This is a succinct description of the development of rural secondary railways in France between 1870 and 1914. These lines were mostly narrow gauge, built economically, and the rail services provided were designated "Les Petits Trains", the Little Trains, by the rural populations served. These trains may have been physically small and quite unreliable, but, nevertheless, they rendered great service to country communities for many decades, until the Age of the Motor Car arrived.
Throughout the 19th century, the main railway network in France was built under the control of the central government which planned the network, financed and constructed the first railway lines, while offering "long term operating concessions" to private companies to lease the infrastructure of the new lines and to construct stations, locomotives, rolling stock and operate services.at their own risk.
The first priority of the government was to link Paris with all the main towns, ("prefectures"), in France and, of course, this represented large, profitable, traffic flows which attracted investors. Ultimately, eight large railway companies emerged from the turmoil of this period; the Compagnie de Chemin de fer de l'Est, du Nord, de l'Etat, de l'Ouest(absorbed by l'Etat in 1909), du Midi, de P.L.M., and Alsace-Lorraine. These companies were nationalized in 1938 to form the S.N.C.F.
But these large railway companies were not interested in constructing secondary railway lines linking small towns and villages, which could be seen, already, as unlikely to be a profitable activity. On the other hand, there was a huge demand from the rural population to be given better transport for access to the towns and cities. All wanted their own community linked to the main railway lines.
So the central government was obliged to force the railway companies to construct some of these unprofitable secondary lines by making that.a condition of its approval of their main line expansion plans. Even so, the large railway companies delayed as long as possible the construction of these secondary lines.
To simplify and speed up the construction of these lines, in 1865, a law was passed which delegated authority directly to the departments and communes to organize the construction of local "secondary" lines.