Most major roadways and many neighborhood streets were passable, although officials cautioned that many on-ramps, acceleration lanes and shoulders were still full of hard-packed snow.
With tens of thousands of people still without power throughout the region, Maryland Gov. Martin O'Malley said Thursday afternoon that "reliability standards" expected of utility companies would be reviewed by the state legislature.
Pepco, which serves the District and much of the Maryland suburbs, said the majority of customers should have power restored by 11 p.m. Friday. The utility was reporting 147,505 customers still without power as of 5 p.m. Thursday.
In Northern Virginia, where 50,777 customers remained without power as of 5 p.m. Thursday, Dominion Virginia Power said it was borrowing work crews from other areas to get the lights back on. The utility said it hoped to have power restored to 90 percent of customers by Friday night.
"We have about 2,000 workers engaged in our restoration effort, including crews from Eastern and Central Virginia and North Carolina assisting in Northern Virginia," said Rodney Blevins, vice president of electric distribution operations.
The outages hit poor and powerful alike. District Mayor Vincent C. Gray (D) returned home after crisscrossing the city and discovered his home had no power, a spokeswoman said. Pepco said 19,683 D.C. customers remained without power Thursday afternoon.
Montgomery County was particularly hard hit. It had by far the largest number of powerless homes, about 105,596 at 5 p.m. Despite a full deployment of Pepco crews, that number had increased by more than 200 since noon, the result of heavy, wet snow continuing to topple trees.
In addition to homes, the outages affected some 200 traffic lights, officials said.
Montgomery County has more power lines above-ground than many of its neighbors, said Pepco spokesman Bob Hainey. In addition, a substation in Kensington suffered damage and had to be shut down, he said.
The county is directing snow-clearing crews to neighborhoods with widespread outages so families without heat can emerge and seek help. A shelter opened at Richard Montgomery High School in Rockville, officials said.
Montgomery officials declared a road emergency about midnight. That allowed hundreds of abandoned vehicles, - which both fed the epic gridlock Wednesday night and hampered emergency workers and repair crews - to be towed.
Prince George's opened a warming shelter for residents without power at the Sports & Learning Complex in Landover.