WASHINGTON -- The National Transportation Safety Board's investigation of track circuit anomalies suspected in June's multiple-fatal Metro crash has led to nine safety recommendations for Metro and the manufacturer of the track circuit modules, including six urgent recommendations.
Letters to Metro, Alstom Signaling, the Federal Transit Administration and the Federal Railroad Administration offer more detail about the anomalies reported over the summer.
"After only 3 months, this complex investigation is far from complete, so we are not ready to determine the probable cause of the accident on WMATA," said NTSB Chair Deborah Hersman in a statement released Tuesday. "However, our findings so far indicate a pressing need to issue these recommendations to immediately address safety glitches we have found that could lead to another tragic accident on WMATA or another transit or rail system."
In addition to letters sent to Metro and Alstom Signaling, NTSB wrote the FTA and the FRA recommending they advise all rail transit and railroad operations that use audio frequency track circuits about the NTSB findings.
NTSB investigators have learned that a track circuit module transmitter generated a spurious signal that micmicked a valid signal was sensed by the module receiver, which is why a stopped train wasn't detected by the train the crashed into it. The track relays should deenergize when a train is present, but on June 22 outside the Fort Totten station on the Red Line, the false signal left the track relay energized, so the stopped train wasn't detected.
“The NTSB has identified a symptom of the problem with the track circuit, but not a root cause or a solution,” said Metro General Manager John Catoe. “We are doing everything we can to make our rail system as safe as possible. The NTSB still has not identified a probable cause for the accident. They made two recommendations and we will implement those recommendations. In fact, we began to do so weeks ago.”
The NTSB offered Metro the following safety recommendations:
- Work with the manufacturers of the train control system equipment to uncover any evidence of parasitic oscillations and stop future spurious signals.
- Periodic examinations of electronic components in its train control system to ensure proper performance.
Metro is addressing the first recommendation by:
- Operating in manual mode until further notice
- Running twice-daily computerized tests of all of its track circuits, once after each rush hour
- Working with a contractor, ARINC, and other outside vendors to develop a real-time monitoring system
Metro is working with Alstom and another signal manufacturer, US&S, to eliminate the problem, officials said.
The NTSB advised Alstom to assist all rail transit agencices and railroads that use its audio frequency track circuit equipment in finding any possible parasitic oscillations or spurious signals.
Nine people died and more than 70 were injured when a train slammed into another train stopped on the tracks near the Maryland state line. Metro has been running all trains in manual mode ever since and has found areas beyond the crash site where signaling equipment has malfunctioned.
“The NTSB investigation is not complete,” Catoe said. “We will continue to cooperate with the NTSB and respond quickly in hope that they can identify a root cause or causes that will allow us to put steps in place to prevent this from happening again.”
The NTSB wants to hear from Metro, Alstom, the FTA and the FRA within 30 days about steps taken or planned in response to these recommendations.