The combination of airbag and seatbelt is considered to be the most effective vehicle safety system. However, despite the widespread availability of airbags and a belt use rate of over 85% U.S. drivers involved in crashes continue to be at risk of serious thoracic injury. One hypothesis is that this risk may be due to the lack of airbag deployment or the airbag \'bottoming-out\' in some cases, causing drivers to make contact with the steering. The objective of this study is to determine the influence of various advanced airbags on occupant injury risk in frontal automobile crash. The analysis is based upon cases extracted from the National Automotive Sampling System Crashworthiness Data System (NASS/CDS) database for case years 1993-2011. The approach was to compare the frontal crash performance of advanced airbags against depowered airbags, first generation airbags, and vehicles with no airbag equipped. NASS/CDS steering wheel deformation measurements were used to identify cases in which thoracic injuries may have been caused due to steering wheel impact and deformation. The distributions of injuries for all cases were determined by body region and injury severity. These distributions were used to compare and contrast injury outcomes for cases with frontal airbag deployment for both belted and unbelted drivers. Among frontal crash cases with belted drivers, observable steering wheel deformation occurred in less than 4% of all cases, but accounted for 29% of all serious-to-fatally injured belted drivers and 28% of belted drivers with serious thoracic injuries (AIS3+). Similarly, observable steering wheel deformation occurred in approximately 13% of all cases with unbelted drivers involved in frontal crashes, but accounted for 58% of serious-to-fatally injured unbelted drivers and 66% of unbelted drivers with serious thoracic injuries. In a frontal crash, the factors which were statistically significant in the probability of steering wheel deformation were: longitudinal delta-V, driver weight, and driver belt status. Seatbelt pre-tensioner and load limiters were not significant factors in influencing steering wheel deformation. Furthermore, belted drivers in vehicles with no airbag equipped were found to have 3 times higher odds of deforming the steering wheel, as compared to driver in similar crash scenario. Similarly, unbelted drivers were found to have 2 times greater odds of deforming the steering wheel in vehicles with no airbags equipped as compared to vehicles with advanced airbag. The result also showed no statistically significant difference in the odds of deforming the steering wheel between depowered and advanced airbag. After controlling for crash severity, and driver weight, the study showed that crashes with steering wheel deformation results in greater odds of injury in almost all body regions for both belted and unbelted drivers. Moreover, steering wheel deformation is more likely to occur in unbelted drivers than belted drivers, as well as higher severity crashes and with heavier drivers. Another potential factor in influencing driver crash injury is the knee airbag. After comparing the odds of injury between vehicles with and without knee airbags equipped, belted drivers in vehicles equipped with knee airbag were found to have statistically smaller odds of injury in the thorax, abdomen, and upper extremity. Similarly, the findings showed that unbelted drivers benefited from knee airbag through statistically significant lower odds of chest and lower extremity injuries. However, the results should be considered with caution as the study is limited by its small sample of vehicles with knee airbags. / Master of Science

Historically, the rear seat has been considered safer compared to the front seat for all restrained occupants; however, studies have found that the front seat in newer vehicles might be safer for older adults than the rear seat. While adults make up only 19% of rear seat occupants in frontal crashes, they make up 48% of fatalities (Tatem and Gabler, 2019). The rate of rear-seat occupancy by adults is expected to increase due to the use of ride share services and the potential of autonomous vehicles. Minimal research has been done to assess rear-seat occupant protection for a mid-sized adult male. Submarining, in which the lap belt slips off of the pelvis and directly loads the abdomen, is of particular concern as a restraint-based injury mechanism of the abdomen. The objective of this study is to investigate submarining protection and abdominal injury risk for rear-seated mid-sized male occupants in frontal crashes and to assess the biofidelity of two anthropomorphic test devices (ATDs) with respect to submarining response when compared to post-mortem human surrogates (PMHS). Twenty-four frontal crash sled tests were conducted with the THOR-50M and Hybrid III 50th-percentile male ATDs in three crash conditions and seven modern vehicles. The vehicles included a minivan, an SUV, 3 compact SUVs, and 2 sedans from the US vehicle fleet (model years 2017-2018). Four