A second part of the equipment at the site of the deadly Metro crash has been showing problems since it was replaced more than 18 months ago, federal investigators said Thursday.
The National Transportation Safety Board had previously said that a bond in the track alert system had been intermittently failing since it was replaced five days before the June 22 crash.
But on Thursday, the agency said a second “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 automatic train 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 train to plow into it near the Fort Totten station of the Red Line, killing nine and injuring more than 70.
The NTSB said it is looking at Metro’s records to see if any of the problems had been reported or if any train operators had noticed problems with that section of track since the equipment was replaced.
The news comes as other problems have since been found in other circuits around the transit system. Metro officials have downplayed those cases, saying they are “blips” lasting a second or less that have been found under tougher testing. They have not said how many circuits have needed repairs but said Wednesday that five had been replaced.
Metro General Manager John Catoe has said the system is still safe and said he would shut it down if it were not.
Officials are still trying to determine what is causing the problems, though. The NTSB said a number of problems, including electromagnetic interference, communication lines or system upgrades, could be causing the failures.
The problems are occurring most often during rush hour, when the transit system is running the most trains and carrying the most passengers.
