In the District of Columbia, at the corner of Jenifer and 42d Streets NW, the sign says: "No Thru Traffic at 43 St. Local Traffic Only."

Across the state line in Chevy Chase, Md., around a traffic circle, Grafton Road Closed to Thru Traffic."

No matter that Maryland highway officials don't know there is no Grafton Road (there is a Grafton Street), the signs are probably just the beginning of a new type of neighborhood guerrilla warfare against the automobile, now that the Supreme Court has upheld neighborhood bans on commuter parking.

Let there be no doubt that emotions are strong on the issue; one Chevy Chase resident was threatened by a motorist just for counting passing cars in anticipation of the barricades.

Quite simply stated, residents on both sides of the District line have moved to block access along previously public but residential thoroughfares with what today are ugly barricades, set across intersections.

It could be an ominous development, for no one knows where it will lead. Will Georgetown, Capitol Hill, Alexandria or Kensington streets be the next closed to all but residents?

Reminiscent of barriers during times of riot or war, the so-called traffic diverters were set up in September by the independent Village of Chevy Chase at several locations between Wisconsin, Western and Connecticut Avenues.

The D.C. roadblocks were installed last weekend, on the eve of the Neiman-Marcus opening, at Jenifer and 43rd Streets NW and Harrison and 44th Streets, based on fear of heavy shopping traffic.

In both instances, commuters who have traveled through the areas and even local residents have been forced to alter their driving habits.

Although the street diversions caught many drivers off guard, local residents took part in extensive planning before their governments agreed to the barricades. Government layers say the barricades are legal.

Albert C. Simmonds III, who lives on West Irving Street in Chevy Chase, heads a traffic committee that convinced that community's Board of Managers to erect street diverters in a "trial program" that has been greeted with mixed results, in terms of local public opinion.

Some residents, for example, now must drive blocks out of their way to get to a store and their neighbors-across-the-barricade are distant by auto.

But Simmonds said 10,000 cars a day were driving through his community - mostly commuters. A week after the barriers were put in place, the daily traffic count was down to 4,000. Many of those presumably were drivers not aware of what happened until they got lost in what amounts to a maze, in terms of trying to find a wy out.

Under a village ordinance, the barriers can stay for six months and the volume of auto traffic and citizen comments is continuously being monitored, Simmonds stated.

In the District, the dirve for some method of curtailing auto traffic on residential streets began in the early 1970s, during debate ad hearings over zoning in the area. In that process, permitted levels of development were reduced sharply.

Margaret McDermott, who lives on Garrison Street NW in the affected area, said recent traffic counts showed 500 cars an hours were being driven down 44th Street, a narrow side street in the affluent-oriented shopping area that now include Neiman-Marcus as well as Lord & Taylor.

"We feel very strongly about this and I'm sure some other neighborhood will want to use this plan," she said.

Added Carol Currie Gidley, chairperson of Advisory Neighborhood Commission 3E: "Western and Wisconsin has the highest auto pollution in all of our fair city . . . this is the only way to stem the tide of more cars, going helter-skelter" down side street not meant to be traffice arteries.

Public meetings were held in Northwest Washington on the plan last spring. Of residents on the streets involved who attended one meeting, the vote was 90-4 in favor of the barricades (which can be travelled over by emergency vehicles).

The D.C. Department of Transportation subsequently moved on its own authority to set up the traffic diverters, for a experimental period. The temporary barriers of today are scheduled to be replaced lated this month by more permanent and less ugly concrete barriers, a spokesman said.

Lawyer John Engel, of the Friendship Neighborhood Coalition, noted that several cul-desacs had been proposed in the area as part of a zoing plan that would confine dense development to the Wisconsin Avenue strip. The barriers are an interim step, pending final Zoning Commission action on on an overall program of parks, bicycle paths, "green" areas and street closings.

If some citizens are inconvenienced, he added, that only points up the classic nature of the confrontation between residential life and commercial development.

With some 45,000 cars a day now traveling up and down Wisconsin Avenue and a similar volume on Connecticut Avenue in and out of the District, the erection of street barriers will only add to congestion on the main streets.

But this development seems to be taking place without any cordinated effort by governments on both sides or any concern about the possible impact in the years before a subway gets to Western and Wisconsin Avenues to absorb some of the traffic.

"If you compel people" to get in the middle of Western and Wisconsin congestion, "maybe they'll explore" other ways to travel, said Simmonds