Case Overview

A modern SUV carrying three occupants left the road after the driver failed to negotiate a hump-back bridge and lost control. The vehicle was then involved in a series of impacts as it travelled along the scene, ending with a tree impact into the rear door on the passengers side of the vehicle. The tree impact resulted in severe damage to the door area, allowing the door to open as the vehicle subsequently moved away from the tree.

The belted front seat passenger was unhurt and remained wholly within his seat. Of the two remaining occupants, one was ejected from the vehicle and received minor injuries; the other was found fatally injured lying between the front seats, with his upper body resting on the back seat.

Objective

Advanced Simtech were asked to carry out detailed analysis of the vehicle and scene in order to discover the identity of the driver. In the event that the survivor was shown to have been in charge of the vehicle, he was likely to face a charge of Causing Death by Dangerous Driving.

Solution/Methodology

The investigation mainly drew upon our tried and tested vehicle and occupant simulation techniques, along with interior examination and laser scanning.

A scene survey supplied by the collision investigation unit was supplemented by our own laser scan of the collision site and a significant portion of the road leading up to it.

A detailed interior examination was performed using our 3D laser scanner. The image below shows the interior data in plan view, illustrating the damage to the occupant space.

The photograph below shows the stripped down front passenger seat frame, situated in the vehicle.

By interrogating vehicle interior to this level, Advanced Simtech are able to gain unique insight into how occupants have moved and interacted during a collision.

A detailed MADYMO simulation of the collision was created, including a vehicle model of appropriate mass properties and with functioning suspension, steering and braking systems.

As seen in our previous work, by the aim was to correlate to the physical markings at the scene by varying several key parameters such as those relating to speed, steering, braking and many more. In this case, over 30,000 iterations were carried out in order to achieve the required level of correlation.

The calculated motion was then applied to an interior model containing 3 virtual occupants. The building of this model was aided by the laser scan data, ensuring accuracy of geometry

Results

By applying the calculated motion to the occupant model, it was possible to clearly identify the trends in the resulting occupant interactions and trajectories.

The main outcomes were:

– The rear occupant showed clear tendency to eject via the nearside rear door.
– The driver model showed no tendency towards ejection via any route
– The driver consistently moved towards the rear, coming to rest in the gap between the front seats
– The drivers motion was consistent with the lateral deformation observed on the passenger  seat.

Conclusion

Based on the above findings, Advanced Simtech were able to state that

– the deceased occupant was the driver of the vehicle
– the ejected occupant was seated in the rear at the time of the incident

As a result, the Police force was able conclude its enquiries on the basis that there was no accountability amongst the surviving occupants.