Metro’s top officials last week alarmed us with the troubling idea that an extended shutdown of entire rail lines might be needed to address the critical problems of Washington’s 40-year-old subway.

On Tuesday, Metro General Manager Paul J. Wiedefeld reassured the region that he has no plans for such drastic action, saying “I don’t see any need for a long closure of any part of the system.

He did however, leave open the possibility of shutting down segments of track between stations.

We won’t know what Wiedefeld intends to do until he presents a “long-range maintenance plan” in a few weeks. But it’s still likely to be more disruptive than what we are accustomed to– and we have dealt with a great deal of single-tracking and weekend disruptions in recent years.

For an idea of what extreme shutdown would bring, we can a look at what happened when Chicago closed 10 miles of track on its busiest rail line for five months in 2013. That unprecedented shutdown didn’t happen overnight, officials say, noting it took at least a year of planning.

In preparation, Chicago Transit Authority hired more than 400 new bus drivers, began to distribute tips to commuters four months before the stations closed, and when the closure took place, used shuttles to connect riders from the closed stations to the closest rail line, and added buses to several routes.

“It was imperative to have an extremely robust and very effective alternative service plan,” said Brian Steele, a spokesman with the Chicago Transit Authority.

Closing the nine stations in the southern portion of the city’s Red Line was not as disruptive as it could have been because most of the line parallels the Green Line, about a mile and a half away.  The CTA ran shuttle buses on a load and go basis, so it was bus after bus carrying commuters from a closed station to an open one. They also moved Red Line trains over the Green line tracks and added service on the Green line to handle a greater number of riders.

“We did this 24 hours a day for five months so it was a significant operational challenge, but it is one that was absolutely critical to be able to serve customers during the construction,” Steele said. “Customers had multiple options. Even though they couldn’t take the line they were accustomed to, they had multiple options that would give them trips that were comparable to what they experienced on the Red line.”

The authority offered a 50-cent discount on bus rides, in an effort to keep riders riding the system.

“It was indeed an incentive for riders to continue to use the bus service and continue to use transit, but also it was a way that we felt would help reduce the inconvenience to customers,” said Steele.  Still, in that process the CTA lost about 10 percent of its pre-construction ridership.

“If you shut anything down for a long time people are going to look at alternatives and when the project is done most of those people come back, but there are cases where people found different ways to make their commute,” Steele said.

Even a partial closure would potentially snarl thousands of daily commutes and worsen congestion in the Washington region.  “It would be a crushing blow to the regional economy and to many workers,” our in-house expert, Dr. Gridlock, aka Robert Thomson, said during his Monday online chat.

And any potential long-term disruption to the rail system in Washington, could impact bus operations.

With plenty of notice, Metrobus could potentially expand service like Chicago did, some transit officials say.  But Metrobus is already running at capacity in many corridors and adding more service could require more buses and drivers than Metro has available.

With a fleet of 1,530 buses and about 1,300 buses on the road during the peak hours, Metrobus has limited capacity to add service.  During the March 16 shutdown of the entire system, for example, Metrobus added about 50 extra buses to some corridors to provide extra service, and the system experienced an uptick in ridership in several routes, in addition to a nightmare of a commute amid greater than usual traffic. This happened even though many federal workers and others chose to telecommute or take the day off.

“There is very little additional capacity to put out there on the bus side,” Metro chief spokesman Dan Stessel said prior to the March 16 shutdown.

If the disruptions are in downtown, many riders could choose to walk or ride a bike to other rail connections or work.  Still, any interruption of service in a portion of the rail system would cause delays on other parts of the system.

Wiedefeld has reassured riders that any plan would be announced with “ample notice.”   Metro is studying many possible options, their impacts and implications.

“I want to reassure you that, while I am keeping options open on how to proceed, no decisions have been made,” Wiedefeld said last week. “Moreover, any service change in the plan that could affect your commute will receive ample notice to customers, businesses, stakeholders and the region as a whole.”