it crashes. The "combined risk" associated with each vehicle model is simply the sum of the risk-to-drivers in all kinds of crashes and the risk-to-drivers-of-other-vehicles in two-vehicle crashes. We find that most car models are as safe to their drivers as most sport utility vehicles (SUVs); the increased risk of a rollover in a SUV roughly balances the higher risk for cars that collide with SUVs and pickup trucks. We find that SUVs and to a greater extent pickup trucks, impose much greater risks than cars on drivers of other vehicles; and these risks increase with increasing pickup size. The higher aggressivity of SUVs and pickups makes their combined risk higher than that of almost all cars. Effects of light truck design on their risk are revealed by the analysis of specific models: new unibody (or "crossover") SUVs appear, in preliminary analysis, to have much lower risks than the most popular truck-based SUVs. Much has been made in the past about the high risk of low-mass cars in certain kinds of collisions. We find there are other plausible explanations for this pattern of risk, which suggests that mass may not be fundamental to safety. While not conclusive, this is potentially important because improvement in fuel economy is a major goal for designers of new vehicles. We find that accounting for the most risky drivers, young males and the elderly, does not change our general results. Similarly, we find with California data that the high risk of rural driving and the high level of rural driving by pickups does not increase the risk-to-drivers of pickups relative to that for cars. However, other more subtle differences in drivers and the driving environment by vehicle type may affect our results.     

A population based estimation of the driver protection provided by passenger cars: France 1996–2005

The technology used in cars to protect occupants is constantly developing. Demonstrating the beneficial effects in the field is complex as the most recent vehicles are generally used by drivers who differ from other drivers and who drive in different traffic conditions. This paper presents an overall estimation of the consequences of changes in the secondary safety of cars, taking account of most of these factors.The data come from information collected about injury road traffic crashes by the police in France between 1996 and 2005. The risk of the driver being killed has been evaluated for the 144,034 drivers involved in two-car crashes and for the 63,621 drivers involved in single-car crashes.The study shows that when a recent car is in collision with an older car the driver of the former is better protected than the driver of the latter. These improvements in secondary safety are not observed in the case of single-car crashes, very probably because of higher impact speeds. Our findings also confirm the need for protection systems to be better adapted to the specific characteristics of users and for an improvement in the crash compatibility of vehicles, in particular to overcome the consequences of differences between the masses of vehicles.     

Overall injury risk to different drivers: combining exposure,frequency, and severity models

Traffic crash risk assessments should incorporate appropriate exposure data. However, existing US nationwide crash data sets, the NASS General Estimates System (GES) and the Fatality Analysis Reporting System (FARS), do not contain information on driver or vehicle exposure. In order to obtain appropriate exposure data, this work estimates vehicle miles driven (VMD) by different drivers using the Nationwide Personal Transportation Survey (NPTS). These results are combined with annual crash rates and injury severity information from the GES for a comprehensive assessment of overall risk to different drivers across vehicle classes.Data are distinguished by driver age, gender, vehicle type, crash type (rollover versus non-rollover), and injury severity. After correcting for drivers' crash exposure, results indicate that young drivers are far more crash prone than other drivers (per VMD) and that drivers of sports utility vehicles (SUVs) and pickups (PUs) are more likely to be involved in rollover crashes than those driving passenger cars. Although, the results suggest that drivers of SUVs are generally much less crash prone than drivers of passenger cars, the rollover propensity of SUVs and the severity of that crash type offset many of the incident benefits for SUV drivers.     

Accident involvement and crash injury rates: An investigation by make, model and year of car

Accident involvement and crash injury rates per million miles of vehicle travel are estimated by make, model and year of car. The accident and injury information was obtained from the North Carolina accident files, while exposure data were derived from paired odometer readings recorded on a statewide sample of motor vehicle inspection receipts.

The resulting estimates show a steady decrease in annual mileage with vehicle age. For the newer model years, large cars have generally higher annual mileages than small cars, and station wagons higher mileages than sedans or hardtops. The accident involvement and injury rates decline for the newer model cars, especially for larger-sized cars. Full-sized cars have the lowest overall accident and injury rates. Among standard-sized cars, two-door cars have higher accident and injury rates than four-door cars, and hardtops higher than sedans or station wagons.     

