Traffic from the outer loop of the Capital Beltway, left, and traffic from Interstate 270 merge in this 2004 image captured during an evening rush hour in Potomac, Md. (MANUEL BALCE CENETA/AP)

The gap between how Virginia and Maryland try to relieve some of the nation’s worst highway congestion keeps expanding.

And far more Marylanders in our region are taking notice.

Northern Virginia is laying pavement. It has built 87 miles of tolled express lanes since 2012 to carry cars and trucks on the Capital Beltway and Interstate 95. It is planning another 114 miles of lanes, mostly for I-66.

Meanwhile, the Maryland suburbs are merely thinking about widening their biggest highways — someday, maybe.

In the four years since Northern Virginia opened its first express lanes, Maryland has added no new capacity along its half of the Beltway or I-270, although drivers there creep through some of the area’s most severe traffic clogs.

Instead, suburban Maryland’s political leadership has focused on pressing for new transit projects, especially the light-rail Purple Line. Analysts say local elected officials have been wary of backing bigger highways partly because they fear a backlash from environmentalists and other road skeptics.

The Northern Virginia business community also has been more active than Maryland’s in lobbying for roads. And Virginia has held down the state’s costs by outsourcing construction and management of the express lanes to a private corporation.

Top Maryland officials of both parties are saying the Free State needs to change its approach. They warn that suburban Maryland will suffer damage to its economic competitiveness and quality of life if it falls far behind Northern Virginia in battling congestion.

“We should be embarrassed as Marylanders,” said U.S. Rep. John Delaney (D-Md.), whose congressional district includes much of I-270. “We’ve done a bunch of little, incremental things, but relative to the problem, our response has been woefully inadequate.”

He and other officials in Montgomery County, together with some business groups, are planning a campaign to widen I-270 and the western part of the Beltway, and to rebuild and expand the American Legion Bridge.

The effort seems likely to touch off a major battle. Transit advocates are set to argue that bigger roads would risk adding to suburban sprawl. They and others could protest that the cost, in the billions of dollars, is too high.

It could become a top political issue in the years ahead, including in the races for governor and Montgomery County executive in 2018.

In theory, Montgomery road advocates should have an enthusiastic ally in Gov. Larry Hogan (R). He is an outspoken supporter of shifting spending from mass transit to roads. When Hogan killed Baltimore’s light-rail Red Line last year, he announced $1.3 billion in new road and bridge projects around the state.

In the Washington suburbs, however, Maryland appears stingy, compared with Virginia, about committing money to big-ticket highway projects. Consider the two major announcements this month on opposite sides of the Potomac:

In Virginia, Gov. Terry McAuliffe (D) on July 5 unveiled the last piece of a transportation package including $835 million for roads on the I-95 corridor. It includes adding 17 miles of tolled express lanes reaching as far south as Fredericksburg.

Hogan announced a plan two weeks later to spend less than a third as much — $230 million — on I-270 between Bethesda and Frederick. Maryland will rebuild an interchange (at Watkins Mill), but add no lanes. Instead, some of the money will go to identifying and funding innovative technologies to ease traffic without actually laying asphalt.

Hogan’s point man on the issue, Transportation Secretary Pete Rahn, is well aware that Washington-area drivers struggle with horrid congestion and has said transit alone is insufficient to solve the problem.

“Very likely we need more [road] capacity,” Rahn said.

But Rahn warned that adding lanes along the I-270 corridor, and rebuilding and expanding the American Legion Bridge, would cost more than $8 billion and require 10 to 15 years for environmental reviews before construction could begin.

He and a Hogan spokesman also faulted Montgomery and Prince George’s officials for listing transit projects as higher priorities for state spending than highway expansion.

“Local governments have determined for themselves that transit is how we deal with congestion,” Rahn said.

He chided some local officials for what he said was a deliberate effort to worsen traffic, and thus discourage driving, through transit-oriented “smart growth” policies.

“It was the policy of some counties to actually create congestion in order to drive people out of cars,” Rahn said. “That’s a very blunt way to say what a lot of smart growth is about: Make it miserable, and people will leave their cars. We’ve seen. They won’t.”

