Understanding pedestrian vulnerability and improving protection: the case of child pedestrians
According to IRTAD, in 2012, 115 children under 14 yearswere killed on French roads, 36 of them were pedestrians. Protecting children is therefore an important issue and we can well ask if the available protection solutions, which were developed for adults, are suitable for the morphology of children. By using dedicated virtual models, we can predict the injuries sustained by a child pedestrian involved in an accident according to the shape of the vehicle.
Accident study and epidemiology
In France, after the vehicle passengers, pedestrians are the largest group of child road traffic accident casualties (IRTAD). The typical injured child pedestrian is six years of age1 , was injured while running across the road outside a pedestrian crossing or when emerging from between two parked vehicles2. In most cases the child is injured by a light vehicle travelling at an average speed of 26.2 km/h3. The most common injuries sustained are to the head (cerebral contusion, subdural haematoma), the torso (spleen injuries, haemo- or pneumothorax and the lower limbs (fractures)4,5.
Computer-based accident reconstruction
The first stage was to study how the shape of the front of the light vehicle affected the typical injuries that occur when a child is impacted. To do this a numerical study was performed in order to reconstruct a large number of accidents. This study made it possible to modify the conventional geometrical parameters of the front of a light vehicle (the height of the bumper above the ground, the distance between the base of the bonnet and the bumper, the height of the bonnet, the angle of the bonnet).
Overall simulation of the accident (left) and local simulation of the head/bonnet impact (right).
To study the influence of vehicle shape on the child, different vehicle models were generated automatically. The accident between the vehicle and a model of a child pedestrian was then simulated on two scales.
First, simulation was performed at the overall scale by simulating of the whole accident. The model used was representative of a six year-old child and provided the kinematics of the accident and all the injury criteria. Second, it was performed at the local scale, for example, the impact between the head and the bonnet. In this case, a representative bio-accurate model (FEMOCS6) of a 6 year-old child6 was used to obtain information on the injury mechanisms7. The selected contacts involved the body segments that in reality sustain the highest severity injuries (head/bonnet, abdomen/bonnet and upper limbs/bumper).
This system allows to predict injuries and provides particularly useful results. In the near future it could help motor vehicle manufacturers to design vehicles that provide better protection for child pedestrians.
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1 H. Fontaine, Y. Gourlet, and A. Ziani, “ Les accidents de piétons : Analyse typologique” Rapp. INRETS, no. 201, May 1995.
2 DiMaggio C, Durkin M. Child Pedestrian Injury in an Urban Setting Descriptive Epidemiology. Acad. Emerg. Med. 2002.
3The FEMOCS6 model wasdeveloped in the Laboratoire de Biomécanique Appliqué de Marseille, UMRT24 Ifsttar/Aix-Marseille Université.
B. Y. Henary, J. Crandall, K. Bhalla, C. N. Mock, and B. S. Roudsari, “Child and adult pedestrian impact: the influence of vehicle type on injury severity,” Annu. Proc. Assoc. Adv. Automot. Med. Assoc. Adv. Automot. Med., vol. 47, pp. 105–126, 2003.
4 Demetriades D, Murray J, Martin M, Velmahos G, Salim A, Alo K, Rhee P. Pedestrians injured by automobiles: Relationship of age to injury type and severity. J. Am. Coll. Surg. 2004.
5 R. Y. Peng and F. S. Bongard, “Pedestrian versus motor vehicle accidents: an analysis of 5,000 patients,” J. Am. Coll. Surg., vol. 189, no. 4, pp. 343–348, Oct. 1999.
6 F. Coulongeat, T. Serre, A. Navarro, M. Behr, and L. Thollon, “Development of a finite element whole-body model of a 6-year-old child for safety,” J. Biomech. Eng, 2012.
7 Coulongeat F. Modélisation numérique de l’enfant: application en accidentologie routière, Thèse de Doctorat, Aix-Marseille Université ; Click on thislink to download the thesis.
