INTERSTATE 66, the main east-west artery through the Northern Virginia suburbs and one of the most congested commuter chutes in the Washington area, is getting a timely and badly needed makeover. Starting next year, much of the highway will be widened to 10 lanes from the current six outside the Beltway, and drivers with no passengers, currently banned from the inside-the-Beltway portion during rush hour, will be welcome — subject to tolls that will fluctuate in order to keep traffic moving at a brisk pace. If things proceed according to plan, the new I-66 — perhaps Virginia’s most ambitious and costly highway construction project in decades — will be finished in 2022.

The 22-mile stretch outside the Beltway will be financed, built, operated and maintained by a private-sector consortium in what giddy state officials say is a steal for taxpayers: a $3 billion deal that includes, as a sweetener, a $500 million lump-sum payment at the outset to the state, to be used for other transportation projects in the I-66 corridor. In return, the consortium, which includes several big multinational firms, gets a 50-year lease, along with the toll revenue that one assumes will run well into the billions of dollars.

Details of the winning bid will not be known until it’s finalized next year, but on the face of it there is reason for optimism for commuters and taxpayers alike. In addition to the $500 million up-front windfall, the state will also receive $850 million for transit improvements in the corridor, including enhanced bus service and park-and-ride lots for Metro, plus another $350 million for other nearby road, bridge and interchange projects.

Risks to the state are minimized; if the consortium goes bankrupt, it will remain on the hook for the debt it will assume for the project. Of course, if it does go bankrupt, the project itself will revert back to the state.

That has happened elsewhere around the country; in this case Virginia officials say they are prepared. Unusually, as part of the bidding process they generated estimates of the project’s cost in the event that it would be borne exclusively by the state, in effect becoming a competitor for the contract. And, they say, the state remains prepared to undertake the project on its own should the deal collapse before it is finalized sometime next year.

The state’s approach was a departure from recent history in Virginia, which has outsourced large chunks of most major highway projects to the private sector for years. In the event, the winning bid, assuming it is finalized, represents a massive savings to Virginia — at least according to state officials’ somewhat self-serving calculations.

Even though most I-66 commuters work in Northern Virginia, not the District, there is a limit to how much will be gained by widening and tolling the highway. Eastbound drivers headed into the city will still need to cross the Potomac over the Roosevelt Bridge, whose narrow contours won’t change anytime soon. Still, the project should provide significant relief for tens of thousands of daily users. That’s a major achievement for Gov. Terry McAuliffe.