Factors associated with chest injuries to front seat occupants in frontal impacts.

Objective: Frontal impact chest protection in European cars has been highlighted as an area where possible improvements could be made. The chest is particularly vulnerable in older occupants whose numbers are forecast to increase significantly in the coming decades. This study aimed to provide some direction to areas for possible improvements in frontal crash chest protection.Methods: Real-world crash injury data were interrogated, focusing on cars with current restraint components. The research examined belted front seat occupants in frontal impacts where airbags, pretensioners, and load limiters were present.Results: The chest was the most often injured body region at Abbreviated Injury Scale (AIS) 2+, 3+, and 4+ injury levels. The rate of AIS 2+ and AIS 3+ chest injuries was highest among elderly occupants and lowest among young occupants, and elderly occupants sustained proportionally more severe chest injuries in low/moderate-speed impacts compared to young and middle-aged occupants. However, it should be noted that rates of AIS 2 chest injury were also significantly higher for middle-aged occupants compared to the young. The front passenger seat was shown to be more often associated with significant chest injury than the driver seat. The higher proportion of elderly female occupants was postulated as a reason for this. Skeletal injury was the most frequent type of AIS 2+ chest injury, and the rate of injury for elderly occupants with such injuries was higher than that for young and middle-aged occupants. With the increase in the number of rib fractures, the risk of pulmonary complications and organ injuries tended to increase. The major cause of chest injury was identified as restraining loads transmitted to the chest via the seat belt. The absence of intrusion in the majority of cases suggests an opportunity for the restraint system to better manage the crash pulse, not only for elderly occupants but for those who are middle-aged as well.Conclusions: This study shows the necessity for safety interventions, through new vehicle crashworthiness systems, to improve chest protection, especially for middle-aged and elderly car occupants. Deployment of appropriate injury risk criteria, use of an appropriate dummy thorax, development of a low-energy restraint test, and the development of more adaptive restraints have been discussed as possible solutions to the problem.

Adapting load limiter deployment for frontal crash diversity.

Objective: Current European restraint systems may not realize their full protection potential in real-world frontal crashes because they are highly optimized for specific conditions. This research sought to quantify the potential benefit of adapting seat belt load limit thresholds to a wider range of occupant and crash characteristics.Methods: Numerical simulations using Hybrid III dummies were conducted to determine how varying load limiter thresholds could affect occupant kinematics and injury outcome in frontal impacts. Occupant-compartment models were developed with a restraint system consisting of a frontal airbag and a 3-point belt with retractor, buckle pretensioner, and load limiting at the shoulder. Load limiting threshold was varied in 5 frontal impact scenarios, covering as wide a range of real frontal crash conditions as possible. The simulated thoracic injury risks were converted into injury probability values using Abbreviated Injury Scale (AIS) 2+ age-dependent thoracic risk curves. These values were then applied to a British real-world frontal impact sample to determine the injury reduction potential of optimized load limiting, taking into account occupant seating position, impact scenario, occupant size, and occupant age and assuming that an appropriate adaptive system was fitted to all cars.Results: In low-severity impacts, a low load limit provided the best chest protection, without increasing risk to other body regions, for both the 50th and 95th percentile dummies in both front seating positions. In high-severity impacts, the low limit was not recommended because it allowed the driver dummy to move into close proximity with the vehicle interior, although there appeared to be some benefit of lower load limiting for the 50th percentile front passenger dummy, due to the increased ride down space in that seating position. Adapting the load limit showed no injury reduction potential for 5th percentile drivers. Utilizing the best load limit threshold in real-world crashes could reduce the number of occupants with AIS 2+ chest injuries from belt loading from 377 to 251 (a 33% reduction), correspondingly reducing the number of occupants with AIS 2+ chest injuries (from all sources) in the whole frontal impact population from 496 to 370. This is a reduction in injury rate from 6.4% to 4.8%.Conclusions: The concept of an adaptive load limiter shows most promise in low-speed frontal crashes where it could lower the AIS 2+ chest injury risk for most front seat occupants, except the smallest of drivers. Generally, adaptive limiters show less potential effectiveness with increased crash severities. Overall, an intelligent adjustment of load limiting threshold could result in a reduction of at least a third of front seat occupants with AIS 2+ chest injuries associated with restraining loads and an overall reduction in AIS 2+ chest injury rate in frontal crashes from 6.4% to 4.8.

