Stand in line. Ride with strangers. Zip past traffic to the city.

WOODBRIDGE

Commuters filled the 2,200 parking spaces of the Horner Road commuter lot on a recent beautiful morning, 25 miles south of the nation's capital.

In the center of the commuter lot - the largest in Virginia - a man wearing khaki pants with a backpack over his shoulder approached an SUV.

He exchanged a few words with the driver. "14th and Penn!" he then called to a line of people behind him.

Two people got into the SUV, which zipped into the coveted HOV-3 lanes of Interstate 95/395 north for a quick ride into Washington.

Known as "slugging," the process is essentially instant carpooling with strangers. The nickname sounds funny, but it's a common expression among Northern Virginia commuters, who sometimes have commutes of up to two hours one way.

Sluggers can slash a lengthy commute on I-95 into a quick, quiet trip to the Pentagon or D.C. They save money on gas, get a free ride at flexible times, and avoid parking once they get to work.

"I can make it to work in like 25 minutes versus the hour, hour and a half," said Stephanie Spears of Woodbridge, who slugged a ride on I-95 on a recent morning.

Commuters started slugging in Northern Virginia more than 30 years ago, according to the Virginia Department of Transportation. Commuters formed slug lines on their own, and no government agency oversees them.

With gasoline prices now averaging nearly $4 a gallon, the commuters at the Woodbridge lot said the practice is growing even more popular.

An estimated 6,500 commuters a day slug or pick up slugs, compared with 3,000 in 1999, according to Virginia Department of Transportation estimates.

"The slug lines themselves are getting larger," said David LeBlanc of Prince William County, who started the Web site slug-lines.com and calls slugging "the best system out there."

About 25 slug lines form each morning in Fairfax, Prince William and Stafford counties, LeBlanc said. Two lines reach south as far as Fredericksburg, and 18 to 20 lines form in the District and at the Pentagon at the end of each workday. Here's how it works:

Two lines form at slug pickup spots: one with people, one with cars.

The first person in line talks to the first driver. The driver tells the "head slug" the destination, and the head slug shouts it to the rest of the slug line. The first two people in line who want to go there get into the vehicle.

The process repeats, over and over, each morning.

In Woodbridge, slugs line up before the HOV-3 opening at 6 a.m. The lines remain at some lots until about 9 a.m.

The slugging concept has not caught on in many other areas of the country, not even in the Maryland suburbs of D.C. or the areas of Northern Virginia off Interstate 66, LeBlanc said. But commuters have started slug lines in Houston and San Francisco, he said.

Would slugging work in Hampton Roads? Probably not, according to Camelia Ravanbakht, the principal transportation engineer with the Hampton Roads Planning District Commission. In Hampton Roads, there are more than 830,000 commuters, but they are not going toward a central location, she said.

"D.C. is very unique because of the employment in the downtown area," she said.

LeBlanc cites a few reasons that slugging has worked so well, for so long, in Northern Virginia.

First, drivers don't allow just one stranger into their car; three people make a small group. The HOV lanes of I-95 require three people in a car; the HOV lanes of I-66 require only two people.

Joan Morris, a spokeswoman for the Virginia Department of Transportation, which has followed the slugging phenonemon, noted that many drivers and passengers are headed to the Pentagon.

"You've got people dressed in military uniform, and that probably has something to do with it," she said. "You feel safe getting in the car, or another car, with a couple of military people."

Also, LeBlanc noted, vehicles can't merge in and out of I-95's HOV lanes. Motorists enter them at gated entry points, and there are few points after that to get on or off.

There's almost never a delay in the I-95 HOV lanes, said Jeff Werling of Woodbridge, who picks up slugs to get into the District on his way to College Park, Md. But the chances are high for a big backup on the non-HOV lanes of I-95, making an hour and a half commute, he said.

"95 down to Woodbridge is a notoriously congested road," he said. "We've got these nice, wide HOVs, and it just turned out to be the most convenient thing."

As gas prices have gone up, so has the number of slugs, Werling said.

One of of Werling's passengers on a recent morning was Mohamed Kaloko of Stafford County, who works for the U.S. Department of Agriculture. Kaloko said slugging saves him money on gas.

He said he previously drove an hour and a half - sometimes up to two hours - to get from Stafford County to his old job in Tysons Corner.

As a slug, he's at work in D.C. in 30 to 45 minutes, which in this area is considered a decent commute time.

"I have been a slug for five months. I do it every day," Kaloko said. "Within 30 to 45 minutes I'm at work, so it's been working out great."

Morris, of VDOT, said slugging is successful because VDOT hasn't gotten involved.

"It was started by commuters probably 30-something years ago, and it's their own system," she said.

"We can't condone it because we're the state, but it works very, very well."

Patrick Wilson, (757) 446-2957, patrick.wilson@pilotonline.com