Commuters wait outside the Auditors Building near the intersection of 14th Street and Independence Avenue SW. Slugging is a popular mode of transportation as drivers stop to pick up riders headed to Northern Virginia. (Nikki Kahn/The Washington Post)

As a kid, Billy Valentine used to pass Bob’s Slug Line every morning on his way to St. Bernadette School in Springfield, Va. Peering out at the line of commuters from Old Keene Mill Road, Valentine recalls asking his mother, “What are these people doing out there?”

Now, the Fairfax County resident and former Metro rider has joined the legion of casual car-poolers who line up daily for rides from Northern Virginia into the District and back.

A lot has changed at Bob’s since Valentine, 29, was in middle school: The old Circuit City has been razed; a rotating cast of restaurants — Chi-Chi’s, Long John Silver’s, Shoney’s — has come and gone; pickup and drop-off points have been relocated.

What has remained for decades is the crush of federal employees, policy wonks and military workers who gather every weekday morning at the lot off Interstate 395, the region’s oldest slug line, to share rides into the nation’s capital. The name, Bob’s, has stuck even as its namesake, Bob’s Big Boy, has ceased to exist.

“It’s an easy way to get to work — it’s faster than Metro; it doesn’t cost anything,” said David Stiles, 54, a 30-year slugger who was commuting from Bob’s to Independence Avenue and 14th Street SW on a recent morning.

Slugger Corey Pickelsimer, of Woodbridge, Va., waits outside the Auditors Building near the intersection of 14th Street and Independence Avenue, SW for a ride to Virginia on Wednesday, May 18, 2016. (Nikki Kahn/The Washington Post)

As Metro begins a yearlong maintenance program that will disrupt the commutes of hundreds of thousands of residents in the region, many of them may want to consider slugging, the nation’s “original ride-sharing” system.

The informal system is thriving. The proportion of slug drivers and sluggers along Interstate 95 has increased by 18 percent since 2014 — according to preliminary Virginia Transportation Department figures to be released in an upcoming report — a likely byproduct of additional parking capacity at commuter lots and the expansion of slug lines with the Interstate 95 Express Lanes project.

And the 41-year-old system is evolving with the times: A Woodbridge, Va., developer has created an app to match drivers with sluggers — an invention driven by the growing number of commuters interested in the service because of the advent of express toll lanes and problems with Metro service.

Commuters point to the myriad advantages of slugging, the preferred mode of transportation for about 6,450 residents in Northern Virginia, according to VDOT.

Valentine made the switch after Metro’s Silver Line opened in the summer of 2014. The new line slowed service on the Blue Line, which he rode from Franconia-Springfield to Foggy Bottom. He got so fed up with the crowding and long waits for trains that he decided to give slugging a try.

“That’s when it hit me — I realized I don’t have to be dependent on Metro at all,” said Valentine, who commutes from the Rolling Valley shopping center lot in Burke to the Foggy Bottom nonprofit organization where he works. It saves him thousands of dollars every year, he said.

Jennifer Gross, 37, also abandoned Metro after her commute from Burke to Foggy Bottom became unbearable. Now she drives her Honda Odyssey with her radio tuned to WMAL and, usually, a couple of strangers in her back seat.

“It’s just so . . . freeing,” Gross said.

“It really is so convenient for everyone involved. And the fact that there’s no money changing hands makes it such a great grass-roots system,” she said. “I think that kind of fellowship is probably really good for this country.”

An app for that

A fascination with the system is what prompted Kalai Kandasamy, who has been slugging for 15 years, to develop an app: Slug­lines. It unites commuters by showing drivers where riders have checked in. He says it eliminates the uncertainty for drivers approaching lots looking for riders. Slug­­lines stays true to the established slugging system and no money changing hands, differentiating it from ride-hailing apps such as Uber and Lyft. It has about 150 users so far, he says.

