Virginia's 21-mile section of the Capital Beltway, between the Woodrow Wilson Bridge and the American Legion Bridge, would be widened from eight lanes to 14 under a plan being considered by state transportation officials.

If approved, the $1 billion proposal would radically alter Virginia's part of the region's Main Street during the next 25 years and replace it with an entirely different configuration than drivers have been traveling since the Beltway opened 26 years ago. Not even California, the home of the freeway, has a 14-lane highway.

"Some people sitting in traffic will probably say, 'Thank God someone is looking at the long term,' " said Virginia highway chief Ray D. Pethtel. "Others will probably be incredulous -- 'My God, 14 lanes of traffic on the Beltway?' "

The inner and outer loops would each have seven lanes. The four inside lanes of each loop would carry through traffic. The three outside lanes would be used by local traffic and would be separated by barriers from the express lanes.

The far left lane in each direction would be restricted during rush hours to car pools, according to a preliminary draft of a consultant's proposal obtained by The Washington Post.

About 35 homes, most of them near the Beltway-Shirley Highway interchange, would be displaced and 93 additional acres of right of way would be needed for the widening, which would take place in stages over 25 years. An estimated 96,000 feet of barrier walls would be built to reduce noise and contain exhaust emissions, the report said.

Although the plan has been in the works for more than a year, many local political leaders will be getting their first look at it next month as the Alexandria consultant hired by the state, JHK & Associates, completes the final draft of a two-year, $1 million study.

The board that makes transportation policy for the state was briefed recently about the Beltway plan and was staggered by its cost and size, said board member Mark R. Warner, of Alexandria. Nevertheless, he said, "We'll need to start introducing this into the debate."

State officials first must decide whether to approve the consultant's recommendation to add a temporary fifth lane between the Shirley Highway and Route 123, using the shoulders and narrowing the existing lanes. That would be an $80 million stopgap measure along the Beltway's busiest stretch until a decision is reached on the long-term widening program.

Beltway traffic is growing at 10 percent a year, compared with 3 percent growth in traffic overall in the region. The capacity of an eight-lane freeway is about 160,000 vehicles a day, but some Beltway sections are now carrying more than 227,000 vehicles daily. That figure will swell to more than 323,000 vehicles by 2010, according to the report.

Faced with these projections, transportation officials view the expansion of the Beltway as inevitable, even if more roads elsewhere and more rail transit are built. The possibility that the Woodrow Wilson Bridge might be widened to 14 lanes also is putting pressure on planners to add lanes to the Beltway.

"Failure to widen the Beltway after the Wilson Bridge is widened will result in even greater congestion than is faced today," the report warned. "While the bridge itself is now congested much of the day, the future could find the bridge with excess capacity while the rest of the Beltway is at a standstill."

No money is available for the project now, and the region's list of transportation needs keeps growing. The cost of the Wilson Bridge expansion could top $750 million, the proposed eastern and western bypasses would cost $1.7 billion each, the widening of Interstate 66 outside the Beltway is pegged at $620 million and the tab for completing the Metrorail system is $2.7 billion.

"I don't see the funding for it under the current federal program and current state statutes," Pethtel said. He said a decision on both the short-term, fifth-lane plan and the 14-lane Beltway probably won't be made until after Congress enacts a new national highway program next year.

Besides finding the money, widening the Beltway also involves other thorny issues, such as what to do about traffic during construction and the impact on Beltway overpasses and feeder roads. Most Beltway bridges were built for an eight-lane highway, so they would have to be rebuilt.

Moreover, the question is how Maryland, which is just finishing widening the Beltway to eight lanes, will respond if Virginia builds a 14-lane Beltway that has car pool lanes.

"They may have the room to do it, but we don't," said Hal Kassoff, Maryland's highway administrator.

Kassoff said he does not think it would be difficult to funnel Virginia Beltway traffic into a smaller number of Beltway lanes in Maryland. Most Beltway traffic is local and does not always cross the two bridges that link the states, he noted.

Maryland has considered adding a lane to the Beltway in the few places where it has the land, Kassoff said, but the planning for the expansion is years away.

Virginia's plan envisions the Beltway as four separate roadways, each with a different purpose.

The existing four lanes in both loops would be used as express roadways, mostly for through traffic. The inside lane would be restricted during rush hour to car pools, and officials might limit trucks to the two right express lanes.

Three local lanes would be added on each loop. Drivers would enter these lanes as they do now at interchanges. But they could get on the express lanes only at major interchanges such as the Shirley Highway, the Dulles Toll Road, I-66 and Route 1.

The concept, similar to the Dulles Toll Road, recognizes the growth in local traffic on the Beltway and attempts to separate that traffic from through traffic.

The Beltway's restricted car pool lanes would be directly linked by ramps into a planned network of car pool lanes, including those on the Shirley Highway, I-66, the Dulles Toll Road and Route 1.

At other interchanges, drivers of high-occupancy vehicles would have to weave across the local and express lanes to reach the car pool lane, which could be a problem if demand is high for the special lanes.

Some transportation officials have long been skeptical of rush-hour car pool lanes on the Beltway because, unlike the Shirley Highway, Beltway traffic isn't always heading toward a single destination such as downtown Washington. The Beltway widening plan assumes that the region's political leaders would take steps to increase demand for car pools.

Fairfax County Board Chairman Audrey Moore said the proposal "would be tough to build, but something like it has to happen. Unless we get some capacity on these roads, and rail and HOV, I don't know where the economy is going to go in this area."

The Beltway study directly challenges the assertion by Virginia and Maryland transportation planners and developers that the eastern and western bypasses would relieve congestion on the Beltway.

"The basic traffic effects of a Washington Bypass on the Beltway will be minimal," the study concluded. "At the most, a Washington Bypass represents less than a lane's reduction in the Beltway's needs."