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Technical Paper

Uncertainty in Accident Reconstruction Calculations

1994-03-01
940722
Three popular techniques are discussed in the context of accident reconstruction. The first establishes upper and lower bounds through calculation of the largest and smallest possible values of the quantity being estimated for all combinations of the input variables.
Book

Vehicle Accident Analysis and Reconstruction Methods, Second Edition

2011-04-12
Thoroughly revised, this new edition builds on the original exploration of accident analysis, reconstruction, and vehicle design. Enhanced with new material and improved chapters on key topics, an expanded glossary of automotive terms, and a bibliography at the end of the book providing further reading suggestions make this an essential resource reference for engineers involved in litigation, forensic investigation, automotive safety, and crash reconstruction. ...Designed for the experienced practitioner, this new book aims to help reconstruction specialists with problems they may encounter in everyday analysis. The authors demonstrate how to take the physics behind accidents out of the idealized world and into practical situations. ...The authors demonstrate how to take the physics behind accidents out of the idealized world and into practical situations. Real-world examples are used to illustrate the methods, clarify important concepts, and provide practical applications to those working in the field.
Technical Paper

Comparison of Tire Friction Test Methodologies Used in Accident Reconstruction

1998-02-23
980367
Many accident reconstructions rely on the use of friction factors for the analysis of vehicle speeds. ...Measurement of the friction factor, or coefficient of friction, at the accident site is usually an important step in achieving a more accurate estimate of the friction factor at the time of the accident. Over the years several on site test methodologies have emerged within the accident reconstruction community. ...Measurement of the friction factor, or coefficient of friction, at the accident site is usually an important step in achieving a more accurate estimate of the friction factor at the time of the accident.
Technical Paper

Crush Energy and Planar Impact Mechanics for Accident Reconstruction

1998-02-23
980025
The algorithm used in the third version of the Calspan Reconstruction of Accident Speeds on the Highway (CRASH3) and planar impact mechanics are both used to calculate energy loss and velocity changes of vehicle collisions. ...A method is proposed that exploits the features of both methods for vehicle accident reconstructions.
Technical Paper

Tire Models for Vehicle Dynamic Simulation and Accident Reconstruction

2009-04-20
2009-01-0102
This is particularly true for accident reconstruction applications where vehicle motions can occur over wide ranging kinematic wheel conditions. ...This paper includes a discussion of tire force terminology, tire force mechanics, the measurement and modeling of tire force components and combined tire force models currently used in simulation software for the reconstruction of accidents. The paper discusses the difference between the idealized tire force ellipse and an actual tire friction ellipse. ...The example simulations presented in this paper are not intended to reflect the way vehicle dynamic simulation programs are used typically in accident reconstruction.
Technical Paper

Least Squares Collision Reconstruction

1987-02-01
870429
A new method is described and illustrated which solves the planar, two vehicle collision reconstruction problem. The method, called LESCOR (LEast Square Collision Reconstruction), determines the initial velocity components when given: (1) final velocity components, (2) vehicle physical data, (3) damage geometry, (4) collision geometry and (5) the impact coefficients (restitution and friction). ...Five example collision reconstructions are presented based on RICSAC collisions and a field example. The method has provided results which range from good to excellent and is superior to trial and error methods used in the past.
Journal Article

Nonlinear Optimization in Vehicular Crash Reconstruction

2015-04-14
2015-01-1433
This paper presents a reconstruction technique in which nonlinear optimization is used in combination with an impact model to quickly and efficiently find a solution to a given set of parameters and conditions to reconstruct a collision. ...These parameters and conditions correspond to known or prescribed collision information (generally from the physical evidence) and can be incorporated into the optimized collision reconstruction technique in a variety of ways including as a prescribed value, through the use of a constraint, as part of a quality function, or possibly as a combination of these means. ...These parameters and conditions correspond to known or prescribed collision information (generally from the physical evidence) and can be incorporated into the optimized collision reconstruction technique in a variety of ways including as a prescribed value, through the use of a constraint, as part of a quality function, or possibly as a combination of these means. This reconstruction technique provides a proper, effective, and efficient means to incorporate data collected by Event Data Recorders (EDR) into a crash reconstruction.
Technical Paper

Reconstruction of Vehicle-Pedestrian Collisions Including an Unknown Point of Impact

