Visualization of Estimated Derailed Car Motion
The three‐dimensional animation shows the estimated derailed car pileup sequence that began at about 12:50:43 a.m. local time. The Office of Research and Engineering reconstructed the train motion to help assess the initial energy state, path, and mechanical impact damage of each derailed car. On-rail vehicle motion was reconstructed from locomotive event recorder, external video, and external audio data as well as car, track, and wayside infrastructure data. Google Earth Pro was used to render the reconstructed train motion.
Derailed car motion was derived from car on-rail and post-derailment position and orientation data as well as the entry speed of the trailing cars recorded by the rear locomotive. Interpolation was used to define the path of each derailed car between its onrail and at rest positions. The resulting derailed car motion is not strictly time accurate, kinematically consistent, or the product of a fully validated, first-principles-based physics model.
Two views of the estimated derailed car pileup sequence are included. The local time after midnight, lead and trailing locomotive consist speed, and throttle position are presented in the right-hand side upper frame. The lead locomotive external camera view looking forward is shown in the lower frame. The lead locomotive external audio data are also synchronized.
The unintended emergency brake application, ethanol ignition and combustion events, and post-accident drone survey data are annotated in the region above the right-hand side upper frame.
The animation does not attempt to portray actual time of day, season, weather, or lighting conditions, except as recorded by the lead locomotive external camera. Car collision dynamics, deformation, component separation/damage, track and bridge damage, and environmental damage are not depicted, except as documented by the aerial drone survey.
Each of the two animation segments begins at 00:49:49 a.m. with a chase view of the eastbound lead locomotive consist, a buffer car, and the first five tank cars. At this time, the train is approaching the bridge over Jack Creek at a speed of 31 mph with the throttle in the idle position.
First Animation Segment
At 00:50:11 the camera transitions from chase view to overhead view as the lead locomotive begins to transit the bridge. Car line number 21, the most forward derailed tank car, comes into view from the bottom of the screen at 00:50:37 with the train speed reduced to 29 mph.
At 00:50:43 an annotation states that the derailed car motion was estimated as car line numbers 21 through 24 begin to derail. At this time car line number 21 is near the bridge midpoint, car line number 22 is straddling the transition region between ballasted roadbed and the bridge, and car line numbers 23 and 24 are trailing on the west approach to the bridge. An emergency braking annotation then appears.
Car line number 21 comes to rest south and east of the bridge, car line number 22 comes to rest south of the east end of the bridge, and car line numbers 23-27 pile up in sequential order, perpendicular to the original bridge with car line number 23 near the bridge midpoint.
Car line number 28 cleaves car line numbers 26 and 27 in half and travels over car line number 25, ending up pitched down nearly parallel to the original bridge with its forward end in Jack Creek.
At 00:50:53 an ethanol ignition/combustion annotation appears as the lead locomotive external camera view transitions from nominal background darkness to near daytime illumination levels at 00:50:59 and then back to nominal background darkness at 00:51:03.
Car line numbers 29-32 pile up sequentially in accordion fashion to fill in the gap at the west end of the original bridge. Car line numbers 33-40 continue to pile up sequentially in zig-zag fashion on the west approach to the bridge. All trailing cars aft of the bridge come to rest by 00:51:12, as the lead locomotive consist and car line numbers 1-20 continue forward at 9 mph with emergency brakes applied. The forward train section comes to rest at 00:51:22.
The aerial drone survey image is overlaid on the scene terrain about 00:51:30 with an accompanying annotation. The drone survey data enable the viewer to compare the estimated at-rest derailed car positions and orientations to the available factual evidence.
Second Animation Segment
The second animation segment differs from the first segment as follows:
1. At 00:50:11 a half-orbit camera view transitions from the original chase view to a view looking toward the approaching string of trailing cars from a position just north of the east end of the bridge.
2. Car line number 21 comes into view from the left side of the screen at 00:50:33 with the train speed reduced to 30 mph and the throttle still in the idle position.
30 окт 2018
