Inward from Pakistan's most western edge, it begins at Spezand Junction and has services that continue beyond Koh-e-Taftan station in high mountains, west.
Many or all primary services since 1940 (and 1922 to 1931) terminate on the natural continuation in eastern Iran at the high city of Zahedan, which sees a change of gauge (of track and rolling stock) for accessing the Trans-Iranian Railway.
The Quetta to Nushki branch was approved by Lord George Hamilton, Secretary of State for India, in August 1902,[7] and it was opened on 15 November 1905.
By the time the railway reached Duzdap, the British had already demobilized their forces in East Persia in March 1921, which took away the importance of the newly built part.
Aid through Persia proved unnecessary (due to successful Arctic convoys of World War II and similar supplies,) but the Quetta-Zahedan link was reopened on 20 April 1940 in Zahedan.