WMATA circuit failure

Apparently, the Frederick (Maryland) News-Post, in "Source: Metro circuits were malfunctioning for five days," reported one week before the Washington Post, about the nature of the circuit failure on the subway's Red Line, which led to the Monday June 22nd crash and nine deaths.

Reading the original article:

The documents show what is known as "flip-flopping," with the circuit alternately reporting the track as "occupied" and then "vacant." The report for track circuit number B2-304, where the stopped train was located, starts at 4:45 p.m. and ends at 5:38 p.m., about 40 minutes after the crash.

Throughout the time period covered by the report, the circuit shows the track either occupied or vacant as often as every couple of seconds.

At 4:57:03 p.m., about the time of the crash, the report shows the track to be vacant until 5:37:44, when it reports the track is occupied. Less than a minute later, the report again states the track was vacant, even though train wreckage was on the track. One second after that, the track was reportedly occupied again. The circuit flip-flopped again before finally showing the track to be occupied at 5:38:40.

and reading the Post article, "Metro Failed to Detect Hazard Before Deadly Crash," it appears as if WMATA leaders understate the significance of the problem:

Five days before last week's deadly Red Line accident, a Metro crew replaced a key piece of equipment designed to prevent crashes, but the circuitry malfunctioned and no one at Metro detected the problem, investigators and transit officials said yesterday. ...

n the aftermath of the crash on the Red Line between the Takoma and Fort Totten stations, Metro officials analyzed track circuit data and found that one circuit in the crash area intermittently lost its ability to detect a train. The circuit would report the presence of a train one moment, then a few seconds later the train would "disappear," only to return again.

The problem started shortly after June 17, when a Metro crew replaced a device known as a Wee-Z bond, a crucial part of the system that maintains a safe distance between trains, said Dave Kubicek, Metro's rail chief.

Instead of completely failing, the track circuit "fluttered" on and off so quickly that, Kubicek said, the failure would not have been obvious in Metro's downtown operations center, where controllers monitor real-time movement of trains by watching an illuminated graphic depiction of the 106-mile railroad.

"It was happening so fast, you would just blink and miss it," he said. "Realistically, you had to be looking at the exact area at the exact place" at the exact time.

It seems that at some point over five days, this problem should have been detected. It wasn't. And that newly installed circuits should have been rigorously tested after installation...