Under the HOT lanes plan, commuters who don’t meet the carpool requirements for I-66 travel inside the Beltway will have the option of paying tolls. (Linda Davidson/The Washington Post)

[This post has been updated.]

HOT lane tolls on Interstate 66 inside the Capital Beltway could be $7 during the morning rush eastbound and $9 at the peak of the westbound rush in the afternoon, according to the Virginia transportation secretary’s office.

In Virginia’s high-occupancy toll lane systems, the toll varies with the level of traffic. It rises as travel demand increases to ensure that traffic remains free-flowing. At 8:15 a.m. Monday, the toll for using the northbound HOT lanes on the Beltway was $12.85.

But the state’s proposal for creating nearly 10 miles of HOT lanes on I-66 inside the Beltway is a bit different from the systems on the Beltway and on I-95/395. I-66 would not be expanded to add HOT lanes. Instead, the existing lanes would all become HOT lanes in both directions during the peak periods. Drivers who meet the carpool rules would travel free, but other drivers would pay the variable toll.

That proposal, which the state hopes to implement in 2017, has riled up long-distance commuters who would rather see the state widen the highway.

Others back the HOT lanes concept. The Coalition for Smarter Growth, a regional environmental advocacy group, issued a statement Friday in support of the state’s plan, emphasizing that the toll revenue would support transit improvements in the I-66 corridor.

“We believe that the package of solutions proposed by VDOT is the most cost-effective and efficient approach to addressing I-66 congestion as soon as possible, and for maximizing the number of people who can commute through the corridor during rush hour, while also guaranteeing a much more reliable trip for everyone,” said Stewart Schwartz, the coalition’s executive director.

Schwartz was my guest for an online discussion Monday, and we talked about this issue.

[See a transcript of Dr. Gridlock’s online chat with Stewart Schwartz]

Using the toll estimates in a transportation department document (reported by WTOP last week), the coalition made some comparisons.

The cost for a Metrorail trip from Vienna to Metro Center is $10.30, including station parking for $4.85 and the Metrorail peak fare of $5.45. The peak toll reported for the I-95 HOT lanes was $20.90, or 72 cents per mile for 29 miles compared with the state’s estimate of a 94 cents per mile toll on I-66. The maximum reported toll on the Beltway HOT lanes was $15.05 for the full 14-mile trip, or $1.08 per mile. (The coalition drew the maximum HOT lanes tolls from the quarterly reports produced by the operator, Transurban.)

The office of Virginia Transportation Secretary Aubrey Layne confirmed Monday that the $7 and $9 figures are the Virginia Department of Transportation estimates for the peak tolls. While the carpool standard for a free ride in the HOT lanes will eventually rise to three people per vehicle, VDOT is considering whether to maintain the current two-person carpool standard for the first few years after the HOT lanes open.

These are some of the other highlights.

The system proposed for I-66 is different from the existing HOT lanes systems in that it would be operated and maintained by the state, rather than a private partner. The toll revenue remaining after expenses would support programs encouraging drivers to leave their cars behind for a trip in the I-66 corridor. These programs would be selected by the Northern Virginia Transportation Commission board. They are to be implemented within four years of the funding allocation.

Under today’s rules, I-66 inside the Beltway is not open to drivers who don’t meet the carpool rules at peak periods. These HOV restrictions have created a pent-up demand among commuters, and the current outlet is to use other roads in the corridor. State transportation officials say that creating HOT lanes would allow some of that pent-up demand to use I-66, if the drivers are willing to pay the toll, and also ease congestion during the morning rush on the local roads that absorb today’s spill-over traffic.

There would be some bailout traffic from I-66 in the reverse-peak direction. These are drivers unwilling to pay tolls estimated at $1 westbound in the morning and $2 eastbound in the afternoon. Today, those trips are free and without HOV restrictions. Virginia transportation officials estimate the effect of this diversion on local roads will be minor.

Many drivers would not pay the full toll, because they don’t make the entire trip on I-66 inside the Beltway.

By 2022, vehicles with fewer than three occupants would pay an estimated toll of $8 during the morning peak and $1 dollar toll during the evening peak hours traveling eastbound. Traveling westbound, they would pay an estimated $1 during the morning rush and $3 during the evening peak hours, according to the VDOT numbers. By that year, VDOT hopes to have rebuild 25 miles of I-66 outside the Beltway so that it has three regular lanes and two HOT lanes in each direction. The department has not yet released estimates for typical tolls in the HOT lanes outside the Beltway.