Virginia Transportation Secretary Aubrey Layne laid out an ambitious agenda on Thursday for the commonwealth’s plan to expand the already substantial network of high-occupancy toll (HOT) lanes in Northern Virginia.

He hopes that the system will total 84 miles by 2021. That includes the expansion along Interstate 66 and along Interstate 395, and the southern extension of the 95 Express Lanes to ease the bottleneck where they merge with the regular lanes of I-95.

Layne also raised the possibility of extending the 95 Express Lanes 10 miles south to Fredericksburg. He also put forward the idea — bound to be attractive to I-395 commuters — of eliminating the pinch point where southbound I-395 narrows around Duke Street.

All this is going to affect travel plans for tens of thousands of commuters over the next few years. This spring will be busy with public hearings and informational sessions on various aspects of these big projects.

Here’s the list, in case you want to mark your calendar.

Information meetings: 395 Express Lanes
These sessions are from 6:30 to 8:30 p.m., with a VDOT presentation at 7 p.m.

April 11. Wakefield High School cafeteria, 1325 S. Dinwiddie St., Arlington

April 13. Francis C. Hammond Middle School, 4646 Seminary Rd., Alexandria

Public hearing: Widening I-395 South from Duke Street to Edsall Road
April 14. 6:30 to 8:30 p.m. at Bren Mar Park Elementary School, 6344 Beryl Rd., Alexandria

Open house/hearing: first group of multimodal improvements
This session is sponsored by the Northern Virginia Transportation Commission, which is in charge of picking programs designed to help commuters leave their cars behind for trips on I-66 inside the Capital Beltway. Those programs are commonly referred to by planners as “multimodal.”

May 5. Open House at 6 p.m.; hearing at 7 p.m. Northern Virginia Transportation Commission, 2300 Wilson Blvd., first floor conference room, Arlington

Information Meeting: Widening I-66
This is about the plan agreed to during the recent Virginia General Assembly session to widen four miles of eastbound I-66 inside the Beltway from the Dulles Connector Road to Fairfax Drive.

May 9. 6:30 to 8:30 p.m., Washington and Lee High School, 1301 N. Stafford St., Arlington

VDOT says a second session will be held in Falls Church, but a date has yet to be announced.

Public hearing: I-66 outside the Beltway
VDOT held three hearings in March on the design for the HOT lanes project inside the Beltway, which is scheduled to begin construction this summer. These next sessions are about procurement issues for the project outside the Beltway and about plans to move the standard for a free carpool ride in the HOT lanes from HOV2 to HOV3. VDOT is pursuing a public-private partnership for the outside the Beltway construction and operation, which is scheduled to be done by 2021. But it could still opt for doing this as a public project, just as it’s doing with the inside the Beltway HOT lanes. All the sessions are from 6:30 to 8:30 p.m.

May 23. Oakton High School cafeteria, 2900 Sutton Rd., Vienna

May 24. VDOT Northern Virginia District Office, 4975 Alliance Dr., Fairfax

May 25. Piney Branch Elementary School cafeteria/gym, 8301 Linton Hall Rd., Bristow