vehicles had conventional restraints (ie. 3-point belt with retractor at the shoulder) in the rear seat and three vehicles had advanced restraints (ie. 3-point belts with a pretensioner and load limiter at the retractor). Two of the crash conditions were vehicle-specific pulses: NCAP85 (ΔV = 56 kph) and Scaled (ΔV = 32 kph). The final pulse was a Generic (ΔV = 32 kph) pulse, created by averaging all seven Scaled pulses. Matched PMHS tests were conducted on four of the vehicles in the NCAP85 condition. Two tests were conducted for each vehicle with 8 PMHS for a total of 8 sled tests. The occurrence of submarining was identified and assessed for severity by: symmetry of lap belt slip, degree of abdominal loading, and forward excursion of the pelvis. Pelvis and lap-belt kinematics were assessed for the matched NCAP85 tests to identify trends with respect to submarining. Damage to the abdomen, pelvis, and lumbar spine of the PMHS was identified during post-test autopsy. The Hybrid III did not submarine in any test, but the THOR submarined in 16/24 tests. Three PMHS underwent submarining in 2/4 vehicles, and the THOR submarined in 3/4 vehicles in the matched NCAP85 tests. Three PMHS did not undergo submarining but sustained pelvis fractures at lap belt loads of 7.4 kN and higher, and damage to the abdominal viscera occurred regardless of submarining occurrence. Pelvis and lap-belt kinematics revealed the complex nature of the interactions of the occupant and the restraints within each vehicle environment, but did not clearly differentiate between submarining and non-submarining tests. The Hybrid III was not able to predict submarining risk for the PMHS in the rear seat environment. While the THOR underwent submarining, it was not perfect in predicting submarining risk. Pelvis geometry, lap belt engagement, and other factors contributed to the differences in submarining between the two ATDs and the PMHS. Restraint type was not indicative of whether or not the THOR or PMHS would submarine. Many other factors in the rear seat environments of these vehicles likely contribute in combination to the effectiveness of submarining prevention and occupant protection in the rear seat. This study provides information regarding submarining and abdominal injury for three surrogate types, two crash severities, and seven modern, real-world vehicle environments. Ultimately, this study found substantive gaps in occupant protection in the rear seats of modern vehicles for mid-sized adult male occupants. Tatem, W. M., and Gabler, H. C. (2019). Differential fatality risk between rear and front seat passenger vehicle occupants in frontal crashes. In Proceedings of the 2019 International IRCOBI Conference on the Biomechanics of Injury (pp. 554–560). / Doctor of Philosophy / Historically, the rear seat has been considered safer than the front seat for restrained occupants in frontal crashes. However, with advances in safety systems for the front seat, studies have found that the front seat might be safer for older adult occupants. The objective of this study is to investigate submarining protection and abdominal injury risk for rear-seated mid-sized male occupants in frontal crashes. Submarining occurs when the lap belt slips off of the pelvis and directly loads the abdomen, potentially producing severe abdominal injuries. Twenty-four sled tests were conducted with the THOR-50M and Hybrid III 50th-percentile male anthropomorphic test devices (ATDs) in three crash conditions and seven modern vehicles. The vehicles selected included a minivan, SUVs, compact SUVs, and sedans from the US vehicle fleet. Three of the vehicles had advanced restraints in the rear seat and four had conventional restraints. The three crash conditions were a generic low speed test and a low and high-speed vehicle-specific crash pulse. Eight tests were conducted with eight different post-mortem human surrogates on a subset of four vehicles (2 with advanced restraints, 2 with conventional restraints) using the high-speed crash condition. The Hybrid III never submarined, but the THOR submarined in 16 out of 24 tests (5 out of 7 vehicles). Three out of eight PMHS submarined, in two of the four vehicles. Three heavier PMHS sustained pelvis fractures, and all but one PMHS had sustained damage to the abdominal viscera. Restraint type was not an indicator of submarining risk in the rear seat, suggesting that other seat and vehicle design variables contribute to submarining risk. Comparison of the responses of the ATDs with the PMHS suggests that the THOR is a more reasonable surrogate than the Hybrid III for submarining assessment in the rear seat. Inclusion of data from other body regions is necessary to make a definitive determination of the appropriate ATD for the assessment of occupant protection for a mid-sized male in the rear seat during frontal crashes. Overall, this study suggests that protection against submarining and injury to the pelvis and abdomen for mid-sized male passengers in the rear seat of modern vehicles in the US fleet could be improved.

