Washingtonians are expected to leave town in record numbers this weekend, topping off a sizzling summer traveling season that traffic watchers predict will grind to a literal halt Tuesday when everyone returns to town.

After a summer of relatively easy mobility, when anywhere from 10 to 15 percent of the region's 1.5 million daily commuters were off the roads, traffic will return to its normal beastly self today as holiday drivers take to the roads for the long weekend. Then comes Tuesday, when an onslaught of returning commuters and the opening of area schools -- plus traffic-stopping security measures and major construction projects -- will remind drivers that they live in a region with the third-worst traffic in the nation.

"People really have to recognize that the last few weeks are not reflective of what they will face Tuesday," said Dan Tangherlini, director of the District Department of Transportation, who predicted that commute times could be double what they've been in recent weeks. "We're going to see lane closures, we'll see restrictions on traffic and then with new security precautions at the Capitol and continued loss of vital pieces of infrastructure, we're forcing more traffic into less space."

But first the beach. AAA Mid-Atlantic is predicting that 537,600 Washington area residents will head to the shore, mountain retreats and other destinations over Labor Day weekend, the overwhelming number of them by car. That would represent a 3 percent increase over last year and set a record for the traditional end-of-summer holiday weekend.

Nationally, AAA is also predicting record travel, estimating that 34 million Americans will vacation over the three-day weekend, a 2.2 percent increase over last year's all-time high.

Travel and tourism officials said travelers have brushed aside high gas prices and are motivated to take trips because of an improving economy, increased confidence in travel security, cheap airfares and a desire to get out and get away.

"Our projections right now are that an enormous number of Washingtonians intend to take advantage of the three-day weekend," said Lon Anderson, a spokesman for AAA Mid-Atlantic, which surveyed 1,300 people. "That inevitably means our major roads are going to be crowded."

Starting Tuesday, the crowding is expected to be especially bad for commuters in the District because a series of security checkpoints around the Capitol is expected to block traffic to a degree that could reverberate across the city.

Drivers on several roads around the Capitol will find that security checkpoints block their way and that they will have to come to complete stops before officers give them a once-over and wave them through. This process has been relatively benign since it was set up last month, because few drivers have been clamoring to get through at the same time. But transportation officials stress that traffic could be halted for dozens of city blocks as drivers wait to get through and others bail out in search of alternate routes.

The checkpoints around the Capitol, which are on major routes such as Independence and Constitution avenues, also will complicate commutes for those who pass through on their way to and from the suburbs. Drivers also can expect delays around Lincoln Circle, where a variety of road improvement projects has slowed traffic on Memorial Bridge, Rock Creek Parkway and other area roads.

Tangherlini suggested that drivers allow for extra time or take mass transit to work.

Suburban commuters aren't going to be much happier. Increased construction on the region's two biggest projects -- the Woodrow Wilson Bridge and Springfield Mixing Bowl -- will cause lane closures and delays on major and minor roads around both sites.

A lane of the inner loop of the Capital Beltway was closed for about a half-mile east of the Interstate 395 exit in Springfield about a month ago. It will stay that way for another year and a half as workers build a new bridge above it, project officials said. Officials also reminded drivers that nighttime lane closures will continue in the area.

Drivers can expect more delays a few miles east, where work on a new Wilson Bridge will cause lane closures on the Beltway and side streets. Project officials said all lanes will be open during peak periods, but lanes would be closed from 9 a.m. to 3:30 p.m. and overnight.

Trish Broud isn't looking forward to any of this. Her summertime commute from Kensington to Northern Virginia has been a breezy 30 minutes. "I love it, I mean I rarely slow down anywhere," she said.

But then her tone changes from ease to anxiety as she starts to consider what it's going to be like next week and beyond. Her departure time of 7:30 to 7:45 a.m. will be moved up to a firm 7:20, and getting into work by 8 is starting to sound unthinkable. She figures it'll be 60 to 90 minutes each way.

So maybe an out-of-town breather before the big backups is just what she needs?

Broud says she doesn't think so: "You think I'd voluntarily drive in Labor Day traffic?"

Northbound traffic on Interstate 95 at the end of the Fourth of July weekend, above, is a likely precursor for Tuesday, when, officials estimate, the return of vacationers to work will boost daily traffic numbers by 10 to 15 percent.