To some, it is a hi-tech wonder that eventually will be run by computers and features the latest in environmental safeguards. To others it is a $28-million-a-mile disaster that has scarred neighborhoods and, in the end, will have no appreciable impact on traffic congestion.

Whatever it may prove to be, however, today, 26 years after it was first proposed, the last 10-mile segment of Virginia's Interstate Rte. 66 opens, carrying traffic between the Capital Beltway and the Theodore Roosevelt Bridge -- and in the process, relegating to history one of the most bitter local controversies ever.

That it is a far different highway from what Virginia highway planners thought it would be just a dozen years ago -- four lanes instead of eight or more with car-pool restrictions at rush hour -- is a tribute to the tenacity of citizen opponents, who in 1970 launched a battle against seemingly overwhelming odds to stop the highway in its tracks.

But that it exists at all is a tribute to the determination of Virginia officials who refused to give up when, just seven years ago, they were jolted to hear then-Secretary of Transportation William T. Coleman Jr. announce that he would not permit I-66 to be built.

In many respects, the 10 miles of I-66 span not just entire communities but a revolution in public perceptions about citizen power, rights and the environment. When it was first proposed in 1956, shortly after Congress established the Highway Trust Fund that was to finance 90 percent of the road's cost, interstate highways were widely viewed as part of the American dream. It wasn't until much later that such roads became targets of protest movements.

Indeed, over much of its proposed 76-mile length, the highway met only limited opposition -- though one skirmish occurred in largely rural Fauquier County where opponents, worried about rapid development, succeeded in blocking a proposed interchange.

Inside the Beltway, the stage had been set for the confrontation when the highway's extension to the Potomac became intertwined with plans for the area's Metro transit system in the 1960s. About that time, Virginia highway officials gave up a chance to construct the Arlington section of I-66 when they agreed to postpone road building so that transit officials might have time to plan a rail line along the highway's median. It did not seem so significant a decision at the time, in view of the esteem in which highway construction was then held by the public.

When officials took steps to start construction in 1970, however, the mood of the public had changed and opposition unexpectedly appeared. Hundreds of Arlington residents began gathering at public hearings to denounce the road. They contended that I-66 would likely cause excessive noise and air pollution, scar the surrounding landscape, disrupt neighborhoods, spur unwanted traffic congestion and commercial development, squander government money, discourage use of mass transit and waste energy by promoting auto travel.

The highway's advocates in Richmond over the next few years would be formidable in their own right, however. They were to include Gov. Mills E. Godwin and former Virginia highway chiefs John E. Harwood and Douglas B. Fugate. All three seemed to share the sentiment of the late Virginia Gov. and Sen. Harry F. Byrd Sr., to whom highway construction was synonymous with progress. Accordingly, they saw big-city attacks on freeways as misguided.

"No rational person believes highways will disappear in urban areas," Fugate said in the mid-1970s.

But that was not the only reason they backed I-66. To them, it was not merely a time-saving commuter road but a vital link between Washington and the Shenandoah Valley, where it now joins Interstate Rte. 81 at Strasburg.

Meanwhile, in Northern Virginia, the opposition organized. To fight I-66, the Arlington Coalition on Transportation (ACT), headed by James and Emilia Govan, was formed. A lawsuit was filed and, though it was initially dismissed by U.S. District Court Judge Oren R. Lewis, the highway's opponents won an appeals court victory in 1972.

That court decision by the 4th Circuit U.S. Court of Appeals overturned Lewis' ruling and barred construction of I-66 through Arlington until an environmental impact statement was prepared and new hearings were held. The appellate ruling was later upheld by the Supreme Court, setting the stage for Coleman's decision against the highway in August 1975.

In announcing his ruling, Coleman said I-66 had been made obsolete by the advent of Metro and by a previous decision by District officials to drop plans for the long-controversial Three Sisters Bridge, a proposed Potomac River crossing intended to carry I-66 traffic to the city from the foot of Spout Run just north of Key Bridge. He also noted that local government officials in Northern Virginia solidly opposed the I-66 extension.

"This is simply the wrong time and the wrong place for an otherwise excellent highway," he said at the time.

Political opposition began shifting, however, as officials drafted revised plans for a scaled-down highway with four lanes rather than the six or eight previously envisioned. In January 1976, a new Fairfax County Board of Supervisors reversed the previous board's opposition and endorsed the four-lane thoroughfare.

Later that year, the board of directors of the Metropolitan Washington Council of Governments, a planning group that played an influential role in the debate, backed the roadway by 66 1/2-to-54 1/2 margin. The vote was weighted to reflect the populations of local governments represented in the council and followed a sharp debate among some District and suburban members.

To some I-66 opponents, the months following Coleman's initial ruling appear to have been crucial, because when Coleman hinted he might consider a compromise, highway advocates quickly started negotiating.

"The critical decision was, of course, Coleman's decision to reopen the case," said Lawrence J. Latto, a lawyer who represented the Arlington coalition. "Virginia just kept pressing. Their persistence ultimately paid off."

At last, on Jan. 5, 1977, Coleman ended his extensive review and announced his acceptance of the proposed four-lane highway, along with special restrictions limiting rush-hour traffic chiefly to car pools and banning heavy-duty trucks. In endorsing the roadway, Coleman contended that any harm to nearby communities would be outweighed by transportation benefits, including shorter travel time, encouragement of car pools, more aid for Metro and improved access to Dulles International Airport.

Opponents were dismayed. "Six years of effort have finally been proven a waste of time," declared James Govan.

Coleman's assent to I-66 only partly reflected the switch to a scaled-down roadway. Another factor was his desire to see the Washington area's Metro transit system completed.

In exchange for Coleman's approval of I-66, Virginia officials agreed to provide what is now estimated at more than $100 million in construction work and funds to help build the Metro system, whose tracks will eventually run along the I-66 median to a station at Vienna in Fairfax County. Such an agreement was not easily extracted from a state where Gov. Godwin once denounced Metro as a "boondoggle."

Even so, the controversy did not end with Coleman's decision or with the start of construction later that year. Three new court actions were brought by the Arlington coalition and a new opposition group called Continued Action on Transportation. The suits were rejected by U.S. appeals courts in Richmond and the District. Meanwhile, Northern Virginia politicians and residents raised new issues, ranging from complaints about the highway's light poles to concern about traffic patterns near interchanges.

Nor is it likely that old opponents will give up their vigil. Many fear that political pressure will quickly mount to relax the restrictions imposed by Coleman limiting rush-hour traffic mainly to car pools.

"I think it's highly likely that they'll be lifted," said Latto, the Arlington coalition's lawyer. "I hope I'm wrong."

Coleman, a man who perhaps more than any other figure played a pivotal role in the fate of I-66, still apppears to regard the highway extension with the same air of deliberativeness he exhibited as transportation secretary.

"I really tried to come up with what I thought was the right answer," said Coleman, now a Washington lawyer, in a recent interview. "As far as I know, it was."

The roadway appears to have "much more public acceptability" than it once had, the former transportation secretary said. He has been told, he added, that highway officials have complied with the special restrictions he imposed on the roadway and have sought to model it after the tree-lined George Washington Parkway.

"Frankly, I have not seen the highway," Coleman noted in the interview three weeks before yesterday's dedication ceremony. "I intend to ride over it some day. I just haven't had time."