Abteilung Fahrzeugtechnik
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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.
During the past five years, a Euro NCAP technical working group on pedestrian safety has been working on improving test and assessment procedures for enhanced passive pedestrian safety. After harmonizing the tools and procedures as much as possible with legislation, the work was mainly focused on the development of grid procedures for the pedestrian body regions head, upper leg with pelvis and lower leg with knee. Furthermore, the test parameters for the head and the upper leg were revised, a new lower legform impactor was introduced and the injury thresholds were adjusted or, where necessary, the injury criteria were changed. Finally, the assessment limits and colour scheme were refined, widening the range and adding two more colours in order to provide a more detailed description of the pedestrian safety performance. By abstaining from an assessment based on a worst point selection philosophy, the improved test point determination procedures that were introduced during the years 2013 and 2014 give a more homogeneous, high resolution picture of the pedestrian safety performance of the vehicle frontends. By using a uniform grid for each test zone approximately 200 test points, evenly distributed within each area, can now be assessed per vehicle. The introduction of the flexible pedestrian legform impactor in 2014 enables a more realistic injury prediction of the knee and the tibia using a biofidelic test tool. With the new upper legform test that has been launched in 2015 the assessment in that area is now focusing on the injured body region instead of the injury causing vehicle part and thus is aligned with the approach in the remaining body regions head and lower leg. At the same time, a monitoring test with the headform impactor against the bonnet leading edge is closing the possible gap between the test areas to identify injury causing vehicle parts that moved out of focus due to the introduction of the new upper legform test. The paper describes the new test and assessment procedures with their underlying philosophy and gives an outlook in terms of open issues, specifying the needs for further improvement in the future. In parallel to the work of the pedestrian subgroup, a Euro NCAP working group on heavy vehicles introduced a set of protocol changes in 2011 that were related to the assessment of M1 vehicles derived from commercial vehicles, with a gross vehicle weight between 2.5 and 3.5 tons and 8 or 9 seats. The paper also investigates the applicability of the new pedestrian test and assessment procedures to heavy vehicles.
Test and assessment procedures for passive pedestrian protection of passenger cars are in place for many years within world-wide regulations as well as consumer test programmes. Nevertheless, recent accident investigations show a stagnation of pedestrian fatality numbers on European roads alongside increasing injury severities for older road users. The EU-funded SENIORS (Safety ENhancing Innovations for Older Road userS) project developed and evaluated a thorax injury prediction tool (TIPT) for later incorporation within test and assessment procedures. Accident data indicates an increasing portion of AIS2 and AIS3+ thoracic injuries of older pedestrians and cyclists which are currently not assessed in any test procedure for vulnerable road users. Therefore, SENIORS focused on the development of a test tool predicting the risk of rib fractures of vulnerable road users (VRU). While injury risk functions were reanalyzed, human body model (HBM) simulations against categorized generic vehicle frontends served as input for the definition of test setups and corresponding impact parameters. TIPT component tests against a generic frontend and an actual vehicle were used for the evaluation of the technical feasibility. The TIPT component tests shows the general feasibility of a test procedure for the assessment of thoracic injuries, with good repeatability and reproducibility of kinematics and results. Impact parameters such as the inclination angles of the thorax, angles of the velocity vector and impact speeds well replicate the parameters gained from the HBM simulations. The proposed markup and assessment scheme offers the possibility of a homogeneous evaluation of the protection potential of vehicle frontends while maintaining justifiable testing efforts. During evaluation testing, the proposed requirements were entirely met. The developed prototype of TIPT and launching system offer impact angles and speeds as suggested by HBM simulations. However, since thorax impacts during pedestrian accidents do not occur perpendicularly to the vehicle surface in most cases, the TIPT built-in linear potentiometers do not acquire the true resultant intrusions on the ribcage and thus, TIPT rib deflections do not reflect the actual human injury risk. However; for the impact forward to the bonnet leading edge, the TIPT seems applicable without further modifications. The test and assessment procedures using the TIPT offer for the first time the possibility of replicating the kinematics of a pedestrian thorax with a component test. The developed assessment scheme gives a first indication on how the risk for thoracic injuries could be implemented within the Euro NCAP Box 3 assessment. Future development of the TIPT may focus on implementing a rib cage that can deflect in all axes in a humanlike way.
Anhand von zwei verschiedenen Versuchskonfigurationen wurde das Schutzpotential von Kopfschutzsystemen (Fahrradhelm und airbagbasiertes System) untersucht. Hierbei wurden die resultierende Kopfbeschleunigung als Messwert sowie das Kopfverletzungskriterium HIC bei Versuchen ohne und mit Kopfschutzsystem vergleichend gegenübergestellt.