SIX CITY DWELLERS are slouching toward nowhere in "Rush Hour." Mouths set, the gray automatons slump, defeated and unheroic. George Segal's sculpted people, modern "Burghers of Calais," pose the silent questions to passersby: Where are you going, and why are you in such a hurry to get there?

"Rush Hour" usually stands in a Dallas shopping mall. At the moment it's in front of the National Gallery's East Building, introducing "A Century of Modern Sculpture: The Patsy and Raymond Nasher Collection." The show is a sculpture garden transplanted, an imaginative installation with sensitivity for the intentions of the modern masters. The sculpture is scattered about the East Building like petals of enormous size and presence.

Under the swinging Calder mobile, one finds its reflection -- a Calder "Spider" teetering in the breeze created by its admirers, its black legs wriggling in space. At the top of a stairway, "The Gossiper" holds court -- Jean Dubuffet's surrealistic takeoff on figurative sculpture. Its giant enthroned body is painted like a map, hollowed by lakes of banality and crisscrossed by the blue roads of its own interminable boringness. And in the well of the concourse towers a Jonathan Borofsky "Hammering Man," 20 feet tall with moveable arm, the silhouette of a laborer, insistently pounding, pounding. In this work, Borofsky's signature number is more like a prisoner's I.D.

The sweeping architecture of the building is made for these pieces and their modern commentary. Where the works require a softer setting, the gallery has accommodated by recreating a garden. On the mezzanine, Henry Moore's lumps lie in the bushes, marvelously misshapen figures reclining languidly. Aristide Maillot's "Night" is nearly invisible among the vegetation, a silent sleeping woman, head on arms. Guarding them is Max Ernst's frightful "Capricorn," a goat man seated like a king, his horns his crown, his queen a nightmarish mermaid. (It's a self-portrait.) Nearby, rounding out the collection, are works by Rodin, Matisse, Brancusi, Picasso and Giacometti.

On the main floor, among a selection of David Smith constructions that echo those across the Mall at the Hirshhorn, is Scott Burton's "Schist Furniture Group." Visitors gingerly sit upon the rustic settee and chairs that have been cut from boulders, and gaze on the sculpture just outside the window. Most delightful of these is Joan Miro's playful painted bronze manimal, "Caress of a Bird." A basket for its yellow head, a red "figleaf" from a tortoise shell, this tall sculpture is just beyond reach. So noseprints have accumulated on the glass in front of it.

The collectors, the Nashers of Dallas, don't have an East Building, but somehow manage to find room for most of the sculpture in their house, garden and woods.

A CENTURY OF MODERN SCULPTURE: THE PATSY AND RAYMOND NASHER COLLECTION -- Through January 3, 1988 at the National Gallery of Art.