A plan to widen part of Georgetown Pike a former buffalo run and now a heavily traveled commuter route through Northern Virginia, was approved last week by the Virginia Department of Highways and Transportation.

The plan calls for widening two of the pike's 16 tortuous miles and leveling off some of the hills and valleys which have made the road a horror for the state Highway Department and a joy for a legion of pike lovers.

"We just hope they don't destroy the rolling character of the road by flattening every little hill," said John Adams, president of the Old Georgetown Pike and Potomac River Valley Association.

Adams and the association, which has almost 100 members, were instrumental in getting the pike designated as Virginia's first scenic byway five years ago.

Association members fought a Highway Department proposal in June which would have added 10 to 20 feet of shoulders and ditches on both sides of the two-mile section, as well as a four-lane roadway between Cloister and Dead Run drives.

The current, compromise plan calls for widening the pike between Potomac School Road and Dead Run Dirve from its present 20 feet to 26 feet. An additional six feet of grass shoulder will be maintained on both sides of the road, bringing the total width of the route to 38 feet.

Association members concede that some trees, which now stand as close as a foot from the road, will have to be cut down. But Adams hopes the "cut-and-fill" project to level off some of the pike's steepest hills will create enough new land to minimize tree-cutting. At the same time, Adams said this week he hopes the Highway Department will not attempt to redesign the pike in a straight line.

"They don't have to eliminate every little rolling crest," said Adams. "That was one of the very bases for it being designated historic."

The Highway Department has been trying unsuccessfully to widen Georgetown Pike since the late 1950s when John F. Kennedy, then a senator with a home near the road, helped foil the attempt. In 1965 area residents, along with state and county conservationists, killed another plan that would have created a four-lane highway. In June, pike lovers organized again to fight the Highway Department's widening plan, which many residents feared was the first phase of another attempt to get four lanes.

"This road should not be treated like just any road," said Donie Rieger, chairman of the Fairfax County History Commission, during a public hearing punctuated by boos and shouting. "We think it deserves special treatment."

"It's already getting special treatment," answered Culpeper District design engineer Fred James. "If it were not a scenic byway . . . we would be proposing a four-lane road divided by an island."

Both pike lovers and the Highway Department agree that the road needs improvement. The transportation section of the current Fairfax County Plan calls the road a "traffic hazard." Officials at the Highway Department blame the accident rate along the pike, more than double the state average for two-lane roads, on its narrowness and steepness, and on the proximity of trees.

But association members have argued that leveling and straightening the road will invite more traffic at increased speeds.

The improvement project is estimated to cost $1,096,000. The Highway Department expects to begin advertising for construction bids in mid-1981.

In other action last week, the Highway Department approved a $2,689,135 project to reconstruct and widen 2.9 miles of Great Falls Street between I-66 at Falls Church and Dolley Madison Boulevard in the Lewinsville area.