Public infrastructure decisions affect many stakeholders with various benefits and costs. For public decisions, it is crucial that decision-making processes and outcomes are fair. Fairness concepts have rarely been explored in public infrastructure planning. We close this gap for a global issue of growing importance: replacing sewer-based, centralized by decentralized wastewater systems. We empirically study fairness principles in this policy-relevant context, and identify possible influencing factors in a representative online survey of 472 Swiss German residents. In a transition phase, innovative, decentralized pilot wastewater systems are installed in households. We designed two vignettes for this context to test the adhesion to principles of distributive justice—equality, equity, and need—at individual and community level. A third vignette tests procedural justice with increasing fulfilment of fair process criteria. The results confirm our hypotheses: equity is perceived as fairer than equality at individual and collective levels. Contrary to expectations and literature, need is perceived as even fairer than equity. Procedural justice results confirm literature, e.g., the majority (92%) of respondents deems a policy fair that includes them in decision-making. Only few demographic and explanatory factors are significantly correlated with respondents’ fairness perceptions. Although unexpected, this is positive, implying that introducing decentralized wastewater technology can be designed for the entire population independent of characteristics of individuals. Generally, our results confirm literature: fairness perceptions depend on the circumstances. Hence, they should be elicited in the exact application context to be able to enter negotiation processes and provide concrete advice to decision-makers.