Driver injury severity: an application of ordered probit models

This paper describes the use of ordered probit models to examine the risk of different injury levels sustained under all crash types, two-vehicle crashes, and single-vehicle crashes. The results suggest that pickups and sport utility vehicles are less safe than passenger cars under single-vehicle crash conditions. In two-vehicle crashes, however, these vehicle types are associated with less severe injuries for their drivers and more severe injuries for occupants of their collision partners. Other conclusions also are presented; for example. the results indicate that males and younger drivers in newer vehicles at lower speeds sustain less severe injuries.     

Discrepancies in vehicular crash injury reporting: Northeastern Ohio Trauma Study. IV

People injured in motor vehicle traffic crashes were identified from a population-representative incidence sample of hospital emergency department visits. Matched police reports of crashes were sought in official state records of motor vehicle traffic crashes. Of the emergency department cases, 55% had matched police reports. The frequency of matched reports was highest for drivers (74%), people transported to the hospital by emergency vehicle (69%), and those requiring hospital admission (74%). The frequency was lowest for people younger than 16 years (28%), people injured as occupants of vehicles other than passenger cars (24%), medicaid recipients (33%), and nonresidents of the study region (40%). Motor vehicle traffic injuries are undercounted in police-reported statistics. For many groups, police reporting is less than 50% of the cases identified through emergency departments. The likelihood that a case of motor vehicle traffic injury will have a matched police report depends on demographic, social and crash factors as well as on injury severity.     

The fatality and injury risk of light truck impacts with pedestrians in the United States

In the United States, passenger vehicles are shifting from a fleet populated primarily by cars to a fleet dominated by light trucks and vans (LTVs). Because light trucks are heavier, stiffer, and geometrically more blunt than passenger cars, they pose a dramatically different type of threat to pedestrians. This paper investigates the effect of striking vehicle type on pedestrian fatalities and injuries. The analysis incorporates three major sources of data, the Fatality Analysis Reporting System (FARS), the General Estimates System (GES), and the Pedestrian Crash Data Study (PCDS). The paper presents and compares pedestrian impact risk factors for sport utility vehicles, pickup trucks, vans, and cars as developed from analyses of US accident statistics. Pedestrians are found to have a two to three times greater likelihood of dying when struck by an LTV than when struck by a car. Examination of pedestrian injury distributions reveals that, given an impact speed, the probability of serious head and thoracic injury is substantially greater when the striking vehicle is an LTV rather than a car.     

Thoracic injuries to contained and restrained occupants in single-vehicle pure rollover crashes

Around one in three contained and restrained seriously injured occupants in single-vehicle pure rollover crashes receive a serious injury to the thorax. With dynamic rollover test protocols currently under development, there is a need to understand the nature and cause of serious thoracic injuries incurred in rollover events. This will allow decisions to be made with regards to adoption of a suitable crash test dummy and appropriate thoracic injury criteria in such protocols. Valid rollover occupant protection test protocols will lead to vehicle improvements that will reduce the high trauma burden of vehicle rollover crashes. This paper presents an analysis of contained and restrained occupants involved in single-vehicle pure rollover crashes that occurred in the United States between 2000 and 2009 (inclusive). Serious thoracic injury typology and causality are determined. A logistic regression model is developed to determine associations between the incidence of serious thoracic injury and the human, vehicle and environmental characteristics of the crashes. Recommendations are made with regards to the appropriate assessment of potential thoracic injury in dynamic rollover occupant protection crash test protocols.     

Are SUVs dangerous vehicles?

