Accident investigation and reconstruction
Accident investigation and reconstruction involve the systematic collection and analysis of evidence at transportation accident scenes to understand what occurred. This process is significant for determining liability in various accidents, including motor vehicle incidents, and is often integral to criminal and civil legal proceedings. Typically, police departments initiate these investigations, but federal agencies like the National Transportation Safety Board (NTSB) may take over in certain cases. Investigators collect various forms of evidence, such as witness statements, vehicle damage assessments, and environmental conditions, to create accurate models of the events leading up to and following an accident.
The investigation phase prioritizes immediate safety and evidence preservation, while the reconstruction phase employs principles of physics and engineering to analyze the data collected. Various methodologies exist for reconstruction, including damage-based and trajectory-based approaches, both of which consider factors like vehicle speeds and angles of impact. Expertise in this field varies widely, from formally educated specialists with advanced degrees to those with vocational training. Ultimately, the credibility of the reconstruction findings relies heavily on the thoroughness of the initial evidence collection and the scientific rigor applied during analysis.
Accident investigation and reconstruction
DEFINITION: Collection and analysis of evidence at the scenes of transportation accidents to create models explaining what happened.
SIGNIFICANCE: In determining responsibility for motor vehicle and other kinds of transportation accidents, forensic scientists attempt to reconstruct what happened during these events by analyzing the available evidence. The testimony of accident investigators often plays a role in criminal and civil proceedings that stem from accidents.
In the United States, transportation accident investigations and reconstruction are usually carried out by police departments. Some accident investigations, however, fall under federal jurisdiction. The National Transportation Safety Board (NTSB), formed in 1967 as part of the US Department of Transportation, replaced the Civil Aeronautics Board and expanded the role of the federal government in accident investigation and reconstruction. The NTSB became an independent agency in 1975; its duties include the investigation of all civil aviation accidents in the United States as well as all major railroad, highway, marine, and pipeline accidents and any transportation accidents that involve the release of hazardous materials. Private companies also offer accident investigation and reconstruction services.
Accident Investigators
When transportation accidents occur, law-enforcement agencies, insurance companies, manufacturers of the vehicles involved, and the persons involved, including those injured, all have an interest in understanding the causes of the accidents and in assigning responsibility. Police officers are normally the first individuals to investigate traffic accidents. Typically, when a serious accident has taken place, the police deal first with any injured people and any hazardous situations created by the accident; they then record information that will allow them to assess how the accident occurred. Most police officers in the United States receive at least brief training in accident investigation; some receive additional specialist training. The accuracy and completeness of the evidence collected by the police at an accident scene affect the degree of accuracy of the accident reconstruction.
In accidents that fall under the of the NTSB, the NTSB becomes the lead investigative agency. In such a case, the role of the local police department initially is to handle any casualties and hazards caused by the accident and then to preserve the scene to the greatest degree possible. NTSB specialists are experienced investigators with strong academic backgrounds in forensic science, physics, structural engineering, aeronautical engineering, and similar fields. NTSB investigators are qualified to serve as expert witnesses in court.
Insurance companies often have their own accident investigators. These investigators, as well as independent investigators hired by attorneys and other interested parties, often enter the accident and reconstruction process after much of the debris from the accident has been cleared away. They may have the opportunity to examine the damaged vehicles, but in attempting to reconstruct the accident, they usually depend on other evidence collected by the police at the accident scene.
Some disagreement exists among experts in accident reconstruction concerning the degree of training and education necessary to qualify an individual as an accident and reconstruction specialist and as an expert witness. Since 1991, the Accreditation Commission for Traffic Accident Reconstruction (ACTAR) has promoted voluntary standards for traffic accident investigators in order to encourage accuracy, consistency, and professionalism in accident investigation and reconstruction. These standards have not been universally adopted, however.
At the highest level, accident reconstruction specialists hold university degrees in engineering, mathematics, physics, or similar fields and have years of experience related to crash analysis and reconstruction. In the United States, the National Academy of Forensic Engineers is empowered by the Council of Engineering and Scientific Specialty Boards to certify accident investigation and reconstruction specialists as “diplomate forensic engineers.” This is the highest level of certification, the engineering equivalent of being a board-certified medical specialist. The International Institute of Forensic Engineering Sciences also awards diplomate status to qualified forensic engineers and professionals.
