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Traffic collision reconstruction is the process of investigating, analyzing, and drawing conclusions about the causes and events during a vehicle collision. Reconstructionists conduct collision analysis and reconstruction to identify the cause of a collision and contributing factors including the role of the driver(s), vehicle(s), roadway and general environment. Physics and engineering principles are the basis for these analyses and may involved the use of software for calculations and simulations. Collision reconstruction is sometimes used as the basis of
expert witness An expert witness, particularly in common law countries such as the United Kingdom, Australia, and the United States, is a person whose opinion by virtue of education, training, certification, skills or experience, is accepted by the judge as ...
testimony at
trial In law, a trial is a coming together of parties to a dispute, to present information (in the form of evidence) in a tribunal, a formal setting with the authority to adjudicate claims or disputes. One form of tribunal is a court. The tribunal ...
s. Collision reconstructions are performed in cases involving fatalities or
personal injury Personal injury is a legal term for an injury to the body, mind or emotions, as opposed to an injury to property. In common law jurisdictions the term is most commonly used to refer to a type of tort lawsuit in which the person bringing the suit ...
. Results from collision reconstructions are also sometimes used for making
road A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types of ...
s and
highway A highway is any public or private road or other public way on land. It is used for major roads, but also includes other public roads and public tracks. In some areas of the United States, it is used as an equivalent term to controlled-acces ...
s safer, as well as improving safety aspects of
motor vehicle A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on rails (such as trains or trams) and is used for the transportation of people or cargo. The veh ...
designs. Reconstructions are typically conducted by forensic engineers, specialized units in law enforcement agencies, or private consultants.


History

The
National Highway Traffic Safety Administration The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes" rel ...
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. 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.


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 A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Background ...
, use of lights,
turn signal The lighting system of a motor vehicle consists of lighting and signalling devices mounted to or integrated into the front, rear, sides, and in some cases the top of a motor vehicle. They illuminate the road ahead for the driver and increase th ...
s,
speed In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quanti ...
,
acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by ...
, engine
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensi ...
,
cruise control Cruise control (also known as speed control, cruise command, autocruise, or tempomat) is a system that automatically controls the speed of a motor vehicle. The system is a servomechanism that takes over the throttle of the car to maintain a st ...
, and
anti-lock brakes An anti-lock braking system (ABS) is a safety anti- skid braking system used on aircraft and on land vehicles, such as cars, motorcycles, trucks, and buses. ABS operates by preventing the wheels from locking up during braking, thereby maintai ...
.
Witness In law, a witness is someone who has knowledge about a matter, whether they have sensed it or are testifying on another witnesses' behalf. In law a witness is someone who, either voluntarily or under compulsion, provides testimonial evidence, e ...
es are interviewed during collision reconstruction, and physical evidence such as
tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface over which t ...
marks are examined. The length of a
skid mark A skid mark is the visible mark left by any solid which moves against another, and is an important aspect of trace evidence analysis in forensic science and forensic engineering. Skid marks caused by tires on roads occur when a vehicle wheel s ...
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 A road surface (British English), or pavement (American English), is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, hoggin, cobbles ...
is also vital, especially when traction has been lost due to
black ice Black ice, sometimes called clear ice, is a thin coating of glaze ice on a surface, especially on streets. The ice itself is not black, but visually transparent, allowing the often black road below to be seen through it. The typically low leve ...
,
diesel fuel Diesel fuel , also called diesel oil, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and ...
contamination, or obstacles such as
road debris Road debris, a form of road hazard, is debris on or off a road. Road debris includes substances, materials, and objects that are foreign to the normal roadway environment. Debris may be produced by vehicular or non-vehicular sources, but in all ...
. Data from an
event data recorder An event data recorder (EDR), more specifically motor vehicle event data recorder (MVEDR), similar to an accident data recorder (ADR) sometimes referred to informally as an automotive black box (by analogy with the common nickname for flight rec ...
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. Motorcycle collision reconstruction relies on knowledge of the five phases of a motorcycle collision. Perception–reaction: This is the phase where the rider perceives a collision hazard and decides on a response. Perception/reaction time is estimated at 1.1 to 1.5 seconds. Avoidance – braking/steering: In this next phase, the rider typically engages in some type of avoidance using steering or braking using the front brake, rear brake or a combination. Physical evidence at the scene combined with statements from witnesses can give clues as to what type of avoidance occurred. Pre-impact sliding: During braking, riders may overuse the motorcycle brakes, resulting in locking the front and/or rear wheel. If the front wheel locks, the rider will almost certainly lose control and crash. If the rider loses control and crashes while braking, the motorcycle and rider usually separate and slide in the same trajectory they were moving in before the crash. Impact: The bike and/or rider may collide with other object like a vehicle or guardrail. Damage caused by impact can be evaluated and combined with sliding distance to help determine the motorcycle's speed during the collision sequence. Post-impact motion: After impact, additional movement to the point of final rest can occur. The rider frequently separates from the motorcycle and travels independently to the final point of rest. Analysis of post-impact travel distance can also determine speeds associated with the collision.


