Loudoun County critics of the Dulles Greenway received support last week from the Virginia State Corporation Commission, which granted the county Board of Supervisors’ request to join an investigation of the controversial rate structure and the tolls charged by the road’s private operators.

The SCC agreed to allow the Loudoun board to serve as a respondent in the case, which will allow the county to cross-examine witnesses and become a formal part of the proceedings, county officials said.

After years of complaints about the high tolls along the privately owned 14-mile road, its operator, Toll Road Investors Partnership II, filed a request in November seeking approval for another rate increase.

Del. David L. Ramadan (R-Loudoun), one of the toll road’s most outspoken opponents, responded by filing a complaint, requesting that the SCC investigate the toll structure of the road and give the public an opportunity to express concerns about the rising costs.

Scores of residents and commuters did just that during several public hearings in the spring and summer.

Loudoun supervisors voted unanimously Sept. 4 to seek permission to join the SCC’s case. Last week, local officials applauded the SCC’s decision to accept that request.

“Greenway tolls are one of the most pressing issues facing our county, and we have limited options to try to relieve the pressure on our citizens,” Loudoun Supervisor Matt Letourneau (R-Dulles) said in a statement. “This case is the most promising opportunity we’ve had to address excessive tolls.”

Board Chairman Scott K. York (R-At Large) said in the same statement that it was in the best interest of Loudoun residents and businesses that the board become a formal part of the investigation, because of “the high number of drivers avoiding the greenway because of its high tolls.”

Ramadan announced last week that the Virginia Department of Transportation had authorized two informational signs displaying the Greenway’s toll rates, which are as high as $4.90 for a one-way trip during peak hours, on the Loudoun County Parkway and Route 606.

“We all know that informational signs are not the ultimate solution for the Dulles Greenway, but while I continue my legal fight . . . at least they will ensure that drivers are able to make informed choices,” Ramadan said in a statement. “Some drivers, especially from outside the area, have no idea they are about to be hit with the most expensive toll per mile in the entire nation, and the new signs will make it harder for the greenway to prey on the uninformed.”

Ramadan said he is leading the effort to prove that Loudoun drivers are actively avoiding the road because of the tolls, resulting in worsening congestion on other county roads. If the SCC were to find that drivers were in fact avoiding the road, the commission would have the power to force a reduction in the rates, Ramadan said.

Ramadan said that Loudoun’s participation in the case will be useful as his legal team prepares for an evidentiary hearing in Richmond on Nov. 12.

The hearing marks the “trial phase” of the proceedings, with both sides presenting arguments, according to a statement by Ramadan’s office.