2020 Heavy Haul Session
Dynamic Simulation of Locomotive Derailments on Crossover Track
Transportation Safety Board of Canada
A combined VIA passenger train derailed when exiting a CN No. 10 crossover at about 53 mph under air braking. The front truck of the middle locomotive derailed to the left side on the tangent track, but remained upright.
This investigation met two unusual challenges: first, the point of derailment was not on the closure curve, but on the tangent track exiting the crossover. Second, the lead locomotive did not derail but the middle locomotive of the combined train derailed.
A longitudinal train dynamics simulation indicated that the in-train force was at a minor level. A vehicle/track dynamics simulation was conducted to research the most likely derailment mechanism and answer the unusual aspects of this accident. The simulations conclude:
- The kinks and reverse closure curves generated high accumulating rock and roll dynamic response on the locomotives and reached the maximum at the exit of crossover.
- On the No. 10 crossover, the wheel lifting on the inner rail of the closure curve would appear at speeds over 45 mph. The locomotives might tip over outward on the closure curve at the extremely large carbody roll angle at speeds over 55 mph.
- The rock and roll dynamic response reached the maximum and the left lifting wheel rebounded from the impact at the exit switch kink and derailed on the tangent.
- The middle locomotive was in a compressive state, its front coupler could be in a zig-zag position, directed the wheelset at a larger angle of attack rebounding from the impact at the exit switch point than the lead locomotive whose front coupler was free, which might result in the different consequences.
- Comparatively on No.12 crossover, the derailment risk is low at speed below 50 mph, and wheel lifting appears at speed 55 mph and extremely large carbody roll angle shows up at speed over 65 mph. These simulated results confirmed the mechanism of tip over on the closure curves at speed of 67 to 70 mph in the several accidents that TSB investigated.