And old nineteenth-century interpretation defined rail-ways as that means of transport which runs on railway tracks. Thus, the same definition included trains, trams, metros, light rail and funicular systems, among others. If we consider this definition, there is no doubt that rail-ways are the urban passenger mass transit system par excellence. They are the urban infrastructure which has the highest cost and the biggest impact on its environment, they are capable of transforming the urban fabric in the medium and long term, and they shape and reflect the history, growth, evolution and changes of the urban system on which they are laid out.

This book aims to delve into the existing interaction between the rail-way network of an urban area and its consequences on a territorial, social and political level. Another of the objectives is to understand the factors that shape urban space and its existing elements. The case study focuses on the city of Barcelona, where we can clearly see the evolution of the rail-way system and how it interweaves with the urban growth of the city. During its maturity stage, Barcelona’s rail-way system has transformed its tree-shaped structure into an actual network, a mesh with multiple connections and a wide centre which virtually covers the entire urban continuum.