To be walkable, a path must rise up from its supportive floor to become an open corridor—a three-dimensional void rumbling silently through the landscape, a continuous tube of air at least as wide and high as a walker. In this sense of a walkable space greater than a treadway, the architect’s notion of a path as a hallway is immediately useful. As the Eastern philosophers are forever noting, the void is what’s critical. If there is no continuously empty space, there is no path.
The corridor must be continuous. Trails leave Route 64 north of Tusayan, Arizona, headed for the Kaibab National Forest 10 miles away, but never reach it; the Grand Canyon blocks the way. By contrast, some paths are known almost exclusively for their continuity. What do most of us know of the Appalachian Trail except that it can be followed without interruption for 2000 miles?
The continuity need not be uniform. The free-flowing path can be interrupted by heavily trafficked intersections or difficult-to-pass gateways. And the treadway need not be continuous at all. Since it needs only support footfalls, it can consist of stepping stones three feet apart with water or voids between. Of course, it’s a different story for those in wheelchairs or with canes or crutches.
Since paths are linear, they convey direction. That helps define a path as a bounded, empty space longer than wide that can support our weight and convey us forward and backward.
Directions to and fro create another kind of heterogeneity. Two points may be equidistant from a walker, but they are not equivalent. One is ahead, the other behind, one to the right, the other to the left. The walker is heading toward the sun or home or city or away from it. As a result, designers use path alignments to direct and orient us and to make memorable landscape sequences.
Because this outdoor corridor is identifiable as a path, it forms a distinct landscape element distinguishable by any of our senses. Sight is the quickest, strongest indicator. A line of brick, a bump in a slope, a lengthy canopy or wall, all suggest a path. But smell can guide us across a swath of chamomile in the lawn, as can borders of rustling grasses. Fences and hedges can form touchably close guardrails. In August, taste can prompt us to walk next to the raspberry patch.
Seen from the outside extending across the landscape, this corridor creates two harmonies worth designing for: an internal harmony consisting of the rhythm of its curves and of the shape it encloses and an external one by the way it resides in the landscape and by the vistas it offers walkers.
For its relationship to the larger landscape, a path noted for its distinct vertical attachment, separate from its surroundings, could be called a self-centered path, while a path strongly linked to adjacent landscapes would be an integrated-plan path. A boardwalk above a marsh is self-centered, refraining from connections with its wet surroundings, while an urban plaza of stone pavers reaches out to unify surrounding buildings.
Although designers lavish attention on treadways—their materials, colors, patterns, edging— more attention should be directed to the vertical elements that strike the eye first and continually mold the corridor. The shape of the corridor as it snakes across the landscape—now ballooning, now constricting, now heightening, now lowering—the materials of its walls, the notched in seats and alcoves, and the views it permits —now enclosed, now open—form design elements of critical concern to walkers.
They combine with an array of other variables—extent and contents of the viewshed, relative and absolute elevations, slopes ahead and across, to name a few—that oblige the designer to make either wide-ranging on-site decisions, employ a wide assortment of graphic symbols, or engage in a systematic back-and-forth between the two. Therefore, the desirability of designing the many constituents of a walkway constantly confronts the difficulty of doing so.