Signal Failure in Fatal DC Metrorail Collision
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IMAGE SOURCE: Wikimedia Commons/ Red Line New York Avenue Metro Station, Washington D.C. / author: Ben Schumin, November 2004
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Safety failures found in an investigation since the Washington D.C. Metro subway system crash last summer have the government issuing a nationwide rail alert.
On June 22, two Washington Metropolitan Area Transit Authority (WMATA) trains on the above-ground section of the Red Line near the Fort Totten station collided. The rush hour wreck killed nine people and injured 70.
Now the National Transportation Safety Board (NTSB) is putting out an alert to other urban areas with the same kind of train control systems using audio frequency track circuits.
After a three-month-investigation, the NTSB finds that a failure occurred when a “spurious signal” generated by a track circuit module transmitter sounded like a valid track circuit signal.
A receiver heard the signal but failed to detect the signal of Metrorail train 214. That’s when Metrorail train 112 plowed into the back of it overriding the rear car by about 50 feet.
There was no communication between the train operators and Metrorail Operations Control Center before the collision, and train 112 received no command to slow or stop in order to maintain train separation.
The NTSB has issued these warnings to the Washington Metropolitan Area Transit Authority and to Alstrom Signaling, Inc. that makes the track circuit modules to monitor track circuits and check on the electronic components elsewhere in the system.
In a news release September 22, the agency says :
“Although the NTSB's investigation is not yet complete and no determination of probable cause has been reached, the NTSB is concerned about the safety of train control system circuitry used in comparable rail and transit operations in other parts of the country. Therefore, the NTSB recommended that the Federal Transit Administration (FTA) and the Federal Railroad Administration (FRA) advise all rail transit operators and railroads that use audio frequency track circuits in their train control systems about these findings from the Fort Totten accident investigation. “
The National Transportation Safety Board (NTSB) is an independent federal agency that investigates transportation accidents to find a cause and solution.
A track circuit signal is an audio frequency signal that is generated in the train control room at each station by a module transmitter. A cable is used “to send the modulated signal to a transmitter impedance bond, which is mounted between the rails and injects the signal into the rails,” says the Safety Recommendations letter to the general manager of WMATA.
IB News reported last June that the operator of the train, 42-year-old Jeanice McMillan, who was killed in the collision, had been on the job for three months after receiving six weeks of training. The story continues that the cars involved in the deadly crash were cited as unsafe three years ago, but were never replaced due to the cost.
The Red Line was constructed in the 1970s. NTSB investigators found that a portion of the track was replaced five days before the accident requiring the track circuit signal strength to be adjusted.
It’s not clear how many rail systems use this type of train detection system since neither the NTSB or Federal Transit Administration keeps a list of such systems, reports CNN. But the NTSB says all railroads should be informed about the system failure and that rail systems that use audio frequency track circuits examine their systems for unintended signals that could cause a track circuit to fail to detect a train.
WMATA should examine track circuits within its system and develop a program to periodically review the electronic components in the train control system, the NTSB says in a Safety Recommendation letter to WMATA.
The NTSB is continuing its investigation into the exact cause of the crash. #