Large-scale changes are expected for urban mobility systems, triggered by digitalization and various other factors such as climate concerns or urbanization. For researchers and planners, it is therefore becoming increasingly important to understand the determinants of variability and stability of travel decisions. The motivation for the study is that, in transportation research and modeling frameworks, travel choices usually derive from individual traits and accessibility variables. What is underrepresented by such an approach is that decisions are also socially embedded. The authors postulate that mobility patterns are strongly interwoven with the way people configure their social networks. The paper introduces and discusses an empirical approach to investigate the social embeddedness of mobility decisions. The basic premise of the approach is that social network configurations provide an important setting for daily life in general and individual travel decisions in particular. Analysis is based on a three-phase interview study, conducted in Karlsruhe, Germany. The analytical approach reveals that a substantial part of travel is only loosely coupled to generalized costs of transport. ... mehrInstead, the motivational degree linked to certain relationships largely influences willingness to travel and the relative stability of everyday life. Relationships that are internally satisfying or extremely familiar to people appear highly persistent. Furthermore, relationships that provide a certain degree of flexibility appear changeable, though not necessarily in all dimensions. Only a very small number of relationships appear both substitutable and changeable.