Legal assistant Michelle Powers won't be in her downtown Washington office this afternoon. Neither will Sue-Ellen Wright, a special events coordinator for a tobacco company. Congressional aide Manor Prewitt and his wife, Rosalind, don't plan to show up for work at all today.

They cut out early, like thousands of Washington-area residents, to get a jump on fellow travelers who every Thanksgiving drive along the 225 miles of Interstate 95 between Washington and New York, the nation's busiest north-south corridor and probably its most dreaded holiday travel experience.

Starting at 4 p.m. today and ending at 9 p.m., I-95 will carry more vehicles between the cities than at any other time of the year. The nightmare will be repeated Sunday evening when turkey-stuffed travelers waddle home on the New Jersey Turnpike and the interstate.

This annual trek prompts people all over the Washington area to swap tales of their travel tortures. It also requires careful planning of work and family schedules around the traffic. Even the timing of the Thanksgiving meal often hinges on the arrival of a weary survivor of I-95.

"I've made this trip all the other holidays at one time or another, and no other holiday is the same as Thanksgiving," said Lawrence Spinelli, a congressional aide who goes each year from Arlington to the New Jersey suburbs of New York City, a five-hour trip on most days. "The first time we went was 1978 and we left at 5 p.m. Wednesday, and got there past midnight. It was a searing experience."

More people will get burned in the future. Traffic is growing 3 percent a year along the corridor, and even with planned widenings of I-95 and the New Jersey Turnpike, the roads still will be unable to handle future holiday loads, several experts said.

The highest traffic counts in Maryland, Delaware, Pennsylvania and New Jersey are along the I-95-New Jersey Turnpike corridor. The Woodrow Wilson Bridge carrying I-95 over the Potomac River averages more than 160,000 vehicles a day; the New Jersey Turnpike will carry 500,000 vehicles a day during the Thanksgiving period.

Holiday drivers will face high gasoline prices. The cost of a gallon of unleaded regular gas has shot up nearly one-third since Iraq invaded Kuwait Aug. 2, and now stands at $1.359 a gallon nationally, according to the American Automobile Association. The record was set Easter weekend in 1981, when gas hit $1.388 a gallon.

AAA is projecting a 3 percent increase in car travel this Thanksgiving over last year, down from the previous year's 5 percent growth. But AAA also is predicting that airline and train travel will not grow from last year's level, indicating that even with the high price of gasoline -- and perhaps because of the high price of air travel -- people still are willing to drive over the river and through the woods to grandmother's house.

Thanksgiving is still the heaviest period at National Airport and Dulles International Airport, where about 100,000 travelers are expected today, up from the usual 75,000. Baltimore-Washington International Airport officials expect a record 44,000 passengers today.

Amtrak, which normally runs 770 trains a week in the Northeast, will add 90 trains to handle the traffic.

Thanksgiving brings out the worst in I-95 because most people leave after work or school Wednesday, meaning local commuter traffic in Washington, Baltimore, Philadelphia and New York is competing with an extra crush of through traffic. Sunday's return is equally overloaded because people wait until the last minute to come home before straggling back to work Monday.

Last year's trip was complicated by a snowstorm. It took the Prewitts 3 1/2 hours to get from Washington to Baltimore; they pulled into Philadelphia about four hours later, twice the usual time.

"My wife couldn't get off work last year, so we left at 6 p.m.," Prewitt said. "She heard me complain all 7 1/2 hours. This year she said, 'I'll never make that mistake again.' So she's taking Wednesday off and we're going up early."

Leaving early avoids many of the annoying bottlenecks, which are acute at the bridges, particularly the Delaware Memorial Bridge over the Delaware River connecting I-95 with the New Jersey Turnpike.

"The bridges are like a fish trap. Everyone gets caught there," said Rutgers University Professor Angus K. Gillespie, who was co-author of a book about the New Jersey Turnpike.

Long waits are common at toll plazas in Maryland, Delaware and New Jersey. Although people fume, traffic engineers said the queues improve the flow of traffic because they space it out.

Drivers relieve their boredom in odd ways. Sue Ellen Wright, who travels from the District to New Jersey on Thanksgiving, said she has worn Halloween masks to entertain motorists.

"New York drivers are so rude," she added. "When the turnpike narrows down to two lanes, many of them will drive on the shoulder. My brother and I sometimes will throw cranberries at them as they go by and the cars around you will cheer."

Part of the trouble with driving along I-95 is the lack of alternative routes, although the AAA recommends that drivers heading for New England use Interstates 83, 81 and 84 through eastern Pennsylvania and southeast New York State.

Statistics show that more people are shifting their travel to the Tuesday before the holiday and the Monday after, often using personal or vacation days.

Jerry Kraft, a traffic engineer for the New Jersey Turnpike, offered this suggestion: "On Wednesday, leave before 2 p.m. or after 8 p.m. On Sunday, stay away between 4 p.m. and 10 p.m. If you can leave later or earlier, you're okay. If you can leave the next day {Thursday or Monday,} you're even better off."

Drivers probably are going to face these problems every year for the foreseeable future.

Maryland officials want to widen sections of I-95 from the Woodrow Wilson Bridge to the Delaware line and build a bypass outside the Capital Beltway.

New Jersey has been trying to widen 35 miles of the 118-mile turnpike, but has run into financial and environmental difficulties. Pennsylvania officials are proposing a $2.5 billion, 20-year plan to turn their part of I-95 into a high-technology "smart highway" that tries to control the speed and location of traffic.

For all the plans, there is no money for many of these projects, and the federal government isn't likely to bail them out. That guarantees more years of Thanksgiving frustration.

"What puzzles me is the difficulty we have persuading people to travel on Thanksgiving morning," said Lois Morasco of the Pennsylvania Department of Transportation. "You don't eat Thanksgiving dinner in the morning. Why not drive that morning, get there in the afternoon, have your cocktails and eat dinner and relax?"

Washington Post staff writer Mark Potts contributed to this report.

If you are taking Interstate 95 and the New Jersey Turnpike today and Sunday, leave today before 2 p.m. or after 8 p.m. On Sunday, leave before 4 p.m. or after 10 p.m. The best advice: Go early Thanksgiving morning and return before Sunday.

Allow more time than usual if you plan to use National, Dulles International and Baltimore-Washington International airports. Meet or drop off passengers in the public parking lots, where there's a no-charge grace period.

If going by Amtrak, try to plan travel on Thursday, Friday or Saturday. Most trains requiring reservations are booked.