Several of Metro’s rail lines had troubles in the Friday evening commute, creating delays for commuters.

Trains on the Yellow line were single-tracking in the 6 o’clock hour between L’Enfant Plaza and Mt. Vernon Square because a “stud bolt” — a part of the third rail was arcing and generating smoke near L’Enfant Plaza stop.

Dan Stessel, Metro’s chief spokesman, said the transit agency’s emergency response team was in the tunnel and crews were working to fix the problem.

There were other problems on Metro.

In the 5 o’clock hour, the Blue/Orange lines had three issues — two where trains, one at Smithsonian and one at Rosslyn, had to be off-loaded because of separate door problems. Another train on the Blue/Orange line had to be off-loaded because of a mechanical problem at Federal Triangle.

At 7 p.m., Orange/Blue line trains were “back on regular service frequency,” Metro officials tweeted. And crews were working on the problem at L’Enfant Plaza.

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