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Metro audit shows Red Line defect similar to the one that caused deadly 2009 collision

December 14, 2017 at 7:12 p.m. EST
This file photo shows the aftermath of the 2009 Red Line crash near Fort Totten. Nine people were killed and many injured when one Metro train rear-ended another. (James M. Thresher/For The Washington Post)

Metro officials said Thursday that this week’s Red Line disruptions and coming weekend shutdown stem from defects in the line’s signal system similar to the one that caused the fatal 2009 train collision near Fort Totten.

A recent audit and emergency testing in the past week found deteriorating insulation on the electrical cables used as part of Metro’s signal system — the network of electrical circuits that communicate the location of trains on the tracks — causing the cables to leak electricity in the area between the Brookland and Takoma stations.

Such leaking could lead to “bobbing circuits,” when the electrical current indicating a train’s presence on the track flickers on and off. Usually it’s a nuisance more than a safety issue, but a rare type of bobbing circuit can cause a train to briefly “disappear.” That was what happened in June 2009, when two Red Line trains collided, killing nine people.

For days before Red Line crash, circuit failures left Metro trains invisible

In this case, Metro officials said at Thursday’s board meeting, there were no indications from employees that problems were detected on that stretch of the Red Line — no trains mysteriously vanishing and reappearing from the display at the Rail Operations Control Center (ROCC), no malfunctioning speed controls visible to train operators, nothing that would indicate there was an urgent problem on the tracks.

Still, recent tests on the signal cables demonstrated there is a small chance that worn insulation would allow a train to “disappear” from the Automatic Train Control tracking system.

To compensate, Metro has been running the affected segment of the Red Line in a pattern known as “absolute block,” with only one train running at a time on each segment in each direction from Brookland to Fort Totten and from Fort Totten to Takoma. The restrictions have been in place since last weekend.

Joseph Leader, Metro’s chief operations officer, told board members Thursday that the limited train traffic on that section of the track was instituted out of an abundance of caution.

But he acknowledged there was a small chance that the deteriorated cables could cause the ROCC to lose sight of a train, or could erroneously instruct a train operator to proceed at full speed — even with another train idling ahead.

“It could be that we lose the location, it could be that [operators] lose a speed command, or it could be that they get the wrong speed command,” Leader said.

Metro General Manager Paul J. Wiedefeld said staff decided to act quickly to fix the problem.

“It reflects the way that we’re managing the system. If we suspect anything, we lean toward safety,” Wiedefeld said.

From the archives: Metro Red Line Crash Kills Nine

This weekend, Metro will shut down that three-mile stretch of track to conduct a hurried replacement of thousands of feet of cable, using Metro signal technicians and outside contractors working from the close of service Friday until Monday morning. The aim, Leader said, is to get service restored by Monday morning, although it’s not certain that will happen.

During the shutdown, shuttle buses will operate between Silver Spring and Rhode Island Avenue stations. Riders are advised to opt for the Green Line between Fort Totten and Gallery Place.

The segment of 40-year-old cables that will be replaced this weekend is in the same place where the 2009 collision happened. The investigation of that crash concluded that errant “flickering” in the signal system caused a train’s autopilot technology to receive the signal that the tracks ahead were empty, even though there was another train idling. The current cable deterioration could lead to similar errant signal communications — although it’s unclear whether such a defect could cause a train to vanish altogether.

. In the aftermath of the Fort Totten collision, Metro began a testing process for signal cables, using a time-intensive process called meggering. Segments of the signal cables are isolated and pumped with electric current. Workers then test to see whether any of that current leaks out, an indication that there is deteriorated insulation.

Metro completed a first round of testing — checking 7,500 cables — in 2014, then started the second phase. Phase two is supposed to be completed sometime in 2019. This year, officials decided to conduct an audit on the work completed so far.

The audit found that of the 1,435 cables tested since 2014, almost all the results were valid. Officials decided to retest 16 cables. Last Friday, they found one bad cable. On Sunday, they found a second. And by Tuesday, they decided it would be faster to just replace all 19,000 feet of cable between the Takoma and Brookland stations rather than keep testing to figure out which part of the cable was the source of the leak.

“In discussing the issue with [Metro’s general superintendent], we asked him, ‘Can you determine where the faults are?’ ” Leader told board members. “The defects could be in the splicing, the defects could be in the cable. . . . We realized that to allow them to continue to investigate and determine exactly where the faults are would not be the most prudent action. So we made the decision to shut down the Red Line and renew the whole cable.”

This week’s scare wasn’t the first time recent memory that officials have raised concerns about Metro’s handling of critical communication cables.

Automatic train operation won’t return to Metro anytime soon

Federal inspectors charged with overseeing the system issued alarming findings about the agency’s treatment of Automatic Train Control cables — responsible for protective functions such as spacing and speed control — in a report last year. The comments came in a 2016 review of SafeTrack work between West Falls Church and East Falls Church.

“Throughout the work area ATC cables were lying directly on the ballast, which could compromise the insulation of these cables,” the Dec. 22 report from the Federal Transit Administration said. “[Metro] should elevate the ATC cables off the ballast or implement a similar solution in order to preserve the insulation of these cables.”

The new details about the source of the problem that has caused commuting headaches for Red Line riders — fresh off a scheduled maintenance shutdown that started last month, — were shared at a Metro meeting where board members also discussed the future of Metro’s signal system, and whether the agency would return to the autopilot train technology that was in use before the Fort Totten crash.

The transit agency is at a crossroads, weighing whether to return to the decades-old system, which would require retraining Metro’s train operations staff, or whether to abandon it and opt for a new communication system.

Metro officials said Thursday that they are hiring consultants to determine the costs and logistical complexities that would be associated with Metro’s auto­pilot technology, which went into operation when the transit system debuted more than 40 years ago.

Faiz Siddiqui contributed to this report.