As Maryland seeks companies to replace the traffic-clogged American Legion Bridge, transit advocates are calling the state’s plan shortsighted for not requiring that a new span be able to carry a rail line to Northern Virginia.

Any bridge built to last up to 100 years, they say, should allow for the possibility that trains could someday circle the nation’s capital through its ever-growing suburbs, alongside the Capital Beltway. Long-term hopes for what some call a Metro “Beltway Line” were incorporated into the Woodrow Wilson Bridge when it was rebuilt with room for rail on the Beltway’s southern end in the mid-2000s.

Precluding that possibility on the highway’s other Potomac River crossing, advocates say, would consign many residents to driving or riding buses for decades. They say it also would miss a critical opportunity for a direct rail link between Montgomery and Fairfax counties — the region’s two most populous suburbs and biggest job centers outside downtown Washington.

“These are 100-year decisions,” said Stewart Schwartz, executive director of the Coalition for Smarter Growth. “It costs a lot less to do it right in the first place, while you’re designing and building this critical infrastructure. … Many people still have a strong vision of a circumferential rail line.”

Those who oppose the idea say a new bridge widened with express toll lanes would significantly improve mass transit by carrying buses that could avoid getting bogged down in traffic.

Under the state’s plan, a team of companies would build the bridge and toll lanes and finance their construction in exchange for keeping most of the toll revenue. It’s unrealistic, some say, to think local governments would ever have the billions of dollars necessary to extend a rail line across the bridge.

“It’s been more than a decade since the [Wilson] bridge was built, and we’re still decades away from rail there,” said Jason Stanford, president of the Northern Virginia Transportation Alliance. “So to assume we’re decades away from rail over the American Legion Bridge seems like a pretty safe bet to me.”

The Maryland Department of Transportation has announced plans to replace and expand the nearly 60-year-old bridge as part of adding four high-occupancy toll (HOT) lanes — two in each direction — to part of its Beltway and lower Interstate 270.

The new 16-lane bridge would be almost twice as wide as the existing 10-lane span because it also would have additional entrance and exit HOT lanes, shoulders and a shared path for pedestrians and cyclists.

In an email, state project spokesman Terry Owens said rail across the bridge is not part of regional or local long-range transportation plans.

He said “an extensive network of commuter buses” will be able to use the HOT lanes at no cost. Because the lanes will be “managed” via toll prices to remain congestion-free, Owens wrote, they will provide “much faster and more reliable transit service throughout the region.”

Another big wrinkle: Leaving room for rail across the bridge wouldn’t do much good if Virginia didn’t have train tracks on its side — something the state will for decades have less financial incentive to build. That’s because under Virginia’s contract with Transurban, the Australian company that operates the state’s Beltway HOT lanes, the company could seek compensation from the state if a new rail line in the corridor siphoned off toll revenue. The contract expires in 2087, said a spokeswoman for the Virginia Department of Transportation.

Maryland recently chose Transurban to develop the HOT lanes proposal, including to replace the bridge, though the selection is under protest by a losing bidder. Unlike in Virginia, Maryland law does not allow the state to compensate a private developer for revenue lost to new transit infrastructure, Owens said.

As suburbs emerged with their own job centers, Washington-area planners and transit advocates have explored for years how to better connect the outer spokes of a Metro system designed in the 1960s to ferry commuters into and out of the city. Transit advocates cite Maryland’s light-rail Purple Line being built to connect Metro lines in Montgomery and Prince George’s counties as the first segment in a future rail loop.

Running express buses in toll lanes would help, transit advocates say, but only rail has the capacity to keep up as suburbs continue to grow.

Metro supported the Wilson Bridge’s rail-ready redesign and, in 2001, publicly shared “conceptual” plans for running trains across the span as the start of a circumferential rail line, according to a Washington Post article.

However, the last known official mention of Metro considering a Beltway Line appears to be in 2016, when the agency reported that it wouldn’t attract enough riders or have enough jobs and homes around stations to meet the “recommended minimums for Metrorail extensions.”

The agency has focused in recent years on rehabilitating and maintaining its aging system.

Metro spokeswoman Sherri Ly declined to say whether Metro still envisioned a loop around the city or if it had weighed in on Maryland’s plans for the American Legion Bridge.

“Metro is focused on addressing our current state of good repair and infrastructure improvements,” Ly wrote in an email.

Transit advocates say much has changed since earlier studies, especially as growing suburban Metro hubs such as Tysons, Bethesda, Silver Spring and White Flint become increasingly transit-oriented under regional efforts to focus development around stations.

Montgomery planners are evaluating the potential benefits of extending the Purple Line from its western terminus in Bethesda to Tysons as they seek to prioritize the county’s transit expansion plans. They say they’re responding to public demand for more equitable and environmentally friendly transportation options.

“We really feel it’s important that the bridge be built to be rail-ready, to be flexible for the future and meet transit demand,” said Carrie Sanders, a Montgomery planning division chief.

Robert O. Eisinger, a Montgomery developer who has championed the idea of building a monorail in the I-270 corridor and potentially into Northern Virginia, said his High Road Foundation has offered to fund preliminary designs of a monorail across a new bridge.

Eisinger said he questions whether the state is forgoing a rail requirement to make the bridge reconstruction less expensive, and more lucrative, for a private partner.

“I don’t know why we’d want to limit ourselves,” Eisinger said. “I think we want the ability and flexibility to do what’s right in the future.”