A woman is transported in a wheelchair onto an ambulance bus as people are evacuated from a smoke filled Metro subway tunnel in Washington, Monday, Jan. 12, 2015. Metro officials say one of the busiest stations in downtown Washington has been evacuated because of smoke. Authorities say the source of the smoke is unknown. (Jacquelyn Martin/AP)

JUST LAST week Richard Sarles, Metro’s general manager since 2010, told the transit system’s board of directors in his valedictory remarks that “safety is top of mind for all employees” and “the state of operations — both customer operations and internal operations — has improved.”

Those confident words were blown away in a cloud of smoke at L’Enfant Plaza on Monday afternoon.

After years of spotty service, single-tracking, sluggish weekend travel and simultaneously sanguine assurances that Metro was single-mindedly building its “culture of safety,” disaster has struck the nation’s second-biggest transit system again. Once again, dozens of Metro train passengers were rushed to emergency rooms; once again, an underground mishap caused the death of a passenger.

With all of Mr. Sarles’s ringing pronouncements these past years about Metro’s “safety culture,” how could it take up to an hour to evacuate a train caught in a tunnel downtown and filling with acrid smoke?

Why did desperate passengers, struggling to breathe, have to wait interminably while Metro officials and firefighters tried to determine whether power had been cut to the third rail so that it was safe for firefighters to mount a rescue, a bumbling pas de deux worthy of Alphonse and Gaston? The D.C. Fire Department too must be accountable for its role in the debacle, so it was distressing that D.C. Mayor Muriel Bowser (D) was unwilling Tuesday to provide any information about the department’s actions. But does Metro’s culture of safety not include well-rehearsed protocols for shutting off power to the third rail and coordinating with first-responders?

A Metro passenger filmed the scene inside the stranded Metro car, in which people can be seen helping and comforting each other. A Yellow Line train abruptly stopped and filled with smoke in a tunnel in downtown Washington on Monday. (Saleh Damiger/YouTube)

And will the transit-using public now have to wait months for a coherent explanation of what went wrong to cause both the electrical mishap and the blundering response, once again courtesy of the National Transportation Safety Board?

On Thursday, the day that Mr. Sarles was delivering his self-congratulatory remarks to the Metro board, passengers on five of the system’s six rail lines were facing major delays. On that very day, while Metro Board Chairman Tom Downs was praising Mr. Sarles for “rebuilding the [system’s] safety culture from top to bottom,” Metro was four days away from its worst passenger train disaster since 2009, when a Red Line crash killed eight passengers and a train operator.

Here is what happened Monday: more than 80 people injured and one woman dead. Passengers were screaming, gasping, choking, panicking, praying and, in some cases, losing consciousness aboard smoke-filled cars. The terror that a fire had broken out, and the endless wait for firefighters to appear on the scene. The sickening stink of smoke as passengers, coughing and gagging, were finally led to safety through the tunnel’s gloom.

Is this the safety culture that Metro has built?