Beyond distance: mapping multimodal forest recreation corridors in the Vienna metropolitan area using PPGIS and origin–destination flow clustering

Urban and suburban forests provide major cultural ecosystem services, yet planning still often relies on destination-based indicators (e.g., nearest forest, simple distance buffers). These measures miss how real access is shaped by corridor continuity, available transport modes, and last-mile connections to entrances. As a result, they can misrepresent both visitation pressure and equity patterns across a metropolitan region.

We analyse forest recreation in the Vienna Metropolitan Area using representative Public Participation GIS (PPGIS) data (n = 3,121). We link anonymised home locations to reported forest destinations and entrances, derive origin–destination (OD) flows, and assess accessibility using both Euclidean distance and mode-specific network travel times for walking, cycling, public transport, and car. To move beyond a destination-only assessment, we apply density-based OD flow clustering (DBSCAN/HDBSCAN) to detect corridor-like patterns and compare clusters by travel time, mode share, and visitation frequency.

We identify six visitor groups (with sub-clusters in the two largest), differing in mobility profiles and spatial structure. We find a clear distance–decay relationship: each additional kilometre to the forest is associated with ~11% fewer annual visits. Importantly, distance alone does not explain use. Corridor structure matters. Multimodal “belts” around the city support access within feasible travel times, while other areas remain underused despite being geographically close, suggesting gaps in connectors and continuity rather than limited forest supply.

This corridor-based perspective complements destination-centric metrics and supports more actionable planning and mitigating environmental impacts. Strengthening gateways and last-mile links, protecting high-performing multimodal corridors, and targeting specific accessibility gaps can improve equity while limiting car dependence.