Case study

Expert Witness: Commercial vehicle rollover

We provided independent expert advice on the likely cause of vehicle rollover that would form evidence at a legal dispute hearing.

The challenge

Frazer-Nash was asked to investigate the root cause of a road traffic accident involving vehicle rollover on a roundabout. We provided expert opinion on whether the accident had occurred as a result of human error, or whether the vehicle itself had not been fit for purpose.

The vehicle, a 4x2 tractor pulling a tri-axle flat bed trailer, was attempting to manoeuvre round the roundabout when it rolled over onto its nearside. That day the weather was reported to be windy and dry and no other vehicles were involved.


Our solution

We examined all witness statements, accident photographs, vehicle evidence and related documentation. We then surveyed the radius of the roundabout and contacted the Met Office to establish the potential impact that the wind may have had on causing the accident. This information was incorporated into our supporting calculations.

We also examined the stability of the vehicle and the weight distribution of the trailer, which was loaded with 88 bales of compressed fibre.

By considering the vehicle geometry and cross-referencing these estimates with photos of the accident, we could calculate the centre of gravity of the trailer. This was sufficiently high enough to warrant the vehicle being driven with extra caution.

At the time of the accident it is also possible that the vehicle’s load was not central due to inappropriate loading or the load shifting sideways during the manoeuvre. From our investigation we could conclude that the vehicle rolled over because it had manoeuvred around the roundabout at too great a speed for the given radius of the turn and the vehicle configuration.


The outcome

Our findings illustrated that the vehicle was fit for purpose and that the accident had occurred as a result of driver error.


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