When new-town planner Robert E. Simon first envisioned creating Reston more than 20 years ago, he brought together seven goals to guide the planning process, including that the importance and dignity of each individual should be the focal point of the development.

Reston residents, however, are beginning to fear that Reston's human scale -- and much of what makes Reston one of Northern Virginia's more desirable neighborhoods -- may be in danger of being overtaken by another original Simon goal: that of creating in the Virginia countryside a community that would be self-sufficient, with an urban core alive with lights, arts and activity.

Known on the Reston master plan as the town center, this proposed high-density core will be the last major piece of the town's development.

Reston Land Corp., the subsidiary of Mobil Oil that is finishing the building of Reston, is close to unveiling a plan for the town center, one that Reston Land Corp. officials have said will feature a high-rise conglomeration with two hotels, restaurants, housing and office buildings.

"The towering of Tysons Corners allows the town center to be more of an urban statement and still be supported by market conditions," said Michael C. Was, executive vice president of Reston Land. "Reston has been, so far, an attractive suburban community, and with the development of town center will become a town."

But for a number of Fairfax County neighborhoods, the promise of a nearby high-density office development is seen as a threat, rather than an enhancement of the quality of life.

This year, for the first time, Fairfax County's office of comprehensive planning has received requests from neighborhood groups, feeling hemmed in by traffic and noise, to have the county's master plan changed so that they can sell their land to a commercial developer.

Many Restonians, already chafing under problems of "occasional gridlock" in Reston and serious congestion on all the major arteries connecting the town to Washington, say they are having second thoughts about how "ambitious" the town center plans should be.

"There are a lot of people who don't like the idea of higher-density development," said Harry Mustakos, a Reston resident and long-time member of the Reston Community Association. "The idea was that when the bottle was full, it was filled, and while there may be some turbulence inside the bottle, some movement within, it is capped. Once Reston is finished you don't fill in with more density."

Mustakos, along with other Reston residents, developers and county planners, gathered together last week to celebrate Reston's 20th anniversary and talk about how the ideal envisioned by Simon has been supplanted by the reality of market conditions in a county experiencing explosive growth.

In a workshop discussing whether Reston had provided an alternative to urban sprawl, planners and developers assessed the reality of Reston, saying that the new town was built-out in ways that significiantly altered the original designs.

One idea scrapped by the developers early in Reston's construction was that of building high-rise apartments. At the same time, the developers decided to build more single-family detached homes to meet market demand, with the result that Reston today is far less dense than originally envisioned.

Reston was expected to have 80,000 people by 1980. There are only 41,000 residents today, with the total build-out now predicted as only 60,000 by the turn of the century.

There are many more jobs in Reston, however, than ever predicted: 20,000 today, with more on the horizon.

This occurred because, planners said, in a twist that Simon did not predict, the businesses that located in Reston came not to be part of the new town's self-sufficiency, but because of its proximity to Washington Dulles International Airport and the easy access from Reston to Washington via the newly built Dulles toll road.

One of the biggest differences between the Reston of the drawing boards and the town that actually developed is the lack of transportation options outside the standard suburban solution of using the car.

"We have found that people don't want to walk to purchase a convenience item in the suburbs," said Was, in a session describing why many of Reston's village centers have been commercial failures. "People have cars and they use them."

While the existing road system is about equal to what the planners thought Reston would need by 1985, Reston does not have an extensive inner transportation system and many residents have avoided using the town's 50 miles of paths because of security problems and lack of trail markers.

Reston Land officials have already said that town center will not include a major retail shopping center, the final major difference between what was envisioned and what has become the reality of Reston.

"There isn't a market for it, not with Tysons Corner and the center at Fair Oaks," said Was. "And I'm not sure Reston residents want it, since it would bring in a lot of traffic."

Some local developers, however, said they believed that the retail component might be necessary to make the town center work.

"Reston has to exert a force to keep what it already has, or development is going to go on by to the Dulles area," said Ed Risse, a planning consultant who has done extensive work in the county for the Hazel/Peterson development company, including helping with the build-out of Burke. "And if it is going to support an urban town center, that town center will have to have a retail component."

Risse and other developers have said that Reston, because it is less dense than originally planned, presents a golden opportunity for in-fill development and that such development will be needed if Reston is going to continue growing and attracting more businesses.

"If Reston wants a town center, it will have to be the center for 180,000 people, not 60,000 or even 100,000, but 180,000," said Risse. "If not, there will be all this development around it, but Reston will just be the hole in the donut."

Residents here, however, say that that might not be such a bad thing, and question whether they want a town center with 1 million square feet of office space at the heart of their community, as Reston Land has planned. While Reston Land officials speak of density, theaters and "a touch of New York" for the town center, residents question whether such an urban landscape will enhance or endanger the Reston they know.

"There's a serious problem of divergent directions in Reston today," said John Dockery, a Reston resident and participant in the 20th anniversary symposium. "The trick is to make the town center the conceptual magnet without all the cars, and we've seen that is difficult to create."