A Capacity-Based Theory of Complexity Control in Megaprojects: Structural Demands, Regulatory Capacity, and Ashby's Law of Requisite Variety

Megaproject research has shown repeatedly that large, technologically demanding, and politically exposed projects are prone to cost escalation, delay, and governance breakdown. Existing project complexity research has produced influential classifications of structural complexity, uncertainty, and stakeholder interaction, but it is less precise about when projects pass from difficult coordination into loss of controllability. This article develops a capacity-based theory of complexity control through a theory-elaboration reconstruction and extension of Huemmer (2020) in dialogue with project complexity, megaproject, and project resilience scholarship. The article argues that complexity becomes critical when the structural variety generated by the project system exceeds the regulatory variety available through the 4M architecture of human, machine, method, and material. Ashby’s (1956, 1958) law of requisite variety is used not as a total theory of megaproject governance, but as a cybernetic condition of controllability. On that basis, the article explains how capacity deficits create vulnerability, why overload propagates across interfaces, how complexity shifts from latent to acute states over the project lifecycle, and why some projects may reach a point of no return at which ordinary control routines no longer recover stability. The contribution is fourfold: reconstruction of a German-language framework for an international audience; clarification of the Ashby-based mechanism; refinement of the 4M architecture as a proto-operational logic; and derivation of propositions, an illustrative diagnostic, and a research agenda. The article is conceptual rather than empirical and should be read as reconstruction, extension, and mechanism clarification rather than ex nihilo theory creation.