Like it or not, your perception of Washington, D.C., is strongly influenced by where automobiles can go.

You see relatively little of the city on foot. The local neighborhoods in which you live, work and shop may be explored as a pedestrian, but your larger geographical framework of familiarity is most likely determined by the pattern of streets and highways on which you drive.

Remember, too, that your "perception" of Washington -- what you actually see and remember from experience -- and your "conception" of Washington -- what you understand intellectually to be its shape (based primarily on maps and other graphic representations) -- are not the same.

Sometimes, what is perceived, even though an incomplete view of the whole, gives sufficient clues to allow you to grasp the "concept" or idea of the whole. Drive through parts of Washington. Experience its grid of streets, diagonal avenues, circles, squares, monuments, rivers, bridges and parks. While you may have seen only 2 or 3 percent of the city, you can still formulate in your mind's eye a reliable and meaningful visual picture of L'Enfant's conceptual strategy.

Try to do likewise driving in Columbia, Md., where finding specific locations, particularly private residences, can be an agonizing challenge. Its network of meandering roadways, although leading you occasionally past sometimes memorable buildings, places or landmarks, does not allow you to comprehend fully the concept underlying Columbia's plan.

Many subdivisions and communities are like Columbia. Their geometries lack comprehensible orientation, points of visual and geometric reference, and conceptual as well as perceptual order. Their layouts are often derived from specific, localized considerations, with roads engineered to follow contour lines and topography. Minimizing cut and fill, while maximizing numbers of lots, may have been the dominant conceptual planning force.

Columbia was planned with a rational organizing concept on paper. It has a major commercial center, sub-centers, separate residential villages, schools, parks and industrial zones. There are primary, secondary and tertiary roadways. Yet its mapped conceptual framework isn't perceivable or comprehensible when you travel there by automobile.

The late Kevin Lynch, a well-known city planner who taught at the Massachusetts Institute of Technology, wrote that a city is seen and understood by inhabitants through memories of specific urban images: certain roads, roadway patterns and streetscapes; landmark buildings, statues or towers; and special places and views containing elements attracting conscious or subconscious attention. He recognized that, like children enchanted by places, spaces and objects that seem vivid, unforgettable, magic and sacred, adults, too, need the enchantment and guidance of stable, familiar landmarks.

What's seen from roadways is critical to imparting a sense of place. Views at the ends of streets, even if distant, or where roads bend are special. Intersections offer unique opportunities for creating landmark events, as do bridge crossings, cul-de-sacs, crests and dips, and access ramps.

Consider the various Beltway exits. These cloverleafs are sometimes marked by nearby buildings -- the steep A-frame church at Georgia Avenue comes to mind -- but many seem to be bland, featureless, indistinguishable places. Sometimes landmark buildings may loom in the distance -- like the axially sited Mormon Temple, the brick high-rise at Route 1 in Beltsville, or the Capital Center in Largo -- providing clues as to where you are, but without being immediately adjacent to interchanges.

Lynch and other planners also observed that people travel in very personalized "urban realms." These geographic realms are shaped by the paths and places that people use and occupy, their actual city space.

For example, suppose you live in Reston or Bowie and work at Tysons Corner or the Federal Triangle. Record your day-to-day travels and create a map of your geographical realm -- home to office to lunch to office to home, with occasional trips to shops and stores, to recreational centers, to restaurants, or to visit friends. Soon you would have drawn a "perceptual" map whose spatial characteristics are very different from the "conceptual" map of Washington carried in your mind and glove compartment.

Likewise, a map of your spouse's or roommate's realm would in turn be different from yours. A teen-ager's realm -- linking home, school, the shopping mall, the local drugstore and perhaps Georgetown -- would be different still. And a child's realm would be focused almost entirely on territory within a few hundred feet or yards of home, except for what he or she might be able to observe peering out the car window.

Think about your driving habits, the familiar routes you follow almost instinctively to get from one point to another in your realm. Some routes may seem to belong to you alone. How often do you spec ulate that your car would know the way, with or without you driving? Recollect the uncertainty and discomfort experienced when obliged to take an unfamiliar route.

Because there are as many perceived realms and routes as there are citizens, the existence of common landmarks, familiar streets, and comprehensible, ordered roadway patterns seems particularly desirable. They constitute a constant reference frame on which to map personal realms of travel and occupancy.

The baffling roadway patterns of Northern Virginia, like parts of D.C.the District and Montgomery and Prince George's counties, provide minimal reference frames. Intersections are visually interchangeable, with roads sometimes radiating in several directions of no particular orientation. Significant or memorable landmarks are hard to identify. Layers of utility poles and wires, commercial signs, traffic signals and parked cars tend to homogenize the streetscape even more.

Traveling radially along Columbia Pike, Arlington Boulevard or Lee Highway is navigationally straightforward, if not aesthetically uplifting. But moving by car in almost any other direction can be confusing and time-consuming. Concentrating on your dog-eared map, your automobile's controls, hard-to-read street signs and building addresses leaves little opportunity for enjoyment of streetscape views. Despite dozens of trips through Arlington, it remains a roadway puzzle.

It's hard to beat the grid. From ancient Roman camps to the undulating streets of San Francisco to mid-town Manhattan to Capitol Hill, street grid patterns seem compelling and fitting.

Grids can accommodate exceptions, distortions, directional shifts, dimensional changes and other superimposed geometries. Gridded blocks can be merged or further subdivided. Grids can flow up and down over hills and through valleys. Grid lines don't even have to be straight; they can curve and turn. Systematic, they are nevertheless incredibly flexible.

Most important, people can relate to such street patterns. Newcomers can find their way and know where they are most of the time. They can see up or down streets to distant landmarks or, looking right and left, catch glimpses of parallel views and landmarks punctuating crossing streets. And they can readily extrapolate their localized experience to formulate a more global conception of their community.

Thus, networks of roads and implicit roadway views are essential determinants of city imagery. Entailing more than civil engineering efficiency or romantic picturesqueness, such road networks and the land parcels they create can exhibit a conceptual order whose geometric composition can be sensed and remembered.

Kevin Lynch and his colleagues were right. A city's image is defined in large measure by what you see from its roads. Fortunately, L'Enfant knew this too.