Vehicular accident reconstruction
Encyclopedia
Vehicular accident reconstruction is the scientific process of investigating, analyzing, and drawing conclusions about the causes and events during a vehicle collision. Reconstructionists are employed to conduct in-depth collision analysis and reconstruction to identify the collision causation and contributing factors in different types of collisions, including the role of the driver(s), vehicle(s), roadway and the environment. The laws of physics and engineering principles such as the conservation of linear momentum, work-energy methods, and kinematics are the basis for these analysis and may make use of software to calculate useful quantities. The accident reconstruction provides rigorous analysis that an expert witnesses can present at trial
. Accident reconstructions are done in cases involving fatalities
, and often when personal injury
is involved. Results from accident reconstructions are also useful in developing recommendations for making road
s and highway
s safer, as well as improving safety aspects of motor vehicle
designs. These reconstructions are often conducted by forensic engineers, specialized units in law enforcement agencies
, or private consultants.
funded the first national guidelines for the standardization training in the field of traffic accident reconstruction in 1985. This led to the establishment of Accreditation Commission for Traffic Accident Reconstruction (ACTAR), an industry accreditation group. This field of motorcycle accident research was pioneered by Hugh H. Hurt Jr. His meticulous accident reconstructions of motorcycle accidents helped to explain that proper helmets reduced head injuries, most motorcyclists needed more driver training to control skids, and a large percertage of motorcycle accidents involved left-turning automobiles turning in front of the oncoming motorcycle.
, use of lights, turn signals, speed
, acceleration
, engine rpm, cruise control
, and anti-lock brakes. Witness
es are interviewed during accident 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 is frequently under-estimated by a driver, so an independent estimate of speed is often essential in accidents. 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 speed of the vehicle a few seconds for a collision.
typically depicts all or part of an accident 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.
Trial
A trial is, in the most general sense, a test, usually a test to see whether something does or does not meet a given standard.It may refer to:*Trial , the presentation of information in a formal setting, usually a court...
. Accident reconstructions are done in cases involving fatalities
Fatality
Fatality may refer to:* Death* Fatalism* A fatal error, in computing* Fatality , a finishing move in the Mortal Kombat series of fighting games* Fatality , a character published by DC Comics...
, and often when personal injury
Personal injury
Personal injury is a legal term for an injury to the body, mind or emotions, as opposed to an injury to property. The term is most commonly used to refer to a type of tort lawsuit alleging that the plaintiff's injury has been caused by the negligence of another, but also arises in defamation...
is involved. Results from accident reconstructions are also useful in developing recommendations for making road
Road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...
s and highway
Highway
A highway is any public road. In American English, the term is common and almost always designates major roads. In British English, the term designates any road open to the public. Any interconnected set of highways can be variously referred to as a "highway system", a "highway network", or a...
s safer, as well as improving safety aspects of motor vehicle
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...
designs. These reconstructions are often conducted by forensic engineers, specialized units in law enforcement agencies
Law enforcement agency
In North American English, a law enforcement agency is a government agency responsible for the enforcement of the laws.Outside North America, such organizations are called police services. In North America, some of these services are called police while others have other names In North American...
, or private consultants.
History
The National Highway Traffic Safety AdministrationNational Highway Traffic Safety Administration
The National Highway Traffic Safety Administration is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation...
funded the first national guidelines for the standardization training in the field of traffic accident reconstruction in 1985. This led to the establishment of Accreditation Commission for Traffic Accident Reconstruction (ACTAR), an industry accreditation group. This field of motorcycle accident research was pioneered by Hugh H. Hurt Jr. His meticulous accident reconstructions of motorcycle accidents helped to explain that proper helmets reduced head injuries, most motorcyclists needed more driver training to control skids, and a large percertage of motorcycle accidents involved left-turning automobiles turning in front of the oncoming motorcycle.
Investigation
Scene inspections and data recovery involves visiting the scene of the accident 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, brakingBrake
A brake is a mechanical device which inhibits motion. Its opposite component is a clutch. The rest of this article is dedicated to various types of vehicular brakes....
, use of lights, turn signals, speed
Speed
In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...
, acceleration
Acceleration
In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...
, engine rpm, cruise control
Cruise control
Cruise control is a system that automatically controls the speed of a motor vehicle. The system takes over the throttle of the car to maintain a steady speed as set by the driver.-History:...
, and anti-lock brakes. Witness
Witness
A witness is someone who has firsthand knowledge about an event, or in the criminal justice systems usually a crime, through his or her senses and can help certify important considerations about the crime or event. A witness who has seen the event first hand is known as an eyewitness...
es are interviewed during accident reconstruction, and physical evidence such as tire
Tire
A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...
marks are examined. The length of a skid mark
Skid mark
A skid mark is the mark a tire makes when a vehicle wheel stops rolling and slides or spins on the surface of the road. More generally, any solid which moves against another can cause visible marks, and is an important aspect of trace evidence analysis in forensic science and forensic engineering...
can often allow calculation of the original speed of a vehicle for example. Vehicle speeds is frequently under-estimated by a driver, so an independent estimate of speed is often essential in accidents. Inspection of the road surface is also vital, especially when traction has been lost due to black ice
Black ice
Black ice, sometimes called glare ice or clear ice, refers to a thin coating of glazed ice on a surface.While not truly black, it is virtually transparent, allowing black asphalt/macadam roadways to be seen through it, hence the term "black ice"...
, diesel fuel contamination, or obstacles such as road debris
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...
. Data from an event data recorder
Event Data Recorder
An event data recorder or EDR is a device installed in some automobiles to record information related to vehicle crashes or accidents. In modern diesel trucks, EDRs are triggered by electronically sensed problems in the engine , or a sudden change in wheel speed. One or more of these conditions...
also provides valuable information such as speed of the vehicle a few seconds for a collision.
Analysis
Vehicular accident reconstruction analysis includes processing data collecting, evaluating possible hypotheses, creating models, recreating accidents, testing, and utilizing software simulations. Like many other technical activities, accident reconstruction has been revolutionized by the use of powerful, inexpensive computers and specialty software. Various types of accident reconstruction software are used to recreate crash and crime scenes and to perform other useful tasks involved in reconstructing collisions. Accident reconstruction software is regularly used by law enforcement personnel and consultants to analyze a collision and to demonstrate what occurred in an accident. Examples of types of software used by accident 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 accident. Forensic animationForensic animation
Forensic animation is a branch of forensic science in which audio-visual recreations of incidents or accidents are created to aid investigators. Examples include the use of computer animation, stills, and other audio visual aids. Application of computer animation in courtrooms today is becoming...
typically depicts all or part of an accident 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.
See also
- Forensic engineeringForensic engineeringForensic engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. The consequences of failure are dealt with by the law of product liability. The field also deals with...
- Skid marks
- Forensic animationForensic animationForensic animation is a branch of forensic science in which audio-visual recreations of incidents or accidents are created to aid investigators. Examples include the use of computer animation, stills, and other audio visual aids. Application of computer animation in courtrooms today is becoming...
- Fatal Accident Reconstruction TeamFatal Accident Reconstruction TeamIn certain local police departments in the United States, the Fatal Accident Reconstruction Team is a group of police officers dedicated to investigating motor vehicle accidents that result in death. These type of investigations can involve vehicle on vehicle, vehicle on fixed object or vehicle on...
- Braking distanceBraking distanceBraking distance refers to the distance a vehicle will travel from the point where its brakes are fully applied to when it comes to a complete stop...