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The goal of the present study was to develop a new legform impactor that accurately represents both the impact force (i.e., force between the leg and impacting mass)and leg kinematics in lateral impacts simulating car-pedestrian accidents. In its development we utilized the knee joint of the pedestrian dummy called Polar-2 (HONDA R&D) in which the cruciate and collateral ligaments are represented by means of springs and cables, the geometry of the femoral condyles is simplified using ellipsoidal surfaces, and the tibial meniscus is represented by an elastomeric pad. The impactor was evaluated by comparing its responses with published experimental results obtained using postmortem human subjects (PMHS). The evaluation was done under two conditions: 1)impact point near the ankle area (bending tests),and 2)impact point 84 mm below the knee joint center (shearing tests). Two impact speeds were used: 5.56 m/s and 11.11 m/s.

The New Car Assessment Program in Japan (JNCAP) was launched in 1995 in order to improve car safety performance. According to this program, installation conditions of safety devices and the results for braking performance and full- frontal crash tests are published every year. Introduction of JNCAP significantly increases the installation rate of safety devices and contributes much in enhancement of safety as seen in the decrease in the average injury severity of drivers and passengers. Side impact and offset frontal crash tests were introduced in 1999 and 2000, respectively. At present, the overall crash safety rating is carried out based on the results of the full-frontal, offset frontal, and side impact tests.

Improvements for pedestrian head protection in a car-pedestrian accident have been discussed in several countries. Test methods for evaluating head protection have been proposed, and most are sub-systems using rigid headforms with or without headskin. In those tests, HIC is used as a criterion for head protection. This paper discusses the test conditions and requirements of the headform impact test. The influence of different test conditions and their importance on head impact test requirements, were verified. The primary items cited are as follows: (1) The results of the rigid headform were similar to that of the human cadaver skull in cases without skull fractures. Consequently, the rigid headform can be used for the impactor simulating a condition without skull fracture. (2) In the cases of HIC≤1000, the force-deformation curves of the hoodtops showed similar characteristics with maximum dynamic deformations over 60mm. (3) Impactor mass affected the maximum acceleration and HIC.

A two-dimensional impact model with a capability of reverse calculation has been developed to reconstruct various types of automobile collisions. The model consists of a law of conservation of momentum and introduces a normal restitution coefficient and a tangential restitution coefficient at the impact center. Sixteen car-to-car impact tests, including side swipe type collisions, were conducted to obtain primary data for validating the model and improving its reliability in accident analysis. The relationship of the normal and tangential restitution coefficients to the collision type was obtained with a generalized impulse ratio from the analysis of test data by using the impact model. This paper presents the formulas used in the model and demonstrates their applications to accident analysis. The following analytical formulas are introduced: The relationship between energy loss and delta-V. The relationship between restitution coefficients and energy loss.

To understand the performance of Event Data Recorder (EDR) for the improvement of accident reconstruction using reliable and accurate information, two types of crash test data are analyzed. The first type is the J-NCAP crash tests for understanding the EDR characteristics under fundamental crash conditions and the second type involves three crash tests reconstructing typical real-world accidents for grasping the EDR performance under more complex crash conditions than J-NCAP crash tests. Data obtained from EDRs are compared with data obtained from instrumented sensors and high-speed video cameras. The velocities determined from pre-crash data and the maximum change in velocity, delta-V, obtained from post-crash data are analyzed. EDR pre-crash data shows good accuracy. In J-NCAP testing, all differences between the EDR recording value and the laboratory test velocity were less than 4%. EDR post-crash data has more difference from instrumented sensor data.

The IHRA Pedestrian Working Group has conducted investigation and analysis on the current status of pedestrian accidents in the IHRA member countries. We collected the accident data that occurred by 1999, then unified the formats of the accident data and established a dataset that makes it possible to make comparison with each other. According to the current status of pedestrian accidents, three parts of the pedestrian’s body have the highest priority for protection, the child and adult heads, and the adult lower leg/knee. As for the motor vehicle, we determined which particular parts of the motor vehicle were involved, which pedestrian body parts they injured and the severity of the injuries, and analyzed the effect of their shapes, corresponding to the items above. It was decided that the test methods should be for motor vehicles for passenger use but not buses and coaches.

Honda has been studying ways of improving vehicle design to reduce the severity of pedestrian injury. Full-scale test using a pedestrian dummy is an important way to assess the aggressiveness of a vehicle to pedestrians. However, from test results it is concluded that current pedestrian dummies have stiffer characteristics than Post Mortem Human Subjects (PMHS). Also, the dummy kinematics during a collision is different from that of a human body. Because of the limitations of current dummies, it was decided to develop a new pedestrian dummy. At the first stage of the project, a computer simulation model that represented the PMHS tests was developed. Joint characteristics obtained from the simulation model were used in building a new pedestrian dummy which has been named Polar I. The advanced frontal crash test dummy, known as Thor, was selected as the base dummy. Modifications were made for the thorax, spine, knee etc.

A new mathematical multibody-system model of the whole human body was developed to simulate the pedestrian in road accidents with cars. The aim with the model was to achieve better correlation with results from impact tests with cadaver specimens. The pedestrian model was created to be used with the Crash Victim Simulation (CVS) computer program. The model consists of fifteen segments connected by fourteen joints. The geometry and the characteristics of the body segments, and the mechanical properties of the joints are based on available anthropometrical and biomechanical data. In order to verify the pedestrian model with pervious cadaver experiments, the computer simulations were carried out in such a way that the set-up of simulations corresponded to those in the cadaver tests. The model response to following parameters was studied in the simulations: impact speed, bumper height and bumper compliance.

An impact test procedure with a legform addressing lower limb injuries in car-pedestrian accidents has been proposed by EEVC/WG17. Although a high frequency of lower limb fractures is observed in recent accident data, this test procedure assesses knee injuries with a focus on trauma to the ligamentous structures. The goal of this study is to establish a methodology to understand injury mechanisms of both ligamentous damages and bone fractures in car-pedestrian accidents. A finite element (FE) model of the human lower limb was developed using PAM-CRASH™. The commercially available H-Dummy™ lower limb model developed by Nihon ESI for a seated position was modified to represent the standing posture of pedestrians. Mechanical properties for both bony structures and knee ligaments were determined from our extensive literature survey, and were carefully implemented in the model considering their strain rate dependency in order to simulate the dynamic response of the lower limb accurately.

Based on a previously presented two-dimensional car-to-car impact model, automobile collision tests were analyzed to understand the relationship of the impact center to the residual vehicle deformation, which is essential for improving the reliability of the impact model. The results from a number of automobile collision tests indicated that the impact centers of the two vehicles at the end of collision were located near the center of the contacting surface when the vehicle deformation is maximized. This leads to a method of defining the impact center from the crush profile at the time of maximum deformation. The relationships of the normal and tangential restitution coefficients to the collision type were also presented, discussed and evaluated to obtain some guidelines on how to choose the restitution coefficients from impact conditions.