The chief characteristic of the history of railways in France is the speed with which a coherently organized operational system was set up. This system was based on the following guiding principles:

Lines were granted to private companies for a limited period. Up to 1852, this was very variable but thereafter was fixed at 99 years, as a general rule.

The lines were grouped into homogeneous geographical zones so as to form a series of réseaux (networks), each run by a company which enjoyed a monopoly. Railway geography was not mapped out permanently until the signing of the 1883 conventions but its overall pattern was traced by 1859. The networks established under this system were the Ouest, Nord, Est, Paris - Lyon - Méditerranée, Paris - Orléans, Midi and, lastly, Etat. The Etat network lay between the Paris - Orléans and the Ouest and was only formed in 1883. It was not granted as a concession but was managed by a state enterprise. In 1908, the Ouest network was taken over and became part of the Etat. Marking the frontiers, in each case, was the outcome of a complex process that involved not only the interests of the concessionary companies but also those of the districts and towns the networks served.

The relationships between the conceding State and the concessionary companies were set forth in a series of agreements confirmed by laws. These agreements were not properly harmonized, however, until 1883 and even then only partially. In the meantime, the terms of the concessions differed widely. The principal feature of the 1883 conventions was that they provided for the application of the interest guarantee. This scheme had been introduced as early as 1839 for the Paris - Orléans and was used after 1857 for lines recently constructed or granted and made up the “new network”. In 1883 its application 70became general. Under its conditions the companies had to accept a twofold form of state tutelage: on the one hand they were bound by a “Cahier des charges”, which listed their responsibilities and liabilities towards government. This measure was finalized in 1847. They were also subjected to a financial control that entailed close administrative supervision. Their freedom of action was curtailed, as both the rates they applied and the investment expenses they incurred had to go through a procedure of authorizations.

Thanks to the interest guarantee, the funding of the construction and investment costs which were designed to cater to the growth of traffic was ensured to a very great extent (about three-quarters in 1883) by the issue of bonds. These were in popular demand precisely because of the guarantee and the French railway network could consequently be extended indefinitely.