D.C. Metro replies to NTSB
Washington Metro officials say they can't immediately comply with a recommendation from the National Transportation Safety Board that they add another layer of safety precautions to the subway system because such a technology is not commercially available.
The NTSB issued an emergency recommendation Monday that the Metro incorporate a new backup system into its crash-protection measures in the wake of the June 22 collision of two trains. Nine people died in that ccrash -- the worst in the history of the Washington Metro.
The NTSB investigation has reached a preliminary finding that a circuit failure in Metro's current crash avoidance system failed, leaving the operator of a following train unaware that another train had stopped on the tracks ahead. The board said the crash showed the Metro "is susceptible to a single-point failure" and should add a level of redundancy to its protections.
However, in its reply, the Metro board said its system is not compatible with any other existing transit system and that any new protection technology would have to be invented.
The Metro system's full reply follows:
Metro’s Board of Directors and General Manager appreciate the recommendations from the National Transportation Safety Board to Metro and the Federal Transit Administration. This has implications that reach far beyond Metro, and extend to the entire transit industry.
In spite of the issuance of this recommendation, the NTSB still has not determined the root cause of the accident. Every component of that circuit has been replaced, but the problem still persists. This is not a simple problem as is evidenced by the NTSB’s statement that “investigators are continuing to examine the train control system circuitry and recorded data to better understand how the train control system functioned prior to the accident."
It is important to know that there are currently no systems available commercially that could provide the Metro system with the kind of alerts that the NTSB has recommended, and that such a system must be invented. San Francisco’s Bay Area Rapid Transit system for example, would not meet our unique needs. We believe the NTSB acknowledged this much in its letter today, stating, “The NTSB believes that software algorithms or additional circuitry could be developed to continuously evaluate the validity of real-time track occupancy data and alert operations personnel when problems are detected.” As a result, we will be developing a new system that will be specifically tailored to Metro. Metro is in the process of contacting vendors who have the expertise needed to help us develop this service, and we are preparing cost estimates on this application.
Metro is also pleased that NTSB has now agreed to allow us to move forward with our plan to initiate an independent panel of experts in signal systems through the American Public Transportation Association before the NTSB investigation has been completed.
The safety of our customers and our employees continues to be our prime concern. As a result of the accident of June 22, 2009, we immediately returned control of all trains to manual mode. We will continue to operate in manual mode until a suitable backup, designed specifically for our rail system is developed. For more than 30 years, the current rail system has operated without a failure like the one we experienced on June 22, but we will devote all of our resources to implementing NTSB’s recommendation as soon as possible
