Northern Virginia developers and real estate agents recently were warned by a top state transportation official that projected growth for Fairfax County will have a severe impact on the antiquated road system in the area.

David Gehr, who heads the Northern Virginia division of the state Department of Highways and Transportation, said current projections for Fairfax County indicate a 71 percent increase in the number of work trips within the county by the turn of the century.

Gehr was one of several transportation officials from Virginia, Maryland and the Metro system who addressed a Regional Economic Development Update seminar sponsored by the Northern Virginia Board of Realtors.

Gehr told the conference that one of the major problems facing the Northern Virginia area is that most of the main routes through Fairfax County, such as Leesburg Pike and Georgetown Pike, are designed to get workers in and out of the District of Columbia. The growth patterns in the area, however, indicate that the major road needs will be cross-county as more and more jobs are created outside the District.

Transportation officials expect some relief from the cross-county transportation problem when construction is completed on the 35-mile Springfield Bypass connecting Route 7 in the western part of Fairfax with Route 1. They also expect some relief from the major improvements to the Route 28 corridor running north-south near Washington-Dulles International Airport.

The recently opened Dulles toll road has relieved some traffic congestion in western Fairfax, but transportation officials are concerned that future growth along that corridor is likely to spur additional traffic both within the county and across county lines during peak work hours. There already are approximately 5,500 acres of land planned or zoned for commercial development in the Dulles corridor.

The area growth projections have revived talk among some developers and government officials about the need for an outer beltway system to alleviate the traffic problems as population growth pushes more and more traffic toward the borders of Loudoun and Prince William counties. Gehr told the conference that work-related trips between Loudoun and Prince William counties will increase 237 percent in the next 15 years, while work-related travel from Loudoun to Fairfax County is expected to rise 185 percent during the same period.

But the idea of an outer beltway, which first was proposed in the 1950s, appears to have little support beyond the Northern Virginia development community.

Larry Saben, assistant director of the Maryland Department of Transportation's office of transportation planning, said at the conference that such a proposal was not likely to find much support from Maryland officials.

"I can't tell you that it is a likely project," Saben said. "It first came to life in the 1950s and was in the inventory wish list in the early '70s. By 1975 we had given up on the section from I-270 over to the Potomac river."

Saben called the idea of the outer beltway "a practical and political impossibility in the near future." He said that "most of the Maryland area's transportation needs are between the 270 corridor and I-95 today."

Maryland plans to pour an estimated $300 million into improvements along the I-270 corridor during the next several years in an effort to relieve one of the biggest bottlenecks in the metro area.

Suburban Maryland communities can expect to get 20 percent of the next $3.7 billion of highway money spent, Saben said. "The biggest improvements will be in the I-270 corridor from the Capital Beltway to Clarksburg. Another $120 million will be spent on I-370, a connector from I-270 to Shady Grove."

Saben warned that construction improvements under way on the Beltway will take another 18 months to complete. After that, work will begin on the Beltway in the I-270 to Georgia Avenue area in Montgomery County.

Another major transportation factor in the Northern Virginia development picture is the expansion of the Metrorail system in the area.

Dick Miller, acting head of the development branch of the Washington Metropolitan Area Transit Authority, said at the conference that "the most dramatic thing in the next 15 months in Virginia is the coming of the Orange Metro line to Vienna. That service will commence within a few days of the first of July."

The Washington rapid transit system will be "second only to New York in the number of passengers when Vienna is opened," Miller said.

He emphasized, however, that Metro itself does not create "opportunities for development." He said "those stations that incorporate roads will prove to be prime locations for development in suburban jursidictions."

However, Miller said that, working with local developers, Metro's development branch can help generate development. He said Arlington, Alexandria and Fairfax are all dealing with the development potential of transit station sites and nearby land in different ways.

"Metro has been given credit for attracting nearly one-half of all the recent commercial development that has come to Arlington," Miller said.

Meanwhile, "Fairfax is in the throes of deciding" if the station sites will be used simply as commuter railroad stations or as development sites, Miller said.

"Fairfax Metro stations have not yet been the focus of significant construction activity," Miller said.

Fairfax County has set up citizen task forces that have been working with Metro and county officials to develop recommendations for land use on a station-by-station basis. Many of those task forces are still in the middle of their deliberations while others remain in the early stages of work. Those reports will be studied by the planning staff, the county planning commission and elected officials before major development decisions are made.

"Hazel-Peterson Cos. has proposed a closely integrated high-rise commercial development at the Vienna Metro station," Miller said. But that proposal has met some trouble at the county level because Fairfax has told the developer it needs a change in the county land-use plan rather than a rezoning to accomplish the proposed development. The plan includes a 34-story building which, if built, would be the tallest building in the county.

"Fairfax is groping for the right relationship," Miller said.

Hazel-Peterson officials said the development, which would include housing, hotels and offices, would be a major employment center and a generator of reverse commuting, attracting those who live along the Metro lines in the District and Arlington to come to work at the Vienna site that would be known as Virginia Center.

While Arlington County has encouraged major development at its station sites and thereby created strong development opportunities, county officials admit development has occurred more slowly than anticipated at the Ballston site, currently the end of the Orange Line. Ground has been broken, however, for several major projects in recent months and others are on the drawing board. Renovation at the nearby Hecht's department store in what is remaining of the old Parkington shopping mall is well under way and has produced a dramatic updated interior for the Hecht Co. building.

According to Miller, "Alexandria is someplace in the middle" between Fairfax and Arlington in Metro station development.

"The King Street station has been the focus of most new development," Miller said.

But the station has generated new construction in areas within walking distance of the station, he said.