Monday, April 30, 2012

Reaction to Switch Malfunction Led to Derailment

What should have been a story about how things went right for Metro turned instead into a derailment, according to several sources familiar with the incident and subsequent investigation.

As the Washington Post reported, the operator of the train saw a red signal at the switch just inside the tunnel on the western end of Rosslyn station. In technical terms, the switch was "out of correspondence."

Correctly, the operator notified operations control center (OCC) which then ordered the operator to hold the train, perform a visual inspection of the switch and get assistance from "nearby crew."

That crew was was an automatic train control (ATC) technician who installed a clamp to the malfunctioning switch. The clamp, had it been properly installed, was supposed to keep the switch in the correct position and would have allowed trains to proceed without incident.

While the ATC tech may have felt the clamp was installed tightly, they apparently failed to notice a "small obstruction" in between the switch point and main track on the switch which prevented the clamp from "tucking" the point snugly under the main rail, leading to the derailment, said sources.

Here's how Metro's own internal reporting system described the incident:
At 2025hrs ATC Supervisor Craven informed MOC that switch 3 was clamped normal, but the switch was clamped with a 2 inch gap and was not tucked.
One source said it was possible that the gap was initially much less than two inches and may have looked OK. They said it's possible that the train wheels, as they derailed, forced the gap to widen to the reported two inches.

According to two sources, after installing the clamp, the tech was supposed to "check the point" to make sure it was properly tucked under the main rail.

"You have to inspect everything," said an ATC worker. "If anything like this happens, it's ATC's fault. The guy should have checked the point. He was just being lazy."

Other sources said that the obstruction in the switch was a "fluke" or "freak occurrence," but they agreed there is no excuse for the ATC tech or the operator not to notice something was still wrong even after the clamp was installed.

This particular tech, two sources confirm, has been written up once before for falling asleep in a truck.

According to Metro's own handbook, "Cranking and Blocking of Switches":
According to FRA specifications, a switch point must close within 1⁄4’’ of the stock rail. In some cases, the point may have a slight opening, but the tip is still under the head of the stock rail. This is perfectly fine.
If a switch point is not within 1⁄4’’ of the stock rail, it is not safe for the passage of trains. If a switch has been damaged by trailing or other accident, it might not be possible to get the switch point to tuck. In this case, train movement must not be allowed over the switch.
And, as with most Metro problems, things were only made only worse by operations control center's (OCC) disconnect from what actually happens on the tracks, said one source.

At first, said one source, OCC was "was under the impression the train was completely in the tunnel" when the majority of the train was actually still on the platform.

Furthermore, Metro's standard operating procedure for a derailment dictates that power is to be cut for both tracks. It makes sense in most places as the tracks are side by side.

However, at Rosslyn (and Pentagon) the tracks are not side by side, they're on different levels, meaning it would have been safe to single track through the area, causing less of a service disruption.

Since the staff at OCC apparently did not realize Rosslyn's configuration, they issued an order to cut power to both tracks and establish a shuttle bus bridge around Rosslyn.

This led to initial confusion for riders at the scene immediately after the derailment.

After about 30 minutes, with several pleas to single track form those on the scene, OCC realized it could single track safely through Rosslyn and the bus bridge was aborted.

"When sh*t really hits the fan, I have to trust my life to those people [at OCC], said one veteran Metro worker. "The only information is what I'm getting from them. That's a scary proposition.They just had a bunch of new controllers come in off the street. They don't know the system."

Other items:
Silver Line phase II in doubt (WaPo)
Advocates question elimination of peak of the peak (Examiner)
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