The Whitehurst Freeway, the highway-in-the-sky that serves nearly 50,000 cars a day, is a vital link in Washington's complex transportation system.

But it is also a bumpy, pothole-filled road that is suffering from old age and the wear that comes from thousands of cars pounding over its surface each day.

Its continued decline eventually could make the road unsafe and too dangerous to drive on, according to city transportation officials.

So the 33-year-old freeway named after Capt. Herbert C. Whitehurst, the District of Columbia's first director of highways, is receiving intensive scrutiny aimed at deciding how best to repair or replace it.

Mayor Marion Barry is expected to make a final decision on a solution to the road's continuing deterioration sometime early next year, after city transportation officials and advisory committees of citizens and technical experts complete studies now under way.

Work on the Whitehurst Freeway or its replacement could begin by late 1985 or early 1986 and could last up to two years. The construction temporarily would disrupt the route of the thousands of commuters who rely on the freeway to bypass often-clogged Georgetown streets.

Planners and neighborhood activists involved in the nearly year-old effort to find a solution have begun focusing on the key issue: whether to patch up the freeway, or replace it with a new elevated structure or a ground-level thoroughfare alongK Street NW between 29th and 35th streets.

The choice will have a lasting impact on commercial and residential development in Georgetown, particularly on the controversial waterfront, as well as in Foggy Bottom and other nearby neighborhoods. It also will determine the length and convenience of trips made to and from downtown Washington by commuters from some Maryland and Virginia suburbs and Upper Northwest, for whom the freeway is the quickest and most direct link to downtown.

While the freeway debate will turn on issues unique to Washington, it also reflects a national dilemma as cities and towns attempt to repair decaying infrastructures in the face of shrinking government revenues and growing concern for preserving urban residential neighborhoods.

In 1949, when the Whitehurst Freeway was completed, its total cost was $3.5 million. Today it would cost some 20 times that, or about $60 million, just to repair the existing structure, and $100 million or more to replace it with a ground-level road, according to city transportation officials. Federal highway funds are expected to cover between 80 and 90 percent of this expense, officials said.

Earlier this year, the citizens' and technical panels whittled the various alternatives from 16 to three, eliminating such proposals as replacing the freeway with a tunnel underK Street.

The three alternatives now being studied are:

Rehabilitate the present freeway and improve the entrance and exit connections on the road's east and west ends;

Replace the Whitehurst Freeway with a new elevated road that would be lower than the present freeway;

Tear down the freeway and substitute a ground-level road that would run along K Street NW and connect to Key Bridge with the aid of an elevated ramp. The ramp would be about three blocks long and extend from Key Bridge toK Street somewhere near where it intersects with Potomac Street, NW. At present, K Street does not connect to the freeway and comes to a dead end just below Key Bridge.

City officials and the citizens' groups have agreed that, whatever alternative is selected, it must maintain present traffic levels on the Whitehurst Freeway corridor and not cause commuters to pour onto nearby Georgetown streets, especially M and Q streets NW, which already are overloaded.

These groups also have decided against selecting a configuration that would create a barrier between the waterfront, where a park and a$154 million residential and commercial development are scheduled to be built, and the rest of Georgetown above K Street NW. Replacing the freeway with a ground-level superhighway that would cut off pedestrian and local traffic access to the waterfront has been ruled out.

Virtually everyone agrees that the present road arrangement effectively segregates local and through traffic, with commuters generally sticking to the freeway and local traffic confining itself to K Street.

Under the ground-level alternative, the Georgetown segment of K Street would be widened and more lanes added to accomodate traffic that now uses the freeway.

But Foxhall and Palisades neighborhood groups from Upper Northwest are concerned that a ground-level replacement might increase the travel time for commuters. Under this plan, for example, three and possibly four traffic lights would be installed along K Street.

"The Whitehurst is our entryway to the city," said Nancy Feldman, the head of the Palisades Citizens Association and Advisory Neighborhood Commission 3-D. "We don't want to make it more difficult to get downtown ."

Georgetown groups have not yet adopted a specific position. Some neighborhood spokesmen have expressed reservations about the ground-level proposal, while others said that they are in favor of it.

"I just wonder if it will function as a bypass if you put it on the ground and add traffic signals," said Donald Shannon, president of the Citizens Association of Georgetown.

Raymond Kukulski, chairman of the Ward Three Advisory Neighborhood Commission, said that he inclines towards the ground-level proposal and is not convinced that it significantly would increase commuters' travel time.

Kukulski noted that the study is looking into ways to improve the congested and narrow traffic connections at the west end of the freeway, where it intersects with Key Bridge and Canal Road NW. The connections are a major cause for rush-hour traffic jams on the freeway.

"If you could uncork the ends of the freeway , I think people would fly through there much better," Kukulski said.

Although the neigborhood groups affected have separate concerns, their spokesmen stressed that they are trying to accomodate each other.

For example, the Foggy Bottom Civic Association and Advisory Neighborhood Commission, concerned mainly about the configuration of exit and entrance ramps at the east end of the freeway near 26th Street NW, have agreed to support whatever position Georgetown adopts for the Whitehurst Freeway's main segment, according to Jenny Brake, a Foggy Bottom representative on the advisory committee.

Representatives of the neighborhood groups also praised the cooperation of city officials and their consultants, DeLeuw Cather and Co.

"This is one of the few times that the government and the private sector have worked really well," said Robert Siciliano, president of the Foxhall Citizens Association. "Nobody is trying to shove anything down anybody's throats."