The first recommendation was to the Washington Metropolitan Area Transit Authority (WMATA) in which the NTSB called for WMATA to improve its train control system to be able to:
"evaluate track occupancy data on a real-time basis in order to detect losses in track occupancy and automatically generate alerts to prompt such actions as immediately stopping train movements or implementing appropriate speed restrictions to prevent collisions."
In a somewhat worrying story in today's Washington Post, DC Metro officials said that they had replaced every component in the track circuit suspected as being the cause of the accident, but the problem persists. As a result, Metro trains continue to be operated in manual mode instead of under computer control.
Metro officials also claim in the story that a safety system such as the one the NTSB is recommending does not presently exist, and would have to be "invented."
However, San Francisco's Bay Area Rapid Transit (BART) system which is very similar in design to the DC Metro system has such a system in place, the Post says, because it experienced a "ghost train" problem in the 1970s. The Post story also says that Metro officials claim that the BART system wouldn't work in DC, but did not offer any detail why not other than saying Metro was different than BART.
Metro officials "thanked" the NTSB for its recommendation, but also not too subtly suggested that the NTSB focus their efforts on helping them find out why the track circuit keeps failing. Given past history, it would not surprise me that Metro management is highly concerned about the cost of developing and rolling out a continuous train monitoring system, and is therefore hoping that the track circuit failure can be traced to something easier and less expensive to correct.
Metro's management hasn't, as far as I know, backed off its belief that the accident was a "freak occurrence."
The NTSB also made a second urgent recommendation to the Federal Transit Administration (FTA) in which it urged the FTA:
"to advise all rail transit operators with train control systems capable of monitoring train movements to evaluate their systems for adequate safety redundancy."
An overdue recommendation from my personal passenger perspective, which also left me asking just how many transit systems of the above type do not have redundant safety monitoring systems in place.
As I mentioned here, major parts of the Los Angeles County Metropolitan Transportation Authority subway system use the same computer control system as the Metro. I suspect that they will be looking closely at this second NTSB recommendation too.
Robert N. Charette is a Contributing Editor to IEEE Spectrum and an acknowledged international authority on information technology and systems risk management. A self-described “risk ecologist,” he is interested in the intersections of business, political, technological, and societal risks. Charette is an award-winning author of multiple books and numerous articles on the subjects of risk management, project and program management, innovation, and entrepreneurship. A Life Senior Member of the IEEE, Charette was a recipient of the IEEE Computer Society’s Golden Core Award in 2008.