The nervous systems acquire skills which they use, self-aware of their needs. The awareness grew to include transportation and communication between complexities. They now could know each other's needs, and adjustments could be made. A complexity, several thousand stone's throws away can drive there in a few minutes or talk there in seconds, depending on which extension of itself you're talking about. Both of these conveniences are made possible by landscraping enough to have a road system, lined of course with electric hand rails suspended by dead trees and metal figurines, with light for night and limbs for the conductivity.
Roads are space dedicated above all to movement.
Any confusion over this is confirmed in the soft scramblings toward the shoulder. Roads are not for the dead, surprisingly, but for life to continue, elsewhere. Almost any where, as long as its inbetween the roads. The grid prides itself on its lines and signs as it digests what it has consumed.