The availability of railroad transport will gather many settlements, specially around those points where several lines connect. This usually takes place in important urban areas.
It is very profitable for enterprises to locate their facilities close to the train transport system, which is a very valuable asset for product distribution or for quicker contact with suppliers. Therefore, many citizens, as employees of this companies, would locate their homes close their workplace as well. Therefore, proximity to railroad, and in general, proximity to means of transport, is one of the factors that contributed at first to the progressive urbanization of developed economies.