Final report

Rapport, 2013

Road safety is a major societal issue. In 2009, more than 35,000 people died on the roads of the European Union, i.e. the equivalent of a medium town, and no fewer than 1,500,000 persons were injured1. The cost for society is huge, representing approximately 130 billion Euros in 2009. In view of this the European road safety policy orientations identify new technologies that have a high potential to improve road safety and should be promoted up to 2020. These new technologies identified as being able to improve road safety include advanced restraint systems. As a contribution to the improvement of road safety the THORAX project studied thoracic injuries. Injury mechanisms and the influence of occupant diversity factors like age and gender were investigated. The gained knowledge was implemented in numerical and experimental tools that enable the design and evaluation of advanced vehicle restraint systems which are capable of offering optimal protection for a wide variety of car occupants. To develop the improved design and evaluation tools THORAX was structured in four work packages related to accident surveys, biomechanical studies, dummy development and dummy evaluations. Work-Package 1 analysed real world car crash data to provide detailed information on the type and severity of injuries in relation to impact type, restraint type, and occupant characteristics. The survey revealed rib fracture as the predominant thoracic injury and focus for the tool developments. Detailed case studies comparing real world accidents and consumer rating tests showed that female occupants generally are at higher risk in car crashes compared to males. In Work-Package 2 a set of biomechanical requirements for an enhanced shoulder thorax complex of a frontal impact dummy was defined. A suit of Post Mortem Human Subject (PMHS) data was collected and documented in detail for reproduction with the new tools. Missing data were identified and additional tests conducted to complete the dataset. In addition injury mechanisms and governing parameters were studied using Human Body Models. For this purpose PHMS tests conducted under welldefined conditions were simulated using human body models identifying excessive bending strain in the ribs as key factor for the initiation of rib fractures. Based on this finding two injury criteria were proposed. The first correlates dummy chest deflections at four locations to fractures observed in PMHS tests under various conditions in matched dummy – PMHS tests. The second uses local strain data measured around the dummy ribs. Based on the biomechanical requirements a demonstrator dummy with improved thorax and shoulder designs was developed in Work-Package 3. Three prototypes were built and installed on available THOR dummies. The demonstrators were subjected to extensive evaluation testing, reproducing the PMHS tests collected under Work-Package 2. Testing showed a superior biofidelity of the demonstrator compared to existing HIII and THOR dummies. The data was used also to generate preliminary injury risk curves related to the criteria proposed. As a final step, in Work-Package 4, the demonstrator dummy was subjected to extensive testing in a vehicle environment to assess its sensitivity to typical state of the art vehicle restraint systems. Full scale and sled tests were performed in which the demonstrators showed increased sensitivity to different loading severities, loading directions and restraint variations compared to the HIII. The injury risk prediction using the THORAX risk curves was in line with assumed real life observations. It was also shown that current restraint systems will need updates to conform to current rating levels in terms of injury risk. As such it is expected that the THOR injury risk evaluation using risk functions for young and elderly people as well as AIS2+ will result in further reduced injuries due to frontal injuries. During the entire runtime of the project information was shared with key stakeholders in the field. Results and findings were forwarded to Euro NCAP and the GRSP Informal Group on Frontal Impacts. Based on the THORAX findings both groups decided to include dummies representing females in their future crash test procedures. Also the GRSP Informal Group placed the THOR dummy on the agenda for their phase 2 update of the frontal impact directive for the 2020 timeframe. Information exchange with the National Highway Traffic Safety Administration resulted in the preliminary adoption of the new shoulder design and thorax updates from THORAX. This design will be evaluated in 2013 by NHTSA for decision making at the end of 2013.