VDOT plans to turn today’s HOV lanes on I-395 into eight miles of HOT lanes, open for free to HOV3 carpoolers and to other drivers willing to pay tolls. (Leslie E. kossoff/AP)

Virginia plans to expand its already extensive system of HOT lanes, creating a tolled network that is likely to dominate the local highway scene for most of the century.

The latest program will push the high-occupancy toll lanes north along Interstate 395 to the D.C. line. Aubrey Layne, Virginia’s transportation secretary, said in an interview that the state has reached an agreement on the plan with Transurban, the private partner that operates the 95 Express Lanes to the south and the 495 Express Lanes to the west of I-395.

On Friday, Layne sent letters to the local governments in Alexandria, Fairfax and Arlington to notify them that the state had reached an agreement to move forward on what will amount to an eight-mile extension of the 95 Express Lanes.

Although each HOT lane system is a bit different from the others, drivers who are familiar with the 95 Express Lanes will have a similar experience: They will need to have a regular E-ZPass transponder to pay the toll or an E-ZPass Flex to claim the free ride for those meeting the HOV3 carpool standard.

The HOT lanes will replace today’s HOV system on I-395, much as the state had intended when it drafted plans a decade ago for the I-395/95 corridor.

VDOT constrained its original plan in part because of a lawsuit filed by Arlington County. Although the legal side of highway planning is difficult to predict, a court challenge is less likely this time. Layne said the new plan comes with guaranteed funding, paid for through the project, to enhance carpooling and other transit services in the corridor.

“This is not the same proposal as in the past,” Layne said.

That’s good, because the transit part of the other HOT lanes has been a disappointment. The most expensive part of the infrastructure — the lane system itself — is in place, but so far, the support system that could encourage commuters to leave their cars behind has been lacking.

The commitment to finance these alternatives is a key feature of the HOT lanes plans developed during the McAuliffe administration.

Deputy Transportation Secretary Nick Donohue described the HOT lanes program as “a game-changer for regional mobility” that was “unimaginable 10 years ago.”

Layne said the new agreement with Transurban is an extension of the 95 Express Lanes contract rather than a totally new project that would require starting from scratch. He estimated that construction could begin in 2017 and take two years to complete.

[Secretary Layne makes pitch for I-66 HOT lanes]

Before that, Layne said, several things will happen. The project will require an environmental assessment, with the basic idea being that today’s two reversible HOV lanes will become three reversible HOT lanes without significantly affecting the overall width of the interstate.

The state also will do a transportation demand management study — planner talk for figuring out how to enhance carpooling and vanpooling while allowing the non-HOV drivers into the lanes if they’re willing to pay the variable tolls.

As with the HOT lanes plans for I-66, the program for I-395 shows how highway travel is evolving in urban areas. There’s only so much new asphalt that can be spread across densely populated areas. We still need extra capacity to move people, but some of it will be created by helping people find ways to travel together.

“It’s a very pragmatic solution to a problem that’s been plaguing the region for 20 years or more,” Layne said. “You had congested roadways with limited right of way. It’s a pragmatic solution for all.”

For commuters and residents along the corridor, the addition of the third lane looks like the biggest physical change. The plan does not require taking any homes or businesses. It’s possible that new sound walls could require some additional space. Planners say they would improve traffic flow at the Eads Street interchange near the Pentagon, but aside from that, not much would happen at the I-395 access points.

That new HOV ramp under construction at Seminary Road near the Mark Center would be open only to HOV traffic, as was the plan before the HOT lanes idea came along. This would be the one access point where the drivers without two passengers could not buy their way in by paying a toll. It will be interesting to see what the planners come up with to enforce this restriction.

While VDOT advanced this big plan for the north side of the HOT lanes corridor, there’s still no definite word on relief at the southern terminus in Stafford County, where the express lanes and the regular lanes flow back together into one congealed mass of traffic.

But there’s reason to hope a solution will be forthcoming. “The governor should be able to say something shortly,” Layne said.

Dr. Gridlock also appears Thursday in Local Living. Comments and questions are welcome and may be used in a column, along with the writer’s name and home community. Write Dr. Gridlock at The Washington Post, 1150 15th St. NW, Washington, D.C. 20071, or ­e-mail drgridlock@washpost.com.