Tysons Corner, already the region's largest suburban "downtown," is going to get so big in the next 25 years that a lot of private and public officials are starting to plan its future.

As they see it, Tysons will need a personality, a sense of community. It will need a way for lots of people to get around, such as a monorail. And Tysons will expand upward, not outward.

In other words, it'll look like Patrick F. Kane's daughters' bedroom.

Kane, a planner, took an oversized bedroom in his home on Lake Anne in Reston and designed enough places to sleep nine people when his six children have overnight guests. Some beds are on the floor and some are built off the floor in the cathedral ceiling, but the room doesn't appear cramped. The key was to fit more people comfortably in the same space without knocking out a wall and adding another bedroom.

Tysons could be developed with the same vertical approach, Kane said. Instead of putting up more isolated buildings separated by large parking lots, forcing people to use their cars to get around, Tysons could be designed in a series of building clusters, creating enough mass for the clusters to be linked by a transit system.

"The private automobile gave us the rope to reach out into the suburbs," Kane said. "Total dependence on the automobile is becoming the noose."

Kane's views are shared by the Tysons business community, including a 70-member group of landowners, business people, community leaders and public officials called the Tysons Transportation Association Inc. The association was awarded an $80,000 federal grant to come up with a vision for Tysons and hired Kane and architect Guy L. Rando of Reston to carry that out.

After a year of study by Kane and Rando, a consensus is building on Tysons's future that generally is being embraced by Fairfax County planners, who are beginning their own process of plotting a course for the county's largest center of jobs and shopping.

The stakes of this planning effort touch thousands of people in Virginia, Maryland and the District. More than 70,000 people work in Tysons, more than in downtown Miami. Because of Tysons's strategic location, any changes in the use of Tysons affect the transportation system of the entire region.

Ed Knauf, the association president, said, "The future of Tysons must provide alternatives to the private automobile -- effective mass transit -- and improved pedestrian opportunities."

In addition, he said, Tysons should offer people more reasons to go there than working or shopping. That means building more housing and including more entertainment, cultural activities, recreation and education.

In other words, as long as Tysons is bigger than downtown Miami, it might as well function more as a community with some personality.

That's hard to imagine now for an area characterized by a seemingly endless series of automobile dealers, strip shopping centers, insular office buildings and two giant malls.

"There's a tremendous need for a lot more things to balance Tysons and make it a full community," Kane said, offering such suggestions as museums, galleries, street festivals, theater, tennis courts, pools and a university branch.

To achieve this sense of place as well as the density needed to support mass transit, Kane and Rando suggest the clusters, or activity centers, in strategic places such as the Greensboro Drive area.

These centers would be like Baltimore's Harborplace, albeit on a smaller scale, combining shopping, green areas, recreation, housing, offices and a focal point like the National Aquarium or a tall building like the World Trade Center -- all within walking distance.

Add to that a transit stop -- monorail, people mover or bus -- that would connect with the regional transit system -- Metrorail and/or the proposed transit line along the Dulles corridor.

The Tysons transit system also would allow office workers to travel within the area without using their cars..

"We want people to get to Tysons from somewhere else and the occupants of Tysons to get somewhere else with something other than a private automobile," Rando said.

Concentrating development in distinct centers also makes it easier for people to figure out where they're going. Now, many people have difficulty figuring out where they're going in Tysons, and there are few buildings or other landmarks to help orient them. Signs don't help much either.

"If you feel disoriented, you feel uneasy," Rando said. "Fear creeps in. You could improve the orientation by adding signs, symbols, special buildings, plants -- even painting the road different colors."

None of this can happen, of course, without public support and money. Nor can greater emphasis on transit at Tysons occur without a similar shift elsewhere in the region. Moreover, the impact on Metrorail of tying in new transit systems has not yet been considered.

"People are blithely saying, 'We'll build light rail and we'll connect with Metro' without talking to us," said Mary Margaret Whipple, chairwoman of Metro's board.

Kane's study didn't attempt to put a price tag on the recommendations, but there are no illusions about the millions of dollars needed.

"The money we're talking about isn't only going to come out of Fairfax County and the community," said Peter A. Polk, a Tysons transportation planner and vice president of the association. "It's got to go beyond that" to the private sector and the federal government.

E. Wayne Angle, project manager for Tysons II and a member of the transportation association, said the association is pragmatic about Tysons's future. If people won't ride transit or move into housing at Tysons, he said, it makes no sense to pursue it.

"Citizens have the right to determine how they want to live," he said.

The Tysons study began last fall, even as the Fairfax County Board of Supervisors was involved in a hot fight with developers, including many in Tysons, over a proposal to limit commercial and industrial growth. The proposal was approved, though part of the action was overturned by the General Assembly.

Against that backdrop, there isn't a lot of interest among some political leaders in a discussion about Tysons future led mostly by developers.

Fairfax board chairman Audrey Moore said that instead of focusing on ways to move people around Tysons, planners should concentrate on solving the transportation problems of the regional road system leading into Tysons, which is connected by the Capital Beltway, Routes 7 and 123, and the Dulles Access Road.

"If we can get rail out to Dulles {International Airport}, then we need to figure out something for Tysons someday," she said. "We need to build an HOV {high occupancy vehicle} network and expand I-66 and the Beltway. You have to walk before you can run."

Kane and the association members don't dispute the need to fix Northern Virginia's road network and build rail to the airport. But planning is necessarily future-oriented.

"Tysons Corner represents a fantastic opportunity because of its location," Polk said. "It's poised to be a model nationally for a suburban business center. It would be a shame if the community didn't try to take advantage of that opportunity by focusing on a long-term plan and where the money is going to come from."