NTSB Identifies Signal Failure in DC Crash

WASHINGTON — The National Transportation Safety Board (NTSB) has issued nine safety recommendations, six of which are urgent, as part of its investigation into the collision between two Washington Metropolitan Area Transit Authority (WMATA) trains on June 22, 2009.

The trains crashed on the Red Line near the Fort Totten station in Washington. The NTSB’s recommendations address concerns about the safety of train control systems that use audio frequency track circuits, authorities said.

As part of its investigation, the NTSB said it discovered that a failure occurred in which a spurious signal generated by a track circuit module transmitter mimicked a valid signal and bypassed the rails via an unintended signal path. The spurious signal was sensed by the module receiver which resulted in the train not being detected when it stopped in the track circuit where the accident occurred.

The NTSB made specific recommendations to the WMATA and to Alstom Signaling Inc., the manufacturer of the track circuit modules at the Fort Totten station, to examine the WMATA track circuits and work together to eliminate adverse conditions that could affect the safe performance of these systems.

Additionally, the NTSB called upon WMATA to develop a program to periodically determine that the electronic components in its train control systems are performing within design tolerances.

Although the NTSB’s investigation is not yet complete and no determination of probable cause has been reached, the NTSB is concerned about the safety of train control system circuitry used in comparable rail and transit operations in other parts of the country. Therefore, the NTSB recommended that the Federal Transit Administration (FTA) and the Federal Railroad Administration (FRA) advise all rail transit operators and railroads that use audio frequency track circuits in their train control systems about these findings from the Fort Totten accident investigation, authorities said.

The NTSB also recommended that the FTA and FRA have transit operators and railroads that use audio frequency track circuits examine their track circuits and work with their signal equipment manufacturer(s) to eliminate adverse conditions that could affect the safe performance of these systems, and to develop programs to periodically determine that the electronic components in their train control systems are performing within design tolerances.

“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,” Chairman Deborah A.P. Hersman said. “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 accordance with NTSB protocol, the letters were addressed to the heads of each organization with a request for a response from each organization within 30 days on the urgent recommendations, addressing the actions taken or planned in response to the Board’s recommendations, the agency said.

“The NTSB has identified a symptom of the problem with the track circuit, but not a root cause or a solution,” Metro General Manager John Catoe said. “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 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.”