Improved access to the western side of Washington Dulles International Airport would have little effect on air cargo activity at the international gateway, a new analysis finds.

Proponents of the Bi-County Parkway, a 10-mile road that would connect Loudoun and Prince William counties, had suggested the north-south link could spur businesses to use the airport more frequently, particularly its cargo operations. However, after looking at what effect avoiding traffic congestion along the Dulles Toll Road and Route 28 might have, the Center for Regional Analysis at George Mason University concluded that a new road would increase demand for air cargo only about 8 percent. That would do little to offset the sharp declines in air cargo activity at Dulles.

“The fact is that we just don’t have as many international flights in and out of Dulles to as many destinations as JFK or Miami have, or even Atlanta or Chicago. [This] puts Dulles at a competitive disadvantage to those locations, regardless of what you do on the ground,” said the report’s author, David Versel, a senior research associate at the George Mason center.

Despite serving the fifth largest metropolitan area, Dulles ranks 21st nationally in air cargo activity. At its peak in 2000, the Northern Virginia airport handled about 846.4 million pounds of cargo. Last year, only 590.7 million pounds of cargo went through Dulles.

Dulles’s decline reflects a national trend. Domestic air cargo has fallen off the past decade as a result of several factors, including increased security measures after the September 11 attacks, rising fuel costs and improved efficiency by ground carriers.

Air cargo is primarily concentrated at a handful of airports — Memphis, Anchorage, Louisville, Miami, Los Angeles, New York (JFK) and Chicago (O’Hare). Prying away business from any of these hubs would require more than just better access to the airport, the report said.

Last year, Dulles handled only 7 percent as much cargo as Memphis, the leading cargo hub and home to Federal Express.

Should Dulles find ways to increase its air cargo capacity, the long-term economic benefits would be substantial, proponents say.

“We’ll be able to get goods and services a lot quicker and cheaper by having direct access,” said Keith Meurlin, senior vice president, Washington Airport Task Force. “We’ll also be able to get our goods from this area out the same way. It helps stimulate business activity.”

“It may not benefit existing shippers, but it may attract new shippers to the area,” said Rex Edwards, vice president, Campbell Hill Aviation Group, an aviation industry consulting firm based in Alexandria. “That’s ultimately the benefit in terms of economic development. You see all the development around Louisville and Memphis because of UPS and Fed Ex hubs there. They are locating there because they can get their freight in and out fast.”