The 30 inch gauge line from Bostan to Zhob (formerly called Fort Sandeman) was built between 1916 and 1930 and was no less than 298 kms long. It was initially constructed to transport chrome ore from Muslimbagh to Bostan, with the extension to Fort Sandeman being presumably for strategic reasons.
Some interesting passenger rolling stock was on view. Yes, the sleeper is 1st Class, as are the vehicles above. The Mobile Dispensary carriage is, well, indispensible in such an isolated location. By the time of our visit, 1 January 1988, the only train to traverse the whole line was the monthly pay train, so really kept going beyond Muslimbagh for strategic purposes.
62 steams through scrubland before arriving at Zarghun.
Summit of the line was at Kanmehtarzi, 64.11 kms from Bostan and 2224 metres above sea level, said to be the highest railway station in Pakistan and often covered in snow in winter.
Muslimbagh was next station along the line. Loaded trains from there came up with just three wagons due to the 1 in 40 gradient.
There has subsequently been a much praised film based around the railway and the situation described, more details at https://en.wikipedia.org/wiki/Moor_(film)