Data sharing in transport has been identified as a key enabler of the development of new digital platforms that aggregate services for the benefit of passengers, both services provided by different transport providers in a mode of transport and beyond, across modes of transport, as in mobility-as-a-service platforms. The aim of this chapter is to differentiate between regulation of naked data-sharing agreements and regulation of ancillary data sharing in the provision of online intermediation services. Furthermore, competition authorities are imposing price parity clauses on transport service providers, which, paradoxically, are prohibited as anti-competitive when imposed by dominant digital platforms.