The Advisian team worked with its client to identify the cause of a derailment, to provide guidance on preventing future derailments, and to design and install an improvement that increased vehicle stability, allowing a temporary speed restriction to be lifted.
Our client operates rail services across a large metropolitan area, and are also responsible for the maintenance of assets including tracks, trains, signals, stations and facilities. In 2016, a track maintenance vehicle derailed on a section of the rail network, causing considerable delays to both passenger and freight services. An initial investigation of the incident found that both the track and vehicle were compliant to applicable standards. The most likely cause of the incident was the combination of vehicle design parameters and allowable track defect conditions.
As this type of derailment involving multiple factors was new to the client and presented a new and unquantified risk, speed restrictions were imposed on all similar track maintenance vehicles. This subsequently caused further delays to both network traffic and maintenance activities. Understanding this was a short-term solution only, the client sought to engage a suitably qualified consultant to investigate the cause of the derailment, so the imposed speed restrictions could be lifted.
Specifically, the consultant would need to:
• Undertake dynamic modelling of the derailed vehicle to determine the cause of derailment;
• Determine the overall performance of the fleet of the single-axle track maintenance vehicles to a range of track and operational conditions; and
• Advise on how to mitigate potential derailment risks for this type of vehicle.
Advisian won the assignment and developed a model of the derailed vehicle (below), validating it against real-world physical tests. A detailed simulation was then undertaken, using measured track conditions of the derailment site. The cause of the derailment was determined to be unstable body dynamic roll behaviour through excitation of the vehicle’s body roll mode, as well as a lack of vehicle damping.