Improving the Chest Protection of Elderly Occupants in Frontal Crashes Using SMART Load Limiters.

OBJECTIVE: To determine whether varying the seat belt load limiter (SBL) according to crash and occupant characteristics could have real-world injury reduction benefits in frontal impacts and, if so, to quantify those benefits. METHODS: Real-world UK accident data were used to identify the target population of vehicle occupants and frontal crash scenarios where improved chest protection could be most beneficial. Generic baseline driver and front passenger numerical models using a 50th percentile dummy were developed with MADYMO software. Simulations were performed where the load limiter threshold was varied in selected frontal impact scenarios. For each SBL setting, restraint performance, dummy kinematics, and injury outcome were studied in 5 different frontal impact types. Thoracic injury predictions were converted into injury probability values using Abbreviated Injury Scale (AIS) 2+ age-dependent thoracic risk curves developed and validated based on a methodology proposed by Laituri et al. (2005). Real-world benefit was quantified using the predicted AIS 2+ risk and assuming that an appropriate adaptive system was fitted to all the cars in a real-world sample of recent frontal crashes involving European passenger cars. RESULTS: From the accident data sample the chest was the most frequently injured body region at an AIS 2+ level in frontal impacts (7% of front seat occupants). The proportion of older vehicle front seat occupants (>64 years) with AIS 2+ injury was also greater than the proportion of younger occupants. Additionally, older occupants were more likely to sustain seat belt-induced serious chest injury in low- and moderate-speed frontal crashes. In both front seating positions, the low SBL provided the best chest injury protection, without increasing the risk to other body regions. In severe impacts, the low SBL allowed the driver to move dangerously close to the steering wheel. Compared to the driver side, greater ride-down space on the passenger side gave a higher potential for using the low SBLs. When applying the AIS 2+ risk reduction findings to the weighted accident data sample, the risk of sustaining an AIS 2+ seat belt injury changed to 0.9, 4.9, and 8.1% for young, mid, and older occupants, respectively, from their actual injury risk of 1.3, 7.6, and 13.1%. CONCLUSIONS: These results suggest the potential for improving the safety of older occupants with the development of smarter restraint systems. This is an important finding because the number of older users is expected to increase rapidly over the next 20 years. The greatest benefits were seen at lower crash severities. This is also important because most real-world crashes occur at lower speeds.

Evaluation of an autonomous braking system in real-world PTW crashes.

OBJECTIVES: Powered 2-wheelers (PTWs) are becoming increasingly popular in Europe. They have the ability to get around traffic queues, thus lowering fuel consumption and increasing mobility. The risk of rider injury in a traffic crash is however much higher than that associated with car users. The European project, Powered Two Wheeler Integrated Safety (PISa), identified an autonomous braking system (AB) as a priority to reduce the injury consequences of a PTW crash. The aim of this study was to assess the potential effectiveness of the AB system developed in PISa, taking into account the specific system characteristics that emerged during the design, development and testing phases. METHODS: Fifty-eight PTW cases representing European crash configurations were examined, in which 43 percent of riders sustained a Maximum Abbreviated Injury Scale (MAIS) 2+ injury. Two of the most common crash types were a PTW impacting a stationary object (car following scenario) 16% and an object pulling across the PTW path (crossing scenario) 54%. An expert team analysed the in-depth material of the sample crashes and determined a posteriori to what extent the AB would have affected the crash. For those cases where the AB was evaluated as applicable, a further quantitative evaluation of the benefits was conducted by considering a set of different possible rider reactions in addition to that exhibited in the actual crash. RESULTS: In 67 percent of cases, the application of AB could have mitigated the crash outcome. Analysis of those real crash cases showed the potential for an expert rider to avoid the collision. An early reaction of the rider, associated with a correct application of the brakes would have avoided 18 of the 37 car following/crossing scenarios. Conversely, according to the analysis, an expert rider would not have been able to avoid 19 of the 37 cases. In 14 of those 19 cases, the AB would have contributed to mitigating the crash outcome. CONCLUSIONS: This study demonstrated significant potential for application of the autonomous braking system in car following and crossing scenarios. In addition, the theoretical benefit curves for the AB globally, were able to provide good quantitative indications of its benefits in real cases where the AB was considered applicable. Further analysis with larger databases is suggested in order to confirm the magnitude of benefits in the PTW crash population.