At the other end of the spectrum, individuals who do not even have high school diplomas can enroll in vocational training programs that focus on accident investigation and reconstruction. These programs call their graduates “certified accident reconstructionists,” although many lack the background to do the necessary mathematical analyses of accident scenes. Some courts in the United States have begun to reject certified accident reconstructionists as expert witnesses, requiring those who provide expert testimony on accidents to have higher levels of education and expertise.
The Investigation Phase
After immediate needs involving injuries and hazards have been attended to at the scene of an accident, the investigation phase begins. In collecting evidence at an accident scene, the investigators perform some or all of the following tasks: taking statements, photographing damage to vehicles and property, measuring and recording tire (skid) marks, recording paint and gouge marks, recording the postcrash locations of all vehicles involved, and recording the positions of all pieces of debris from the accident with photographs and measurements. Using this information, the investigators create a grid map of the crash scene that shows, with measurements, where each skid mark, vehicle, and piece of collision debris and damaged property is located in relation to all others.
Primary accident investigators also use a Haddon matrix to record situational evidence relative to the accident. This tool, developed around 1970 by Dr. William Haddon, the first head of what later became the National Highway Traffic Safety Administration, is a grid on which investigators record information about various conditions before, during, and after the accident at the accident scene. The most common Haddon matrix used for traffic accidents has three rows and three columns, creating nine cells. The rows represent events occurring before the crash, during the crash, and after the crash, respectively, and the columns identify the following factors that could have affected the accident in each time period: human factors (for example, impaired vision, precrash alcohol consumption, speeding, failure to wear a seat belt), vehicle and equipment factors (for example, failed brakes, nonfunctioning lights, malfunctioning airbags, poorly designed fuel tanks that leaked or exploded), and physical, social, and economic factors (for example, missing road signs, nonfunctioning traffic signals, absence of or poorly designed guardrails, cultural attitudes toward alcohol consumption or speeding, interference with or delayed emergency services response).
The Reconstruction Phase
During the reconstruction phase, accident investigators apply their knowledge of the laws of physics to the evidence to determine such elements as the speeds of the vehicles involved, the angle of initial impact, the occurrence of secondary impacts, mechanical failures that may have caused the accident, and environmental factors that may affect responsibility for the accident. Damage-based reconstruction is one of the oldest and simplest forms of accident reconstruction. In this approach, the reconstructionist looks at the damage done by and to vehicles and the damage caused to property.
By using information from vehicle manufacturers and applying knowledge of the laws of physics and structural analysis, the reconstructionist is able to determine the approximate rates of speed of the vehicles and their angle of impact. Damage-based reconstruction requires many assumptions and simplifications. For example, car manufacturers provide the results of crash tests for reconstruction engineers, but in using such results, a reconstructionist must assume that the vehicle involved in the accident had the same structural properties as a new vehicle of the same model that was used in the crash tests.
Ideally, damage-based reconstruction should be done in conjunction with trajectory-based reconstruction, which is based on the principle that momentum (speed multiplied by mass) is conserved in a crash. Starting with where the vehicles and debris ended up after a crash, reconstructionists work backward to determine the speed of each vehicle at impact. This method must also take into account forces such as the friction of tires on the road, which reduces momentum, and whether the road is wet or dry. The mathematics required to perform trajectory-based reconstruction can be complex, and software programs are available to help with these calculations.
Ultimately, the reconstruction of an accident is only as good as the original information provided by those who measured and recorded the accident scene. All reconstructions involve assumptions, simplifications, and interpretations. Good reconstruction engineers are able to explain their analyses and provide scientific justifications for their conclusions that will stand up to expert examination in a court of law.
Bibliography
Andrews, Dennis R. “Accident Reconstruction from the Outside In.” Claims 54 (June 2006): 18-22.
"Crash Investigation." Virginia Department of Motor Vehicles, 2024, www.dmv.virginia.gov/safety/programs/crashes. Accessed 12 Aug. 2024.
Hermance, Richard. Snowmobile and ATV Accident Investigation and Reconstruction. 2d ed. Tucson, Ariz.: Lawyers & Judges Publishing, 2006.
Palmer, Scott. “Fighting fraud with Forensic Intelligence.” Claims 55 (September 2007): 54-59.
Rivers, R. W. Evidence in Traffic Crash Investigation and Reconstruction: Identification, Interpretation, and Analysis of Evidence, and the Traffic Crash Investigation and Reconstruction Process. Springfield, Ill.: Charles C Thomas, 2006.
Wheat, Arnold G. Accident Investigation Training Manual. Clifton Park, N.Y.: Thomson/Delmar Learning, 2005.