Metro is a mess this morning for riders on the Orange, Blue, and Silver lines. “Fire department activity” and reports of smoke have closed the Orange and Silver lines between Foggy Bottom and Clarendon and the Blue Line between Foggy Bottom and Arlington Cemetery.

Meanwhile, a separate incident this morning shut down service around the Capitol Heights station on the Blue and Silver lines, although that problem has since been resolved. What do these two incidents have in common, other than wreaking havoc on thousands of commutes to and from the D.C. suburbs? They were both caused by “arcing insulators,” according to the Washington Post. (Metro spokesman Dan Stessel did not immediately return a call to confirm the causes of the incidents.) Once an arcane term, “arcing insulator” has become a regular part of the Metro lexicon, ever since arcing on a Yellow Line track caused a train to fill with smoke on Jan. 12, leaving one passenger dead and sending more than 80 to the hospital. An arcing insulator causes sparking or smoke on the electrified third rail. It’s an altogether too common problem for Metro and one that’s striking the system on an increasingly regular basis. According to a 2013 Metro report, arcing insulators were occurring about twice a month at the time. The number of smoke or fire incidents on Metro tracks has only increased since then. In 2013, there were 86 such incidents; last year, the number rose to 104. Metro is compensating for the service suspension this morning with free shuttles:

But passengers would likely prefer not to encounter smoke and delays in the first place. Metro’s in the process of replacing its aging insulators. Until it completes the task, incidents like these won’t be going away.

Update 11:20 a.m.: Metro has restored service to the affected stations, but trains there are single-tracking. Expect continued delays.

Photo by Aaron Wiener