Disruption in horizontal collaborations: a cost-trust analysis for coalition-based supply chain network design

Horizontal collaboration in distribution networks can reduce transportation costs and environmental impacts, yet many initiatives fail due to rising coordination expenses and fragile trust among partners. This paper proposes a bi-objective, two-stage robust optimisation model for designing coalition-based supply chain networks under uncertainty, explicitly accounting for collaboration costs and measurable trust between carriers. The model captures how first-stage coalition decisions may be affected by potential disruptions in the second stage, where trust levels determine coalition feasibility and influence worst-case recourse flows. To handle realistic coalition sizes, we develop a decomposition-based solution approach using a column-and-constraint generation algorithm that incrementally adds the most informative coalition and disruption constraints. Computational experiments across multiple spatial network structures show that partial coalitions with strong inter-firm trust often outperform grand coalitions, yielding lower total costs and reduced disruption exposure. Results further reveal that transportation savings increase with coalition size only up to a threshold; beyond that point, collaboration costs dominate, producing an optimal coalition range rather than a single best partner set. The model also identifies strategic distribution centers and carrier relationships whose trust characteristics disproportionately influence coalition stability. Overall, incorporating trust as a formal decision factor leads to more resilient and cost-efficient coalition structures.