Commuters at the Friendship Heights Metro station. (Astrid Riecken for The Washington Post)

The federal government has a plan for shutting down the entire Metro system that includes putting its own transit staff in the agency’s rail operations center and bringing in the Federal Railroad Administration for help should regulators deem there are significant safety risks that warrant such action.

Federal safety officials would first have to determine a “substantial risk” exists, such as a serious defect in the steel rails used throughout the system or a batch of faulty track circuits, or a dangerous mechanical problem affecting an entire series of rail cars.

In other words, a showstopper of the variety that precipitated General Manager Paul J. Wiedefeld’s emergency day-long shutdown of the system in March 2016.

Such a discovery would trigger a chain of events involving agencies from the National Security Council and the Federal Emergency Management Agency to the Metropolitan Washington Council of Governments, culminating in the U.S. transportation secretary issuing the following order:

“FTA Emergency Order 1X-X requires the Washington Metropolitan Area Transit Authority (WMATA) to indefinitely suspend all Metrorail revenue operations.”

The internal planning document, prepared by the Federal Transit Administration, has existed since December 2016, but it was never made public or shared with officials outside the Transportation Department — even in Metro.

“We only became aware of its existence after The Washington Post began asking about it,” Metro spokesman Dan Stessel said.

The document, obtained by The Post through a Freedom of Information Act request, is a 22-page delineation of the transportation secretary’s authority over the Washington region’s subway, the only transit system in the country whose chronic safety problems have warranted a step-by-step plan to address the possibility of a federally mandated shutdown. But it could serve as a framework for responses to other transit systems if extreme action became necessary, said the FTA, which under legislation approved by Congress in 2012 has broad authority to take action in response to unsafe conditions at transit agencies across the United States.

In October 2015, former U.S. transportation secretary Anthony Foxx exercised his authority under the same law and took the unprecedented step of ordering the FTA to assume safety oversight of Metro from the failed Tri-State Oversight Committee.

“I was not only worried about the possibility of shutdown under my tenure — I was also concerned about the possibility [Metro] would have to be shut down or would be forced to shut down under some safety problem,” Foxx said in a recent interview. “So what I wanted was essentially a document that would outline the steps to be taken under such an occurrence, not only for my immediate purposes but for future purposes.”

The FTA said the shutdown plan remains active. In the most extreme scenario — a rail system shutdown lasting 72 or more hours — FRA inspectors could be called in to examine Metro’s track conditions, signals, power equipment, operating practices and track geometry, according to the plan. The FTA could also dispatch crews to Metro’s Rail Operations Control Center and areas across the system to monitor the agency’s response to an urgent problem.

Those individuals would supplement a team of up to 30 FTA personnel responsible for conducting inspections, performing field work and overseeing Metro’s efforts to return the system to service. Among those the FTA would call in: accident investigators, rail operations specialists, rail and signal engineers, and track and infrastructure engineers.

“While [Metro] is taking significant steps to enhance the safety and reliability of the Metrorail system, it is possible that ‘an unsafe condition or practice, or a combination of unsafe conditions or practices, [could] exist such that there is a substantial risk of death or personal injury’ to passenger or workers,” the plan says. “If a Substantial Risk arises, [the U.S. Transportation Department] must restrict or prohibit Metrorail system operations in whole or in part ‘for as long as necessary to ensure that the risk has been substantially addressed.’ ”

The FTA says officials developed the plan as a road map for carrying out a shutdown or restricting service in a “safe, timely and orderly manner.” Foxx said he nearly did shut down the system at the height of its safety crisis in 2016. But Wiedefeld’s day-long emergency shutdown for critical cable repairs and his year-long SafeTrack plan gave federal officials confidence Metro was taking its chronic safety problems seriously.

Since then, the FTA has issued several sweeping edicts related to Metro safety issues — including in May 2016 when it threatened to shut down all or parts of the system unless Metro took urgent action to ensure passenger safety. The threat followed Metro’s botched response to two smoke and fire incidents at the same station in one day.

In June, the FTA ordered the transit agency to retrofit all of its 7000-series rail cars with chain guards to address a safety issue where blind and visually-impaired riders have fallen through the gap between cars. Metro risks losing 25 percent of formula-based funding if it fails to meet the FTA’s Dec. 31 deadline for retrofitting the more than 500 cars.

The FTA shutdown plan addresses such a scenario.

The FTA could issue an emergency order mandating all 7000-series rail cars be removed from service. The order would then direct Metro to install the chain barriers by a set date, with the implementation overseen directly by FTA officials and support staff.

Metro would craft a response plan to the order. FTA would oversee the rollout, dispatching technical experts and providing resources where necessary. Because sidelining half of Metro’s fleet could have a substantial impact on service, the Transportation Department would notify bodies such as the NSC, FEMA and the Office of Personnel Management to address potential security issues for dignitaries and to ensure the timely transport of the federal workforce. Responses at the regional level would be coordinated through COG.

Ahead of the service stoppage, the FTA would notify the news media and regional and congressional officials, using a distribution list that includes outlets covering Congress, transportation reporters and “key social media influencers.”

To restore service, Metro would ultimately have to write to federal officials attesting that the risk had been “substantially addressed.” From there, it would be up to the transportation secretary to decide whether the transit agency could return the trains to service; they could be sidelined indefinitely and the FTA could withhold the aforementioned funding if Metro failed to comply.

The shutdown plan will remain active, even when safety oversight of the rail system is handed over to the new Metrorail Safety Commission.

“The plan will continue to be available to FTA as a planning resource even after direct safety oversight of WMATA Metrorail is eventually relinquished to the Metrorail Safety Commission (MSC) upon that agency obtaining certification of its State Safety Oversight (SSO) Program,” FTA spokesman Benjamin Lockshin said in an email. The “Secretary’s authority to impose restrictions and/or prohibitions applies to all transit operators and is not dependent upon FTA assuming direct safety oversight of an agency.”

Meanwhile, the commission, which has not seen the plan, says it will develop one of its own.

“Once the MSC is certified by the FTA to provide safety oversight of Metrorail, one of its enforcement powers will include restricting, suspending, or prohibiting rail service on all or part of the system, if necessary,” said David L. Mayer, panel’s chief executive.

A shutdown has been on commuters’ minds recently following a July 15 vote by Metro union members authorizing a strike.

A strike would be illegal under the transit agency’s governing compact — and would cripple transportation in the region. Metro does not have a strike contingency plan.

“There is no way to replicate the transportation service provided by more than 7,500 employees,” Stessel said, although he noted a rail-only strike would mean “you could press into service every available bus in the region and take some meaningful steps to keep people moving.”

He said if workers decided to strike, a court could quickly intercede, declare it illegal and compel them to return to work.

“In either case, though, Metro management would take a series of coordinated actions to notify the public, protect assets and restore service as quickly as possible,” Stessel said.