Returning to normal after being buried by two feet of snow proved daunting Tuesday, as plows struggled into neighborhoods and snow- and ice-clogged Metrorail lines and streets made it tough for Washington-area residents going back to work.

Metro was unsure whether Silver Line service would be restored by Wednesday, but it said that its five other lines would be running and that service would resume on about half of its 320 bus lines. Testing was to continue on the Silver Line through the night, and if it was found unable to provide reliable service by morning, free shuttle bus service would be available from the five outer Silver Line stations to West Falls Church.

Driven by temperatures in the 40s and light rain Tuesday, the thaw threatened to flood some low-lying areas in the next few days and on Wednesday cause slick spots on roads and sidewalks in areas where overnight temperatures dipped to freezing.

Federal offices in the region will open with a three-hour delay and public schools in the District planned to reopen Wednesday, but virtually all of the region’s suburban school systems remain closed.

The storm that began midday Friday and continued until almost midnight Saturday shut down virtually everything through Tuesday, and it has cost the region an estimated $570 million in lost economic activity, according to the investment firm Moody’s.

Capital Weather Gang's Jason Samenow has your weekly forecast and reports on just how much snow fell in the D.C. area during "Snowzilla." (Jason Samenow,Ashleigh Joplin/The Washington Post)

There were many small signs Tuesday that the region was regaining its balance. The District said its snow emergency would end at 6:30 p.m. Wednesday, as would the $15 surcharge that city cabbies collected while it lasted. The Ride On bus system in Montgomery County said it would restore operations on most bus routes Wednesday.

On the roads, most major highways reopened and snowplows continued to tackle secondary residential streets, but officials warned it might be days before they fully excavate some homeowners who have been snowbound.

On Tuesday, Metro had aimed to resume full service on all but the Silver Line, but those plans changed when overnight tests on the western portion of the Orange Line ran into snow and ice on the electrified third rail that powers the system.

The transit agency decided to keep four Orange Line stations closed. That move, combined with the closing of the Silver Line, limited rail options for many people in the Virginia suburbs. When riders arrived at the Orange Line stations to catch shuttle buses to open stations, they faced long, cold waits.

Grace Lin, 35, a lawyer in the District who lives in McLean, said she went to bed Monday night after hearing that Metro was going to be running, but she always had her doubts.

At 6 a.m. Tuesday, she said, she checked Metro’s website “just to see, because their accuracy is not always good.” She saw there were no trains on part of the Orange Line, so she waited at West Falls Church for a shuttle bus.

“Immediately, I’m thinking, ‘Can I just stay home?’ ”

Metro General Manager Paul J. Wiedefeld explained Tuesday’s problems.

Metro work crews spent the weekend and Monday plowing the system’s 60-plus route-miles of aboveground rails during and after the blizzard, he said.

Hulking, diesel-fueled rail cars with plow blades in front pushed snow to the sides of the tracks, Wiedefeld said. After more snow accumulated, it, too, was plowed. Behind the plow blades, large scrapers attached to the rail cars ripped ice off the third rails. Then a liquid de-icer was sprayed on the third rails.

Unlike snow-removal crews on roads, Metro does not have an efficient way of moving plowed snow farther from its tracks, Wiedefeld said, because most rails are in confined spaces, flanked by chain-link fences or retaining walls.

The snow often drifts back onto the third rails, causing more ice.

“The trains are losing [contact] with the third rail and becoming disabled,” Metro spokesman Dan Stessel said Tuesday. “Part of it is ongoing ice and snow buildup. The snow banks are higher than the third rail, and the snow continues to get onto the third rail,” causing them to “ice over.”

He added: “The last thing we want to do is put passengers out on the railroad where [trains] become disabled.”

Across the region, the work of cleanup crews on roads also was complicated by the massive amount of snow, which could not be shoved aside easily in many places. Much of the snow had to be hauled to open spaces, creating mountains that will take weeks or months to melt.

The mountains of snow, combined with icy and unshoveled sidewalks, also made travel difficult for bus riders and pedestrians, who often were forced into the street.

In Loudoun County, where 36 inches of snow fell in some areas, two Virginia Department of Transportation snowplows damaged their blades while carving through the stubborn mounds of snow and ice.

“This equipment being worked that hard, it’s not uncommon to have some breakdowns and some issues with machinery,” said VDOT spokeswoman Jennifer McCord.

Facing an increasingly impatient public, the District, Montgomery County and Virginia state officials all said they hope to have neighborhood roads “passable” by early Wednesday morning. Arlington and Alexandria set similar goals. Prince George’s County made a 9 p.m. commitment, saying that was more realistic.

VDOT said it aims to have one lane open in all the subdivision streets it maintains by 6 a.m. Wednesday.

McCord warned, however, that roads would be tighter and riskier than commuters are used to.

Snow mounds at intersections and in medians will reduce visibility, turn lanes might still have snow in them and piles could encroach on travel lanes, pushing drivers over to one side or the other.

“It will be a slow-going commute, because everyone will be negotiating those types of things,” McCord said.

The District’s emergency management chief, Christopher Geldart, said the city’s goal also was to have at least one lane open on all streets by Wednesday morning, though he, like officials regionwide, conceded that they may not get to all of them.

D.C. Mayor Muriel E. Bowser (D) told business owners to get out and shovel their sidewalks or face a $150 fine.

“You must get out and remove snow from your sidewalks immediately,” Bowser said.

She also warned that it is illegal to park “sort of in the middle of the street.”

“A legal space is one that is no more than 12 inches from the curb,” Bowser said.

Montgomery officials said their goal was to have passable residential roads by 7 a.m. By that time, spokesman Patrick Lacefield said, “all of our neighborhood roads should have gotten a pass from a plow. All neighborhood roads should be passable.”

He cautioned that “by ‘passable,’ we mean you can get out. It doesn’t mean bare pavement.”

In Fairfax County, Sharon Bulova, chair of the County Board of Supervisors, said that plows were making progress but that the cleanup effort could take several days more.

“They’re now saying that the clearing may not be completed until the weekend, which is frustrating for homeowners and businesses,” Bulova said.

Officials were looking ahead for other possible weather dangers.

Flooding remained a “slight risk” in the District, Geldart said.

But a bigger concern is another rush-hour freeze like the pre-blizzard storm last Wednesday, which paralyzed the region and left some commuters stuck in eight-hour ordeals.

“The precipitation I’m worried about: Thursday afternoon,” Geldart said. “We’ve got our contingency plans in place now if we need to — early on Thursday, pull our crews from what they’re doing, load up and treat so we don’t have what we had last Wednesday.”

Angela Fritz, of The Washington Post’s Capital Weather Gang, said that potential problems could shift slightly later.

“Forecasts earlier this week were pointing to snow potential on Thursday, but it now looks like that system will stay well to our south,” Fritz said. “We’re now more concerned about freezing temperatures on Thursday night. That could make the Friday morning commute icy in places where the road aren’t completely dry.”

Lori Aratani, Moriah Balingit, John W. Cox, Dana Hedgpeth, Arelis Hernández, Luz Lazo, Robert McCartney, Antonio Olivo, Katherine Shaver, Faiz Siddiqui, Donna St. George, Patricia Sullivan, Ovetta Wiggins and Martin Weil contributed to this report.