The private consortium that has offered Virginia more than $1 billion in exchange for revenue on the Dulles Toll Road for 50 years has outlined 19 upgrades to the highway that it hopes will help sway public opinion in favor of the unusual proposal.

Topping the list of upgrades is a series of improvements to the ramps that link the eastern end of the toll road to the Capital Beltway. One new ramp would take drivers directly from the Beltway to the Dulles Airport Access Road, a separate roadway that is not part of the proposed deal. Linking to the access road would relieve drivers from cutting across several lanes of traffic on the toll road, a move that causes daily tie-ups.

The group also proposes to upgrade the ramps that take drivers from the toll road to the outer loop of the Capital Beltway.

The consortium said that it plans to immediately repave the eight-lane road, a project that it said could be done in about four months, and to refurbish several bridges and sound walls along the route.

Most of the other fixes would involve widening or lengthening ramp lanes and converting toll plazas so that fees would be paid electronically. The group said those changes would improve traffic flow by easing backups.

Other proposed upgrades include widening the exit and entry ramps at Wiehle Avenue and lengthening the exit lane ramp at Reston Parkway, so drivers would be able to make a continuous right turn onto the parkway.

A separate loop ramp would be built to connect the southbound lanes of Centreville Road to the eastbound toll road. Entry and exit ramps would be widened at Hunter Mill Road.

Toll plazas at all these intersections would be upgraded and converted to charge fees electronically. Other minor fixes for the interchange and parkway also are planned.

The Dulles Toll Road is a 14-mile highway that connects the Beltway to the Dulles Greenway, a privately operated toll road. The highway is one of Northern Virginia's premier commuter routes, carrying about 200,000 vehicles a day.

Morning and night, it is filled almost bumper-to-bumper with traffic heading to and from some of the region's largest employment centers at Tysons Corner, Reston and Herndon. The road is also something of a main street for fast-growing communities in eastern Loudoun County and more established areas such as McLean.

Tolls on the road cost 50 to 75 cents for two-axle vehicles. Tolls were raised in May to help pay for Virginia's portion of a proposed Metro line through Tysons Corner to Wiehle Avenue. State officials have approved a second increase in five years to help pay to extend that line to Dulles International Airport. State officials said they would maintain control over toll rates under the terms of any deal.

The price estimate on the first phase of the Metro line rose in June from $1.5 billion to as much as $2.4 billion, a 60 percent increase that threatens the financing plan for the rail project.

Members of the private consortium said the deal is a way to pay for Metro, even as costs rise, as well as to improve the toll road.

"We are stepping in to provide excess capital," Curtis M. Coward, a principal of Infrastructure Investment Group, a member of the consortium, said at a news conference last week.

The consortium said the roadway improvements would address criticism that drivers were being forced to pay for a transit line that would benefit them little. None of the 19 improvements is proposed, scheduled or funded as part of the state's six-year transportation plan.

The group behind the proposal includes some of the biggest names in the road-building industry, including Clark Construction Group, Shirley Contracting, Dewberry LLC and Autostrade, which operates the Dulles Greenway. It also includes former governor Gerald L. Baliles (D) and J. Kenneth Klinge, a former member of the Commonwealth Transportation Board.

State officials were intrigued but reacted to the unsolicited offer with caution.

Many transportation officials and Virginia politicians favor selling some state assets in return for large sums of money upfront. Yet many others are reluctant to trade assets for such a long time, especially the Dulles Toll Road. In fiscal 2005, which ended June 30, the tolls generated a $28.5 million surplus.

Officials are clear on one thing: They would like more offers from the private sector. Under the state's public-private transportation act, the consortium's unsolicited offer opened a 90-day window for other investors to step forward. The window for rival offers closes Oct. 28.