DURING THOSE ancient days before this country discovered limited-access asphalt, the American motorist navigated his way down two-lane highways and through small towns with nary a golden arch to guide him. Often the only ray of comfort on those darkened back roads was an occassional oasis of light, a huge neon sign blazing into the gloom like a beacon to the weary: DINER. It was a reliable sign promising a good cheap meal and maybe a friendly conversation.

Once a fast-food way of life in the Northeast, diners have dwindled from more than 6,000 in 1950 to around half that today. As the Interstates passed them by, so did the crowds. But the rise and fall of the diner empire has not gone unnoticed, and shall soon be fully chronicled.

Richard Gutman is a multi-media consultant from Boston, and John Baeder is a New York artist; each stands as a leading authority in the realm of dinerdom. Gutman is writing a cultural history of diners, which he hopes to publish next year. Baeder's book of his own dinner paintings will appear this fall. From persuing the writings of both, the following 106-year story emerges:

In 1872, Walter Scott of Providence, R.L., transformed a horse-draw freight wagon into a rolling sandwich shop and set up a lucrative all-night business catering to the newspapermen at the Providence Journal. These "night owls" or "dog wagons" soon became common sights along the East Coast.

An enterprising Massachusetts man took the next step in the late 1890s by constructing his own mobile eateries with stools, a marble counter and flashy exteriors. A few years later, money-minded entreprenenurs snapped up hundreds of scrapped horse-drawn trolleys, stuck in stoves and dragged them out onto streets at night. Respectable citizens avoided such questionable locales and even banned them in Buffalo and Atlantic City.

After World War I, Patrick "Pop" Tierney and Sons of New Rochelle, N.Y., began manufacturing well-lighted and equipped units patterned after railroad cars. Unlike the seedy trolleys, thses new restaurants opened the business to families by providing booths for women and children.

Throughout the '30s and '40s, diners retained their railroad flavor on the outside while reflecting current design trends on the inside - Art Deco, for example. As the structures grew larger in the '50s, they were shipped in separate sections and eventually abandoned the traditional look altogether. The first brick-facade diner appeared in 1962, ushering in the current style of "Meditarranean-Romanesque." For diner purists, 1962 was a very dark year.

Amidst this perversion of a noble tradition, how is one to recognize a surviving Real McCoy? Whence springs the dinerlickheit of the eatery? To make our backroads search easier, Gutman and Baeder have lent us their expertise to define a mythical beast: the "Quintessential Diner."

Imagine parking your 18-wheeler across the street from the fictitious "Wes's Diner," a small model from the late '30s with a rounded roof and corners. Stainless-steel and blue-enamel bands alternate across the front, interrupted in the center by a glass-block vestibule and its door with an elliptical porthole. Sculpted bushes stand beneath wooden-framed windows, open transoms above that. A red-and-blue roll-back awning shelters the glass. The overall impression is that of a nice, neat package.

Inside, leather-jacketed truckdrivers and a town local or two sit hunched on the stools, nursing cups of java, elbows on the marble countertop. Just like on the boys, you grab a seat and order the usual: liver and onions, mashed potatoes with gravy, string beans, a fresh-baked roll and a cup of coffee.

Rose marks it down and replaces the pencil in her bouffant. Rose is a pump 58, wears a white uniform, knows your name, and probably knew what your going to order. She's been working for the Wes since The War, when she riveted B-17s instead.

Back then Wes was a cook for the Army, and before that he worked at his father's lunch wagon in Philly. Now he's a paunchy guy of about 60, with a crawling panther tattoo on his left arm, a white paper "soldier's cap" cocked over his right ear and a pack of Camels in his apron pocket. Fascinated, you watched as he fries up a patty with his choreographed routine: peel away the paper, plop it on the grill, sizzle, flip, scoop, plop. A perfect burger.

With a couple of minutes on your hands, you spin on your stool to study the rest of the joint. The booths are chrome and leather, the Formica tops inset with little stripes. Each booths has a railroad-style light fixture just above the juke box. Covered sugar bowls sit on each table, or perhaps salt and pepper holders with little plastic flowers.

The floor is patterned ceramic tile, similar to the larger squares on the wall. Long porcelain fixtures with exposed fluorescent lighting run the length of the ceiling. A couple of three-panel menu boards hang on the back wall wiht post cards and old photographs pested to them. A stainless-steel sunburst peeks around the cooking equipment.

Finally Rose slaps down a steaming plate and expertly refills your mug. You smile your thanks, dig in, and idly wonder what time Rose gets off work.

The quintessential diner remains imaginary, but approximately do exist. For the most authentic diner experience locally, stop by the Tastee Diner in Bethesda about 2 some Sunday morning. Unlike most places, the grill is still out front, so you can watch the cook sizzle up your steak and home fries while you enjoy the last-night menagerie.

The 40-year-old building on Woodmont Avenue is a small structure with wood instead of stainless steel window frames, wall paneling and booths. With its patterned tile floor and blue-and-white canopy, the diner exudes a cozy atmosphere lacking in the flashy newer models.

Occassionally other spicemens hang on along old Federal highways like U.S 29 or U.S. 40, more or less intact from their glory days. Though these diners are elusive prey, we have tracked down a few. The following is an incomplete yet representative list of what's within an hour or two of the Capital. When you stop by for yourself, bring a big appetite, plenty of time to loiter, and enough quarters to keep the juke box playing.