Fairfax and Loudoun counties have 90 days to decide whether they’ll help fund Phase 2 of the Dulles Rail Project.
The Metropolitan Washington Airports Authority announced Tuesday that $2.7 billion will be needed to cover the costs.
That money would pay for 11.4 miles of rail from Reston to Dulles International Airport and beyond. It would also foot the bill for six new Metro stops.
More than a billion dollars was shaved off earlier estimates by eliminating an underground station at the airport among other cost-saving measures.
If all parties agree to invest and move forward, construction could start as early as next year.
Phase 2 could be built and open to riders in 2018.
Seventy-five percent of its financing would come from tolls.