But Wednesday's storm added another factor to the mix, as some local officials blamed the federal government's decision for creating an early rush hour at exactly the time the snow came down in an unusually intense burst.
"I wonder how many of these we have to go through before we learn that if we keep people until 4 p.m. and dump people into the middle of the chaos, this is going to happen," said David F. Snyder, vice mayor of Falls Church, who has focused on emergency preparedness as a member of the Metropolitan Washington Council of Governments.
John Lisle, a spokesman for the D.C. Department of Transportation, said the government should have pushed workers to leave earlier. "Looking back, I wish we had told people at 3 o'clock, 'The storm's going to hit at 4 p.m. If you don't leave by then, you may not get home,' " he said.
But John Berry, the federal government's personnel management director, stood by his decision to release workers at 3 p.m. "The reality is, with human nature being what it is, many people did not choose to take advantage of the option" to leave early, he said. "They looked out the window, saw no snow and said, 'I can wait until I see snow.' "
The storm had been predicted all week, but hours of rain washed salt and other chemicals off roads that had been treated Tuesday night. Then, just as hundreds of thousands of federal workers were being sent home early, a sudden dump of heavy, wet snow - no more than half a foot - turned major thoroughfares into icy, slushy parking lots.
Cars and buses stalled along 16th Street NW and Connecticut Avenue, four tractor-trailers jackknifed on the Capital Beltway, and wreckers towed 17 trucks near the Wilson Bridge, scenes duplicated by the dozens on major commuter routes from Annapolis to Dulles.
As frustrating minutes turned into hours, commuters by the hundreds ran out of gas or left their cars, making it even more difficult for plows and tow trucks to get to arteries such as the Beltway, Interstate 66 and the George Washington Memorial Parkway.
"It just felt hopeless," said Shaun Gholston, 33, who said it took him 11 hours and 19 minutes to drive from Rockville to his Capitol Hill home, which usually takes 55 minutes. "Like I was never going to get home."
Wednesday began with a burst of bravado, as D.C. transportation officials said they were ready for the storm. They, like their suburban counterparts, had spent the night treating major roads to keep them from freezing. But then came the rain. Then the temperature dipped below freezing, the rain turned to snow and the federal workers hit the roads. Re-salting the roads was now impossible. In the District, traffic control officers were unavailable to man intersections because they had been ordered to drive plows, which immediately got stuck in traffic.
By 4:30 p.m. in Maryland, a tractor-trailer had jackknifed on the inner loop of the Beltway near River Road, blocking several lanes. Just as a wrecker pulled that rig away, three more tractor-trailers broke down near the Beltway and Interstate 270.
One of the truck drivers walked away from his rig, making it more difficult to tow. Maryland State Police in Montgomery County ended up towing 180 vehicles from the Beltway and I-270. Montgomery police towed several hundred vehicles from local roads and were still doing so Thursday afternoon, officers said.
In the District, more than 40 accidents tied up traffic on thoroughfares such as 16th Street and Connecticut and Georgia avenues. At 6:30 p.m., at Connecticut and Albemarle Street NW, a Metrobus slid into a curb and blocked three lanes of traffic.
Within a half-hour, three more buses and several cars got stuck trying to maneuver around the first bus. Traffic on the avenue didn't recover for hours.
In all, 70 Metrobuses stalled in the snow, officials said.
Suitland Parkway, which carries thousands of commuters between the District and Prince George's County, was shut down after 5 p.m. because the snow made it impassable, officials said. President Obama's return from Andrews Air Force Base to the White House during that hour had no effect on the traffic; it took the presidential motorcade 63 minutes to return from Andrews, a trip that had taken 24 minutes that morning.
An hour-long commute became an eight-hour ordeal for Alan Creamer, 44, a biologist for the federal government. The 4:30 p.m. Martz bus to his home in North Beach was blocked from the Suitland Parkway and got stuck on Interstate 295.
"At the beginning, people had a sense of adventure, everyone was talking," Creamer said. His seatmate offered crackers to fellow passengers. But after a few hours, people lost their patience. "There was someone yelling, 'We shouldn't go this way!' " he said. "Someone else yelled, 'I want to get off!' " The driver let a few passengers out at the Anacostia Metro station.
On nearly every major road, vehicles slipped and stalled. Frustrated, cold and running out of gas, hundreds of motorists left their vehicles, turning roads into slalom courses.
In Northern Virginia, nearly 450 vehicles became disabled, and 100 others were abandoned on the GW Parkway, officials said.
"I understand that people were frustrated," said Virginia State Police Lt. James DeFord, "that they were running out of gas and were worried about freezing. But they really contributed to the problem by leaving their vehicles in the road. A lot of our police cars have push bumpers, so if people had stayed with their cars, we could have given them a shove and got them going."
Jon Redman, who owns the Redman Fleet Services towing service in Lorton, said it was difficult for his crews to keep up with demand. "You would get a call for a tow truck at a location, but when we got there it was five, eight, 10 cars," he said. "At one spot, there were 17 vehicles waiting to be towed."
Tammie Grice, an executive assistant at Marriott who commutes to Gaithersburg from Fort Washington, wanted to stay with her car. By midnight, she had been stuck in traffic for more than nine hours, and she was out of gas.
Stranded in the left lane of the GW Parkway, with a line of cars behind her and no help in sight, she decided to walk. She slipped off her high heels, put on some flats and hiked to a nearby service station, where she spent the night with six other stranded drivers, sleeping in wooden chairs until her son came to pick her up at 6 a.m.
"I wasn't scared or worried, to tell you the truth. I was just cold," she said.
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