Traffic is bumper to bumper at rush hour on westbound I-66 in Vienna, as commuters head home. (Marvin Joseph/The Washington Post)

The plan to create HOT lanes on Interstate 66 passed two of its many governmental tests last week, although the approvals by the Fairfax County Board of Supervisors and the regional Transportation Planning Board came with contingencies about future modifications.

Virginia Transportation Secretary Aubrey Layne addressed many questions about the I-66 projects during my online chat Monday. I have selected some key issues and edited the questions and responses for space.

The first question is from me, and the rest are from readers.

Q. Many commuters write to me and say, Why don’t they just widen the highway and forget about this tolling part?

Layne: The goal is to move more people in the limited space we have by car, bus and train. Because of limited resources and space, tolling has to be a part of megaprojects like I-66. Right-of-way is expensive and impactful to residents. HOT lanes on I-66, combined with I-95 and I-495, will produce a regional HOT lanes network, affording more reliable travel choices.

Q. What is Virginia’s long-term plan for I-66 corridor congestion inside and just past the Beltway? Converting HOV2 to HOT3 lanes will raise money and lessen traffic on I-66, but it will simply route travelers who can’t afford the extra toll to smaller side roads. [Under the high-occupancy toll system, drivers ride free if they meet the carpool requirements. The current standard of at least two persons per car, or HOV2, is scheduled to rise to HOV/HOT3 by 2020.]

Layne: We have studied the I-66 corridor three times in the last 15 years. We think the current plan offers the best hope for congestion relief and improvements along the corridor. I-66 inside the Beltway is different from the Dulles Toll Road and the Greenway, because solo drivers cannot use the road. Our tolling solution reduces traffic on parallel routes by allowing solo drivers, who today are stuck on Route 50 and Route 29, the option to use I-66 inside the Beltway.

Q. Some commuters simply have no choice — we live along I-66, and we work further down I-66. We work abnormal or long hours and can’t have others relying on us for a carpool. What alternatives will Virginia provide to get us to and from work in a reasonable amount of time without having to drive on toll lanes?

Layne: Outside the Beltway will continue to have free lanes. Inside the Beltway will remain a free alternative outside of rush hours. During rush hours, it will be maintained as a managed facility. [The toll will rise or fall to regulate the flow of traffic.] We are working to provide enhanced commuter bus service throughout the corridor.

Q. You stated, “Inside the Beltway will remain a free alternative outside of rush hours.” I’m a little confused. I thought HOT lanes ALWAYS have a toll, it just may drop as low as $1 outside of rush hours?

Layne: No. I-66 inside the Beltway is different. It will be free on weekends, evenings and midday for all drivers.

Q. Will a park-and-ride be placed near the intersection of I-66 and the Beltway to provide nonstop commuter buses into the District?

Layne: The I-66 project will include new park-and-ride lots and new bus service, providing a one-seat ride into the District. Because of its constrained right-of-way, nothing is planned for the intersection of I-66 and I-495. Hopefully, other options will prove to be convenient for you.

Q. My estimate is that at least 25 percent of the drivers [on I-66 HOV lanes] do not meet the three basic requirements of two or more passengers, or coming from Dulles International Airport, or a fuel-efficient car [with the proper state-issued license plates]. It appears to be enforced very loosely. What will stop commuters from flaunting the system on new HOT lanes?

Layne: On the 95 Express Lanes [the HOT lanes that Virginia opened in December], we have seen the violation rate drop dramatically. The toll gantries and video cameras provide new mechanisms for better enforcement of the rules.

Q. What makes you think that solo drivers who are using side roads will be willing to pay the big tolls on I-66? And if large numbers of them do so, wouldn’t that defeat the whole plan by increasing congestion?

Layne: Our experience with the 95 Express Lanes shows drivers will switch from general purpose to express lanes. We expect the same behavior on I-66. Tolls will vary based on congestion to ensure free-flowing traffic. HOV2 will change to HOV3 in 2020 regardless of this project.

We believe this project will mitigate that impact. In addition, excess revenues generated in the corridor will be available for enhancements to I-66 and other roads should traffic deviate from our modeling.

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.