Deep transport decarbonisation requires not only technological measures, but also large-scale changes towards sustainable mobility behaviour. Researchers and decision-makers need suitable tools for corresponding strategy development on a macroscopic scale. Aiming at broad accessibility to such methods, this paper presents an open source passenger transport model for policy analysis in German medium- to long-distance transport. It discusses model design and data, limitations, alternative approaches, and its base year results and concludes, that macroscopic transport modelling is very suitable for policy analysis on national scales. Alternative approaches promise more insight on smaller scales. As an exemplary case study, the model is applied to ambitious technology projections for the year 2035, showing the ambition gap towards reaching the 1.5 degree-target of the Paris Agreements. Results indicate that 66 million tCO$$_{2eq}$$
2
e
q
per year must be mitigated through further technological substitution or demand-side mitigation strategies.