Clad in power suits and armed with PowerPoint presentations, the lobbyists roam from board chamber to conference room across Northern Virginia, trying to gather support for private toll highways.

Two competing plans would add privately funded lanes on Interstates 95 and 395 on which tolls would be collected. The high-occupancy toll -- or HOT -- lanes would be free for carpools of three or more people, but others would pay for the privilege of using them. To keep the lanes from getting congested, fees would increase as traffic became heavier.

Representatives of the companies interested in building the lanes have spent the last few months traveling the circuit and briefing local leaders as they try to sell their plans. In return, they have heard many local concerns. Alexandria is skeptical about more inside-the-Beltway exits. Prince William County wants sound walls. Fairfax County wants to know how the companies would solve the bottleneck at the 14th Street bridge. Arlington County is interested in bus rapid transit. All are looking for less traffic on their local roads.

"Everybody thinks it is a good idea, but they all want to know what is the benefit for them," said Garry Palleschi, a manager for Lorton-based Shirley Contracting Co., part of a group of companies that made its pitch to the Prince William Board of County Supervisors last week.

Virginia and Maryland leaders are studying a network of toll highways that they say would help unclog roadways in a region with the third-worst traffic in the nation. In addition to the proposed lanes on I-95 and I-395, Virginia officials are planning HOT lanes on parts of the Capital Beltway. Maryland officials are exploring plans to build HOT lanes on the Beltway, Interstate 270, the Baltimore Beltway and I-95 north of Baltimore.

Such so-called congestion-priced lanes (named for the tolls that rise as traffic gets worse) are gaining favor across the nation as budget-strapped states look for affordable ways to free drivers from daily jams. Officials in Texas and California proclaim the benefits of HOT lanes in their states, while Minnesota, Colorado, Washington and others are considering proposals.

One plan, submitted by the group that includes Shirley Contracting, part of Clark Construction Group, would convert the two existing high-occupancy vehicle lanes on I-95 to three HOT lanes from the Beltway south to Route 234 in Prince William. The group would then extend three HOT lanes south to Route 610 in Stafford County and build two HOT lanes from Route 610 to Route 17. It would also create additional connections at the Springfield interchange and expand existing commuter lots. The plan is estimated to cost $407 million, according to Palleschi.

Fluor Virginia, the company that is proposing to build the Beltway HOT lanes, is pushing a rival plan for the I-95 corridor that would create a 56-mile HOT-lane system from the 14th Street bridge to the Massaponax interchange in Spotsylvania County. The Fluor plan would also include a bus rapid transit system and five new commuter lots. The company estimates construction costs at $1 billion.

Gary L. Groat, who is working to gain approval for Fluor's proposal, said he has talked to officials in almost every jurisdiction in Northern Virginia, as well as to Virginia Railway Express and other transportation groups.

"For many of these, it is a second time back," Groat said. "We'll talk to anybody who will listen."

In their rounds, representatives from the competing companies have fielded questions from Fairfax Board of Supervisors Chairman Gerald E. Connolly (D), who asked how they would handle the 14th Street bridge bottleneck. Both Fluor and the Shirley group said that would have to be worked out. Both have pledged to expand commuter lots and say they have foolproof plans to monitor compliance with HOT-lane usage.

The Virginia Department of Transportation will meet with Fluor and the Shirley group Dec. 14 for an initial review of the proposals, according to company representatives.

Groat said he has not experienced any overt opposition to the HOT lanes. "It is more, 'Can you clarify this' or 'explain that,' " he said. Which is likely to be what they will be doing for the foreseeable future.

Fairfax Board of Supervisors Chairman Gerald E. Connolly (D) expressed concern about the traffic bottleneck at the 14th Street bridge.