Virginia transportation officials are studying a series of traffic improvements for the perpetually congested portion of Interstate 66 inside the Beltway, an effort that may include road widening and the addition of high-occupancy toll lanes — and would require buy-in from historically resistant Arlington County.

“We’ve got their agreement to work through this process,” Aubrey Layne, the commonwealth’s secretary of transportation, said Friday, referring to Arlington. Layne said that creating toll roads, improving rail capacity and adding bus lanes would also likely be parts of the solution.

“In terms of what may result from it, obviously we’re constrained physically,” he said. “I can see maybe creating an additional lane using the shoulders, but I don’t see a whole lot of additional right of way there.”

The leafy and narrow portion of I-66 that runs inside the Beltway has been choked with traffic for decades — a period punctuated with calls to widen that portion of the highway and resistance from Arlington County out of concern that it would lead to more noise, pollution and traffic.

In 1970, Arlington residents filed a lawsuit to block the highway’s construction, but the suit was thrown out. Even so, opposition delayed construction inside the Beltway until 1977, when an agreement was reached to build four lanes while prohibiting truck traffic in the corridor.

That stretch was completed in the early 1980s. With the exception of small improvements and new merge lanes, Arlington has served as an unofficial boundary ever since for road improvements planned along I-66 that stretch all the way to Prince William County.

On Friday, Arlington County officials said they are willing to engage in a study of traffic congestion that would consider rail and bus improvements and other “multi-modal” options.

One major change could be creating high-occupancy toll lanes, or HOT lanes, inside the Beltway, which could be tricky on such a narrow stretch of road.

But Jay Fisette (D), chairman of the Arlington County Board, disagreed that the changes could lead to widening the road.

“The county board has not revisited our long-standing opposition to widening I-66,” Fisette said in a phone interview. “The way I read this is, it’s building on the study of multi-modal options, which Arlington and Fairfax counties have been heavily involved with. This is an opportunity for us to shape the result.”

The state’s plans for an environmental assessment come as transportation officials are also moving forward on improvements outside the Beltway — plans that include building new high-occupancy toll roads in place of HOV lanes, creating space for rail and implementing other traffic-calming measures.

Sharon Bulova (D), chairman of the Fairfax County Board of Supervisors, said those efforts are likely to involve land acquisition.

“Some houses will have to be taken. Some property will have to be taken,” Bulova said. Calling the plans to study options inside the Beltway “great news,” she added, “I’m sure that will happen inside the Beltway as well.

“It is a great first step toward improving mobility throughout the I-66 corridor,” she said. “I look forward to working with the commonwealth, Arlington County, and the city of Falls Church on this critical project.”

With the state assessment yet to begin, news of possible changes inside the Beltway sparked immediate interest among planners long familiar with woeful congestion in the corridor.

Stewart Schwartz, executive director of the Coalition for Smarter Growth, cautioned that dependence on HOT lanes could lead to too many cars trying to fight their way into the District. He suggested that any revenue from HOT lanes should be directed toward bus and Metrorail.

“The focus should be on moving the most people at the peak hour, and transit offers the best opportunity to do that,” Schwartz said. “In addition, HOT lanes should not be used as a back doorway to widen I-66, which is destructive of Arlington neighborhoods.”

Layne cautioned that solutions are far off. He added that the hope is for the effort along I-66 to combine with improvements along Interstate 95 for an overall, dramatic easing of regional traffic.

“It’s a long ways away,” Layne said. But “I think we’ve gotten agreement from everyone that we need to look at this and work toward a solution together.”

Lori Aratani, Patricia Sullivan and Robert Thomson contributed to this report.