Case Study – Multiple Occupant Ejection

This case study involves a dual ejection, single vehicle incident which was investigated by Advanced Simtech in the UK for Avon and Somerset Police during 2007.

There was insufficient data to allow the case to be solved using other well-established police methods. Our methodology and toolsets allowed the incident to be successfully reconstructed, securing a conviction as a direct result of our analysis.

The reconstruction was conducted in two separate phases. The purpose of the first phase was to obtain an accurate motion for the vehicle during the event- using a vehicle dynamics reconstruction simulation that correlated to the physical evidence and tyre markings left at the scene. This was followed by an occupant analysis phase which focused on the opportunity of ejection for the people involved. Both phases incorporate DOE techniques which allow us to understand fully the effect and influence of each of the input parameters involved.

(This case study was published at the 2008 EVU Conference)

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Case Study:   Dual Ejection (published at 2008 EVU Conference)  

Customer:    Avon & Somerset Police


Case Overview

This incident involved a single vehicle, carrying two unrestrained occupants.

  • The vehicle entered a narrow village road and a loss of control on a right hand bend led to it leaving the road along a curved path to the right hand side, while rotating in a clockwise direction.
  • The front of the vehicle then impacted a lamp post stone wall, resulting in a violent spin.
  • The post-impact motion of the vehicle consisted of almost two full rotations, during which both occupants were fully ejected, one of whom later died of the injuries sustained.

The survivor stated that the deceased was driving at the time of the collision.





To reconstruct the collision and ascertain the validity of the statement made by the surviving occupant.


Summary of Case Results – Vehicle Motion

Based on the simulation work carried out, it was concluded that the driver lost control of the vehicle while travelling at approximately 60 miles per hour, as a result of deceleration followed by sharp steering input to the right.

These inputs caused the vehicle to begin yawing in a clockwise manner, following a curved path onto the opposing lane of the road. This is indicated by the geometry of the tyre marks which is consistent with only this type of motion.

The tyre marks also indicate that, by the time it reached the roadside objects, the vehicle was travelling fully sideways, presenting its nearside front corner to a heavy impact.

This impact caused the vehicle to rotate rapidly in a clockwise direction. After almost two full rotations, the vehicle then came to rest facing the original direction of travel.


Summary of Case Results – Occupant Motion

Initially rather than using detailed occupants we utilised a simple projectile study to allow us to understand the timing required for each of the occupants to leave the vehicle from one of three possible locations.

This study clearly demonstrates that the three possible ejection points have minimal effect on where the occupants would end up, whereas the time that they left the vehicle was the major contributory factor to their end position. 

The occupant simulation work provides a very strong indication that the occupant found furthest from the crash site was the driver of the vehicle. The deceased occupant, found nearest the crash site, was the passenger. 


A conviction of Causing Death by Dangerous Driving was secured based on our findings.

With ever increasing applications, specialized software and highly advanced methodologies; contact Advanced Simtech today to find out how we could benefit your organization.

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If you have any questions about any of our specialist engineering services including Occupant Biomechanics, Vehicle Safety Systems such as restraints and airbags, Advanced Driver Assistance Systems (ADAS), Autonomous Vehicles or 3D Data Capture and Processing, please do not hesitate to get in touch. Our knowledgeable, professional, and experienced team is always on hand to answer any of your questions.

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Stratford Upon Avon, CV37 8NF

Tel: +44 (0) 1789 264 782

Advanced Simtech Ltd.

Simtech Ltd

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    Advanced Simtech is an privately owned engineering consultancy specialising in the areas of human biomechanics, vehicle safety and real world accident reconstruction.

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    Advanced Simtech

    Alscot Estate, Atherstone Hill, Atherstone on Stour
    Stratford Upon Avon
    CV37 8NF

    +44 (0) 1789 264 782