A computer implemented method of reconstructing vehicle behaviour for a vehicle that has been subject to a critical event, the method comprising: receiving vehicle sensor data associated with vehicle motion; receiving a critical event notification signal, the critical event notification signal being associated with a critical event time for the critical event; deriving, from the received vehicle sensor data, a vehicle trajectory within a time window prior and adjacent to the critical event time; analysing the vehicle trajectory to determine forces acting through the vehicle system; outputting a notification signal in the event that one or more of the determined forces exceeds one of more of the operating parameters of the vehicle.