Crash reconstruction of pedestrian accidents using optimization techniques

The influence of vehicle front-end design on pedestrian ground impact

Effects of Vehicle Impact Velocity, Vehicle Front-End Shapes on Pedestrian Injury Risk

Pedestrian head translation, rotation and impact velocity: the influence of vehicle speed, pedestrian speed and pedestrian gait.

This study examines how pedestrian anthropometry affects response kinematics when pedestrians are struck by an automobile. Seven post-mortem human surrogates were tested under identical conditions in full-scale vehicle-pedestrian impact experiments using a mid-sized sedan. The ability of a geometric scaling technique to predict the response of a mid-sized pedestrian from the responses of pedestrians of other statures was evaluated. Pedestrian kinematic response to sedan impacts was shown to be sensitive to the pelvis and hood interaction, which was largely determined by the height of the pelvis relative to the hood leading edge. The scaling method was shown to be not sufficient to predict mid-sized pedestrian response in impacts with the test vehicle used in this study.

Pedestrian kinematic response to mid-sized vehicle impact

The goal of the current study was to perform dynamic bending experiments on legs and thighs from post mortem human surrogates (PMHS) and combine the failure data with that of previous applicable studies to perform an injury risk analysis. Four leg and 12 thigh specimens were loaded dynamically (∼1.5 m/s) in latero-medial 3-point bending. The four leg specimens and six of the thigh specimens were loaded at the mid-diaphysis and the other 6 thigh specimens were loaded at a third of the length from the distal end. Data from four other studies were used with data from the current study to develop injury risk functions for the human thigh loaded at the distal third (50% probability of femur fracture = 372 Nm), and at the mid shaft (50% probability of femur fracture = 447 Nm) and for the human leg loaded at the mid shaft (50% probability of tibia fracture = 312 Nm).

Tolerance of the human leg and thigh in dynamic latero-medial bending

A primary function of pedestrian dummies is biofidelic representation of whole body kinematics. To assess the biofidelity of a pedestrian dummy, corridors for the kinematic response of post-mortem human surrogates (PMHSs) tested in full-scale pedestrian impact tests were developed. Three PMHSs were tested in full-scale pedestrian impact tests using a late-model small sedan with an impact velocity of 40 km/h. Three additional tests using the Polar-II dummy were conducted in identical conditions to those used in the PMHS tests. All impacts were conducted with the PMHS or dummy positioned laterally at the center line of the vehicle, in a mid-stance gait position, with the struck-side limb positioned posteriorly and the upper limbs placed anterior to the torso. Initially supported by a harness, each surrogate was released prior to impact and was unconstrained through a 250 ms interaction with the vehicle. Using photo targets mounted at the equivalent locations of the head center of gravity (CG), top of the thorax, thorax CG, and pelvis CG, the kinematic response of the pedestrian surrogates was evaluated using parametric trajectory data. To account for simultaneous variability in multiple kinematic parameters, boxed-corridors based on a percentage of trajectory path length were developed from the trajectory data. Given the significance of head impact for pedestrian injury outcome, head velocity-time corridors were also developed. Comparing dummy response and PMHS corridors, the Polar-II generally replicated the complex kinematics of the PMHS and demonstrated good overall biofidelity. Greater sliding up the hood by the PMHS, and lack of neck muscle tension in the PMHS have been identified as potential causes for differences in the length and shape of body segment trajectories. More testing is necessary to assess the effects differences in pre-test orientation, surrogate stature, and clothing will have on surrogate response.