“The major problem we are trying to solve is the unpredictability,” said Kandasamy, who lives in Woodbridge in Prince William County and commutes to Crystal City. “With the app, people can stay in their closest location and say, ‘Hey, I’m available to go to Pentagon.’ ”

Kandasamy says the free app — which is available for Apple and Android phones — aims to pair commuters during “non-peak time frames” — for instance, 6:30 a.m., when HOV restrictions are enforced but many commuters are not yet on the road. It shows drivers whether sluggers are waiting at key locations and, if not, directs them to places where they can quickly pick someone up. He sees Safe­Track, Metro’s coming maintenance overhaul, as an opportunity to attract even more riders.

“If somebody checks the time going from Franconia-Springfield to Pentagon, then if they start slugging from the same spot, they will not go back to the train,” he said.

He wants officials to reserve some of the Franconia-Springfield Metro station’s 5,000 garage spaces for sluggers during SafeTrack.

Anna Nissinen, a spokeswoman for the Fairfax County Transportation Department, said that those spaces are “open to everyone, whether meeting a car pool or taking transit” but that the county is not aware of any formal plans to arrange a slug line at Franconia-Springfield.

So what made slugging the commuting option of choice for so many in the D.C. area?

Authorities on the subject point to several factors. Slugging, which is also common in San Francisco and has a smaller following in Houston, debuted about 1975 during the Middle East oil crisis and with the opening of high-occupancy vehicle lanes for car-poolers. According to David LeBlanc, curator of Slug-Lines.com, the unofficial authority on slugging, it carried a dual benefit for the government: reduced gas consumption and environmental sustainability.

The name derives from the word for counterfeit bus tokens — “slugs.” Bus drivers began to refer to these commuters, who originally lined up at bus stops, as “slugs” because they weren’t actually taking the bus.

‘Security in numbers’

For sluggers, it’s not just car-pool lanes that have been key. It’s been HOV-3 lanes, requiring three or more commuters, according to Howard Jennings, the managing director of Mobility Lab, the research branch of Arlington County’s commuter services program.

“The common wisdom on it is the HOV-3 is pretty critical to give people a sense of security in numbers,” Jennings said. “There’s a lot of government employment in the corridor there, so you had folks with relatively regular hours who could and would take advantage of that situation.”

Now, as the slug system has expanded to encompass more than two dozen destinations in the region, many of the existing HOV lanes have been converted to high-occupancy toll lanes — and the proportion of sluggers has increased along I-95, where HOT lanes now extend to Stafford County. An upcoming project will convert the existing I-395 HOV lanes into tolled express lanes up to the D.C. line, with construction set to be finished by 2019.

Cars with three or more passengers will continue to travel for free; others who want to use the express lanes will have the option of paying a toll to do so.

“You’re going to have some people who, rather than pick up slugs, will just pay the eight to 10 dollars,” Valentine said. “Or you can have people who say, ‘I want to use those lanes. I don’t want to pay the money. I’m going to pick up some slugs.’ ”

Sluggers admit that there are downsides to sharing a ride with a stranger. Valentine remembers getting into a black Jeep Wrangler with a zip-down top, where the driver blasted heavy metal music all the way down the interstate. Flora Arabo, 38, of Springfield said she got into a car in which a couple were having a “marital dispute.” And Gross recalled the “mini stroke” she had when a stranger banged on her window on 20th Street NW — it ended up being the man she had just dropped off, who had forgotten his lunch in the back seat.

One of the most frightening incidents in recent memory occurred in 2010 and involved a former Army sergeant major driving more than 90 mph on Interstate 95 after picking up two passengers. After the passengers asked to be let out, he proceeded forward and struck one of them with the vehicle, causing an apparent concussion, according to police. The passenger had been trying to take a picture of the vehicle and tag number to file a complaint. LeBlanc says such incidents are anomalies.

With looming disruptions tied to the introduction of Metro’s SafeTrack, a program that is expected to snarl traffic across the region, he just hopes more commuters will try it.

“I think it’s amazing,” said Le­Blanc, who wrote the 1999 book “Slugging: The Commuting Alternative for Washington, DC .” “As long as slugging has been around — it’s been around a long time and there’s been a lot of transportation changes­ over the years — it seems to be resilient and it’s weathered the test of time.”