[iferencik]

Valhalla generates internal isochrones inside barriers because it evaluates connectivity strictly through network topology, not geographic containment. In economic terms, it models supply chains along defined infrastructure lines rather than assuming a blanket regional embargo.RAPIDA's routing engine converts spatial road data into a binary optimized Direct Acyclic Graph (DAG). When a barrier polygon (like a flood extent or landslide zone) is introduced, the system applies it as a dynamic impedance, meaning it only deactivates the specific road segments that physically intersect the polygon's boundary. It effectively builds a tariff wall around the zone, severing external trade routes while leaving the internal market infrastructure intact. If a health facility—the service provider—is located inside this barrier, Valhalla evaluates the immediately adjacent, unsevered roads and calculates a local catchment area. It routes along this trapped internal network until the paths hit the penalized perimeter edges. The engine successfully maps a localized economy of accessible nodes, completely unaware that the entire geographic zone is compromised and functionally offline.For crisis mitigation, this default behavior creates a severe analytical distortion. RAPIDA’s connectivity analysis is designed to quantify the actual post-crisis reach of the health system by modeling a population's real-world ability to traverse a compromised landscape. A facility trapped within a disaster zone effectively has a functional reach of zero. By generating isochrones for these trapped facilities, Valhalla falsely signals available healthcare capacity. This skews the automated intersection of isochrones with population grids and miscalculates the true headcount of disconnected people. Programmatically filtering out these trapped origins before routing ensures the data accurately reflects the total loss of service provision in the affected area