Before the line was without passenger service I once rode the line with mr Cor from Sakov Tours in 2009 travelling from Beograd to Sofia.
Serbia Rail
Beograd Stacia –
Beograd main railway station was built between 1882 and 1885. Opened for traffic on August 23, 1884
Nis – Dimitrovgrad Ниш – Димитровград
This 99 kilometer single track line is on this moment without passenger traffic. To the Bulgarian border is another 4 kilometer. It is a European corridor between Nis and Sofia. All stations are staffed and control the line. Some iron bridges do have speed restrictions. The line is well growed in by trees and bushes but still has some very nice spots. Ofcourse the new highway is being build and no action on the railline yet ……