Data-driven operations are critical for an efficient and compliant European transport ecosystem. Real-time analysis and visualisation of data about vehicles, drivers and goods being transported across Europe enable optimisation and compliance. However, progress is limited by legacy systems, fragmented data, capability gaps and barriers to data sharing. The project Knowledgeable comprehensive and fully integrated smart solution for resilient, sustainable, and optimised transport operations (KEYSTONE (Official website of the project: https://www.keystone-project.com/ )) aims to contribute to a roadmap for the digital transformation of the European transport ecosystem by creating standardised, truly Plug and Play solutions that will bridge the gaps and pave the way towards this goal, regardless of the existing legacy systems. The project is a major step forward in current efforts to build data-driven operations capabilities by integrating existing data-driven platforms, services, and skill development solutions across a range of European stakeholders. In addition to its technology and management components, the project will provide policy recommendations to address shortages in data literacy and digital leadership, fostering collaboration between regulators, operators, and service providers to capitalise on data for the purpose of compliance. This paper provides an overview of the initial findings in the efforts by the KEYSTONE consortium to unify transport data for compliant operations across Europe, with particular emphasis on the current state of the art, interoperability challenges and requirements as perceived by key European stakeholders.