More than two dozen Tysons Corner landowners are asking Fairfax County to double the development permitted on much of their land -- allowing skyscrapers and mid-rises and laying the groundwork to attract riders to Metrorail stations proposed for the sprawling suburban crossroads.

The property owners are pushing to optimize their profits from the intense, transit-oriented development that Virginia officials are encouraging as they lobby for federal money to help extend Metro to Tysons and eventually to Dulles International Airport.

Fairfax leaders have long hoped to transform Tysons, a place of impersonal, 1960s-era office campuses surrounded by moats of parking, into an old-fashioned downtown, friendly to pedestrians who might hop a train to work or home.

Now, with the go-ahead from the federal government this summer to begin engineering on the first 11 miles of rail from West Falls Church to Tysons and Wiehle Avenue in Reston, the blueprint to reshape the capital region's second-largest job hub is unfolding.

Property owners are seeking changes to the county's development guidelines that would allow hotels, offices and condominium towers -- some up to 25 stories tall -- on about 790 of the 1,700 acres in Tysons. Buildings would front on streets rather than parking lots and include shops and restaurants on the ground floor -- much of it within walking distance of four planned Metro stations.

With only slivers of vacant land left in Tysons, much of the current hodgepodge of auto showrooms, warehouses, offices and garden apartments would be torn down to make way for a new urban center, where pedestrians could dine at sidewalk cafes, window shop or even take in outdoor lunchtime concerts at public greens.

If the Board of Supervisors approves the proposals sometime next year, the 46.4 million square feet of commercial and residential space in Tysons could be expanded by tens of millions. Construction would have to wait until federal funding for the rail line is guaranteed.

"The advent of rail is changing things," said board Chairman Gerald E. Connolly (D), a rail booster who represented the area until this year. "The idea of an office park is clearly obsolete. . . . We're looking for a lot of urban attributes now."

He cautioned that landowners will "have to prove that with the extra density, they're going to push people to transit. . . . If 90 percent of people are going to get in their cars, it's not going to work."

The proposed changes are years away.

"In many cases, the applicants are saying, 'Let me hold my place' for when rail comes," said Hillary Zahm, an attorney for five property owners.

But as much as county leaders want a downtown, they don't want a Tysons that's too urban. Even the highest densities under consideration -- 3.5 square feet of building area for each square foot of land -- don't come close to the compressed development around Metro stops in Bethesda, Rockville or the Ballston corridor in Arlington. Those areas are by and large twice as dense. And while Fairfax planners hope to wipe out thousands of surface parking spaces and put them underground, it's a given that cars would not disappear from Tysons.

The area is too big, and much of it lies too far away from the planned Metro stations, for a comfortable walk. A certain amount of driving is a necessity. In fact, planners estimate that when the stations open, only 12 percent of weekday trips into Tysons would be by transit.

"Tysons is really big. Arlington is not," said Supervisor Linda Q. Smyth (D-Providence), whose district includes Tysons. "The farther toward the city you are, the more transit accessibility you have, and the density can be higher."

Dense development would bring more cars to an already jammed network of roads, many with limited access. County planners are looking to design a new grid of small streets and extra turn lanes for Tysons that would feed into the stations.

The four Tysons rail stations would be laid out along a rail line stretching from the edge of the Dulles Toll Road east along Route 7 and then along Route 123 across the Capital Beltway.

West Group, one of the area's leading developers, is proposing to build a bridge over the Beltway to tie together its 356-acre property straddling the artery. That change would ease traffic and allow pedestrians to walk to more than one train station.

"The main thing is going to be getting people in and out of there," said Supervisor Joan M. DuBois (R-Dranesville), whose district includes several residential neighborhoods at the western edge of Tysons.

Tysons is a gold mine of potential rail riders, drawing close to 100,000 daily commuters and 25 million annual visitors to its two malls. Metro estimates that when the extension opens through Tysons, its five stations, including the last one at Wiehle Avenue, would generate 59,000 rail trips on an average weekday.

Rail boosters favor higher density as a key selling point to justify the $1.5 billion project to the Federal Transit Administration. The agency must decide which of several competing projects to fund, and the density of development around stations is one factor federal officials say they will consider.

"Fairfax County has developed practices that permit development around transit stations," said Drucie Andersen, an agency spokesman. "What the county has done is very substantive," she said, and played a role in the decision to fund engineering work.

Yet some residents on the edges of Tysons say an urban setting in a place already beset by gridlock represents more bad planning. "The traffic is going to be overwhelming," said Susan Turner, president of the McLean Citizens Association, which has not taken a position on the proposed changes. Turner lives two miles west of Tysons.

"I already have trouble getting out of my neighborhood," she said. "People are going to need to go places like the hardware store. But we don't have a system like New York City's, where people just run down to the station and go wherever they want to go."

The county board has tried to address the area's imbalance between jobs and housing in recent years, approving thousands of condominiums and allowing developers more density if they build residential instead of commercial projects. Some of the housing does not fall within walking distance of a rail station, irking some activists who complain of increased traffic.

The area's six schools are expected to reach capacity within five years, school officials say. While they acknowledge that the small residential market in Tysons attracts relatively few families with children, some new classrooms would be necessary. They may be built in unusual places.

"We may be locating a school in an office complex," said Gary Chevalier, director of facilities planning for Fairfax schools.

Before the first high-rise goes up, the Federal Transit Administration must guarantee its full share of funding for rail, county officials say. From there, the pace of construction would be tied to the laying of new tracks, expected to start in 2006, so Tysons is not overwhelmed by extra people with no way to get around. The first leg to Reston is expected to open in 2011.

In the meantime, developers hope the area's soft office market, with 5.1 million square feet sitting empty, will rebound.

In evaluating the applications for more density in Tysons, the county will focus on land within a quarter-mile to a half-mile of stations, development that would be close enough for an easy walk. The county's land-use plan, in place for a decade, already allows builders to put up bigger buildings around rail stations, with more density encouraged the closer to the station. Proximity to rail allows building heights to increase by 30 percent.

The current round of applications asks for even more density. For example, Science Applications International Corp., the research and engineering company off Route 7, wants to expand its Tysons campus of 3,600 employees.

The company, whose property sits above the only rail station in the plan that would be underground, is asking for land-use changes that would allow up to 2.7 million square feet of offices, hotels and condominiums to be built on 18 acres that now house a 1 million-square foot campus.

"We're not in the development business, but it's an opportunity, and the density should be increased for Metro," said Joe Renzetti, the company's director of construction.