WASHINGTON -- The signaling system that detects stopped trains on the tracks of Washington's transit system has been having problems for a year and a half in the area where a fatal crash occurred last month, according to federal investigators.
In its investigation of last month's deadly Metro train crash, the National Transportation Safety Board said records show the signaling system on the track circuit where the accident occurred has been intermittently malfunctioning since a piece of equipment was replaced in December 2007.
The equipment, known as an impedance bond, communicates information such as speed and distance between the tracks, trains and operations control center. None of the fluctuations would would cause the loss of the track circuit's ability to detect trains, Metro said. Investigators said earlier this month that an impedance bond at the other end of the same stretch of track had been replaced five days before the accident and failed periodically before the crash.
The NTSB is looking to see whether any trouble ticket reports from the past 18 months or records from train operators might have noted problems with the circuit. "Anomalies" also have been found on other circuits, the board said, and investigators are trying to find out whether the problems are similar to those found near the accident site.
“Though we have found anomalies in other areas of the rail system, we have not found anything that resembles the magnitude of the track circuit problem at Fort Totten,” Metro General Manager John Catoe said.
Federal investigators said they also are working to determine if other factors could have interfered with the automatic train control system, such as system upgrades and changes.
Nine people were killed and more than 70 injured June 22 when a train slammed into another train stopped on the tracks near the Maryland state line. Since then, Metro has been running all trains in manual mode and has found areas beyond the crash site where signaling equipment has malfunctioned.
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The transit agency has increased its track circuit reviews from once every 30 days to twice a day. After each rush hour, engineers review reports and investigate each anomaly they find.
“It’s important to know that an anomaly does not necessarily indicate a failure in the track circuitry or train detection system,” Catoe said. “It’s like when a doctor does an EKG on your heart. A blip in the data doesn’t mean you’re having a heart attack, but the doctor may want to conduct more tests.”
Some of the problems have been quickly corrected, but repairs that take more time sometimes require Metro to take a track circuit out of service, which requires trains to slow to 15 mph as they travel through the area.
Two signal companies that designed and manufactured Metro's automatic train control system are helping with the investigation, officials said. They are Ansaldo STS USA and Alstom Signaling Inc.
Metro is working with an Annapolis, Md., firm to design a backup for the train control system that is supposed to prevent crashes, the transit agency said. The NTSB had recommended that Metro add real-time, continuous backup to its train protection system.
Federal investigators have not determined what caused the accident and said testing will continue. So far, tests have shown circuit problems occur more frequently during rush hour.
A sight-distance test from Saturday that tried to determine what train operators would have seen must be further compared with other data from the crash site, officials said. Investigators have said there is evidence the operator of the oncoming train applied the emergency brake before the crash.
