Achieving network performance is a vital goal in response to the increase of inter- organizational networks public organizations involve. The primary aim of this research is to examine the factors that predict performance in inter-organizational networks by disentangling the idea that collaboration requires both diversity and unity. Drawing upon diversity theories, social capital theory and management literature as theoretical lenses, this paper serves to investigate the following questions: (1) how does social capital mediate the relationship between network member diversity and performance? (2) how does network management strategy moderate the relationship between social capital and network performance?

This paper answers these questions by examining Metropolitan Planning Organizations (MPOs) in the United States, one of the regional transportation networks. MPOs are formal inter-organizational networks that go beyond informal and intra-organizational networks. The focus here is on collaborative decision-making activities by individuals (mostly top-level administrators) who represent organizations working across their boundaries. This paper provides an important evidence of the interactive effects between network management behaviors and structural properties of networks on performance; it also contributes to the existing knowledge of inter-organizational dynamics in transportation planning networks.