[Pete Rahn Web chat: “Congestion-busting” on I-270 would cost more than $8 billion.]

He pointed to comments by former Montgomery planning director Rollin Stanley, who told Bethesda Magazine in 2009, “Traffic jams are good” because they force people “to think about alternative transit, like biking, walking or mass transit.”

Montgomery County Council Vice President Roger Berliner (D-Potomac-Bethesda) said it was “disingenuous” of Rahn to blame local officials for a failure to move ahead on major highway projects. He noted that the council had voted unanimously as far back as 2009 to support adding tolled express lanes on I-270.

But Berliner and others also said the Hogan administration wasn’t the only entity responsible for the lack of action. The previous, Democratic administration in Annapolis, led by then-Gov. Martin O’Malley , also showed little interest in major road spending in Montgomery.

Berliner said that was partly because the Maryland Democratic Party historically has been oriented toward helping Baltimore rather than the Washington suburbs.

“Both the American Legion Bridge and I-270 have been sort of a stepchild,” Berliner said. The burst of road-building in Virginia “drives people in Montgomery County crazy,” he added. “People say, ‘It happened there. Why can’t it happen here?’ ”

Some analysts said Hogan also wanted to short-change the heavily Democratic Washington suburbs on transportation. But instead of helping Baltimore, the analysts say, Hogan sought to allow for more spending in GOP-friendly areas of the state.

Rahn dismissed that theory as “hooey,” and current budget plans suggest the two close-in suburbs are getting a fair share of total spending.

It is true that Maryland’s six-year capital spending plan devotes just 17 percent of road monies to Montgomery and Prince George’s, which together have 32 percent of Maryland's population.

But the picture changes when transit investment is included. Then, the two counties get 35 percent of total capital spending on transportation, or slightly more than their share of the population.

A leading backer of the Purple Line, Montgomery council member George L. Leventhal (D-At Large), said that adding lanes to the I-270 corridor should be the county’s next top transportation priority, now that the light-rail project has been approved.

“I-270 gives us the most bang for the buck,” Leventhal said. “I would like to see something similar to what they’re doing in Virginia.”

The Virginia express lanes have sped up traffic to a measurable degree during rush hour, according to government traffic data.

Using the I-95 express lanes shaves 25 minutes off a weekday morning trip from Fredericksburg to Reagan National Airport, according to a May study by the National Capital Region Transportation Planning Board. The Beltway lanes trim seven minutes off a similar trip from Springfield to Dulles International Airport.

But influential transit activists aren’t necessarily supportive. They’re prepared to fight efforts to widen roads in Maryland unless consideration is given to other solutions that would be less likely to promote driving.

“We’re not going to say we would necessarily oppose it, but we want to see the alternatives fairly studied,” said Stewart Schwartz, executive director of the Coalition for Smarter Growth.

He thinks the new express lanes in Northern Virginia were too costly and will not relieve congestion in the long term — partly because bigger roads encourage more development.

Such skepticism worries road advocates such as Richard Parsons, vice chairman of the Suburban Maryland Transportation Alliance. He’s organizing a coalition of business and civic groups to lobby to widen I-270 and rebuild the American Legion Bridge, which is the Beltway’s link across the Potomac between Montgomery and Fairfax counties.

In Parsons’s view, Maryland has fallen behind Virginia in road building because transit advocates and environmentalists have had too much influence in local Democratic Party politics.

“There’s an entire cottage industry of groups whose only purpose is to defeat road projects,” Parsons said. In low-turnout Democratic primaries, he said, such groups wield considerable clout.

Given such pressures, observers predict many years of politicking and debate over whether suburban Maryland widens its biggest highways.

Former Montgomery County executive Doug Duncan, a veteran of years of battles over another controversial highway, the Inter-County Connector, said the current discussion is painfully familiar.

“It’s the old routine of paralysis by analysis,” Duncan said. “We’re going to keep talking about things and telling people it’s being addressed, but we never build it.”