The planned Dulles Access Toll Road has won approval from the National Capital Planning Commission, with the exception of a controversial noise barrier near Wolf Trap and an administration building proposed near the Springhill Road toll plaza.

The new highway would run parallel to the Dulles International Airport Access Road, with two-lane roadways on either side of the airport route.

At its meeting last week, the federal planning agency refused final approval of the proposed noise barriers and landscaping, particularly near Wolf Trap. It also urged a new design for the administration building, a one-story, warehouse-like structure that commission member T. Eugene Smith called "absolutely ridiculous along a major gateway to the nation's capital."

Several citizen groups urged the commission to withhold any approval of the entire toll road project until additional noises studies, now being done by the Federal Aviation Administration, are completed, a suggestion rejected by the commission.

The FAA, which owns Dulles Airport and the right of way for the new toll road, is committed to the construction of noise walls at Wolf Trap and "where practical" to protect residential areas, FAA chief regional engineer Francis J. Conlon told the commission.

At a commission meeting earlier this month, several citizens expressed concern about the noise problem.

"There isn't a sound barrier built that will protect Wolf Trap from an additional four lanes of traffic," said one citizen, who predicted persons would stop attending the outdoor music complex after the toll road is built.

"What if the latest studies show Wolf Trap cannot be protected?" asked Ann Hummel, speaking for the Trails Homeowners Association, which represents about 125 families who live across from Wolf Trap.

Some citizens groups, such as the Cinnamon Creek Homes Association near Wolf Trap, have criticized an environmental impact statement completed earlier this year because it used controversial "average noise" levels to predict the impact on Wolf Trap and because of its low estimates of truck traffic on the toll roads.

"Even if one grants the assumption that traffic volume will be no greater than 51,000 (vehicles a day) and the truck percentage will be no greater than 8 percent and vehicles will travel no faster than 55 miles an hour, the protection recommended by the FAA will be inadequate because it is designed to provide protection against an average noise level experienced during a 60-minute period," Cinnamon Creek president Pat Levinson told the commission.

"The problem is that people in an audience do not hear average noise," Levinson added. "They hear the peaks of noise, such as loud trucks rolling by only 300 feet away from the stage."

The environmental study proposed that the toll roadbed dip about five feet along Wolf Trap and a retaining wall backed by a 950-foot sound barrier as high as 30 feet be built behind it on the Wolf Trap side of the road.