The idea of connecting the two of the closest urban and suburban rail-based public transport systems was proposed more than 40 years ago and it boasts a proclaimed support from the regional authorities. However, many of the systems either did not achieve their goals or became financially inefficient as they replaced the conventional railway systems in a wider range than it had initially been planned. That resulted in an inappropriate competition between the public transportation modes.
This paper aims to define the prerequisites needed for the establishment of a successful, both financially and operationally sane tram-train system as a substantial part of the regional railway network An analysis of the various current tram-train systems in the selected European cities is made and special attention is paid to their distinctive features including the offered capacity, density, technical compatibility, and operational aspects. Using the conclusions of the analysis and the current technical and operational requirements to be met, a recommendation for the design and organization of the planned tram-train lines and networks is stated, which may help the transport planners design such costly systems in a way it can use its overall advantages in favor of the passengers and an increase of the public transportation modal share.

tram-train, suburban transport systems, regional railways, interoperability, urban tram systems, mixed operation