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Technical Paper

PC-Crash and HVE, an Overview of Similarities and Differences

HVE 1 and PC-Crash 2 have been the subject of numerous SAE papers. Both programs have been offered to reconstructionists for the purpose of analyzing vehicle accidents and presenting the resulting motions in 3D graphical form.
Technical Paper

An Analytical Review and Extension of Two Decades of Research Related to PC-Crash Simulation Software

PC-Crash is a vehicular accident simulation software that is widely used by the accident reconstruction community. ...The goal of this article is to review the prior literature that has addressed the capabilities of PC-Crash and its accuracy and reliability for various applications (planar collisions, rollovers, and human motion). ...In addition, this article aims to add additional analysis of the capabilities of PC-Crash for simulating planar collisions and rollovers. Simulation analysis of five planar collisions originally reported and analyzed by Bailey [2000] are reexamined.
Journal Article

Reconstructing Vehicle Dynamics from On-Board Event Data

These predictions were generated by directly integrating the VCH data and by using the VCH data as inputs to PC-Crash simulations. The predicted positions and headings were then compared to the actual position and heading data measured using differential GPS synchronized to the VCH data record.
Technical Paper

Essential Considerations in Delta-V Determination

While Delta-V has been one of the most used indicators of accident severity for vehicle occupants, its actual determination remains a mystery to many who refer to it and use it. Delta-V is a term of art applied to a rapid change in vehicle velocity caused by impact forces during a collision. The Delta-V is associated with the high decelerations, which cause it and are applied to the occupants through restraint systems and collisions with the interior of the vehicle. This paper will serve as a primer for those new to the subject and a review for those who are familiar with the subject. Previous works by the authors will be referenced and other pertinent literature and data sources will be discussed. The analytical methods and test data used to calculate Delta-V will be presented and the relationship between Delta-V and other measures of impact severity, such as Barrier Equivalent Velocity and Energy Equivalent Speed will be discussed. The use of air bag sensor data will be included.
Technical Paper

Accuracy and Sensitivity of Yaw Speed Analysis to Available Data

Accident reconstructionists rarely have complete data with which to determine vehicle speed, and so the true value must be bracketed within a range. Previous work has shown the effect of friction uncertainty in determining speed from tire marks left by a vehicle in yaw. The goal of the current study was to assess improvements in the accuracy of vehicle speed estimated from yaw marks using progressively more scene and vehicle information. Data for this analysis came from staged S-turn maneuvers that in some cases led to rollover of sport utility vehicles. Initial speeds were first calculated using the critical curve speed (CCS) formula on the yaw marks from the first portion of the S-maneuver. Then computer simulations were performed with progressively more input data: i) the complete tire marks from the whole S-maneuver, ii) measured vehicle mass, iii) measured suspension stiffness and damping, and iv) measured steering history.
Technical Paper

Effectiveness of Side-Airbags for Front Struckside Belted Car Occupants in Lateral Impact Conditions - An In-Depth-Analysis by GIDAS1

Accident documentations on GIDAS (German In-Depth-Accident Study) from 1999 to 2005 are used for this study dealing with the effectiveness of the side airbag protection for car occupants. An analysis of real world accidents was carried out by ARU-MUH (Accident Research Unit - Medical University Hannover). The data were collected based on the spot documentation in time after an accident event. Based on the accident sampling process, the results of this study are representative for the German traffic accident situation. In order to determine the influence and the effectiveness of airbags, only those accident configurations with comparable conditions on impact direction are used for the study, therefore only cases with impact to the compartment, a delta-v-range 5 to 50 km/h and for struckside seated belted occupants were selected.
Technical Paper

The Accident Research Unit Hannover as Example for Importance and Benefit of Existing In Depth Investigations