An In-depth Study of Abdominal Injuries Sustained by Car Occupants in Frontal Crashes.

Currently, neither abdominal injury risk nor rear seat passenger safety is assessed in European frontal crash testing. The objective of this study was to provide real world in-depth analysis of the factors related to abdominal injury for belted front and rear seat occupants in frontal crashes. Rear occupants were significantly more at risk of AIS 2+ and 3+ abdominal injury, followed by front seat passengers and then drivers. This was still the case even after controlling for occupant age. Increasing age was separately identified as a factor related to increased abdominal injury risk in all seating positions. One exception to this trend concerned rear seated 15 to 19 year olds who sustained moderate to serious abdominal injury at almost the same rate as rear occupants aged 65+.No strong association was seen between AIS 2+ abdominal injury rates and gender. The majority of occupant body mass indices ranged from underweight to obese. Across that range, the AIS 2+ abdominal injury rates were very similar but a small number of very obese and extremely obese occupants outside of the range did exhibit noticeably higher rates. An analysis of variance in the rate of AIS 2+ abdominal injury with different restraint systems showed that simple belt systems, as used by most rear seat passengers, were the least protective. Increasing sophistication of the restraint system was related to lower rates of injury. The ANOVA also confirmed occupant age and crash severity as highly associated with abdominal injury risk. The most frequently injured abdominal organs for front seat occupants were the liver and spleen. Abdominal injury patterns for rear seat passengers were very different. While they also sustained significant injuries to solid organs, their rates of injury to the hollow organs (jejunum-ileum, mesentary, colon) were far higher even though the rate of fracture of two or more ribs did not differ significantly between seat positions. These results have implications for the design of restraint systems, particularly in relation to the occurrence of abdominal injury. They also raise issues of crash protection for older occupants as well as the protection afforded in different seating positions.

Real-world performance of vehicle crash test: the case of EuroNCAP.

OBJECTIVE: To investigate whether the occupants in vehicles with better safety ratings according to EuroNCAP sustain fewer fatal and severe injuries than occupants in vehicles with worse experimental safety ratings when in frontal crashes. DESIGN: Case-control study. SETTING: A representative sample of crashes in Britain from 1996 to 2008 as gathered in the Cooperative Crash Injury Study (CCIS) database under the auspices of the UK Department of Transportation and augmented with EuroNCAP experimental ratings for each crashed vehicle. SUBJECTS: Drivers and front seat passengers while occupants of vehicles for which EuroNCAP test results were available and who met inclusion criteria meant to select those in crashes similar to those in the frontal experimental setting. MAIN OUTCOME MEASURES: Fatality and severe MAIS3+ injuries to the head, thorax, pelvis and lower extremities. RESULTS: The multivariate Poisson regression models on the 1259 cases who sustained crash conditions most similar to the experimental ones showed no statistically significant effect on either mortality or MAIS3+ injury in real-world crashes when travelling in cars with better safety ratings. For example, when compared to a driver in a vehicle rated as safest for head injuries MAIS3+ in frontal crashes, drivers in vehicles rated yellow or orange presented adjusted ORs of 0.6 (0.2 to 1.7) and 0.8 (0.3 to 2.1), respectively. CONCLUSIONS: No statistically significant relationships between the EuroNCAP safety scores and real-world death or severe injury outcomes were found, suggesting the need to review biomechanical criteria chosen to set cut-off points for the rating system.

The potential for further development of passive safety.

