Abstract This note defines Temporary Route Residue (TRR) as a reversible continuity layer within navigation systems. Unlike stateless routing, where movement leaves no usable afterstate, and unlike persistent route logging, where trajectories accumulate as durable records, TRR describes a middle regime in which recently used paths leave a temporary, fading, context-sensitive trace. The trace is not treated as permanent memory, identity-bearing storage, or full symbolic history. Instead, it functions as a soft afterfield of route use: visible enough to support continuity, weak enough to remain reversible. The central claim is that route residue is initially contextual and reversible, but can scale into a qualitatively different regime when reinforced through repeated use, shared visibility, and comparative legibility. Under these conditions, temporary traces no longer function only as personal or situational guidance. They begin to produce collective route attractors: popular paths, socially reinforced route habits, recognizable movement corridors, and eventually rankable or competitive route layers. This transition is described as a phase shift from Temporary Route Residue (TRR) to Collective Route Attractor (CRA) and then to a Social Route Layer (SRL). The contribution of the note is not the invention of popular routes as such, but the formalization of the reversible intermediate regime through which temporary contextual residue can become socially structured route infrastructure. Domain Ambient Navigation