The deaths of nine people in the crash involving two Washington Metro subway trains Monday evening was, as more than one person on the scene described it, a horror. It seems all the more so because such an event is so uncommon on commuter rail systems, particularly compared to the automobile-related carnage that takes place on our nation's highways each day.
While it will take some time for investigators from the National Transportation Safety Board to determine the exact cause of this tragedy, myriad troubling questions have already arisen. They range from why Metro's management failed to heed numerous NTSB safety recommendations in the past - including removing or reinforcing older cars like the one that rear-ended the stopped train near Fort Totten station Monday - to whether the relative inexperience of that train's operator may have been a factor.
But perhaps the most disconcerting possibility of all - and one that could have implications for many other transit systems, including Baltimore's subway - is the widespread speculation that Metro's automatic train control system may have somehow failed or otherwise contributed to the accident.
Within the transit community, such a scenario is considered unthinkable. Subway trains are largely computer-driven, and a system of sensors and signals closely monitors and regulates train speeds. During rush hour, trains like the ones involved in Monday's accident are generally run by the Metro's central computer system, not by the conductors. The on-board human operators are, in a sense, another form of fail-safe; they can also force an emergency stop, if necessary.
The components of an automatic train control can malfunction, of course, as all electronic devices sometimes do. But when they misfire or fail, the system is programmed to force the safest state of operation - generally, to bring the train to a full stop. For any other result to take place is considered as unlikely as encountering a modern highway traffic light turning green in all directions at once.
Might the train's brakes have failed? Had the operator engaged the manual override and ignored the signals? Had she become distracted? Is it possible Metro's aging infrastructure and financial problems set the stage for this deadly event?
All these questions and more will need to be answered, though the task will be made more difficult because Metro failed to heed another piece of the NTSB's advice: to retrofit older trains with black boxes like the ones installed in commercial airplanes. The safety of not only Metro but many other commuter rail systems hangs in the balance.
But in the meantime, commuters ought to be reminded that subways and other forms of rail transit remain far safer than most forms of travel, and particularly safer than driving on the roads. According to the National Safety Council, the number of accident fatalities per vehicle miles traveled is about 14 times worse for passenger cars than trains and subways. Only transit buses are considered safer.
