Metro has made considerable progress in making the nation’s second-largest subway system safer for both riders and workers, but recent gains are fragile and could be undermined by a lack of focus or a loss of key personnel, according to a federal audit released Wednesday.

The 43-page review by the Federal Transit Administration’s office of safety and security was requested by Sen. Barbara A. Mikulski (D-Md.) after a series of incidents in July, including a botched evacuation, a derailment and a computer failure that forced the shutdown of the system twice within 24 hours.

Other incidents auditors examined included one in which a worker was hit by a train and critically injured in a rail yard near the Shady Grove station and reports of train doors opening at random.

The Washington Metropolitan Area Transit Authority’s “progress over the last two years is a critical but fragile foundation for the future,” the report said. “Any major changes in personnel, relaxation in attention to safety, reduction of resources devoted to safety, or reemergence of complacency in the reporting and investigation of unusual occurrences and conditions could easily reverse WMATA’s gains.”

The audit outlined several recommendations for the transit agency:

●Determine whether additional precautions are needed to protect workers in rail yards.

●Undertake a more thorough examination of the heat kink blamed for the July 6 derailment of a Green Line train.

●Take steps to reduce the risk that rail-car doors will open between stations.

“I call on Metro to implement the safety recommendations in the Federal Transit Administration’s latest audit,” Mikulski said. “I applaud Metro’s new leadership for beginning to change its organizational culture to put safety first. But I insist Metro continue making progress in creating a culture of safety.”

Metro officials said they will work to implement the additional recommendations.

“We welcome the recognition of our significant safety progress in this report and agree that vigilance is key to continuing our progress,” said senior official Jack Requa. “We accept the recommendations by the Federal Transit Administration and are committed to addressing them as part of our ongoing improvement program. In fact, we have already taken action in several areas.”

Auditors said that Metro officials have addressed the findings of the federal agency’s 2010 final audit — a scathing review that found pervasive flaws in rail safety.

The FTA initiated that audit at the request of Mikulski and Transportation Secretary Ray LaHood, who acted in response to safety lapses reported in The Washington Post after the 2009 Red Line crash in which nine people were killed. FTA officials said auditors found Metro to be fully cooperative with this recent effort.

Citing a heat kink that caused the July derailment of a Green Line train and the breakdown of another Green Line train earlier in the same week, auditors said that Metro’s engineering and maintenance departments should have been more attuned to potential problems resulting from this season’s extreme weather patterns.

Auditors also noted that some “unusual occurrences and unexpected failures” in the system may not have been handled as well as they should have been because of the loss of hundreds of veteran Metro employees who had retired in the last 18 months. Based on interviews with employees, auditors found that it can take from two to five years for a new employee to fully master all elements of Metro’s complex operating and maintenance environment.
In evaluating Metro’s progress, FTA auditors noted that the transit authority has continued to reduce the number of fatalities, although injury rates for workers and passengers are higher than they were in 2010.

They also noted that Metro’s appointed board of directors, which includes representatives from the District, Maryland, Virginia and the federal government, has taken a more active role in monitoring safety.