<p>Feedback control of Chest Acceleration or Chest Deflection is believed to be a good way of minimizing the risk of injury. In order to implement such a controller in a car, an observer estimating these responses is needed. The objective of the study was to develop a model of the dummy’s chest capable of estimating the Chest Acceleration and the Chest Deflection during frontal crashes in real time. The used sensor data come from car accelerometer and spindle rotation sensor of the belt, the data has been collected from dummies during crash tests. This study has accomplished the aims using a simple linear model of the chest using masses, springs and dampers. The parameters of the model have been estimated through system identification. Two types of black-box models have also been studied, one ARX model and one state-space model. The models have been tested and validated against data coming from different crash setups. The results show that all of the studied models can be used to estimate the dummy responses, the physical grey-box model and the black-box state-space model in particular.</p> / <p>Genom att använda återkoppling av storheterna bröstacceleration och bröstintryck antas man kunna minska risken för skador vid krockar i personbilar. För att kunna implementera detta behövs en observatör för dessa storheter. Målet med denna studie är att ta fram en modell för att kunna skatta accelerationen i bröstkorgen samt bröstintrycket i realtid i frontala krockar. Sensordata som använts kom från en accelerometer och en givare för att mäta rotationen i bältessnurran. Detta har gjorts genom att modellera bröstkorgen med linjära fjädrar och dämpare. Dess parametrar har skattats från data från krocktester från krockdockor. Två s.k. black-box-modeller har också tagits fram, en ARX-modell och en på tillståndsform. Modellerna har testats och validerats mha data från olika sorters krocktester. Resultaten visar att alla studerade modeller kan användas för att skatta de ovan nämnda storheterna, den fysikaliska modellen och black-box-modellen på tillståndsform fungerade bäst.</p>

Feedback control of Chest Acceleration or Chest Deflection is believed to be a good way of minimizing the risk of injury. In order to implement such a controller in a car, an observer estimating these responses is needed. The objective of the study was to develop a model of the dummy’s chest capable of estimating the Chest Acceleration and the Chest Deflection during frontal crashes in real time. The used sensor data come from car accelerometer and spindle rotation sensor of the belt, the data has been collected from dummies during crash tests. This study has accomplished the aims using a simple linear model of the chest using masses, springs and dampers. The parameters of the model have been estimated through system identification. Two types of black-box models have also been studied, one ARX model and one state-space model. The models have been tested and validated against data coming from different crash setups. The results show that all of the studied models can be used to estimate the dummy responses, the physical grey-box model and the black-box state-space model in particular. / Genom att använda återkoppling av storheterna bröstacceleration och bröstintryck antas man kunna minska risken för skador vid krockar i personbilar. För att kunna implementera detta behövs en observatör för dessa storheter. Målet med denna studie är att ta fram en modell för att kunna skatta accelerationen i bröstkorgen samt bröstintrycket i realtid i frontala krockar. Sensordata som använts kom från en accelerometer och en givare för att mäta rotationen i bältessnurran. Detta har gjorts genom att modellera bröstkorgen med linjära fjädrar och dämpare. Dess parametrar har skattats från data från krocktester från krockdockor. Två s.k. black-box-modeller har också tagits fram, en ARX-modell och en på tillståndsform. Modellerna har testats och validerats mha data från olika sorters krocktester. Resultaten visar att alla studerade modeller kan användas för att skatta de ovan nämnda storheterna, den fysikaliska modellen och black-box-modellen på tillståndsform fungerade bäst.

