New biofidelic corridor and biofidelity test procedure for pedestrian legform impactors.

The objectives of this research are to propose a new impact response corridor for the ISO legform impactor and to determine the biofidelity of the current legform impactor with rigid leg and thigh developed by the Transport Research Laboratory (TRL). The latest data obtained from Post Mortem Human Subject (PMHS) knee impact tests were analyzed in connection with the proposal, and biofidelity legform impact tests were conducted using the current rigid legform impactor. New normalized biofidelic corridors of impact force corresponding to adult male 50th percentile (AM50) are proposed. The impact test results indicate the current rigid legform impactor does not have sufficient human knee biofidelity. The present results suggest that human tolerance can not be used directly for the injury reference value of the legform impactor. A conversion method is needed to interpret the data measured by current legform impactors as the injury reference value.

Finite element analysis of knee injury risks in car-to-pedestrian impacts.

In vehicle-pedestrian collisions, lower extremities of pedestrians are frequently injured by vehicle front structures. In this study, a finite element (FE) model of THUMS (total human model for safety) was modified in order to assess injuries to a pedestrian lower extremity. Dynamic impact responses of the knee joint of the FE model were validated on the basis of data from the literature. Since in real-world accidents, the vehicle bumper can impact the lower extremities in various situations, the relations between lower extremity injury risk and impact conditions, such as between impact location, angle, and impactor stiffness, were analyzed. The FE simulation demonstrated that the motion of the lower extremity may be classified into a contact effect of the impactor and an inertia effect from a thigh or leg. In the contact phase, the stress of the bone is high in the area contacted by the impactor, which can cause fracture. Thus, in this phase the impactor stiffness affects the fracture risk of bone. In the inertia phase, the behavior of the lower extremity depends on the impact locations and angles, and the knee ligament forces become high according to the lower extremity behavior. The force of the collateral ligament is high compared with other knee ligaments, due to knee valgus motions in vehicle-pedestrian collisions.

Comparative analysis of vehicle-bicyclist and vehicle-pedestrian accidents in Japan.

Bicyclist and pedestrian injuries in collisions with vehicles in Japan were investigated based on national and in-depth accident data analyses and mathematical simulations. In an impact with a bonnet-type vehicle, a bicyclist slides over the bonnet of the vehicle, behavior that is not observed for pedestrians. As a result, the bicyclist's head tends to strike a bonnet-type vehicle at a more rearward location in comparison with pedestrians. The first contact position of a bicycle with a vehicle, the vehicle front-end geometry and the bicycle velocity affect whether the bicyclist's head strikes the vehicle or not. Due to the bent-knee posture of a bicyclist's legs, the types of leg injuries sustained by bicyclists and their causes differ from those seen for pedestrians. Component test procedures have been proposed for evaluating pedestrian safety, but some modifications of the head impact area and angle are necessary when applying these methods to bicyclists.

Mathematical Modelling of Muscle Effect on the Kinematics of the Head-Neck Complex in a Frontal Car Collision: A Parameter Study.

A 2-dimensional multibody model of the head-neck complex with muscle elements was developed to estimate the influence of muscles on the kinematics of the head-neck complex in a frontal car collision. With this model the authors evaluated how strongly the calculated influence of muscles depends on 3 important factors: (a) impact severity, (b) reflex time, and (c) parameters that determine characteristics of different components of the muscle model. When muscles were triggered at the beginning of impact, the maximum angle of the head flexion was decreased by the muscles by 40% in a frontal collision with an acceleration of 15g. The influence of muscles was significant for reflex times lower than 60 (80) ms. The calculated influence of muscles was not sensitive to most parameters of the muscle model.