Most Serbian railway lines were built as a result of an expansion of railway networks by Austro-Hungarians. Several 760 mm (2 ft 5+15⁄16 in) gauge railways were planned to link the extensive narrow-gauge railways in the Austro-Hungarian Empire with those in Bosnia and Herzegovina. Until the outbreak of the Balkan Wars in 1912 several of these were constructed, the first ones in Eastern Serbia:
Serbian railway (narrow-gauge) network began to develop in the 1880s.
In the 1920s the network was extended from Bosnia and Herzegovina to Belgrade.
The Šargan Eight is Serbia's only narrow-gauge railroad line in service, albeit as a heritage railway. It operates passenger travel from Mokra Gora to Šargan. Originally, the Šargan Eight connected Serbia with Bosnia and Herzegovina (Belgrade-Sarajevo line) when it was first constructed in 1916; the original link extended all the way to Višegrad. Today, however, the train only uses 9.6 miles of track on its trips from Mokra Gora to Šargan, reconstructed in 2003 and in service since then.[4]
In Veliki Crljeni and Vreoci there is a private narrow-gauge railway that is used to transport coal from the Kolubara Mine to the Kolubara Thermal Power Plant (A). There is no passenger service on this line as the line is used only for cargo and freight. Unlike the Šargan Eight, the Kolubara narrow-gauge line is electrified. There is very little information about the railway, but a historical note is that the railway uses about 5.95 km of the old route from the old Mladenovac-Lajkovac narrow-gauge railway .The gauge of the track is a mixed gauge although the true width is unknown.