NTSB Issues Safety Alert on Railroad Signals' Visibility

The agency's 35th Safety Alert concerns light-emitting diode railroad signals' ability to mask nearby incandescent signals, preventing the incandescent signals from being visible to train crews, and it cites a $3.2 million September 2014 accident in Kansas as evidence of the problem.

A new Safety Alert from the National Transportation Safety Board, the 35th it has issued, concerns light-emitting diode railroad signals' ability to mask nearby incandescent signals, which can prevent the incandescent signals from being visible to train crews. The alert cites a $3.2 million September 2014 accident in Galva, Kansas, as evidence of the problem. The accident involved two Union Pacific freight trains, one eastbound and the other westbound, and a new control point where LED signals had been installed just three days earlier. The eastbound train collided with the fifth car from the rear of the westbound train near the new control point, according to the alert.

Railroads are increasingly replacing traditional incandescent signals with LED signals and installing new LED signals, NTSB reports. "If LED and incandescent signals are installed in close proximity to one another, the LED signal may appear brighter or closer, causing crews to confuse the sequence of the signals as they approach. This effect may be more pronounced the closer the train gets to the signals," the agency warned Dec. 31 when it issued the alert.

Where LED and incandescent light units have been installed close together, the alert recommends actions that include evaluating the railroad computer-aided dispatching software to prevent confusion when lining routes non-sequentially at multiple control points; conducting a hazard analysis that includes testing signal visibility with input from train crews; and using configuration management.

NTSB explained that the UP dispatcher planned to route the westbound train onto a siding and have the eastbound train stay on the main track so the trains could pass each other. The computer-aided dispatch system stacked the requests, so the eastbound train should have been stopped at a red signal until the entire westbound train was in the siding. As the trains were passing, an incandescent signal at the east end of the main track displayed red, while the LED signal beyond it was displaying green. "Event recorder data show the engineer of the eastbound train advanced the throttle and increased the speed of the train as it continued past the westbound train. However, the end of the westbound train was still on the main track as the eastbound train passed, causing the eastbound train to collide with the side of the westbound train. Two locomotive units and four multi-platform intermodal cars on the eastbound train derailed; five multi-platform intermodal cars derailed from the westbound train. The train crew was not seriously injured in the accident, and there was no fire. The railroad estimated damages at $3.2 million," NTSB reported. "During the interviews with NTSB investigators, the train crew said they observed a clear or green signal and proceeded accordingly." NTSB's post-accident test of the signal's visibility indicated the new control point's green LED light was visually dominant and masked the red incandescent lamp.

Following the accident, Union Pacific implemented a procedure for dispatchers at the Harriman Dispatch Center in Omaha, Neb.; it prevents a dispatcher from lining the control point signals for a route in non-sequential order at Galva until a train clears the main track. And UP has changed the incandescent signal to an LED light unit and used a higher mast so the signal will be easier to see, and the railroad has reviewed other signal locations with signal block spacing of less than 10,000 feet and where LED and incandescent signals are used, according to NTSB.

All 35 NTSB Safety Alerts are available here.

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