Yujin Song, Dagyo Kweon, Jooho Kim, Sang Jin Kweon
Disruptions to drinking water systems require emergency distribution strategies that are not only efficient but also equitable. Motivated by the Flint water crisis, this study develops a multiperiod location-allocation model for mobile points of distribution (PODs) to enhance spatial equality and spatial equity in emergency water distribution. Traditional fixed-site PODs often fail to ensure equitable access, particularly in low-density, underserved, or transportation-disadvantaged areas. To address these limitations, we propose a biobjective mixed-integer linear programming model that determines optimal mobile POD placements and demand assignments across multiple time periods. The model simultaneously aims to (1) maximize population coverage within a defined travel distance threshold, and (2) minimize total travel time by accounting for disparities in transportation access, such as vehicle ownership and income levels. The proposed model is validated using real-world data from Flint, Michigan, including road networks, demographics, and socioeconomic status. Compared with fixed-site PODs, the mobile POD strategy reduces average travel time by up to 59.03% and achieves full population coverage at 61.68% lower operational cost. Vulnerable communities, particularly those with limited transportation access, benefit the most from this approach. Sensitivity analysis reveals that travel distance thresholds exert a greater influence on accessibility than budget levels, highlighting the importance of context-specific strategies reflecting the spatial and socioeconomic characteristics of each ward. The results demonstrate that mobile PODs offer a scalable and policy-relevant solution for improving access to emergency water in disadvantaged areas. These findings underscore the need to integrate spatial equality and spatial equity into emergency water distribution planning, positioning mobile PODs as a viable strategy for strengthening community resilience in the face of increasing disaster risk.