B-double jackknife reconstruction

When a pocket B-double tanker jackknifed on a sweeping downhill bend on a wet night, Advantia was engaged to reconstruct the incident by computer simulation. Project summary by Rob Di Cristoforo.

An air line had failed between the prime mover and trailers, causing the trailer axles to lock on the wet road. The combination reportedly jackknifed and the trailer wheels slid onto the steep verge, pulling the combination into a rollover.

Advantia was engaged to reconstruct the incident by computer simulation to confirm the sequence of events. Advantia put its TruckSim software package into action.

A necessary input into the reconstruction was a survey of the road, performed by a local surveyor, to provide the 3D road geometry in terms of lane curvature, crossfall, grade and cross-sections of the verge. The surveyed road geometry was input into the TruckSim environment.


Also required were the technical details of the combination: the prime mover and trailer specifications, all relevant dimensions, and the payload at the time of the incident. The on-board computer had recorded the speed at the time of the incident, which was also an input.

The only other information available was the point on the road at which the trailer tyres had crossed the road shoulder, and the location of a damaged fence post at the point where the combination came to rest against a fence. These locations were used to validate the results of the simulation. Both were identified by traffic cones in the simulation.

The rest was done by TruckSim. With all of the input parameters in place (the road geometry, the vehicle design, the load condition, the initial speed), all that had to be done was lock the trailer’s wheels at the right moment. The video below shows what happened next.

Incident reconstruction can help to determine the cause of an incident if there is any uncertainty. It can be used to rule out certain scenarios, such as conflicting witness statements. It can determine whether the incident could have b een avoided had a particular causal factor not been involved. It can also be used for driver training purposes. Reconstructions are admissible as evidence in court if Advantia is engaged as an expert witness.

Please contact Advantia for more information.

B-double jackknife reconstruction

Date Commenced
January 2015
Services Provided
Heavy Vehicle Simulation
Route Surveys and Route Assessments