Training facilities (North America)

The
Royal Canadian Mounted Police The Royal Canadian Mounted Police (RCMP; french: Gendarmerie royale du Canada; french: GRC, label=none), commonly known in English as the Mounties (and colloquially in French as ) is the federal police, federal and national police service of ...
conducts On-Scene Collision Investigation (Level-2), Advanced Collision Analysis (Level-3), and Forensic Collision Reconstruction (Level-4) as well as Commercial Vehicle Collision and Pedestrian/Bicycle Collision courses at the Pacific Region Training Center (PRTC) located in Chilliwack, British Columbia. These courses are also available to Non-RCMP Police Agencies. Northwestern University Center for Public Safety conducts Traffic Crash Investigation courses utilized by both law enforcement and public agencies. The Institute of Police Technology and Management (IPTM) is a recognized institute for Crash Investigation for Law Enforcement as well as professional agencies.


Law enforcement / police agencies

The
Royal Canadian Mounted Police The Royal Canadian Mounted Police (RCMP; french: Gendarmerie royale du Canada; french: GRC, label=none), commonly known in English as the Mounties (and colloquially in French as ) is the federal police, federal and national police service of ...
utilize full-time Forensic Collision Reconstructionists and Analysts as a service line. In British Columbia, they are referred to as ICARS (Integrated Collision Analysis and Reconstruction Service). ICARS units are located in each RCMP District within the Province of B.C.
California Highway Patrol The California Highway Patrol (CHP) is a state law enforcement agency of the U.S. state of California. The CHP has primary patrol jurisdiction over all California highways and roads and streets outside city limits, and can exercise law enforcem ...
utilize a team deployment called MAIT ("Multidisciplinary Accident Investigation Team"). Each team consists of inspectors with specialized training in traffic collision reconstruction, traffic engineering, automotive engineering, and vehicle dynamics. MAITs are composed of one CHP sergeant (the team leader), two or more CHP officers, one Motor Carrier Specialist I (MCS I), and one Senior Transportation Engineer from Caltrans.California Highway Patrol, Multidisciplinary Accident Investigation Teams
, Accessed 2014-Oct-17


See also

*
Accident data recorder The accident data recorder (ADR, German commonly abbr.: UDS, also accident (data) writer), is an independent electronic device that records before, during, and after a traffic accident relevant data and thus resembles a flight recorder. It ca ...
*
Assured clear distance ahead In legal terminology, the assured clear distance ahead (ACDA) is the distance ahead of any terrestrial locomotive device such as a land vehicle, typically an automobile, or watercraft, within which they should be able to bring the device to a h ...
* Forensic animation *
Forensic engineering Forensic engineering has been defined as ''"the investigation of failures - ranging from serviceability to catastrophic - which may lead to legal activity, including both civil and criminal".'' It includes the investigation of materials, produ ...
*
Human factors Human factors and ergonomics (commonly referred to as human factors) is the application of psychological and physiological principles to the engineering and design of products, processes, and systems. Four primary goals of human factors learnin ...
* Skid marks * Total stopping distance


References


External links


National Highway Traffic Safety Administration
{{Road accidents Traffic collisions Law enforcement techniques Forensic techniques