But the guidelines also would allow developers to pack houses closer together in large new developments or in established neighborhoods--a measure that already is drawing objections from slow-growth activists.

Most of the proposals, included in a report just released by county planners, are aimed at calming residents increasingly upset over developments that alter the landscape and character of older neighborhoods. The report, requested by the Board of Supervisors, comes at a time of growing rancor over development throughout metropolitan Washington, from the cornfields of fast-growing Loudoun to crowded neighborhoods in the District.

"This is the worst time in my 17 years" for disputes over proposed development, said Supervisor Elaine N. McConnell (R-Springfield). "You have all these established neighborhoods who are used to seeing the land around them green, and they can't understand why we can't stop the developments. We need to answer that."

Supervisor T. Dana Kauffman (D-Lee) said most of the recommendations are long overdue. "My main concern is to make sure that it goes far enough," he said. "This recognizes that we are now an urban area and need to take an urban approach. We can no longer rely on a suburban model."

Perhaps the most far-reaching of the 12 main recommendations is to consider creating neighborhood conservation districts, which would limit the type and scale of development allowed in certain areas.

Fairfax residents could ask the county board to establish their neighborhood as a district, thus creating restrictions on how many more homes could be built there and rules governing the sizes of lots, yards and buildings.

Developers, who argue that stringent anti-growth rules will threaten not just their livelihoods but also the region's economy, expressed fear that the county may be getting carried away.

"On the surface, there's some pretty scary stuff in there," said Craig Havenner, a Fairfax developer and president of the Northern Virginia Building Industry Association. "Let's figure out a way to make it work without hammering us with all these new regulations. . . . We're concerned about being hit on so many fronts."

And planners warn there may be significant obstacles to the conservation district proposal, including the question of whether it is even legal in Virginia. McConnell said such a policy would almost certainly spark court challenges from landowners.

The report also suggests stricter definitions for open space to preserve more trees and parkland, as well as rules requiring that new subdivisions be compatible with the architecture, scale and landscaping of the surrounding area.

Although sweeping in scope, the recommendations are notably lacking in details. Marianne Gardner, one of the planners who helped craft the report, said the ideas were purposely kept vague to prompt a more detailed public debate.

"This is a list of ideas for further discussion, rather than the mechanics of how they would occur," Gardner said.

Board Chairman Katherine K. Hanley (D) said development is "the issue that existing neighborhoods are grappling with," and predicted that the board will likely adopt some of the recommendations. Public meetings on the proposals will be held in each supervisor's district in September and October, followed by hearings at the Planning Commission and final consideration by supervisors before the end of the year.

"There's no doubt that some of these will be implemented in varying degrees," Hanley said. "But one of the things we are going to discover is there are a lot of trade-offs. As we move through this, we are going to have to balance all of these things."

For example, Hanley said, one of the proposals--giving developers the right to cluster their new houses on a small corner of land--would allow supervisors to preserve trees on the rest of the parcel. But it also would create developments that are much more tightly packed and may not match the surrounding communities.

Lilla Richards, a former supervisor from the Dranesville district, said she will fight the proposal to allow developers to cluster their houses.

"No, no, dear God, no. We fought for years to stop that," she said, recalling previous efforts to require developers to get permission from supervisors before clustering houses on their land. "This is the worst proposal I have heard in 30 years."

Stewart Schwartz, spokesman for the Coalition for Smarter Growth, said that many of the recommendations are a move in the right direction but that Fairfax needs to be bolder in rejuvenating older areas and encouraging transit use. "Three hundred thousand people are coming to Fairfax in the next 20 years, and we need to figure out how to accommodate them gracefully," he said.