This study was a population cohort study of all licensed passenger vehicles in New Zealand in the years 2005–2006. The objective of the study was to evaluate the effect on road safety of sports utility vehicles (SUVs) compared to other passenger vehicle types. Statistical models were fitted to the population of 2,996,000 vehicles of which 17,245 were involved in an injury crash. Controlling for distance driven, vehicle and owner characteristics, SUVs were found to be relatively safe vehicles in terms of injury crash involvement and in terms of the injury rate of their own occupants or other road users into which they crashed. Current research on SUV safety clearly shows them to be a road safety concern, but only once a collision occurs. The present study shows that SUVs in New Zealand have relatively few collisions compared to other passenger vehicle types, allowing for factors such as distance driven, some allowance for the type of driving exposure (via the owners’ addresses) and for owner age and gender. Overall, the vehicle type implicated most frequently in injury crashes and involving the highest rate of road injuries was sports cars, causing clearly the most harm per licensed vehicle. Instead of concerning themselves primarily with SUVs, the focus of road safety agencies should be on the relatively high crash risk of sports cars, which are clearly a road safety concern. Their high crash involvement rate and injury rate is likely to be largely due to the way they are driven rather than to inherent characteristics of the vehicles themselves.     

New evidence concerning fatal crashes of passenger vehicles before and after adding antilock braking systems

Fatal crash rates for passenger cars and vans were compared for the last model year before four-wheel antilock brakes were introduced and the first model year for which antilock brakes were standard equipment. A prior study, based on fatal crash experience through 1995, reported that vehicle models with antilock brakes were more likely than identical but 1-year-earlier models to be involved in crashes fatal to their own occupants, but were less likely to be involved in crashes fatal to occupants of other vehicles. Overall, there was no significant effect of antilocks on the likelihood of fatal crashes. Similar analyses, based on fatal crash experience during 1996-98, yielded very different results. During 1996-98, vehicles with antilock brakes were again less likely than earlier models to be involved in crashes fatal to occupants of other vehicles, but they were no longer overinvolved in crashes fatal to their own occupants.     

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.     

Characteristics of motor vehicle accidents resulting in spinal cord injury

The majority of cases of spinal cord injury (SCI) occur during car crashes. Yet, relatively little is known about the precise accident factors involved. The present study investigated 30 cases of SCI in automobile drivers that occurred in a series of 91 spinal cord injuries. A matched control group was also studied. SCI drivers were not different from controls in terms of mortality, number of rollover crashes, alcohol use, citations for contributing human factors, nighttime accidents, or unfavorable weather and road conditions. However, SCI drivers less frequently used restraints. Results are discussed in terms of preventive measures, specifically, those concerning restraint use, alcohol use, and driving behavior.     

Will the light truck bumper height-matching standard reduce deaths in cars?

Background

In a collision between a car and a sport utility vehicle (SUV) or pickup truck, car occupants are more likely to be killed than if they crashed with another car. Some of the excess risk may be due to the propensity of SUVs and pickups with high bumpers to override the lower bumpers in cars. To reduce this incompatibility, particularly in head-on collisions, in 2003 automobile manufacturers voluntarily established a bumper height-matching standard for pickups and SUVs.

Objective

To assess whether height-matching bumpers in pickups and SUVs were associated with the risk of death in either car occupants or pickup and SUV occupants.

Methods

Case–control study of collisions between one car and one SUV or pickup in the US during 2000–2008, in which the SUV or pickup was model year 2000–2006. Cases were all decedents in fatal crashes; one control was selected from each crash in a national probability sample of crashes.

Findings

Occupants of cars that crashed with SUVs or pickups with height-matching bumpers may be at slightly reduced risk of death compared to those that crashed with other SUVs or pickups (adjusted odds ratio: 0.83 (95% confidence interval 0.61–1.13)). There was no evidence of a reduction in risk in head-on crashes (1.09 (0.66–1.79)). In crashes in which the SUV or pickup struck the car on the side, height-matched bumpers were associated with a reduced risk of death (0.68 (0.48–0.97)). Occupants of SUVs and pickups with height-matching bumpers may also be at slightly reduced risk of death (0.91 (0.64–1.28)).

Conclusions

Height-matching bumpers were associated with a reduced risk of death among car occupants in crashes in which SUVs or pickups struck cars in the side, but there was little evidence of an effect in head-on crashes. The new bumper height-matching standard may not achieve its primary goal of reducing deaths in head-on crashes, but may modestly reduce overall deaths in crashes between cars and SUVs or pickups because of unanticipated benefits to car occupants in side crashes, and a possible beneficial effect to SUV and pickup occupants.