When I-66 opens in 1982 between the Beltway and Washington, it will be an interstate novelty and a road so closely watched by police that it may make some motorists nervous.

Cars on the 10-mile, no-truck interstate will be constantly monitored by television cameras, observed by state police and their radar sets and counted by thousands of underground vehicle detectors. a

That's if a motorist can get on the road in the first place. Most ramps onto the new four-lane segment of I-66 between the Beltway and Washington will be metered, so traffic controllers can slow or completely stop traffic onto the road if it becomes jammed during rush hour. To keep drivers posted of their chances, huge "variable message" signs, 18-by-8-foot lighted signs, will be posted along all 10 miles of the new road.

The Washington end of I-66, which will extend to I-81 just beyond Front Royal, will be the first interstate in the nation restricted to buses and carpools during rush hour and the only interstate purposely limited to two lanes in each direction.

The details of how I-66 will work are included in an inch-thick, consultant's report on the "I-66 Traffic Management System." The current estimated cost for the construction of I-66 is $273 million.

Virginia highway officials predict the car-pool restriction will noticeably reduce weekday traffic into Washington by encouraging commuter carpools. Few other area officials share that rosy vision, although increasing gasoline prices and the extension of the subway system south of Alexandria in 1982 and to Vienna in 1985 could help prove Virginia correct.

National Park Service and District officials are concerned primarily about possible traffic problems on Potomac River bridges in 1982. When I-66 opens, Virginia plans to allow only carpools to exit from the George Washington Memorial Parkway onto Roosevelt Bridge (I-66) during rush hour. Park Service planners fear this could cause major traffic jams for other commuters forced to use Key, Memorial or the 14th Street bridges.

To monitor the goings and comings of motorists on I-66 and on nearby I-395 (Shirley Highway), which by 1983 also will be monitored by TV, a two-story, $750,000 control center is to be constructed near the Pentagon and operated by nine workers. The total annual operating cost of the 10-mile section of I-66 is estimated to be $667,000, including salaries of at least 11 state troopers.

The control center, with banks of TV monitors, radios and a giant computer-operated wall map, will resemble the war room at the Pentagon. Even bicyclists and joggers on the I-66 bike trail will be on camera. Like the interstate beside it, the bike trail will be lighted -- for safety and so TV cameras can observe bike and pedestrian traffic at night.

Scrutinizing motorists may be necessary to make sure they obey the four-person carpool requirement during rush hour, state highway officials say. The carpool-and-buses-only requirement was stipulated by former U.S. secretary of Transportation William Coleman in 1977 as one of several conditions for federal funding to complete the controversial section of I-66 through Arlington. Other requirements were that I-66 be a truckless, four-lane parkway-type road.

How long the carpool restriction will last is uncertain.

Jack Benjamin, the Park Service official overseeing the impact of I-66 on federal parkland here, said this week, "All the traffic predictions are questionable. They don't know what the hell's going to happen out there, what with gasoline prices and Metro . . . and if carpool usage of that monstrously expensive highway is minimal, then we'll see pressure to open it up to all cars. And they will open it."

So many violations of the carpool regulations are expected that 18 enforcement areas are being built along the road, where police can pull motorists over to give them traffic tickets.

Washington's only existing carpool-and-bus highway, the center lanes of I-395 inside the Beltway, "has a remarkably low violation rate, about 2 percent and never above 4 or 5 percent," said W. C. Jeffrey, assistant transportation planning engineer for the Virginia Department of Highways and Transportation.

The I-66 study notes that carpool-only roads in California have an average violation rate of 2 to 15 percent. "The potential violation rate on I-66 would be higher, however, as no alternative freeway routes are available to lower occupancy vehicles," the study states.

"We've been fortunate in Northern Virginia . . . the I-395 bus-carpool lanes have limited access, there's been good enforcement and people up there are obeying the law . . . but we may have problems on I-66, especially when the Dulles Access Road is finished," Jeffrey said.

Spotting carpool violators should be relatively easy during the first year I-66 is open, when there will be saturation enforcement by state police and any car with less than three occupants during rush hour will be stopped.

But in 1984, when the extension of the Dulles Airport Access Road connects with I-66, cars going to or from Dulles will be permitted on I-66 during rush hour, regardless of the number of people in the cars.

The trick for police will be to distinguish the legal from the illegal cars, since troopers will have no way of knowing if a non-carpool car on I-66 came legally from Dulles or illegally from any of a half-dozen ramps from the Beltway to Washington.

"It will be difficult," Jeffrey said, "and there will be people willing to risk an expensive ticket, at least once."

But he hopes the price of getting caught (now about $45 including court costs and points on a driver's record) and stric enforcement on the Dulles Access Road by the Federal Aviation Administration will prevent numerous vioations.

The FAA, which prohibits non-airport traffic on the existing access road but has not enforced the regulation, is now completing a study on the best method of stopping the illegal traffic in the future and preventing it from using I-66. Thousands of Reston-area commuters daily drive to Dulles in order to use the existing Access Road, which extends to Rte. 123.