Even commuters who are familiar with high- occupancy toll lanes haven’t seen anything like Virginia’s plan to go all HOT on Interstate 66 inside the Capital Beltway at rush hours.

We already have a HOT lanes network more than 40 miles long in Northern Virginia, and HOT lanes are planned for I-66 outside the Beltway. Each program involves extra pavement.

But in a question submitted for my weekly online discussion Monday, a traveler picked up on a unique feature of the latest plan.

Tolls for I-66: I saw that the Virginia Department of Transportation is considering . . . making I-66 inside the Beltway a toll road, but not planning to add new lanes. The times I have been on I-66 inside the Beltway during the normal commute hours, it has been pretty crowded. How will adding more cars to the mix make it better? Even going from HOV2 to HOV3 won’t solve the problem of limited capacity.”

Virginia’s planners do think that raising the High Occupancy Vehicle standard from two to three people per auto is an important part of the overall plan to ease congestion. The carpoolers will travel free, while other drivers will pay a toll. But why sell any extra space on the interstate to other drivers?

Virginia officials have been saying for a long time that the traffic problems on I-66 are so bad that no single relief program will be sufficient. The toll revenue can raise money for other programs that could help get commuters out of their cars and open more highway space. Those efforts can include extra bus service and enhanced commuter lots.

Success on all fronts would change the culture of commuting on I-66. But will it work? Advocates and experts have concerns.

“The proposal caught a lot of people by surprise and hasn’t really been vetted in public, as has been the case with plans for I-66 outside the Beltway,” said Bob Chase, president of the Northern Virginia Transportation Alliance, an advocacy group for transportation improvements. The plan “would be far more effective and workable if the HOV-tolling shift occurred in conjunction with the addition of new lane capacity, as will be the case on I-66 outside the Beltway.”

Robert Poole of the Reason Foundation think tank, who has played an important role in the study and development of the HOT lanes concept, sounded cautious about the complete conversion inside the Beltway. Most HOT lanes or express toll lane programs provide alternatives within the corridor for travelers who have time-sensitive trips and for those who don’t.

The Virginia plan would charge all non-HOV3 commuters the same price, “which will either be too high for most users or will be too low to have a big impact on congestion,” Poole said.

A better solution, he said, would be to create a reversible lane within the highway’s existing footprint. Use that lane to charge a premium price for highly time-sensitive trips while imposing a more modest toll for peak period travel in other lanes.

He also noted the value to drivers in having a consistent experience with the HOT lanes throughout the region’s entire network rather than encountering a different operating style inside the Beltway.

Several advocates for sane travel focused on the prospect of using toll money to support auto alternatives. Stewart Schwartz, executive director of the Coalition for Smarter Growth, noted that the state plans to operate the inside-the-Beltway lanes, rather than enlist a private company.

Eliminating the profit margin needed by a private concessionaire could allow more revenue to be invested in transit, such as rapid bus service and Metrorail, he said.

The Arlington Coalition for Sensible Transportation, a citizens group, is most attracted by the idea of raising the carpool requirement to HOV3. It’s “the sort of smart, cost-effective and permanent solution to I-66 traffic congestion that ACST and Arlington County have sought for the past 15 years,” said Allen Muchnick, the group’s president.

The HOT lanes program layers some other potential advantages: Helping control HOV cheating among drivers, providing predictable trips for toll payers who don’t meet HOV requirements and supporting alternatives to driving alone.

But like Schwartz, Muchnick wants to make sure that investment in solo-driving alternatives actually happens. “Based on VDOT’s track record with the I-495 and I-95 express lanes, we are very skeptical that VDOT is truly committed” to funding those much-needed options, Muchnick said.

This week, visit the Dr. Gridlock blog at www.washington post.com/blogs/dr-gridlock to read more about Virginia’s plans for I-66.

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 .