Dulles Greenway tolls will keep rising under a new ruling from the Supreme Court of Virginia.

WASHINGTON — Dulles Greenway tolls will keep rising under a new ruling from the Supreme Court of Virginia.

The court ruled Thursday against a long-running challenge by the Loudoun County Board of Supervisors and former state Del. David Ramadan that a State Corporation Commission ruling upholding the toll rates was correct.

Ramadan promised after that ruling a year ago to take the case to the state supreme court.

The Greenway is a privately-owned toll road that runs northwest from the end of the Dulles Toll Road to the Leesburg Bypass. It’s more than $6 to take the toll road at rush hour.

Loudoun County Board Chair Phyllis Randall said in a statement Thursday that Loudoun supervisors are disappointed in the decision.

“By any standard, the tolls charged on the Greenway are excessive and we continue to believe that reducing the cost of using the Greenway would help to alleviate traffic congestion in the region without digging into the profits of TRIP II,” she said.

TRIP II is the group that owns the road. An Australian company, Macquarie Infrastructure Partners, owns 50 percent of the road, and has been considering taking complete control.

The underlying reason that toll rates are allowed to rise is specific legislation passed in 2008 that provided for annual increases from 2013 through 2020.

“While we knew that our appeal would be a long shot, if nothing else it demonstrates that the county has exhausted all judicial means to rectify this problem,” Loudoun Supervisor Matt Letourneau said in a statement.

Thursday’s ruling does not decide the question of what is allowed to happen with Dulles Greenway tolls after 2020.

Greenway tolls are required to be “reasonable to the user in relation to the benefit obtained,” “not materially discourage use of the roadway by the public,” and “provide the operator no more than a reasonable return.”

To show that the tolls are reasonable, the toll road owners submitted studies showing that rate increases have had minimal impacts on the amount of traffic on surrounding roads.