Khwaja Amran Railway Survey
The Khwaja Amran Railway Survey was undertaken in 1887
The section from Bostan to Chaman through the Khwaja Amran mountains became known as the Chaman Extension Railway. Built to a steep ruling gradient it rises to 6394 feet (1948m) at Shelabagh and drops to 4304 feet (1312m) at Chaman. Six tunnels were needed in its 68 mile length including the mighty Khojak Tunnel which at 12870 feet (3922m), was the longest tunnel in India. 
The line was opened in 1891 as part of the North Western Railway network.
- Google Books "Engines of Change: The Railroads that Made India" by Ian J. Kerr, page 58; Retrieved 13 Jul 2016