In Europe, emphasis is being transferred from injury prevention to accident prevention to reduce road casualties. This study attempted to identify the current potential for serious casualty reduction using passive safety by examining the crash performance of new cars with seriously injured occupants. The Co-operative Crash Injury Study conducts in-depth investigations of around 1200 vehicles per year from seven sample regions around England. Attention was focussed on passenger cars manufactured from 2004 to 2008 with at least one occupant injured to AIS level 3 or more. 28% of MAIS 3+ occupants were unbelted and 40% were belted but involved in crashes with limited potential for passive protection. A further 32% of occupants were belted and involved in crashes with potential for improved crashworthiness design. For these occupants, five major functional requirements were identified for crashworthiness improvement: a reduction of seatbelt loads on the chest and abdomen in frontal crashes, particularly for seniors; reduction in femur and tibia loads in frontal crashes; provision of head and chest protection in near-side crashes; and reduction of occupant lateral excursion in far-side impacts. Together these functions accounted for 70% of the identified requirements. Other smaller requirements were identified, each contributing up to 5% of total. Overall, the case supporting further developments in passive safety still appears significant.

An evaluation of the EuroNCAP crash test safety ratings in the real world.

We investigated whether the rating obtained in the EuroNCAP test procedures correlates with injury protection to vehicle occupants in real crashes using data in the UK Cooperative Crash Injury Study (CCIS) database from 1996 to 2005. Multivariate Poisson regression models were developed, using the Abbreviated Injury Scale (AIS) score by body region as the dependent variable and the EuroNCAP score for that particular body region, seat belt use, mass ratio and Equivalent Test Speed (ETS) as independent variables. Our models identified statistically significant relationships between injury severity and safety belt use, mass ratio and ETS. We could not identify any statistically significant relationships between the EuroNCAP body region scores and real injury outcome except for the protection to pelvis-femur-knee in frontal impacts where scoring "green" is significantly better than scoring "yellow" or "red".

Factors related to fatal injury in frontal crashes involving European cars.

Despite considerable improvements in frontal impact crashworthiness, frontal crashes still account for a major number of front seat occupant fatalities in Great Britain. This study attempted to determine the remaining potential for further fatality reduction with passive safety improvements in frontal crashes. No evidence was found to support an increase in crash test speeds. Instead, assessment of scope for survival showed that at least 27% of all fatal drivers and 39% of all fatal front seat passengers have survival potential given attention to older occupant's chest injury tolerance and passenger compartment intrusion under 60 km/h. Considering only fatal frontal crashes that might be assessed with a barrier test, showed an estimated survival potential of at least 49% of belted drivers and 60% of belted front seat passengers. The high proportion of unbelted fatalities suggested that targeting unbelted occupant protection could have additional benefit.

Thoracic aortic injury in motor vehicle crashes: the effect of impact direction, side of body struck, and seat belt use.

BACKGROUND: Using in-depth, real-world motor vehicle crash data from the United States and the United Kingdom, we aimed to assess the incidence and risk factors associated with thoracic aorta injuries. METHODS: De-identified National Automotive Sampling System Crashworthiness Data System (U.S.) and Co-operative Crash Injury Study (U.K.) data formed the basis of this retrospective analysis. Logistic regression was used to assess the level of risk of thoracic aorta injury associated with impact direction, seat belt use and, given the asymmetry of the thoracic cavity, whether being struck toward the left side of the body was associated with increased risk in side-impact crashes. RESULTS: A total of 13,436 U.S. and 3,756 U.K. drivers and front seat passengers were analyzed. The incidence of thoracic aorta injury in the U.S. and U.K. samples was 1.5% (n = 197) and 1.9% (n = 70), respectively. The risk was higher for occupants seated on the side closest to the impact than for occupants involved in frontal impact crashes. This was the case irrespective of whether the force was applied toward the left (belted: relative risk [RR], 4.6; 95% confidence interval [CI], 2.9-7.1; p < 0.001) or the right side (belted: RR, 2.6; 95% CI, 1.4-5.1; p < 0.004) of the occupant's body. For occupants involved in side-impact crashes, there was no difference in the risk of thoracic aorta injury whether the impacting force was applied toward the left or toward the right side of the occupant's body. Seat belt use provided a protective benefit such that the risk of thoracic aorta injury among unbelted occupants was three times higher than among belted occupants (RR, 3.0; 95% CI, 2.2-4.3; p < 0.001); however, the benefit varied across impact direction. Thoracic aorta injuries were found to be associated with high impact severity, and being struck by a sports utility vehicle relative to a passenger vehicle (RR, 1.7; 95% CI, 1.2-2.3; p = 0.001). CONCLUSION: Aortic injuries have been conventionally associated with frontal impacts. However, emergency clinicians should be aware that occupants of side-impact crashes are at greater risk, particularly if the occupant was unbelted and involved in a crash of high impact severity.

