At the beginning of the First World War in 1914, the total length of the secondary railway network in France had nearly reached its peak, at 18,000km, although it continued to grow slowly until 1928 when it reached its maximum size at 22,000 km ( 13,750 miles). This was a vast network being more than half the length of all the main lines in France
( 40,000km in 1930 ).
But it could not be sustained without subsidies, and these were gradually reduced. After the War, costs of coal and wages increased drastically, while competition in the form of motor vehicles changed the economics of the Little Trains.
After the first thirty years of development of secondary railways, two specialist companies emerged as leaders in the field of secondary rail transport; Compagnie des chemins de fer departementaux ( "CFD") and Societe Generale d'exploitation des chemins de fer economiques ("SE"). The latter company later became C.F.T.A. (Ste des Chemin de fer et transport automobile) and survives today.