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Citation
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Forman J, Östling M, Mróz K, Lubbe N. 27th International Technical Conference on the Enhanced Safety of Vehicles (ESV); April 3-6, 2023; Abstract #: 23-0334, pp. 11p. Washington, DC USA: US National Highway Traffic Safety Administration, 2023 open access. |
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Abstract
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27th International Technical Conference on the Enhanced Safety of Vehicles (ESV): Enhanced and Equitable Vehicle Safety for All: Toward the Next 50 Years
https://www-esv.nhtsa.dot.gov/Proceedings/27/27ESV-000334.pdf
Background: Collisions with heavy goods vehicles (HGVs, large trucks) comprise approximately 21% of fatalities in two-vehicle collisions in the United States, and 14-15% of car occupant fatalities in Europe. While the immediate need in these collisions lies in compatibility and the structural integrity of the smaller vehicle, once these are addressed it will be up to the restraint system to manage protection of the occupants at collision severities that are greater than are commonly evaluated now. For restraint evaluation in high-severity collisions where survivability is the focus, different injury criteria targets may be warranted, focused on balancing injury risk across the body regions to fully utilize the load- bearing capability across the body. In this study we seek to identify potential injury criteria target values (and knowledge gaps) for predicting injury risk across the body in evaluations of high-severity collisions.
Methods and Data Sources: This study consisted of a literature review, combined with a field data analysis to contextualize the types and distributions of injuries that occur among collisions of various severity. Data from NASS-CDS (years 2010-2015) and CISS (years 2017-2019) were examined to observe the relative distribution of injury severities by injury type, focusing on belted occupants in frontal collisions. Contemporary injury risk functions were then reviewed (using exemplar high-severity collision simulations) to observe the relative injury risks predicted across the body in collision severities representative of car-to-HGV collisions. Injury risks were further evaluated in high-severity collision simulations with an improved restraint system designed to manage occupant energy in such scenarios, demonstrating that injury risk can be reduced by adapting the restraint system to the severity of the crash.
Results and Discussion: Across collision severities, injury risks were relatively balanced among the body regions. Most AIS2+ and AIS3+ injury cases occurred in relatively low-severity collisions, due to the very high exposure to low-severity collisions. AIS4+ injury cases occurred with similar total counts in low-severity and high-severity collisions, affected by the balance of exposure and per-crash risk. In high-severity collisions, the most common injury types were to the ankle, tibia & fibula, brain, thorax, and lumbar spine, all occurring with similar frequency. In simulations with the THOR- 50M finite element model in high-severity impact scenarios, the injury risk predicted across the body regions exhibits similar balance to that observed in the field data, except for the risks predicted in the chest and the hip. Upon examination of the risks observed in the field data, as well as those observed in high-severity impact simulations with different restraint systems, injury assessment reference values were developed targeting a risk of 40%, representing a target that is feasible to achieve and which has a high likelihood of providing a tangible benefit to the field.
Conclusions: Injuries occur as a result of both exposure and per-incident risk. Injury reduction likely requires safety systems that can adapt to the crash severity, providing more compliant restraint in low-severity collisions (where the exposure is very high), and stiffer restraint designed to eliminate strike-through in higher severity collisions (where the per-crash risk is high). Such adaptive-restraint design requires injury risk targets designed for the specific collision severities targeted for evaluation – including more conservative targets for low-severity evaluations, and higher practical targets for high-severity evaluations (focusing on survivability). This study has identified potential means for defining injury criteria values specifically for evaluations in high-severity collision scenarios, targeting a balance among the body regions informed by recent field data. |