When the residents of The Oaks move into their new million-dollar-plus French country-style homes, they may thrill to the stainless-steel and granite sheen of their gourmet kitchens, lounge beside extra-large marble fireplaces and retire to master bedroom suites befitting a palace.

And when they step outside, they may hear the ceaseless whoosh of traffic on Interstate 270, which runs right by their back yards.

"The vitality of Provence, the practicality of America," the sales brochure says.

Not that long ago, a suburban home buyer with enough money to purchase at The Oaks -- prices start at $1.2 million -- would have aspired to the natural serenity of a country estate. But the construction of highway mansions like those planned at The Oaks reflects not only the scarcity of buildable land around Washington but also the erosion of the old suburban ideal: The yearning for a stately acreage has been trumped by the consumer demand for speed and mobility.

Catering to this dynamic, developers around Washington are placing luxury subdivisions not on rural hillsides, but next to major highway interchanges. There's The Oaks, at Old Georgetown Road and I-270; Beaufort Park, on the Capital Beltway at the Georgetown Pike exit; and Carrington, recently completed at the Route 7 exit off the Dulles Toll Road. Each is equipped with a variety of noise-control measures, from simple sound barriers to thicker window glass.

"You wouldn't really want to open the windows on that side of the house at night," said Molly Margenau, who lives in Beaufort Park in a house overlooking the Beltway and assessed by Fairfax County at $1 million. "It's loud. But I think the highway is a plus. I love that I am 15 minutes away from anywhere."

Growing traffic tie-ups and daily time pressures drive the demand for such homes, housing experts say.

"The convenience outweighs the nuisance," said Margenau's husband, Casey, a real estate agent.

Even so, the phenomenon has surprised many in the field.

David Flanagan of Elm Street Development had hoped to develop The Oaks property but said he doubted that people would spend that much for a house in that location. He was outbid for the property, he said.

"I remember thinking people will not spend a million dollars to live next to the highway -- nobody wants to live next to the noise," Flanagan said. "Boy, was I wrong. He has people standing in line to buy in there."

Though the model home at The Oaks is not yet finished, five of the 30 lots are under contract. Three others are on hold.

"First of all, it's Montgomery County, so it's gold to begin with," said the developer, Morton Levine of the Associated Companies/Chase Communities.

Transforming a highway site into a neighborhood fit for mansions demands an array of acoustical techniques, beginning with sound monitors and traffic projections and ending with a variety of remedies from noise walls and berms to solid-core doors and alterations in the height of the homes.

At The Oaks, the highway noise wall and brick screening walls alone will cost nearly $1 million, Levine said. The barriers range in height from eight to 12 feet. Noise consultants also recommended lowering the elevation of some homes to duck the worst noise rising over the wall.

During peak traffic, the highway sound levels "will average out to be about normal speech," said Michael A. Staiano of Staiano Engineering, a noise-control consultant. "It will vary. A truck that might be going by might be louder, but then there might be a pause where it would be quieter."

"The traffic sounds inside the house would be rarely, if ever, perceptible," he said.

At the Carrington development in Fairfax County, where a prohibition on building within 200 feet of the Dulles Toll Road was waived for the high-end project, meeting the county's standards for noise control involved a wider array of mitigation measures.

The noise engineers from Miller, Beam & Paganelli of McLean called for solid-core wood doors, fewer windows and doors on some facades, and a system of metal connectors in exterior walls not made of masonry to dampen vibrations from the exterior.

Residents of Carrington said their homes are hush-hush quiet inside.

The noise they hear outside, they said, is well worth the easy highway access.

"It just makes everything easier to juggle: One right turn and we're on the highway," said Ingvild Brown, a Carrington resident. "We don't consider it noisy at all -- it depends on what you're used to."

Even though her lot backs up to the wall on the toll road, she says she frequently uses the back yard.

"Inside, we don't notice the highway at all," she said. "Outside, we'll gladly put up with the extra noise to have the convenience."

While there are no firm statistics on the number of new home developments springing up near highways, local governments increasingly are wrangling with the noise regulations for highway sites.

Prince William County added a noise ordinance to its design and construction standards two years ago. Fairfax revised its standards for noise studies earlier this year. Regulators in Montgomery are rewriting their noise guidelines.

The changes come as builders say there is a scarcity of buildable lots.

"We're seeing a lot of very difficult sites come back in with developments planned," said Mark Pfefferle, a planner with the Maryland-National Capital Park and Planning Commission. "Developers are really searching out places to build."

Meanwhile, the time pressures on many families have raised the premium some home buyers will pay for convenience, while the role of outdoor activities, which are most affected by highway noise, may be shrinking along with back yards.

The average size of new single-family homes has grown since 1990, but the average size of lots has shrunk by 12 percent, according to the National Association of Home Builders.

"People don't have time to be outside so much," said Gopal Ahluwalia, the group's vice president of research. "What they want is a big house."

While it is difficult to gauge at what point highway noise will annoy someone, noise engineers said, typical guidelines in the region call for it to be no louder than 65 decibels (in a commonly used frequency and time-weighted noise measure), or about the level of normal conversation.

Development guidelines also regulate noise levels inside a house. In Fairfax, for example, they should fall under 45 decibels. This is significantly quieter than the outside standard of 65 decibels, because a drop of 20 decibels is perceived roughly as a fourfold decline in loudness.

"The [65] level is arbitrary," Staiano said. "It doesn't mean that everyone's going to be happy if it's less or that everyone is going to be upset if it's more. People are different. Some people are disturbed by a pin drop."

At none of the sites does the traffic noise interrupt normal conversation. It varies from place to place on any given site, too, depending on topography.

"It's kind of like a whooshing sound, a hum almost," said Jeff Palmucci, a real estate agent with Weichert Realtors, who recently had a $2.4 million house for sale in the Beaufort Park neighborhood. "But that's not what people talk about. They talk about the convenience."

Annoying or not, it is a far cry from the suburban ideal that historians have traced to the ancients.

"Our property seems to me the most beautiful in the world," reads a letter sent to the King of Persia in 539 B.C. "It is so close to Babylon that we enjoy all the advantages of the city, and yet when we come home we are away from all the noise and dust."

Residents of Beaufort Park have done what they can about the noise. They have built a berm to dampen the sound. And they have grown accustomed to it.

"In the morning, the birds are singing and the chipmunks are barking so loud they wake me up, not the traffic," Molly Margenau said. "It's unbelievable how loud the nature is.

"I went to the beach one time, and I woke up in the morning and I heard the crashing waves outside. I thought I was at home with the windows open."

High-end homes in Beaufort Park in Fairfax sit within sight of Capital Beltway traffic. "It's loud. But . . . I love that I am 15 minutes away from anywhere," said Molly Margenau.Casey and Molly Margenau and daughter Madison live in a $1 million home near the Beltway in Beaufort Park.Beaufort Park is equipped with a variety of noise-control measures. Real estate agent Jeff Palmucci said of area traffic noise: "It's kind of like a whooshing sound, a hum almost."