HALL - CARPENTER, CO.
By Edwin T. Scallon, Copyright © 1990, 1995, 2008, 2020 All Rights Reserved
ACCIDENT RECONSTRUCTION AND BAC CALCULATION PROGRAMS
HISTORY OF ACCIDENT RECONSTRUCTION
History
The National Highway Traffic Safety Administration funded the first national guidelines for the standardization training in the field of traffic collision reconstruction in 1985. This led to the establishment of "Accreditation Commission for Traffic Accident Reconstruction" (ACTAR), an industry accreditation group.[1] This field of motorcycle collision research was pioneered by Hugh H. Hurt Jr. His meticulous collision reconstructions of motorcycle collisions helped to explain that proper helmets reduced head injuries, most motorcyclists needed more driver training to control skids, and a large percentage of motorcycle collisions involved left-turning automobiles turning in front of the oncoming motorcycle.Skid marks on an asphalt road.
Investigation
Scene inspections and data recovery involves visiting the scene of the collision and investigating all of the vehicles involved in the collision. Investigations involve collecting evidence such as scene photographs, video of the collision, measurements of the scene, eyewitness testimony, and legal depositions. Additional factors include steering angles, braking, use of lights, turn signals, speed, acceleration, engine rpm, cruise control, and anti-lock brakes. Witnesses are interviewed during collision reconstruction, and physical evidence such as tire marks are examined. The length of a skid mark can often allow calculation of the original speed of a vehicle for example. Vehicle speeds are frequently underestimated by a driver, so an independent estimate of speed is often essential in collisions. Inspection of the road surface is also vital, especially when traction has been lost due to black ice, diesel fuel contamination, or obstacles such as road debris. Data from an event data recorder also provides valuable information such as the speed of the vehicle a few seconds before the collision.
As part of the investigation of a vehicle collision, an investigator typically documents evidence at the collision site and the damage to the vehicles. The use of 3-dimensional laser scanning has become a common method for documentation. The product of scanning is a 3D point cloud that can be used to take measurements and create computer models used in the analysis of the collision. The 3D data can be incorporated into many of the computer simulation programs used in collision reconstruction. The 3D point clouds and models can also be used for creating visuals to illustrate the analysis and to show views of witnesses and the involved drivers.
Technology
Many new vehicles are equipped with onboard "Crash Data Recorders or Event Data Recorders" (CDR or EDR). The Bosch CDR Tool is a commercially available tool, allowing to image crash data directly from all supported vehicles giving a detailed report of critical data parameters leading up to and during a crash. Some of the parameters include pre-crash data, vehicle speed, brake status, throttle position, ignition cycles, delta-V, seat belt status, and others.
Hyundai and Kia as well as most heavy commercial vehicles are equipped with EDR, however are not supported by Bosch equipment. To access this information a diagnostic retrieval tool unique to these manufacturers is required.
Analysis
Vehicular collision reconstruction analysis includes processing data collecting, evaluating possible hypotheses, creating models, recreating collisions, testing, and utilizing software simulations. Like many other technical activities, collision reconstruction has been revolutionized by the use of powerful, inexpensive computers and specialty software. Various types of collision reconstruction software are used to recreate crash and crime scenes and to perform other useful tasks involved in reconstructing collisions. Collision reconstruction software is regularly used by law enforcement personnel and consultants to analyze a collision and to demonstrate what occurred in a collision. Examples of types of software used by collision reconstructionists are CAD (computer aided design) programs, vehicle specification databases, momentum and energy analysis programs, collision simulators, and photogrammetry software.
Presentation
After the analysis is completed, forensic engineers compile report findings, diagrams, and animations to form their expert testimony and conclusions relating to the collision. Forensic animation typically depicts all or part of a collision sequence in a video format so that non-technical parties, such as juries, can easily understand the expert's opinions regarding that event. To be physically realistic, an animation needs to be created by someone with a knowledge of physics, dynamics and engineering. When animations are used in a courtroom setting, they should be carefully scrutinized. Animation software can be easily misused, because motions which are not physically possible can be displayed. A reliable animation must be based on physical evidence and calculations which embody the laws of physics, and the animation should only be used to demonstrate in a visual fashion the underlying calculations made by the expert analyzing the case.
Motorcycle collision reconstruction
Motorcycle collision reconstruction is similar to other collision reconstruction techniques and relies on the same basic principles of conservation of energy and momentum as automobile collision reconstruction plus adds the specifics of motorcycle dynamics and rider control. Proper reconstruction of a motorcycle collision requires detailed knowledge of motorcycle dynamics plus knowledge of how motorcycles react to rider input.
Motorcycle collision reconstruction follows reverse a chronological order of events, working from the point of rest of the motorcycle and/or rider backwards to a point in time before to the start of the collision sequence to when possible actions could have prevented the crash.