A second part of the equipment at the site of last month’s deadly Metro crash has been faltering since it was replaced more than 18 months ago, federal investigators said Thursday.
The National Transportation Safety Board previously said that a bond in the track alert system at the crash site had been intermittently failing to detect trains since it was replaced five days before the June 22 crash.
But on Thursday the investigators said another “impedance bond” on the other end of the same circuit had been showing problems since it was replaced in December 2007.
The equipment is a key part of the system that is supposed to alert trains — and even stop them — when they get too close to another train. Although the crash remains under investigation, it appears the equipment may have failed to sense a stopped train, causing another Red Line train to plow into it near the Fort Totten station, killing nine and injuring more than 70.
The discovery, with Metro’s admission that other circuits in the system are showing anomalies, may indicate that the system designed to protect trains from crashing has more widespread problems than initially thought.
Officials are trying to determine what is causing the problems. The NTSB said several factors including electromagnetic interference, faulty communication lines or even upgrades could be causing the problems.
The NTSB said it is looking at Metro’s records to see if any of the problems on the second bond had been reported or if train operators had noticed problems with that section of track since the equipment was replaced.
Metro General Manager John Catoe said he had not received any reports of earlier problems with that equipment. But he added, “That’s what we’re going through.”
Catoe said such bonds are tested after they are installed. Metro also conducted tests of the entire system monthly, but those tests took a sample of just one hour of rush-hour train service per month. Those tests looked at a different parameter than the federal investigators did.
Now, Metro is looking at three hours of data twice a day after each rush hour, spokeswoman Candace Smith said. Last week, the NTSB had labeled such testing insufficient and called for a continuous testing system that Metro has tasked Annapolis company ARINC to build. It is not clear, though, how much such a system will cost, nor when it could be ready.
