Metro as an example of an urban rail system. Four case studies from Europe

Underground, tube, subway or metro are common expressions used to describe a rapid transit system serving urban areas. Such a system uses dedicated rail corridors, can run underground or overground, and often includes tunnels and viaducts. Although there are 148 cities in the world with metro systems, each system is different, in terms of layout, length, capacity, etc., as it serves different geographical and socio-economical areas. In this context, the paper presents four European metro systems (Sofia, Warsaw, Lisbon, and Tyne and Wear), introduces the systems dimensions, rolling stock and ticketing strategies and compares similarities and differences between the systems. The analyses suggest a number of recommendations and improvements, which if implemented, could benefit other metro systems in Europe and beyond.