EDITOR’S NOTE: The Virginia Department of Transportation says that the deadline for proposals has been pushed back to Oct. 11.

WASHINGTON — Final proposals to build two new toll lanes in each direction on Interstate 66 between the Capital Beltway and Gainesville, Virginia, are due Tuesday.

The public-private partnership proposals will be reviewed to ensure that they meet technical standards, then scored based on construction, design and operations plans.

Financial aspects of the proposals will be reviewed separately. The proposals are not expected to be posted for public review.

It’s expected that the selected team will be announced no later than mid-November, which would allow the initial parts of the deal to be agreed to before the end of the year. Construction would begin next year; the lanes would be scheduled to open around 2021.

Virginia transportation leaders have held out the possibility that the project could be built and operated under a more traditional construction arrangement, but the long-term deal with private companies to design, build, operate and maintain the lanes remains the most likely scenario.

Separately, but related to this deal, a new expansion of rush-hour restrictions from 2.5 hours to 4 hours begins next year on I-66 inside the Beltway, with the option for solo drivers to pay a toll to use the lanes.

Virginia Transportation Secretary Aubrey Layne has said the outside-the-Beltway project was more attractive to private bidders when they knew that solo drivers would be able to legally continue trips all the way to Arlington and the D.C. line.

The inside-the-Beltway tolls and High Occupancy Vehicle rules will only apply in the peak direction at rush hour when they begin next year. Inside the Beltway, the state retained control of the project by awarding separate construction and operations contracts.