Kinematic Corridors for PMHS Tested in Full-Scale Pedestrian Impact Tests

A primary function of pedestrian dummies is the biofidelic representationof whole-body kinematics. To assess the biofidelity of a pedestrian dummy, the kinematic response of post-mortem human surrogates (PMHS) tested in full-scale pedestrian impact tests was compared with the kinematic response of the Polar-II dummy. Two PMHS were tested in full-scale pedestrian impact tests using a late-model sport-utility vehicle with an impact velocityof 40km/h. Three additional tests using the Polar-II dummy were conductedin identical conditions to those used in the PMHS tests. Using photo targets mounted at the equivalent locations of the head centre of gravity, topof the thorax, thorax centre of gravity, and pelvis centre of gravity, the kinematic response of the pedestrian surrogates was evaluated by comparing their parametric trajectory data. Given the significance of head impactfor pedestrian injury outcome, head velocity-time signals were also compared. To provide insight into the effect of exterior vehicle geometry, the kinematics response of the Polar-II and PMHS tested using a late model small sedan were also compared with the dummy and PMHS response from the SUV tests. Comparing dummy and PMHS response, the Polar-II generally replicated the complex kinematics of the PMHS and demonstrated good overall biofidelity. For the covering abstract see ITRD E134311.

Kinematic comparison of the Polar-II and PMHS in pedestrian impact tests with a sport-utility vehicle

The complexity of vehicle-pedestrian collisions necessitates extensive validation of pedestrian computational models. While body components can be individually simulated, overall validation of human pedestrian models requires full-scale testing with post mortem human surrogates (PMHS). This paper presents the development of a full-scale pedestrian impact test plan and experimental design that will be used to perform PMHS tests to validate human pedestrian models. The test plan and experimental design is developed based on the analysis of a combination of literature review, multi-body modeling, and epidemiologic studies. The proposed system has proven effective in testing an anthropometrically correct rescue dummy in multiple instances. The success of these tests suggests the potential for success in a full-scale pedestrian impact test using a PMHS.

Design of a Full-Scale Impact System for Analysis of Vehicle Pedestrian Collisions

The purpose of this study is to determine the loads in the long bones of the lower extremities during vehicle-pedestrian impact tests, and to correlate load data with observed kinematics in an effort to understand how stature and vehicle shape influence pedestrian response. In tests with a large sedan and a small multi-purpose vehicle (MPV), four post mortem human surrogates (PMHS) in mid-stance gait were struck laterally at 40 km/h. Prior to the tests, each PMHSwas instrumented with four uniaxial strain gages around the mid-shaft cross section of the struck-side (right) tibia and the femora bilaterally. After the tests, the non-fractured bones were harvested and subjected to three-point bending experiments. The effective elastic moduli were determined by relating the applied bending loads with the measured strains using strain gage locations, detailed bone geometry, and elastic beam theory. Using the strains measured in the vehicle-pedestrian tests and the calculated effective elastic moduli, the axial load and bending moments in the instrumented bone cross-sections were calculated. Peak longitudinal strains in the mid-shaft cross-sections approached 1% in the right tibiae and exceeded 0.5% in the right femora with peak strain rates of 200%s(-1)-750%s(-1) in the right tibiae and 100%s(-1)-170%s(-1) in the femora. While peak axial forces were consistent for both vehicles and ranged from 1 kN to 3 kN, bending moments in the right lower extremity exceeded 300 Nm in the sedan impacts but were substantially lower in impacts with the MPV. The right tibia bent predominantly in the medial direction during the impact whereas bi-modal patterns were observed in the sagittal bending moment time histories of the femora. Stature differences caused variations in hip and knee impact locations relative to the hood edge and bumper of each vehicle that may have been a contributing factor resulting in more severe struck-side lower extremity injuries in the tall subject tested with the MPV, and more severe struck-side lower extremity injuries in the shorter subject tested with the sedan.

Check Y. Kam

Papers

Tolerance of the human leg and thigh in dynamic latero-medial bending

Kinematic Corridors for PMHS Tested in Full-Scale Pedestrian Impact Tests

Kinematic comparison of the Polar-II and PMHS in pedestrian impact tests with a sport-utility vehicle

Design of a Full-Scale Impact System for Analysis of Vehicle Pedestrian Collisions

Correlation of strain and loads measured in the long bones with observed kinematics of the lower limb during vehicle-pedestrian impacts.