Mechanisms Of Head Injuries In Road Traffic Accidents; A Potential Solution For Data Collection

Despite advances in road safety, head injuries still account for many of the most serious and fatal injuries in road traffic accidents. This PhD thesis provides a summary of knowledge regarding the current position in head injury research with regard to: Previous assertions as to head injury mechanisms Existing head injury criteria The availability of data to explore potential confounding factors in predicting head injury risk and to propose or validate a new injury criterion or criteria. On the basis of the existing information the question was posed, whether it is possible to validate advanced head injury criteria and head models using additional (new) head injury case data so as to make their application more robust in efforts to mitigate future injuries. In order to answer this question, priority was given to the pursuit of new data, offering six degree of freedom time-series data with detailed information on the exact injuries sustained. A working in-ear sensor system was deemed to offer a potential solution in obtaining elusive data regarding the kind of impact events that could cause head injuries for road users. An in-ear accelerometer system used by the FIA Institute was evaluated through experimentation. Then a low-cost solution was developed with the aim to give similar sensor performance for a wider market of potential wearers. The prototype low-cost sensor system was evaluated in a small series of drop tests and also in a very small real-world data collection trial. This evaluation identified a series of issues that need to be resolved before the system can be used to generate valuable data. A viable system is not ready immediately, but could be following modifications to the prototype system evaluated. Taking this revised system, the next step would be to initiate a larger trial to start the collection of high fidelity data and impact event details; in order to address the need for such information and confirm that even the low-cost system would be fit for that purpose

Biofidelity requirements for the THORAX project

Biofidelity requirements are to be used to ensure that a crash test dummy loads the vehicle and restraint system in an accident in a similar way to the human, and to ensure that the response of the dummy to this loading is relevant to the prediction of injury risk in simulated crashes that are representative of real-world accidents. The main aim of this deliverable is to provide a set of biofidelity requirements for the thorax and shoulder for evaluation of an advanced frontal impact crash test dummy. This report has reviewed existing thorax and shoulder biofidelity requirements for frontal crash test dummy evaluations. The load cases used in these requirements were compared to the loads in actual collisions. It was identified that inclusion of additional requirements in which the thorax is exposed to various types of distributed and belt-only loads would be beneficial. To identify additional tests, post mortem human subject data and volunteer data were reviewed and test conditions and available data documented. Inclusion criteria used to assess e.g. the quality of documentation of a data set, or the representativeness of the subjects that were tested, were established. Using these criteria the reported test conditions and results were analysed with the target to specify biofidelity requirements and engineering guidance for the design of an enhanced dummy shoulder-thorax complex. None of the available datasets were ideal for specifying biofidelity requirements for frontal impacts in modern restraint systems as available in the market now. These systems typically include belt pretensioning and force-limiting and carefully combined belt and airbag contributions to the occupant protection. Instead a broad set of requirements has been used in an attempt to capture biofidelity under various restraint system types and load conditions. It is hoped that a dummy with a good level of biofidelity throughout this broad range of conditions will still demonstrate an appropriate level of biofidelity in modern restraint systems and common crash conditions.The biofidelity requirements document a well-defined set of test conditions and the dummy responses that are required in those loading conditions. The engineering guidance includes biomechanical data that will be used to define relative - rather than absolute - targets for dummy performance. These relative targets are useful to guide the design of an enhanced dummy.Various methods used to normalise the response data to that of a standard size of subject or scale data to other sizes were reviewed, benefits and limitations discussed and recommendations were made. Finally, a set of biofidelity target corridors for the 50th percentile male are presented in the Appendix B to Appendix K

