The project is set to pay for a series of carpool or transit incentives, including free rides on all Loudoun County Transit buses that go to Metro stations for the next month and a half.

WASHINGTON — With years of construction-related backups about to begin along Interstate 66, the project is set to pay for a series of carpool or transit incentives, including free rides on all Loudoun County Transit buses that go to Metro stations for the next month and a half.

The Virginia Department of Transportation officially announced the start of major construction Wednesday, with temporary lane closures or shifts this weekend on I-66 between Virginia Route 123/Chain Bridge Road and U.S. Route 50, and on I-66 near the Capital Beltway.

More significant construction work — including long-term lane shifts, concrete barriers and, soon, the end of the “red X” lanes — is scheduled to ramp up over the next few weeks.

The expected long-term traffic delays are why the project has promised to support carpooling and transit during construction as a way to mitigate backups over the next 4½ years.

Private companies are building two HOV or toll lanes in each direction between the Beltway and Gainesville next to three regular lanes and a permanent shoulder, with construction due to end by late 2022. The separate toll lane restrictions inside the Beltway at rush hour will also remain in place.

Other increased carpool, vanpool and commuter bus incentives are expected to be announced shortly as part of the broader program funded through the project.

Free, discounted rides

From Monday through at least June 2, all rides between Loudoun County Transit stops and the Wiehle-Reston East or West Falls Church Metro stations will be free, Loudoun County Transit said Wednesday. That includes routes 901/902 to West Falls Church; and routes 72, 83, 84, 87X, 88X, 921/922, 923/924, 925/926, 927/928, and 990-993 to and from Wiehle-Reston East.

PRTC OmniRide Commuter Bus riders on routes along I-66 from Prince William County and the Manassas area will get significant discounts soon, too, but those will start sometime in May, spokeswoman Christine Rodrigo said.

OmniRide buses on I-66 will be 50 percent off for the entire 4.5 years of major toll lane construction. For OmniRide express buses to Metro, the SmarTrip fare will drop from $3.45 to $1.75 when the discounts begin. For OmniRide buses to D.C. and nearby stops, the fare will drop from $6.90 to $3.45 for all buses serving Gainesville and Manassas.

Certain Fairfax Connector routes will also have discounted fares during toll lane construction, said Robin Geiger, head of communications for the Fairfax County Department of Transportation. The details of those discounts are expected to be ironed out in the coming weeks.