Sometimes they travel alone: a breathless woman briskly wheeling her suitcase down Connecticut Avenue's rough sidewalk through the morning mist. Sometimes they rove in pairs: a young couple, straining under the weight of their backpacks, trudging toward the Metrorail stop at Dupont Circle.

But mostly they roam in vast flocks, queued up by the dozens and snaking ever closer to the ticket counters at Dulles International Airport, or by the thousands, drawn toward any daylight in the cascading traffic along Interstate 95.

These are the seasonal peregrinations of that migratory creature called the Thanksgiving traveler, and yesterday hundreds of thousands in the Washington area took this autumnal journey, crowding the roads and rails while setting record levels at the area's airports.

Even for a region steeled by the daily ordeal of commuting on some of the country's most congested highways, the holiday getaway yesterday proved arduous. "People definitely had a slow exit in the region," said Virginia State Police spokeswoman Lucy Caldwell. "It's been very slow all day, and it's continued into the evening."

With both Dulles and Baltimore-Washington International airports far exceeding passenger levels of last Thanksgiving, the region's three commercial airports are on a pace to surpass 1 million travelers during the long holiday weekend. Amtrak, meanwhile, carried more than 60,000 passengers yesterday on its Northeast Corridor service, connecting Washington and Boston, and anticipates more than a half-million travelers across the system by Sunday evening.

In Union Station yesterday, Amtrak employees herded hundreds of waiting passengers into single-file lines that wound from the boarding gates past Sbarro's fast-food restaurant and a liquor store and around the corner along the B. Dalton's bookstore.

"It seems a lot more crowded than last year," said Kathryn Putsavage, a 20-year-old junior at the University of Maryland, hoping to board an afternoon train that would take her home to Trenton, N.J. As she waited, Putsavage passed the time with a book about Chinese literature, perched on a duffel bag stuffed with dirty laundry. "Who wants to do it at school when you can do it at home for free?" she asked.

On area roads, traffic started building by 10 a.m., a time when most morning rush hours are finally, thankfully, dissipating. The Virginia portion of the Capital Beltway and I-95 south of Springfield were heavy all day. A spate of minor accidents that typically would have had little effect snarled traffic because of the exceptionally high volume. In Maryland, the worst tie-ups were on northbound I-270 from the Beltway to the Frederick County line, caused in part by a crash involving an armored truck.

At Dulles, which has been growing at breakneck speed since last Thanksgiving, officials said the volume of travelers was 25 percent higher yesterday than a year ago, exceeding 70,000 passengers.

To accommodate the crush, the airport opened 8,000 more parking spaces this year--including 4,000 this week--boosting the total to 23,000 spots, according to Tara Hamilton, spokeswoman for the Metropolitan Washington Airports Authority. The airport also added gates earlier this year by opening a new regional terminal for Atlantic Coast Airlines. But passengers--many traveling with young children as well as dogs and an occasional cat--still encountered moderate delays at ticket counters, security checkpoints and baggage claim areas.

Between Tuesday and Sunday, more than 750,000 travelers are projected to use Dulles and Reagan National, the two airports operated by the authority. About 50,000 passengers yesterday passed through National, which was expected to remain relatively busy this morning as last-minute passengers flew to nearby destinations in New York and Boston.

"It's clearly busy," Hamilton said late yesterday afternoon. "But there aren't any major traffic jams out front and no long lines at the ticket counters."

Baltimore-Washington International Airport, which has also been growing rapidly, recorded nearly 60,000 passengers yesterday, an increase of about 15 percent over last year, said spokeswoman Marilyn J. Corbett. More than 350,000 travelers are expected during the holiday week, a dramatic increase from last year, when fewer than 300,000 used the airport. BWI has pressed into service 5,000 spaces in its overflow parking lot, increasing the total number to more than 23,000.

Most Amtrak service ran on schedule yesterday, though two trains bound to Washington in the mid-afternoon were delayed after a 17-year-old girl was struck and killed by a train south of Philadelphia, officials reported. The incident is under investigation.

The company added 61 trains with 46,000 seats across the country between Tuesday and Sunday to accommodate the crowds, according to spokesman Jim Waddington. In the Northeast Corridor alone, where passenger volumes were double their usual midweek level, Amtrak has added 50 trains with more than 30,000 seats.

Francesca Caretto, of Germantown, had her hands full in the waiting area of Union Station outside Gate B, carrying her 3-year-old daughter, Fiona, with her left arm while pushing luggage with her right. Her other daughter, Katarina, 8, pushed Fiona's stroller and together, the trio boarded a train to Philadelphia to visit with Caretto's sister. The juggling could have been worse, Caretto said. "I shipped a box ahead--clothes and blankets--so I wouldn't have to carry as much," she said.

Donald Easum, a Manhattan-based consultant who was in Washington yesterday for a meeting at the State Department, dropped by the station to see if he could reserve a seat on any train that would take him to Metro Park, N.J., last night. "Every one is full," he said, as he reached for a pay phone to check airline availability.

CAPTION: Francesca Caretto, of Germantown, with daughters Fiona, 3, in her lap, and Katarina, 8, at left reading, waits at Union Station to take a train to Philadelphia.

CAPTION: U-Md. junior Kathryn Putsavage, 20, left, sits with Jennifer Lamprecht, 23, at Union Station. "It seems a lot more crowded than last year," Putsavage said.