In Europe, the deployment characteristics of frontal crash restraints are generally optimised to best protect an average young male, since a 50th percentile male dummy is used in a stylised frontal impact scenario. These single point restraint systems may not provide similar levels of effectiveness when the crash scenarios vary with respect to the regulatory and consumer crash test procedures. Previous research has demonstrated that varying restraint deployment characteristics according to occupant and crash variation can provide further injury reduction in frontal impacts. This thesis reports the investigation conducted to assess the potential real world injury reduction benefit of smart restraint systems in frontal impacts. The intelligent capability of the restraint was achieved by varying the seat belt load limiter (SBL) threshold, according to the frontal crash scenario. Real world accident data (CCIS) were analysed to identify the target population of vehicle occupants and frontal impact scenarios where employing smart load limiters could be most beneficial, particularly in reducing chest injury risk. From the accident 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 old) 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. Numerical simulations using MADYMO software were conducted to examine the effect of varying the load limiter thresholds on occupant kinematics and injury outcome in frontal impacts. Generic baseline driver and front passenger numerical models were developed using a 50th percentile dummy and were adapted to accommodate a 5th and 95th percentile dummy. Simulations were performed where the load limiter threshold was varied in five frontal impact scenarios which were selected to cover as wide a range of real frontal crash conditions as possible. From the simulation results, it was found that for both the 50th and 95th percentile dummy in front seating positions (driver and passenger), 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 dummy to move further towards the front facia, thus increasing the chance of occupant hard contact with the vehicle interiors. The Smart load limiters predicted no injury risk reduction for the 5th percentile drivers, who are shorter and tend to sit closer to the steering wheel. The potential injury reduction of the smart load limiters was quantified by applying the estimated injury risk reduction from the simulation to the real world accident data sample. Thoracic injury predictions from the simulations were converted into injury probability values using AIS 2+ age dependent thoracic risk curves which were developed and validated based on a methodology proposed by Laituri et al. (2005). Real world benefit was quantified using the predicted relative AIS 2+ risk reduction and assuming an appropriate adaptive system was fitted to all the cars in the real world sample. When applying the AIS 2+ risk reduction findings to the weighted accident data sample, the risk of sustaining an AIS 2+ seat belt injury reduced from 1.3% to 0.9% for younger front seat occupants, 7.6% to 5.0% for middle aged front seat occupants and 13.1% to 8.6% for the older front seat occupants. The research findings clearly demonstrate a chest injury reduction benefit across all age groups when the load limiter characteristics are varied. It suggests that employing a smart load limiter in a vehicle would not only benefit older occupants but also middle aged and young occupants. The benefit does appear to be most pronounced for older occupants, since the older population is more vulnerable to chest injury. As the older population of car users is rapidly rising, the benefits of smarter systems can only increase in the future.

Lower leg injury is an important issue in frontal car crash. Although safety in cars has been improved by developments such as seat belts and airbags, lower leg injuries have not been reduced. These injuries are not life threatening but can result in long term disability and cost a lot to society. This study focused on the passenger occupant in offset frontal crashes and aimed at understanding and finding ways to reduce the injury criteria for the lower leg: tibia index. A finite element model was simplified to introduce parameters which influence on tibia index was investigated with a multivariate analysis. The model simplification consisted in removing irrelevant parts and replacing other parts by simple foam blocks. More than 1300 simulations were run with different parameter values. The results were then analysed by calculating correlations and effects of the parameters on tibia index. It was concluded that the presence of a knee bolster decreased tibia index. The results also showed a decrease of tibia index when the toe pan was angled towards the legs of the passenger. Moreover, a correlation between tibia index and the movement of the feet during the crash was found. It was concluded that restrained lower legs also presented decreased tibia indices compared to unrestrained ones. Most of the results proved to be also valid on the initial, unsimplified finite element model. / Underbensskador är ofta förekommande vid frontalkrock. Även om fordonssäkerheten har förbättrats i och med utveckling av bland annat säkerhetsbälte och krockkudde, har antalet underbensskador inte minskat. Denna typ av skada är inte livshotande men kan resultera i långvariga besvär och kan leda till stora kostnader för samhället. Detta examensarbete fokuserar på passageraren vid frontalkrock (offset) och syftet var att skapa förståelse kring skadekriteriet för underben: tibia index, samt hitta lösningar på hur tibia index kan minskas. En finit elementmodell förenklades och parametrar introducerades. Parametrarnas påverkan på tibia index undersöktes med en multivariat analys. Modellen förenklades genom att eliminera några delar och ersätta andra delar med enkla block. Simuleringar med olika värden på parametrarna skapades och ungefär 1300 kördes. Värdena från simuleringarna analyserades genom att beräkna korrelation och effekt på tibia index. Resultaten visade att implementering av ett slags mjukt knäskydd påverkar tibia index positivt. De visade också att tibia index förbättrades när den främre delen av golvet vinklades mot passagerarens ben. Vidare, fanns en korrelation mellan tibia index och fötternas förflyttning under krockförloppet. Slutsatsen var att kontrollerade underben förbättrar tibia index i jämförelse med okontrollerade ben. De flesta resultaten stämde även för den ursprungliga modellen.