Peter Smith has dreams of a museum that will be 15, perhaps 20, miles long.

"It will be a museum of roadside Americana," explains Smith, who earns his living in the field of historic preservation, "and it will show the development of our roadside culture through all the eras of this century. People will drive through it, beginning with a mud road, then it will be asphalted, and it will grow through two lanes to three up to interstate highway standards.

"Alongside the road there will be structures appropriate to each period -- cabins, tourist courts, diners, food stands, perhaps a miniature golf course. And the museum should be self-supporting because people will stop to patronize these places -- and every once in a while there will be a toll booth.

Smith was the host and master of ceromonies for the third annual meeting of the Society for Commercial Archeology, which met over the weekend in the Museum of History and Technology, at the Kennedy-Warren appartment house on Connecticut Avenue ("a vintage building," one architect member explained) and along Route 1 between Baltimore and Washington, where members took a bus tour to examine relics of roadside culture.

Approximately 150 architects, educators, artists and miscellaneous fans of pop culture attended the meeting, which had a lighthearted, scholarly spirit seldom found in national convention American motel, the architecture of Atlantic City, how to document the culture of a roadside strip and how to explore the riches of commercial art at the Smithsonian and the Library of Congress, the convention included walking tours of the city featuring not the White House or the Lincoln Memorial but a vintage gas station, a classic neon sign, an interesting pizzeria.

A lot of attention was given to the Little Taverns, which are an endangered speies, and to the fabulous displays of actual neon signs, sculptural ornaments from the late, lamented Capital Garage and other memorabilia now kept in the Smithsonian.

"I may get to see the White House another time," said Arthur Krim, vice president of the SCA, "but on this visit I was fascinated by National Airport, which is a genuine antique -- the finest example of an old airport building on the East Coast."

He hastened to explain that he was not describing the runaways or technical equipment as antique but the administration building -- whose design, decor, window arrangements and plaques are all vintage relics of the early 1940s. "It's surrounded by later developments," he said, "but it's still preserved in its original form."

"Archeology" (even without the "ae" beloved of etymologists in the middle) based on two Greek words and means "the study of old things." There is a bit of a shock at first in finding it applied to such modern phenomena as motels and hot-dog stands -- but we live in rapidly changing times, and there is a distinct possibility (as several people at the convention pointed out) that the automobile is now going the way of the dinosaur.

"I see very little difference," says Smith, "between preserving Colonial Williamsburg and preserving a segment of Route 1. In either case, you are just preserving a bit of cultural history."

He adds that the interest of the SCA is "not basically a preservation interest -- we're just looking and having fun."

SCA president Douglas Yorke explains that the still-young organization has some members interested in preservation, but its basic purposes at this point are "to draw people's attention to the commercial environment --for example, as clear indicators of social change in our rapidly changing times" and to "generate contacts -- a network of people with common interests." t

"We're not out to preserve every old diner in existence," says Yorke, "but to make people sensitive to them." Diners are his specialty, as motels are Smith's. Other members specialize in gas stations, neon, hand-lettered signs and a variety of other objects in which the commercial and artistic instincts collide.

One specialist at the convention was Len Davidson, who had several scrapbooks, full of pictures of his specialty, which he plans to develop into a book, "Papier-Mache Giants of America."

"We call them papier-mache giants," he explained, flipping through pictures of giant dogs, cows, dinosaurs, hamburgers, covered wagons and, of course, human beings, that have stood outside various roadside commercial establishments. "But a lot of them now are made of fiberglass.

"It's a highly perishable form of art, partly because a lot people think it's tacky." He paused at a series of pictures showing the same 40-foot-high figure in different costumes. In the first panel, the figure was a rather menacing-looking American Indian. In the next, it had a white apron and a chef's hat.

"This figure stoood outside a motor lodge in Florida which was called the In-Di-Inn," he said. "Then the lodge was sold and became a pizzeria, so the emblem was changed too, from Indian to Italian in one easy paint job. It still has its hair in Indian braids, but you can't see that from the street."

What you can see from the street is the basis of roadside culture -- quick, simple, hard-hitting and super-heated symbolism meant to attract the attention of people going by in cars.

Enthusiasts though they are, the members of the SCA showed no delusions about the qualities of the objects of thieir affection. "This is garnish --which it's supposed to be," murmured one, looking at a picture of a diner in the classic railroad-car style and another commented with ambivalent devotion on a photo of a schlock souvenir stand in Atlantic City:

"It's tacky and it's a rip-off -- but something will be lost when this becomes a Gucci shoe store."

Atlantic City, which is now undergoing tremendous upheavals because of new money pouring in to fuel the gambling concessions, was an object of special concern at this year's meeting. Pictures of vanishing temporary monuments (everything in Atlantic City has always been temporary) were flashed on a large screen with appreciative comments:

"This is a rip-off, but there will never be another rip-off quite like it."

"That's the entrance to the aquarium. There's probably nothing inside but a couple of guppies -- but they sure make it look interesting on the way in."

A lot of nostalgia was voiced for the "Mom and Pop" era of roadside culture -- before national franchises made the roads leading into one American city look like the roads leading in to all the others. "You can still see a lot of that kind of work on secondary roads -- Route 1 beyond the beltway, for example," says Peter Smith. "It's still there, not because its value is recognized, but because it would be expensive to tear it down."

One of Smith's ideas in connection with his fantasy of a roadside museum is that people will through it in vintage cars -- perhaps drive a Model T through the dirt road phase, and later switch to such historic relics as the Edsel -- perhaps the Chrysler -- driving an antique through the antiques.

When he gets the idea fully developed, it sounds like something he might be able to franchise -- and then a few decades down the road people may be fighting to preserve his work the way they're fighting now to preserve a historic Coca-cola sign.