Virginia authorities yesterday reported four traffic deaths of Northern Virginia residents, including one in which a Fairfax County man was killed when he walked in front of a tractor-trailer on I-66. Three persons were injured in the accidents.

Virginia State Police said David Lowden, 48, of 9932 Commonwealth Blvd., was struck by an eastbound tractor-trailer early yesterday on I-66 just west of Rte. 29.

No other injuries were reported in the 12:30 a.m. accident, police said.

Lowden's death is being investigated as a possible suicide, police said, but no other details were available last night.

State police also are investigating an early-morning Fauquier County collision involving two cars that fatally injured an Arlington County man and a Winchester woman, both of whom were passengers, police said.

William Harold McCreary, 29, of 6066 Ninth St. was flown to the Washington Hospital Center's MedStar unit after the 1:25 a.m. accident and was pronounced dead at 4:37 p.m.

Karen Ann Smith, 37, of 1545 Ash Hollow Dr. was flown to Fairfax Hospital and pronounced dead at 5:55 p.m, they said. McCreary was riding in a pickup being driven by Jeffrey Sandora south on Rte. 17, about three miles north of Warrenton, police said.

Sandora lost control of the truck, which skidded off the right side of the roadway and skidded back onto the roadway, where it was struck broadside by a northbound car, police said.

Smith was a passenger in a 1976 car that struck Sandora's truck, police said.

Sandora, 51, of 4335 Wedgewood Dr., Annandale, and the otherdriver, Royce Hagerman of Winchester, were in fair condition at Fauquier Hospital in Warrenton, hospital officials said.

They said none of the victims appeared to have worn seat belts at the time of the crash. Police said the collision is under investigation.

Arlington police yesterday reported the Saturday night death of an 80-year-old woman whose car went off Old Dominion Drive and struck a tree.

Police said Alice Powers Beggs' car ran off Old Dominion Drive at North Dickerson Street shortly before 7:50 p.m. Saturday. Beggs was pronounced dead at Arlington Hospital slightly less than an hour after the accident, police said.

They said Beggs' husband, who was not further identified, was a passenger in the car and received a broken leg. No other details were available.