A westward facing view of Dulles Toll Road from the Wiehle Ave overpass where the Silver Line of the Metro is being extended to Dulles Airport in Reston, VA. (Jahi Chikwendiu/WASHINGTON POST)

The Dulles Toll Road is key to the financing for Metro’s planned Silver Line, and that means rate increases on the toll road are going to be closely watched in coming years.

The Metropolitan Washington Airports Authority, which operates the road and is building the line, is considering a proposal that would double the base rate to $4.50 by 2015.

Officials have long warned motorists that toll increases were coming for the eight-lane, 14-mile roadway, which runs between the Capital Beltway and Dulles International Airport.

“I don’t want to mislead anyone. Tolls have to go up,” Andrew Rountree, MWAA’s chief financial officer, said. over the summer. “There’s a minimum level of toll increase that really has to occur in order for the board to meet its responsibilities.”

But even when expected, toll increases aren’t popular and this month, the authority is hosting three meetings to solicit feedback on the proposed toll hike.

“Motorists are being asked to shoulder a disproportionately and unfair amount of this project,” said Mahlon G. “Lon” Anderson of AAA Mid-Atlantic. “For people who need to use the Dulles Toll Road, this is patently unfair. It is a huge expense for them.”

More than $1.3 billion in toll road revenue bonds have been issued. That makes it likely that at least some increases have to occur, said state Del. Jim LeMunyon (R), who represents parts of Loudoun and Fairfax counties.

“They need to generate the tolls to pay for these bonds,” LeMunyon said. “So these tolls are going up no matter what the public thinks, and that’s just too bad.”

But he said the public’s input is still important, if only to encourage officials to find alternate financing down the line, LeMunyon said.

Rob Yingling, spokesman for the authority, said feedback from the public “will be fully considered before any decision is made.” All comments will be put into a detailed report that will be provided to the board committee in October and to the full board in November.

Local residents have fretted about the impact of the project, which they worry will push drivers from the toll road and onto adjacent routes.

Officials at the Virginia Department of Transportation said it was possible but unlikely that the toll increases would create a surge on nearby roads such as Route 7, Route 28 and even Interstate 66 to the south.

“Traffic tends to reach an equilibrium,” said Randy Dittberner, a regional traffic engineer at VDOT. “If one vehicle decides the toll is too high, that makes the traffic conditions a little better on the toll road, and that might attract someone else.”

The cost for a two-axle vehicle is now $1.50 at the main toll plaza and 75 cents at the on/off ramps, for a total of $2.25. That rate, which has been in effect since Jan. 1, was the third in a series of increases approved in 2009.

Under the proposed adjustments, each of those fees would go up 25 cents Jan. 1, to bring the cost to $2.75. Subsequent increases would push the combined cost to $3.50 in 2014 and $4.50 in 2015.

Some of the additional revenue would be used for operating and maintaining the toll road. Increases in 2016 and beyond would depend on the finances of the Silver Line, the first leg of which is due to being operating next year.

The first public hearing is scheduled for Thursday at Stone Bridge High School, 43100 Hay Rd., Ashburn. The others are set for Sept. 12 at South Lakes High School, 11400 South Lakes Dr., Reston; and Sept. 13 at Spring Hill Elementary School, 8201 Lewinsville Rd., McLean. The three hearings will all run from 5 p.m. to 8 p.m.

In addition to the three meetings, the public comment period is open through Sept. 16. Go to mwaa.com/tollroad to submit comments online or mail your comment to Dulles Toll Road Proposed Toll Rate Increases, 3900 Jermantown Rd., Suite 300, Fairfax, Va., 22030.