There was something different about the streams of automobiles moving north toward Washington on Interstate Rte. 95 at 6:50 a.m. yesterday. For one thing, said Carl Peterson and John Powell, the cars were, in fact, moving.

Moving in the normal sense of the word: not crawling, creeping, or plodding along, not jerking to a start only to jolt to a stop moments later. They were moving.

Northern Virginia commuters wondering who to thank for this unusual circumstance might have found the answer with a glance in the rearview mirror at the silver Cadillac Fleetwood where Peterson and Powell were incredulously marveling at their handiwork.

Virginia highway officials say the two Prince William County residents deserve the most credit for pressing their often-stubborn highway bureaucracy into opening a fourth lane that will allow car pools and commuter buses to zip all the way from the Fairfax-Prince William County line to Washington on a restricted HOV (high occupancy vehicle) lane. Yesterday, the state opened the 6 1/2-mile section of the lane that connects the Woodbridge area with the Shirley Highway express lanes in Springfield.

Peterson and Powell founded a group of frustrated suburbanites called "The Forgotten Commuters" and prodded the state to devise a temporary solution to alleviate the maddening daily delays on I-95 that have been produced by the dramatic growth in Fairfax and Prince William counties. Construction of permanent express lanes into Prince William on I-95 is scheduled to start in 1987 and be finished by 1991.

Commuters and state officials said the new lane, which was created by converting the right shoulder of the highway into an active lane, dramatically reduced congestion yesterday.

Peterson and Powell, sharing a triumphant ride to work, shaved 15 minutes off the usual hour it takes them to commute to the Mitre Corp. in Tysons Corner, where they are engineers.

It was still dark yesterday when Peterson eased the Cadillac past the Rte. 1 interchange and into Fairfax County on I-95. "That's amazing -- there's no backup there," he said, marveling at how the traffic was moving. "For seven years there's been a backup there."

In the passenger seat, Powell was dumbfounded. "This is incredible, this is really incredible. We're doing 50 now. We're usually lucky to do 10."

Peterson's pace later slowed, but remained steady most of the way.

State officials said the lane's first day was a success, but a qualified one. There were eight minor accidents during rush hour, said Capt. Herbert Northern of the Virginia State Police. Also, Northern said, many cars using the far left lane -- now reserved between 6 a.m. and 9 a.m. for vehicles carrying four or more people -- did not have the required number of passengers. Other motorists have been using the new right lane at hours other than 6 a.m. to 9 a.m., when it is supposed to be closed.

For Peterson and Powell, yesterday was the happy ending to an extraordinary saga of ordinary citizens making a dent in the bureaucracy.

Peterson, 47, and Powell, 45, both mild-mannered men, had observed for some time that their commute was growing by about 10 minutes a year. One day in February 1984, after arriving at work an hour late, two unlikely zealots were born over lunch in the Mitre cafeteria.

Rankled because work on other projects such as I-66 and the Woodrow Wilson Bridge went ahead while their own problems were ignored, Peterson and Powell called themselves The Forgotten Commuters. They began to solicit residents and community organizations to join the ranks.

The response was immediate. "Usually people are reluctant to sign a petition, but people were so desperate for something to be done, they didn't hesitate," Peterson said.

Letters of support poured in. "You could tell it from those letters -- the emotion, the intensity of frustration," said Peterson.

The group devised a plan for an interim solution, and sent it, along with the petition, to Gov. Charles S. Robb.

He passed it along to officials at the Virginia Department of Highways and Transportation.

"The initial response was the expected one: 'Please leave us alone,' " Peterson said.

Soon, however, the wheels at what is often considered one of Virginia's most ponderous bureaucracies began to churn. Although the plan that state and federal officials eventually agreed upon is different from the one The Forgotten Commuters submitted, the group was instrumental in providing the impetus for a solution, said David Gehr, Northern Virginia district engineer for the highway department.

"The credit really belongs to the public officials," Peterson said yesterday. "They had to deal with a very angry, very frustrated public."

The frustration comes from the dominant role that traffic plays in the lives of people in Washington's outer suburbs, coloring almost every aspect of daily routine.

"The delays can be horrendous . . . . There's a lot of people that have very different schedules because of the traffic," Peterson said. Some awake as early as 4:30 a.m. to ensure they arrive to work on time.

"For me, time on the road is really lost time," said Powell. "It's not usable at all. You can't distract yourself simply for safety reasons."

Increasingly, Powell said, he finds himself dashing into the office late, with no time to prepare himself for the day's work.

"You arrive at work frustrated. And you certainly arrive home frustrated," adds Peterson. "A lot of time it takes an hour at home just to settle down."

Peterson said he even knows of couples who have experienced marital strife due partly to frustration over the lengthy commute. Others have decided to leave Prince William altogether.

Powell said he has considered the prospect himself, and each time the answer is the same: "I wouldn't want to leave the county . . . . The life in Prince William is very good. The only bad thing about it is getting in and out."

And with that problem getting at least a bit better, there are some who have suggested that the next logical step for the two commuters-turned-activists would be to take a plunge into Prince William politics. But it's not likely.

"Everyone keeps asking me when I'm going to declare," Peterson said. "I'll declare right now: I'm not running for anything. I just want to live in the suburbs and get to work on time."