Loudoun County supervisors have unanimously approved a development plan for an area south of Dulles International Airport that proponents said could allow construction of a grand new entrance to the county along Route 50.

A split Board of Supervisors also voted to allow consideration of proposals for two large developments just outside Leesburg, known as Creekside and Crosstrails, that would include thousands of new homes. The board had instructed county staff in February to cease work on the proposals pending a joint planning effort with the town.

The two actions were the latest indications of the intense development pressures in Loudoun, which has grown faster than any other county in the United States since 2000. The decisions also showed the divergent approaches to development policies on the board, which controls land-use rules and thus holds sway over lucrative projects that will shape Loudoun's growth for decades.

At their meeting Tuesday, supervisors voted to amend Loudoun's countywide plan governing more than 300 acres along and near Route 50 just west of the border with Fairfax County. Scott Plein, president of Equinox Investments LLC, and Supervisor Stephen J. Snow (R-Dulles) had been key proponents of the changes, which will give developers more flexibility.

"It changes the landscape and allows for higher and better uses," said Snow, who has pushed to allow more development in his large district.

Snow said that the plan changes, known as East Gate, that were passed on Tuesday will be used to evaluate specific development proposals. He said the changes should promote such developments as a business park, upscale restaurants and a hotel rather than strip malls. Housing will also be a key component.

One objective, Snow said, is to set that part of the county apart with high-quality development that is different from what is visible, for instance, along Route 1, which stretches south through Alexandria and can be a hodgepodge.

"We're going to change the whole vista of the corridor," Snow said, adding that he also hoped new development would generate funds to widen Route 50 and make it more attractive. Supporters of the plan amendments argue that landscaping and design could give the road more of a parkway feel.

Plein controls about half of the land and is seeking county approval to build commercial and housing developments. He said Tuesday's vote has given the county the ability to look at the area holistically.

"This area's always been a challenge because it's so many different small parcels," Plein said. "The crux is it gave the county the flexibility to look at how they really wanted that area to develop."

The plan changes state that the county will discourage one project from consuming "all of a single land use" in the area. That wording was added to quell concerns of some smaller landowners who expressed fears they could be locked out of development opportunities.

"The language was changed such that it was not too bad," said Supervisor Jim G. Burton (I-Blue Ridge), adding that the plan changes should bring benefits to the county. "It changes the land-use pattern and transportation routes, and I think it's going to help spruce up the entrance to the county."