Biofidelity requirements for the THORAX project

Biofidelity requirements are to be used to ensure that a crash test dummy loads the vehicle and restraint system in an accident in a similar way to the human, and to ensure that the response of the dummy to this loading is relevant to the prediction of injury risk in simulated crashes that are representative of real-world accidents. The main aim of this deliverable is to provide a set of biofidelity requirements for the thorax and shoulder for evaluation of an advanced frontal impact crash test dummy. This report has reviewed existing thorax and shoulder biofidelity requirements for frontal crash test dummy evaluations. The load cases used in these requirements were compared to the loads in actual collisions. It was identified that inclusion of additional requirements in which the thorax is exposed to various types of distributed and belt-only loads would be beneficial. To identify additional tests, post mortem human subject data and volunteer data were reviewed and test conditions and available data documented. Inclusion criteria used to assess e.g. the quality of documentation of a data set, or the representativeness of the subjects that were tested, were established. Using these criteria the reported test conditions and results were analysed with the target to specify biofidelity requirements and engineering guidance for the design of an enhanced dummy shoulder-thorax complex. None of the available datasets were ideal for specifying biofidelity requirements for frontal impacts in modern restraint systems as available in the market now. These systems typically include belt pretensioning and force-limiting and carefully combined belt and airbag contributions to the occupant protection. Instead a broad set of requirements has been used in an attempt to capture biofidelity under various restraint system types and load conditions. It is hoped that a dummy with a good level of biofidelity throughout this broad range of conditions will still demonstrate an appropriate level of biofidelity in modern restraint systems and common crash conditions.The biofidelity requirements document a well-defined set of test conditions and the dummy responses that are required in those loading conditions. The engineering guidance includes biomechanical data that will be used to define relative - rather than absolute - targets for dummy performance. These relative targets are useful to guide the design of an enhanced dummy.Various methods used to normalise the response data to that of a standard size of subject or scale data to other sizes were reviewed, benefits and limitations discussed and recommendations were made. Finally, a set of biofidelity target corridors for the 50th percentile male are presented in the Appendix B to Appendix K

Assessment of Integrated Pedestrian Protection Systems with Autonomous Emergency Braking (AEB) and Passive Safety Components

Autonomous Emergency Braking (AEB) systems for pedestrians have been predicted to offer substantial benefit. On this basis, consumer rating programmes, e.g. Euro NCAP, are developing rating schemes to encourage fitment of these systems. One of the questions that needs to be answered to do this fully, is to determine how the assessment of the speed reduction offered by the AEB is integrated with the current assessment of the passive safety for mitigation of pedestrian injury. Ideally, this should be done on a benefit related basis. The objective of this research was to develop a benefit based methodology for assessment of integrated pedestrian protection systems with pre-crash braking and passive safety components. A methodology has been developed which calculates the cost of pedestrian injury expected, assuming all pedestrians in the target population (i.e. pedestrians impacted by the front of a passenger car) are impacted by the car being assessed, taking into account the impact speed reduction offered by the car’s AEB (if fitted) and the passive safety protection offered by the car’s frontal structure. For rating purposes, this cost can be normalised by comparing it to the cost calculated for selected cars. The methodology uses the speed reductions measured in AEB tests to determine the speed at which each casualty in the target population will be impacted. The injury to each casualty is then calculated using the results from standard Euro NCAP pedestrian impactor tests and injury risk curves. This injury is converted into cost using ‘Harm’ type costs for the body regions tested. These costs are weighted and summed. Weighting factors were determined using accident data from Germany and GB and the results of a benefit analysis performed by the EU FP7 AsPeCSS project. This resulted in German and GB versions of the methodology. The methodology was used to assess cars with good, average and poor Euro NCAP pedestrian ratings, with and without a current AEB system fitted. It was found that the decrease in casualty injury cost achieved by fitting an AEB system was approximately equivalent to that achieved by increasing the passive safety rating from poor to average. Also, it was found that the assessment was influenced strongly by the level of head protection offered in the scuttle and windscreen area because this is where head impact occurs for a large proportion of casualties. The major limitation within the methodology is the assumption used implicitly during weighting. This is that the cost of casualty injuries to body areas, such as the thorax, not assessed by the headform and legform impactors, and other casualty injuries such as those caused by ground impact, are related linearly to the cost of casualty injuries assessed by the impactors. A methodology for assessment of integrated pedestrian protection systems was developed. This methodology is of interest to consumer rating programmes which wish to include assessment of these systems. It also raises the interesting issue if the head impact test area should be weighted to reflect better real-world benefit

Development of an Advanced Thorax / Shoulder Complex for the THOR Dummy

Thoracic injuries are one of the main causes of fatalities and severe injuries in car crashes. The tools available today for studying these injuries are not up to par with the latest implementation of restraint systems and airbags. THORAX-FP7 is a collaborative medium scale project under the Seventh Framework. It focuses on the reduction and prevention of thoracic injuries through an improved understanding of the thoracic injury mechanisms and the implementation of this understanding in an updated design for the thorax-shoulder complex of the THOR dummy. The updated dummy should enable the design and evaluation of advanced restraint systems for a wide variety (gender, age and size) of car occupants. The hardware development involves fi ve steps: 1) Identifi cation of the dominant thoracic injury types from fi eld data, 2) Specifi cation of biomechanical requirements, 3) Identification of injury parameters and necessary instrumentation, 4) Dummy hardware development and 5) Evaluation of the demonstrator dummy. The THORAX project started in February 2009. This paper presents results achieved so far including outcomes of accident surveys, selection of human response data suitable for the assessment of the dummy performance, human body simulation into the injury criteria and the dummy developments done so far

