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It’s likely to be a while before we learn the full story of what caused yesterday’s Metro incident that filled L’Enfant Plaza station with smoke and claimed a life. When two Red Line trains collided near Fort Totten in June 2009, killing nine, it took a full year for the National Transportation Safety Board to issue a final report on the causes of the disaster.

It seems unlikely that factors contributing to the 2009 crash were at play in this most recent incident. In the 2009 accident, one train essentially vanished from the automatic control system, leading the system to direct the second train forward at full speed; the driver of the latter didn’t have time to stop upon seeing the stationary train ahead. A crash of this sort was predictable, concluded the NTSB, given that nearly half of Metro’s 3,000 track circuit modules were prone to malfunction and the older rail cars, comprising a quarter of its fleet, did not offer adequate protection in a crash.

“Metro was on a collision course long before this accident,” NTSB chair Deborah Hersman said at the time. “The only question was when Metro would have another accident—-and of what magnitude.”

The real problem, she said, was that Metro didn’t learn from a 2005 incident, when a breakdown in the automatic train control system nearly caused a crash near the Rosslyn station. (That wasn’t the first failure of Metro automation, either; in 1996, a Red Line train’s automatic braking system malfunctioned, and the resulting crash killed a Metro driver.)

So was yesterday’s incident also a product of lessons not learned? We won’t really know until we have a fuller sense of the causes. But there are a few hints of red flags that were out there.

First, 1000-series cars were involved in the incident. These are precisely the old cars that the NTSB warned in 2010 were not well equipped for a crash. Granted, this wasn’t a crash, but it does raise questions about Metro’s speed in upgrading its problematic fleet.

Second, there’s the matter of smoke. NBC4 reported last year that the number of fire and smoke incidents on Metro nearly doubled in the first quarter of 2014, compared with the previous year. One of the worst recent incidents took place in January 2013 near Anacostia, when smoke caused people on a train to self-evacuate and walk through the tunnel to the station. Metro’s follow-up report blamed the incident on an arcing insulator, which Metro defines as “an insulator along the third rail that may be giving off sparks or smoke.” According to that report, “arcing insulators occur about twice a month when electrical current arcs because an insulator fails to buffer it, thereby generating smoke.”

An “electrical arcing event” appears to have played a role in yesterday’s incident, too. When the NTSB delivers its final report on this incident, expect to see a push to bring down the frequency of these events.

After the 2009 Red Line incident, Hersman emphasized that Metro was still much safer than street-level transportation. In the system’s 34-year history to that point, she said, 13 people had lost their lives on Metro trains.

Sadly, there’s now another death to that tally.

Photo by Darrow Montgomery