Accidentology: the reconstruction of traffic accidents

After protective accidentology measures are set up on-site (see article Road Accidentology: spotlight on precautionary measures), the loss adjuster proceeds to reconstruct the accident using calculations and accidentology software. The meticulous work carried out as part of the damage survey is supported by new 3D technologies used to scan and model the scene of the accident. Accidentologist Antoine Jarry explains the stages involved in his work.


Recreating the exact configuration using a 3D scanner

The accidentologist must carefully examine the configuration of the collision between the vehicles involved. The crash configuration determines the position and orientation of each vehicle involved in the accident at the time of the initial collision (ISO 12353-1 standard) and it indicates the exact position of participants at the precise moment of the collision I in a fixed coordinate system (ISO 6813-1998 standard).

New technologies like 3D scanners allow us to complete this stage even when the damage surveys are conducted at different locations. A 3D scan is taken of each vehicle involved and these scans are superimposed via special software in order to determine the precise angular position of the vehicles at the time of the crash.



Once the angular position of the vehicles at the time of the crash is confirmed, we can reposition them on the road using a detailed accident map created by the police or following the ground markings made by the police, which we make note of during our on-site damage surveys.


Analysing victim injury reports

The accidentology loss adjuster will then continue recreating the accident by analysing victim injury reports. This investigation reviews the medical data; although we are moving away from the work of an automotive technician, this is still an important step in the reconstruction stage. The injury report makes it possible to corroborate whether or not a seatbelt was worn (presence of chest injuries potentially leading to a collapsed lung, etc.). It also shows the initial collision points on the vehicle (the body of a person inside the vehicle always moves initially towards the point of impact*) and clears up any doubts about the places occupied by the protagonists (driver, front passenger, etc.).


Calculating the speed of vehicles before a collision

The calculation of the vehicles’ speed is measured during the different stages of the incident: post-collision stage and collision stage. At the moment of collision, certain indications such as braking marks or tyre scrubbing on the road help us understand the vehicle’s behaviour before impact and determine the driving speed before any avoidance action by the drivers (pre-collision stage).

The drivers’ reaction time is also an important data point to determine. This varies by age, weather conditions and physiological condition (fatigue, alcohol or medication consumption).

This calculation stage is obviously essential for determining whether or not the vehicles involved were following the speed limit at the time of the incident. If not, this brings up a crucial question to determine who is responsible: Could the accident have been avoided if the speed limit had been followed by vehicle A or vehicle B?


Using 3D modelling

After gathering all this vehicle speed and position data from the event, the loss adjuster accidentologist then proceeds to create a 3D model of the accident using a special software programme.



This modelling confirms or invalidates the previous calculations, thus confirming the results obtained.

In addition, the digital simulation provides a clear, simplified reading of the accident when a 3D video is created.

Remember, though, that the accidentology software only translates the data entered by the user. The model is an illustration of the analysis already completed by the accidentologist. Perfectly defining the collision’s configuration is still the most important part of accidentology analysis. The loss adjuster must know how to control the validity of the data entered and the consistency of the results obtained.


Antoine JARRY, Transport & Lifting Loss Adjuster

Find out more about his area of expertise


* In many cases, the kinematics of occupants inside a vehicle will cause injuries to their skin. These bodily injuries enable us to locate the initial impact on the vehicle, given that the body inside will always move towards the side of the collision.