Analysis of pedestrian leg contacts and distribution of contact points across the vehicle front

Determining the risk to pedestrians that are impacted by areas of the front bumper not currently regulated in type-approval testing requires an understanding of the target population and the injury risk posed by the edges of the bumper. National statistics show that approximately 10% of all accident casualties are pedestrians, with 20% to 30% of these pedestrian casualties being killed or seriously injured. However, the contact position across the front of the bumper is not recorded in national statistics and so in-depth accident databases (OTS, UK and GIDAS, Germany) were used to examine injury risk in greater detail. The results showed that some injury types and severities of injuries appear to peak around the bumper edges. Although there are sometimes inconsistencies in the data, generally there is no evidence to suggest that the edges of the bumper are less likely to be contacted or cause injury

Analyses of thoracic and lumbar spine injuries in frontal impacts

In general the passive safety capability is much greater in newer versus older cars due to the stiff compartment preventing intrusion in severe collisions. However, the stiffer structure which increases the deceleration can lead to a change in injury patterns. In order to analyse possible injury mechanisms for thoracic and lumbar spine injuries, data from the German Inâ€Depth Accident Study (GIDAS) were used in this study. A twoâ€step approach of statistical and caseâ€byâ€case analysis was applied for this investigation. In total 4,289 collisions were selected involving 8,844 vehicles, 5,765 injured persons and 9,468 coded injuries. Thoracic and lumbar spine injuries such as burst, compression or dislocation fractures as well as soft tissue injuries were found to occur in frontal impacts even without intrusion to the passenger compartment. If a MAIS 2+ injury occurred, in 15% of the cases a thoracic and/or lumbar spine injury is included. Considering AIS 2+ thoracic and lumbar spine, most injuries were fractures and occurred in the lumbar spine area. From the case by case analyses it can be concluded that lumbar spine fractures occur in accidents without the engagement of longitudinals, lateral loading to the occupant and/or very severe accidents with MAIS being much higher than the spine AIS

Evaluation of Near-Side Oblique Frontal Impacts Using THOR With SD3 Shoulder

<div><p><b>Objective:</b> Within the EC Seventh Framework project THORAX, the Mod-Kit THOR was upgraded with a new thorax and shoulder. The aim of this study was to investigate whether the THOR ATD met a set of prerequisites to a greater extent than Hybrid III and by that measure whether the dummy could serve as a potential tool for future evaluation of serious head and chest injuries in near-side oblique frontal impacts.</p><p><b>Method:</b> A small-overlap/oblique sled system was used to reflect occupant forces observed in oblique frontal crashes. The head and thoracic response from THOR was evaluated for 3 combinations: belt only with no deformation of the driver's side door (configuration A), belt only in combination with a predeformed door (configuration B), and prepretensioning belt and driver airbag (PPT+DAB) in combination with a predeformed door (configuration C). To evaluate head injury risk, the head injury criterion (HIC) and brain injury criteria (BrIC) were used. For evaluation of the thoracic injury risk, 3 injury criteria proposed by the THORAX project were evaluated: Dmax, DcTHOR, and strain (dummy rib fractures).</p><p><b>Results:</b> Unlike Hybrid III, the THOR with SD3 shoulder interacted with the side structure in a near-side oblique frontal impact. HIC values for the 3 test configurations corresponded to a 90% (A) and 100% (B and C) risk of Abbreviated Injury Scale (AIS) 2+ head injury, and BrIC values resulted in a 100% risk of AIS 2+ head injury in configurations A and B. In C the risk was reduced to 75%. The AIS 2+ thoracic injury risks based on Dmax were similar (14–18%) for all tests. Based on DcTHOR, AIS 2+ injury risk increased from 29 to 53% as the predeformed door side was introduced (A to B), and the risk increased, to 64%, as a PPT+DAB was added (C). Considering the AIS 2+ injury risk based on strain, tests in A resulted in an average of 3 dummy rib fractures (17%). Introducing the predeformed door (B) increased the average of dummy fractures to 5 (39%), but in C the average number of dummy rib fractures decreased to 4 (28%).</p><p><b>Conclusions:</b> THOR with an SD3 shoulder should be the preferred ATD rather than the Hybrid III for evaluating head and thorax injuries in oblique frontal impacts. Thoracic interaction with the predeformed door was not well captured by the 3D IR-Traccs; hence, use of deflection as an injury predictor in oblique loading is insufficient for evaluating injury risk in this load case. However, injury risk evaluation may be performed using the strain measurements, which characterize loading from seat belt and airbag as well as the lateral contribution of the structural impact in the loading condition used in this study.</p></div