By Katherine Shaver
Washington Post Staff Writer
Wednesday, October 23, 2002; Page B01

The busy stretch of Route 50 between Bowie and the Capital Beltway yesterday became the fifth major highway in the Washington suburbs to open carpool lanes.

Motorists who use the new lanes, which cost $26.3 million to develop, will cut five to seven minutes from their trips along that eight-mile corridor, state officials said.

To travel in the high-occupancy vehicle lanes, the first in the region to be open 24 hours a day exclusively for carpoolers, a driver will have to bring along at least one passenger. About 10 to 15 percent of the vehicles using Route 50 already carry two or more people, Maryland officials said.

State highway planners hope to speed travel between Washington and the quickly growing communities in Anne Arundel and Prince George's counties. In Bowie, the east-west lanes of Route 50 connect with Route 301, a major north-south highway.

While rewarding people who don't drive alone, the new lanes aren't likely to offer the added bonus of those along Interstate 395 in Northern Virginia. People who don't want to drive and don't want to commit to a formal carpool can catch free rides along I-395 in a loosely organized system known as "slugging."

The slugs, people who wait in line for drivers to pick them up and form a carpool, are vital to the performance of the HOV lanes in the crowded I-395 corridor. An estimated 3,000 slugs climb into strangers' vehicles each morning in Northern Virginia, freeing up space on roads and on Metrorail cars and commuter trains. About one out of four vehicles using the I-395 HOV lanes in 1999 carried a slug, said Valerie Pardo, a senior transportation engineer for the Virginia Department of Transportation.

"It's a big factor in the success of those HOV lanes out there," Pardo said.

But slugging hasn't caught on in Maryland's only other HOV lanes, on Interstate 270.

"So far, our methods are to encourage people to form carpools" through help from government programs, said Valerie Burnette Edgar, a spokeswoman for the Maryland State Highway Administration.

The Washington area's slugging phenomenon has drawn nationwide attention. Slugs have their own Web site, www.slug-lines.com, complete with slugging "etiquette" (no smoking, eating or talking except a brief "thank you") and new locations where drivers and riders can meet.

Northern Virginia transportation officials don't sanction slugging because of potential liability. But they say it's so important to freeing up road space that they build queuing areas into new park-and-ride lots and Arlington County helps pay for the Web site. Slugging takes vehicles off the road by allowing people to share rides without having to commit to the strict meeting times of most carpools, Pardo said.

But unlike I-395, where HOV lanes require vehicles with three or more people, those in Maryland require only two people. That's probably a key reason slugging hasn't caught on in Maryland or along I-66 in Northern Virginia, where the carpool lanes also require only two people, Pardo said. HOV-2 lanes also are available on the Dulles Toll Road.

It's not as difficult to find one neighbor or co-worker to carpool with as it is to find two, Pardo said. Moreover, she said, many people don't feel comfortable getting into a car alone with a stranger, while they might feel fine in a group of three travelers.

"If there's someone else getting in there with you, it's a shared risk," Pardo said.

Engineers determine how many people per car should be required for the carpool lanes by measuring how the road space can be used most efficiently. They require enough people per vehicle to limit use of the lane while still attracting enough vehicles to avoid wasting the road space.

For example, when VDOT officials in 1999 considered making the I-395 carpool lanes HOV-2 instead of HOV-3, Pardo said, they found that it would allow so many additional vehicles into the carpool lanes that they would back up from the Pentagon to the Beltway.

Edgar said that requiring only two people in a vehicle works well on I-270's HOV lanes and that state officials wanted to try to keep the requirement consistent on Route 50.

"If it gets too congested and the HOV lanes aren't working well, we could always go to HOV-3," Edgar said.

The addition of the HOV lanes means there are four travel lanes in each direction on Route 50. State officials said they needed 24-hour HOV lanes because they placed them in what were the highway's inner shoulders. As a matter of safety, the officials wanted to avoid any confusion about whether the new lanes were for travel or breakdowns.

David LeBlanc, an Army lieutenant colonel who runs the slugging Web site and wrote a book about slugs, said he thinks HOV lanes won't attract slugs unless they are separated by a barrier and heavily patrolled, like those on I-395.

"Slugging is really only successful on I-95 because of those dedicated HOV lanes with jersey barriers and discrete exit points," LeBlanc said. "I think that's the single reason slugging hasn't flourished anywhere else."