Fairfax County is expected to give the green light to the $2.7 billion second phase of the Dulles Rail project on Tuesday.

The approval means the county will agree to pay for about 16 percent of the project’s capital costs, as well as its share of the operating costs for the new Silver Line.

Phase two of the project will extend the line from Reston into Loudoun County and won’t be open until 2018 at the earliest.

Most observers believe that the Democrat-controlled Fairfax board will seal the deal on the project, but say the decision is still up in the air for the all-Republican Loudoun County board, which is composed mostly of first-term members, many of whom doubt the rail line is worth the cost.

Also on Tuesday, the Fairfax County board is expected to recommend new station names for the first phase of the Silver Line, which extends from East Falls Church to Reston. It is expected to open in late 2013.

The name revisions, which must go to Metro and the Metropolitan Washington Airports Authority for approval, were based on public input from an online survey of 16,231 area residents. Metro board members rejected the original names used by planners for being repetitive and confusing.

The proposed name changes are:

  • Tysons East would be McLean
  • Tysons Central 123 would be Tysons Corner
  • Tysons Central 7 would be Greensboro Park
  • Tysons West would be Spring Hill
  • Wiehle Avenue would be Wiehle-Reston East
  • Reston Parkway would be Reston Town Center
  • Herndon-Monroe would be Herndon
  • Route 28 would be Innovation