Collision Reconstruction Glossary & Terminology
A reference glossary of collision reconstruction, vehicle electronic-data and crash-scene investigation terminology. These definitions are provided for professional education and do not constitute legal advice or a guarantee regarding any matter or outcome.
Collision Reconstruction
The technical analysis of available physical, vehicle and roadway evidence to evaluate how a motor vehicle collision occurred. Also called accident reconstruction or traffic crash reconstruction. A reconstructionist applies physics, engineering principles and forensic methods to reach objective technical conclusions.
Collision ReconstructionAccident Reconstruction
A common alternate term for collision reconstruction. M&M Security Services uses 'collision reconstruction' as its preferred professional terminology; the terms describe the same technical discipline.
Collision ReconstructionCrash Reconstruction
Another term for collision reconstruction — the technical evaluation of how a crash occurred using available evidence.
Collision ReconstructionEvent Data Recorder (EDR)
A device in many vehicles that records certain information related to a crash event, such as vehicle speed, brake status and throttle position in the seconds before, during and after impact. Not every vehicle has an EDR, and the data recorded varies by manufacturer, model and year.
Crash Data Retrieval (EDR/ACM)Airbag Control Module (ACM)
The electronic module that controls airbag deployment. In many vehicles, the ACM also serves as the Event Data Recorder (EDR), storing crash-event data. ACM data availability and content vary by manufacturer, model and year.
Crash Data Retrieval (EDR/ACM)Crash Data Retrieval (CDR)
The technical process of downloading available event data from a supported vehicle's EDR or ACM using specialized equipment. Retrieval is a distinct step from interpreting what the data means in the context of a specific collision.
Crash Data Retrieval (EDR/ACM)Vehicle "Black Box"
A common term for the event data recorded by a vehicle's EDR or ACM. Unlike an airplane flight recorder, a vehicle EDR typically captures only a short window of data around a crash event, not a continuous recording.
Crash Data Retrieval (EDR/ACM)Engine Control Module (ECM)
The electronic control unit that manages a commercial truck's diesel engine. In many heavy vehicles, the ECM may also record event-related data such as hard-brake events, vehicle speed and engine RPM. Data availability depends on the engine manufacturer and model.
Heavy-Vehicle Data RetrievalAnti-lock Braking System (ABS) Module
The module that manages commercial-vehicle braking and may store braking-event data. ABS module data availability depends on the system manufacturer, model and the vehicle's configuration.
Heavy-Vehicle Data RetrievalHeavy Vehicle
A commercial vehicle such as a tractor-trailer or 18-wheeler. Heavy vehicles use different electronic systems, braking configurations and data-storage methods than passenger vehicles, and their inspections may involve multiple modules and physical brake examinations.
Heavy-Vehicle Data RetrievalSpeed Analysis
A reconstruction method that uses physical evidence such as skid marks, yaw marks and vehicle damage to estimate vehicle speeds before and during a collision. The methods and accuracy depend on the quality and quantity of available evidence.
Collision ReconstructionCrush Analysis
A reconstruction method that evaluates the extent and pattern of vehicle deformation to estimate the energy involved in a collision and the change in velocity (Delta-V). It is one of several analytical tools a reconstructionist may use.
Collision ReconstructionTime-and-Distance Analysis
A reconstruction method that examines the timing and spacing of events to evaluate questions such as how long a driver had to react or whether a collision was avoidable. It relies on accurate measurements and the available evidence.
Collision ReconstructionDelta-V (ΔV)
The change in velocity experienced by a vehicle during a collision. Delta-V is often estimated through crush analysis and electronic data and is one factor a reconstructionist may consider when evaluating a crash.
Collision ReconstructionCrash Scene Investigation
The documentation and examination of physical evidence, roadway conditions, traffic-control information and available visual evidence at the location of a collision. Also called collision scene or accident scene investigation.
Crash-Scene InvestigationScene Documentation
The recording of physical and visual evidence at a crash scene, typically through photography, drone documentation, video, measurements, CAD diagrams and 3D scanning. Early scene documentation helps preserve information that may be lost quickly.
Crash-Scene InvestigationCAD Scene Diagram
A scaled drawing created using measurements taken at a crash scene that shows the roadway, vehicles, physical evidence and other relevant features. CAD (Computer-Aided Design) diagrams can be used for analysis, reports and trial exhibits.
Crash-Scene InvestigationWitness Canvassing
The process of identifying and interviewing people who may have seen a collision or its aftermath. Witnesses are not always available, and canvassing identifies what is present rather than guaranteeing results.
Crash-Scene InvestigationExpert-Witness Testimony
The presentation and explanation of technical findings under oath in deposition or at trial, subject to cross-examination. A reconstructionist may provide expert reports and testimony in civil and criminal proceedings. Testimony does not determine legal liability, which is the role of the court or jury.
Collision ReconstructionExpert Report
A written document that records a reconstructionist's findings, methods and conclusions. An expert report may support deposition or trial testimony and is prepared based on the evidence available for the specific collision.
Collision ReconstructionRelated Resources
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