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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-000278.pdf
The design of advanced ATD is moving towards being more human-like and therefore is more complex. More complexity generally leads to more degrees of freedom, the uncertainty of an ATD as a measurement tool rises. The uncertainty of a measurement tool is described by the repeatability and the reproducibility. An ATD alone can only provide measurements. These measurements do not directly reveal the safety level of a vehicle in a crash test. By using a mathematical function, a so-called injury risk function, the ATD measurements can be related to injury risks. The injury risk is a measure to show how well a vehicle protects the occupant or vulnerable road user. The influence of a poor repeatability or reproducibility on the calculation of the injury risk is obvious. For a given measurement variability it is simple to check the associated risk variability by putting the values in the relevant injury risk function. Much less obvious is the effect of poor repeatability and reproducibility on the injury risk function itself. The injury risk function for an ATD is typically a combination of PMHS test results and matched ATD test results. This simple fact reveals that the repeatability as well as the reproducibility of an ATD can already influence the development of the injury risk function and not only the calculation of the injury risk. This study aims to get a basic understanding how the measurement variability of ATD can influence the resulting injury risk function. The study uses data from real repeatability and reproducibility tests with the THOR-50M. For reasons of simplicity the study focuses on the influence of the reproducibility, that is, a perfect repeatability is assumed. Two theoretical PMHS data sets are used to study the reproducibility influence: one with current status data (left and right censored data) and one with exact data. In addition, two different methods for the mapping of ATD measurements onto PMHS results in the risk function development are deployed. This study shows that injury risk curves depend on ATD reproducibility. Current injury risk function development is only reliable with a good ATD reproducibility. Data of THOR-50M used in this study reveals that the current injury risk function development procedure should consider the reproducibility of the ATD. The study used only one data set for the reproducibility of the ATD which limits the generality of the results. In addition only a theoretical and simple injury risk function was applied. More complex injury risk functions with additional co-variants or complex criteria may lead to diverging results. The general effect that the reproducibility is influencing the injury risk function is unaffected. As reproducibility cannot be easily improved because of technical and practical reasons, a methodology needs to be developed that includes the effects of reproducibility in the calculation of injury risk curves.
Language: en |