Icy suburban roads snarled rush-hour traffic yesterday morning and prompted outlying school districts in Maryland and Virginia to open late or close entirely.

Side roads, driveways and parking lots in the outer suburbs bore the brunt of the trouble, state highway and police officials said. The District of Columbia reported few problems on the roads, but plenty on icy sidewalks.

"The major difficulty . . . was the sidewalks where businesses haven't put salt down," D.C. Department of Public Works spokeswoman Tara Hamilton said. "There was some slippery going."

Fire officials in both Montgomery and Fairfax counties said ambulance crews responded to a flood of calls early yesterday from people who had fallen on the ice.

The worst traffic accidents occured south and west of the city, police said, including one ice-related fatality in Spotsylvania County. Virginia State Police reported that an early morning 10-car pile-up near the 14th Street bridge blocked a ramp and a lane of northbound Interstate 395 for half an hour.

And in Loudoun County, rescue vehicles sent to emergencies were in some cases rescued themselves by Virginia Transportation Department crews, according to department spokeswoman Mary Ann Reynolds. Crews helped one ambulance that had slid off the road while trying to take a patient to Loudoun Hospital Center. The woman, who had a head injury, was in fair condition, a hospital spokesman said.

Although many area roads had been salted, the freezing conditions meant the salt had no chance to act.

"A salt hasn't been invented that can melt 'frizzle,' drizzle that freezes as soon as it hits the pavement," said Reynolds.

Overnight temperatures stayed below freezing in most areas. While National Airport's overnight low Tuesday was 31 degrees, temperatures at Dulles International Airport dropped to 25 degrees early yesterday and did not rise above freezing until 11:30 a.m., said National Weather Service meteorologist Bill Comeaux.

However, once the sun came out, it made quick work of the ice, and the Virginia Transportation Department began sending its crews home yesterday afternoon after 60 straight hours of work, Reynolds said.

Schools closed in Montgomery, Howard, Fairfax, Manassas, Manassas Park, Loudoun and Prince William and opened late in Arlington and Falls Church. District of Columbia, Alexandria and Prince George's schools opened on time.

"We had a tremendous amount of ice on the parking lot . . . and driveways," said Manassas Park Acting Superintendent Bert Hatcher. "You could get the kids to the school easier than you could get them {inside}."

Area school districts build three to four "snow days" into their calendars, and most have used only two. Only after all built-in snow days are used, do school systems begin adding days to the school year.

Rosemary Hoffman, 62, was killed when her car slid off a Spotsylvania County road and hit a tree yesterday morning, said Virginia State Police spokeswoman Lucy Caldwell.

The ice prompted Jake Hammersly, who lives on Bull Run Mountain in western Prince William, to take his third straight personal leave day from work.

"If I can't walk to the truck, there's no sense in trying to drive it down the mountain," he said. "We're pretty well stuck in the house."

Staff writers Robert O'Harrow Jr., DeNeen L. Brown, Veronica T. Jennings, Stephen Buckley and Gabriel Escobar contributed to this report.