The In-Depth Investigations of the Accident Research Unit Hannover (Germany), which have been carried out since 1973 are described in the paper. The importance of the detailed analysis consists in the method, in the statistical approach and the continuous data collection over the years. The government as well as industrial manufacturers use this data. Since 1985 a statistical procedure including a mathematical weighting procedure has been applied. About 1000 cases per year are collected. In the paper, principal aspects in the technique of data collection, definitions of variables and possibilities of data usage are described. The limitations of in-depth investigations are discussed in principle, and demands for a worldwide level are pointed out.
Technical Paper

Documenting Scientific Visualizations and Computer Animations Used in Collision Reconstruction Presentations

Scientific visualizations and computer animations are frequently presented to show the results of simulation models or the opinions of a reconstructionist. In these cases it is important to properly document the graphical images being presented. Proper documentation depends somewhat on the methodologies used to produce the images, but every scientific visualization, computer animation, and computer generated image should be documented sufficiently to allow others to duplicate the images. There are also some basic data that should accompany any computer generated images that will reveal the basis of the motion for all primary objects being depicted. This paper presents some basic definitions and outlines the data that is required to document scientific visualizations and computer animations.
Technical Paper

RICSAC-97 A Reevaluation of the Reference Set of Full Scale Crash Tests

Research performed in the 1970's revealed significant limitations in the available documentation of vehicle crush information and trajectory spinout information. As a result a series of full-scale crash tests were performed which became known as the Research Input for Computer Simulation of Automobile Collisions (RICSAC) crash tests. Previous research using the RICSAC test results, particularly in relation to the validation of accident reconstruction computer programs, has varied widely in acceptance, interpretation and presentation of the RICSAC test results. This paper presents a detailed review and decipherment in useable form of the original 12 crash tests that were performed within the RICSAC program. A new method of analyzing accelerometer data from arbitrary sensor positions, on the basis of discrete measures of the vehicle responses rather than complete time-histories, is defined.
Technical Paper

An Evaluation of Rectified Bitmap 2D Photogrammetry with PC-Rect

Without good-quality measurements taken at the time of an accident the analyst is faced with the need to extract measurement data from incident scene photographs. This paper discusses the history and development of the mathematical model for two-dimensional (2D) single exposure analytical photogrammetry, presents the software PC-Rect, and compares the analytical results obtained with PC-Rect to survey results. The sensitivity of the analytical results to the variation in such parameters as subject distance, camera height, digital photograph resolution, and bitmap density is discussed. The concept of using the directly rectified scanned photograph in the reconstruction task is introduced, and the utility of performing the dynamic simulation directly on the rectified photograph is discussed.
Technical Paper

The Effects of Measurement Uncertainty on the Reconstruction of Various Vehicular Collisions

This paper continues a previous study of the effects of uncertainty of measurement upon accident reconstruction. The task is to identify, given the many inevitable errors of observation, the few of greatest import, so that these errors may be reduced, and to document the accuracy of the associated reconstruction. Until recently, it was not for lack of method that such studies could not be properly performed, but for lack of good data on uncertainty of measurement. The essential data was provided in 2002 in a report by Bartlett and others of juried studies performed by volunteer field investigators, summarized and supplemented in 2003 by Bartlett and Fonda in the form of a single table of all likely errors of measurement (furnished again here). In that paper, Finite Difference Analysis (FDA) was reviewed and with the aid of the new data was applied to automotive accident reconstruction.
Technical Paper

A Critique of Critical Speed Yaw Mark Research

Critical speed yaw marks are commonly used in collision reconstruction to estimate vehicle speed. Research and laboratory testing have demonstrated that critical speed calculations can be used to accurately estimate vehicle speed. Thus, the principles supporting critical speed yaw analysis are fundamentally and theoretically valid and are not being challenged in this study. However, there are observed and documented limitations with respect to the appropriate application and execution of critical speed yaw analysis. This paper reviews the published research to-date and identifies limitations of critical speed yaw analysis. Examples of collision scenes are provided which quantify the inaccuracies associated with the misuse of critical speed yaw calculations. Areas for further research are identified and detailed.