The same year that Metro opened the Silver Line may be remembered by commuters as the year that highways launched a comeback.

On Monday, the 95 Express Lanes will become high-occupancy toll lanes, combining with the 2-year-old HOT lanes on the Capital Beltway to form a network stretching from the outer suburbs in Stafford County, Va., to the office buildings and shopping centers of Tysons Corner.

This people-moving system already dwarfs the mileage that the Silver Line is adding to Metrorail. And the administration of Virginia Gov. Terry McAuliffe (D) is studying an expansion of the HOT lanes to Interstate 66.

Meanwhile, Maryland this fall completed the Intercounty Connector, which now stretches between Route 1 in Prince George’s County and Interstate 370 in Montgomery County. The state also opened the I-95 Express Toll Lanes along a congested portion of the interstate northeast of Baltimore.

The District Department of Transportation announced in 2014 that it would study the possibility of adding HOT lanes to freeways stretching from I-295 at the Maryland border to the 14th Street Bridge.

Highway users will note that the various programs have one thing in common: tolls.

So is this the way of the future for the region’s travel network?

They speed travel for many thousands of commuters, but aren’t a cure-all for congestion.

Whether the toll revenue goes to the government or a private company that built the lanes, there are practical limits on such projects. Highway programs based on tolls make financial sense only along corridors where there are vast amounts of traffic. Otherwise, the revenue may be insufficient to cover the costs.

The latest addition, the 95 Express Lanes project, has the market potential. Some segments of I-95 in Northern Virginia carry more than 200,000 vehicles a day. The express lanes hold the promise of quicker, more reliable commutes for drivers willing to pay the variable toll, and a free ride for carpoolers. (Hybrid drivers who had an exemption from carpool rules in the HOV lanes become toll payers in the HOT lanes.)

AAA Mid-Atlantic, a travel association that initially was unimpressed with the HOT lanes concept, now calls the 95 Express Lanes “game-changers.”

“They will change the way we — motorists, carpoolers, and the owners of hybrid vehicles — commute on one of the busiest highways on the Eastern Seaboard,” AAA said in a statement about the year’s transportation developments.

Their “very existence disproves the notion in some circles that more roads won’t solve traffic problems on I-95 in Northern Virginia,” the statement said.

Alan Pisarski, a nationally known expert on commuting, said he was “fundamentally positive” about the trend in toll-based expansion of highway capacity. But he offered several cautions.

For many drivers, tolling is not yet a routine part of travel. The tolling concept is often presented to them as a “user fee.” If that notion is to hold up, Pisarski said, then the toll revenue really needs to be associated with the service provided by that particular roadway and not spread around to fill other funding gaps.

He also remarked on the cloud that accompanies the silver lining of a “premium service lane.” In an operation like the 95 Express Lanes, or any system in which drivers have a clear choice about paying a toll or riding free, there needs to be an incentive to pick the toll lanes. The incentive is avoiding congestion in the regular lanes.

Cure the congestion problem someday and you’ve undermined the appeal of the premium service.

Stewart Schwartz, executive director of the Coalition for Smarter Growth, noted that express lanes have yet to live up to their early promise as transitways, for those who would prefer to leave driving to someone else.

“Proponents of HOT lanes have always made ‘bus rapid transit,’ ‘express bus’ or ‘rapid bus’ a prime selling point for the HOT lanes, along with citing the extension of routes for carpooling. Yet the funding for expanded transit hasn’t followed,” Schwartz said.

The impact of HOT lanes on carpooling is uncertain, he said. The option to drive alone and pay a toll may introduce more uncertainty into daily routines that bring carpools together, leading to a breakdown in the very successful carpooling system on I-95.

As 2014 ends, express toll lanes are deeply embedded in the transportation network. Several generations of commuters now are going to discover whether this is a source of relief or an investment in congestion.

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 .