WASHINGTON — In its continuing investigation of the June 22 wreck involving the collision of two Washington Metropolitan Area Transit Authority (WMATA) trains on the Red Line in Washington, D.C., the National Transportation Safety Board has developed the following factual information:
— The examination of factors leading up to the accident continues. Investigators have been conducting nightly tests of the train control system at the accident site. Test progress was delayed by some water in underground access areas that made it unsafe for technicians to work on electrical cables until the water could be pumped out. The components being tested include track impedence bonds, wayside cables, and train control system circuitry for the track segment between the Fort Totten and Takoma stations.
— As previously reported, initial testing showed that when the test train was stopped at the same location as the train that was struck in the accident, the train control system lost detection of the test train. Additionally, in subsequent testing over the weekend the train detection system intermittently failed; data is currently being collected to further analyze each component in the train detection system. Investigators are reviewing recorded track circuit data for each test configuration.
— Maintenance records show that an impedence bond for the track circuit where the accident occurred was replaced on June 17, five days before the accident. After a post-accident review of recorded track circuit data, WMATA reported to the NTSB that the track circuit periodically lost its ability to detect trains after June 17; the NTSB is reviewing documentation on the performance of that track circuit both before and after the June 17 replacement.
— The weekend of July 18 investigators intend to conduct sight distance tests using trains consisting of similar cars to those involved in the accident. The tests will establish when the struck train would have been visible from the striking train. The previously reported rail streak marks consistent with heavy braking were approximately 125 feet long, and began approximately 425 feet prior to the point of collision.
The investigative groups have concluded the on-scene phase of the investigation except for the Signals Group that continues to examine the train control system both at the scene of the accident and at the WMATA Operations Control Center.