2015-04-14
2015-01-1419
Numerous algebraic formulas and mathematical models exist for the reconstruction of vehicle speed of a vehicle-pedestrian collision using pedestrian throw distance. ...Example reconstructions are presented in this paper for wrap and forward projection collisions using the relative rest positions of the vehicle and the pedestrian. ...Comparisons of the example wrap collision reconstruction are made with other formulas found in the literature. The main features of the Han-Brach model are summarized and discussed.
Technical Paper

Uncertainty of CRASH3 ΔV and Energy Loss for Frontal Collisions

2012-04-16
2012-01-0608
An understanding of the nature of such uncertainties is of particular importance as both the ΔV and EC are frequently used as inputs to reconstruction methods and become variations in the reconstruction process. These variations lead to uncertainties in the results of the reconstruction which are generally the preimpact speed of one or both of the vehicles involved in the collision. ...These variations then are used in the CRASH3 damage algorithm, through the use of Monte Carlo analysis, to calculate the uncertainty in the ΔV and EC for each of the six vehicle models colliding with a fixed, rigid barrier. ...These variations lead to uncertainties in the results of the reconstruction which are generally the preimpact speed of one or both of the vehicles involved in the collision.
Journal Article

Analysis of High-Speed Sideswipe Collisions Using Data from Small Overlap Tests

2014-04-01
2014-01-0469
The test data were further evaluated to understand the nature of high-speed, small overlap, sideswipe collisions and establish appropriate parameter ranges that can aid in the process of accident reconstruction. An example reconstruction of a small overlap, sideswipe collision using optimization methods based on the planar impact mechanics model is included in the paper. ...The results of the example reconstruction show that the reconstruction method developed in the paper, using the physical evidence and EDR data, produces useful results. ...Little experimental data have been reported in the crash reconstruction literature regarding high-speed sideswipe collisions. The Insurance Institute for Highway Safety (IIHS) conducted a series of high-speed, small overlap, vehicle-to-barrier and vehicle-to-vehicle crash tests for which the majority resulted in sideswipe collisions.
Technical Paper

An Analytical Assessment of the Critical Speed Formula

1997-02-24
970957
The Critical Speed Formula is used in the field of accident reconstruction for the estimation of the speed of a vehicle that has been given a sudden unidirectional steer maneuver by the driver and when the tires develop a high enough sideslip to leave curved visible marks on the pavement. ...The experimental results of Shelton (Accident Reconstruction Journal, 1995) are analyzed statistically and are compared to the results of the simulations. ...This and other uses of the formula are investigated in this paper. Reconstructions are done using computerized dynamic simulations of a turn maneuver for 3 different, driver forward control modes: braking, coasting and accelerating.
Technical Paper

Residual Crush Energy Partitioning, Normal and Tangential Energy Losses

2007-04-16
2007-01-0737
The simplest and most popular form of this crush energy relationship is a linear one and has been exploited for the purpose of accident reconstruction in the well known CRASH3 crush energy algorithm. Nonlinear forms of the relationship between residual crush and collision energy also have been developed. ...Nonlinear forms of the relationship between residual crush and collision energy also have been developed. Speed reconstruction models that use the CRASH3 algorithm use point mass impact mechanics, a concept of equivalent mass, visual estimation of the Principle Direction of Force (PDOF) and a tangential correction factor to relate total crush energy to the collision ΔV values. ...The use of point mass mechanics, equivalent mass, a tangential correction factor and zero restitution are unnecessarily restrictive and their use reduces the accuracy of the crush energy methods in crash reconstruction. This paper shows that planar impact mechanics can be adapted to significantly improve the rigor of using residual crush for crash reconstruction.
Technical Paper

A Review of Impact Models for Vehicle Collision

1987-02-01
870048
Automobile accident reconstruction and vehicle collision analysis techniques generally separate vehicle collisions into three different phases: pre-impact, impact and post-impact.
Technical Paper

Modeling of Low-Speed, Front-to-Rear Vehicle Impacts

2003-03-03
2003-01-0491
By selecting stiffness and damping coefficients to match contact duration and coefficient of restitution, the model can be used to determine peak accelerations and ΔV's for the purpose of accident reconstruction and for occupant motion studies.
Technical Paper

Energy Loss in Vehicle Collisions

1987-10-01
871993
Reconstruction methods typically are based upon impact velocity changes computed by one of two approaches.
Technical Paper

Impact Analysis of Two-Vehicle Collisions

1983-02-01
830468
The National Highway Traffic Safety Administration has conducted twelve staged collisions with the purpose of furnishing collision data for use with accident models. In this paper the data is fit to a two-vehicle impact model using the method of least squares.
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