RICHMOND, JULY 15 -- Virginia is expected to approve on Thursday the final design of the proposed Springfield Bypass, thus removing the last major bureaucratic hurdle from the path of the long-awaited 33-mile highway through Fairfax County.

With the approval of the final engineering plans by the Commonwealth Transportation Board, the state could begin buying land for the $242 million road, which would traverse Fairfax County between Rte. 7 in the northwest and Rte. 1 in the southeast on a route roughly parallel to the Capital Beltway. It is widely viewed as a critical first step toward relieving some of Northern Virginia's worst traffic congestion.

Construction could begin on some segments as early as next year, officials said. "It's been a long struggle," Robert Hundley, chief environmental engineer for the Virginia Department of Transportation, said yesterday. "Almost as long as I-66."

Like that bitterly debated highway, the Springfield Bypass has been shaped at every turn by environmental concerns, some community opposition and vagaries of local politics.

As a consequence, the road awaiting approval would look substantially different from the road envisioned by highway planners in the late 1960s. Conceived as a high-speed expressway, the new Springfield Bypass would be a conventional four- and six-lane county road with 16 interchanges, 49 intersections and 35 traffic lights -- more than one a mile.

Virginia Transportation Commissioner Ray Pethtel described it as a "vital cross-county link with a fair amount of stop-and-go traffic." The speed limit would range between 35 and 50 miles per hour.

Some questions about the road have yet to be resolved, among them environmental concerns and the final design of a two-mile stretch between Braddock Road and I-66, which the board is expected to approve at a later date.

The state is awaiting federal approval of its plans to minimize the effects of the road on legally protected wetland areas. In addition, the state has not secured federal permission to build the road through four parks, as it would prefer to do.

The design that is being submitted to the board shows the road avoiding the parks but includes a provision to reroute it through the parks if the government approves. In all cases, except in South Run Park, that is considered unlikely, sources said.

The matter of selecting an appropriate name for the highway remains. Although it has long been known as the Springfield Bypass, highway officials said they are taking steps to name it the Fairfax Parkway.

By any designation, the road would be among the most ambitious public works projects being planned for Northern Virginia.

Beginning at Rte. 7 near Dranesville, the road would drop through the booming development areas near Reston and Dulles International Airport, would cross I-66 to the west of Fairfax City, then would veer southeast on its way to Fort Belvoir and Rte. 1. It is supposed to tie in with most major routes in the county, and provide direct access to car-pool lanes on I-95. The bypass plans include a Franconia spur that would tie in with the proposed Franconia Metro station, just southeast of Springfield Mall.

Most of the road will be four lanes, with a six-lane section in an area of heavy development between Sunrise Valley Road and Baron Cameron Avenue in Reston. The Franconia spur would include a six-lane section between Gambrill Road and Beulah Street.

The road is expected to carry up to 60,000 vehicles a day by 2005.

Most county residents appear to be in favor of the road, having voted in 1985 for a $135 million bond referendum to help pay for its construction. Nevertheless, residents have voiced opinions in numerous public hearings over the years on how the road should be built.

"It's neighbor against neighbor," said Jack Hodge, chief engineer for the department. "One will say, 'I want an intersection right here in my subdivision,' the other will say, 'I'd rather drive a mile to someone else's neighborhood' " to get on the road.

Hodge cautioned against raised hopes of completing the road on time. "We were behind when I started {in 1959}, and I don't think we're ever going to catch up," he said. "You have the frustration of knowing this was needed years ago."

The road would be financed with county, state and federal funds, with the county assuming responsibility for building a six-mile section between Rte. 50 and the Dulles Toll Road, a section that would probably be built first, officials said. The 33-mile road would displace 55 families and five businesses.