Factors related to serious injury in post-NCAP European cars involved in frontal crashes.

ABSTRACT This study examined the relationship between EuroNCAP ratings for body region protection and real world injury risk for 653 belted drivers in frontal crashes. It was also able to comment on further improvements in crash protection for post-EuroNCAP cars. Protection for the head and lower leg appeared good. In terms of life threatening injury, results showed a need to prioritise chest protection, whilst for impairment, protection for the upper leg and ankle/foot should be considered. The EuroNCAP body region scoring system reflects trends in real crash injury risks to all body regions, except for the chest, where there is no clear trend. More generally, further development in the testing regime could usefully concentrate on a restraint system test and the use of smaller dummies seated appropriately, rather than an increase of the test speed.

A preliminary analysis of aortic injuries in lateral impacts.

Injuries to the aorta are among the more serious injuries that result from vehicle impacts, and often may be fatal. This article examines the incidence of aortic injuries in the United States and United Kingdom by using two international databases of real-world crashes. The main outcome of interest was the level of risk associated with each principal direction of force for drivers and front-seat passengers with respect to sustaining aortic injuries. The results indicate that the risk of sustaining an injury to the aorta is greater for near-side crashes than for far-side crashes. Further it is apparent that, given a near-side crash, the risk of an aortic injury is greater on the left side of the body (and left side of the vehicle) than on the right. It also was found that the delta-V of crashes where occupants sustained an injury to the aorta was considerably higher than crashes where occupants did not sustain aortic injuries. It is speculated that the anatomical asymmetry of the thorax might play a role in the differences seen in injury risk associated with different impact directions. The results presented in this article could be of use to both the emergency physician treating patients involved in motor vehicle collisions as well as the engineer involved in occupant design countermeasures. Limitations and further planned research are discussed.

Belted driver protection in frontal impact--what has been achieved and where do future priorities lie?

Examining injuries to real people in real crashes is the most meaningful way to validate improvements in crashworthiness as well as to determine where future priorities lie. Examination of U.K national statistics showed that, coincident with the introduction of airbag/pretensioner restraints, there was a significant fall in the rates of killed/seriously injured car occupants as well as a significant fall in the number of car occupant fatalities. Interrogation of the UK in-depth crash injury data for belted drivers in frontal crashes between 20-70 km/h ETS showed substantial reductions in AIS 2+ injury to the head in newer cars. In the same sample of crashes, no corresponding reductions in AIS 2+ injury were found for the chest, thigh and leg.

Aortic injuries in side impacts: a preliminary analysis.

Injuries to the aorta are among the more serious injuries that result from vehicle impacts, and may often be fatal. This paper examined the incidence of aortic injuries in the US and UK using real-world crash data. The main outcome of interest was the level of risk associated with each principal direction of force for drivers and front seat passengers with respect to sustaining aortic injuries. The results indicate that the risk of sustaining an injury to the aorta is greater for near side crashes than for far side crashes. Further, it is apparent that given a near side crash, the risk of an aortic injury is greater on the left side of the body (and left side of the vehicle) than on the right. It was also found that the delta-V of crashes where occupants sustained an injury to the aorta was considerably higher than crashes where occupants did not sustain aortic injuries. It was speculated that the anatomical asymmetry of the thorax might play a role in the differences seen in injury risk associated with different impact directions. Limitations and further planned research are discussed.

An overview of requirements for the crash protection of older drivers.

For some time now, it has been recognised that a major shift is occurring in the population age distributions of most motorised countries resulting in a growing number of older persons with an increasing need for mobility. It is expected that the mobility of older persons will become even more reliant on the motor vehicle as European countries in particular undergo transitions towards decentralisation and suburbanisation and because of the well-established longevity factor. As a group, older drivers do not currently represent a major road safety problem in most Western societies when compared with other age groups such as the young. However, they are involved in significantly more serious injury and casualty crashes per head of population. Furthermore, as older drivers are likely to become a more significant problem in the years ahead, it is now necessary to examine some vehicle design factors that affect the safety of the older driver in a crash.