The Trans-Iranian Railway connects the Caspian Sea in the northeast with the Persian Gulf in the southwest crossing two mountain ranges as well as rivers, highlands, forests and plains, and four different climatic areas. Started in 1927 and completed in 1938, the 1,394-kilometre-long railway was designed and executed in a successful collaboration between the Iranian government and 43 construction contractors from many countries. The railway is notable for its scale and the engineering works it required to overcome steep routes and other difficulties. Its construction involved extensive mountain cutting in some areas, while the rugged terrain in others dictated the construction of 174 large bridges, 186 small bridges and 224 tunnels, including 11 spiral tunnels. Unlike most early railway projects, construction of the Trans-Iranian Railway was funded by national taxes to avoid foreign investment and control.

Brief synthesis The 1,394-km-long Trans-Iranian Railway (TIR) connects the Caspian Sea in the north to the Persian Gulf in the south of Iran. Opened fully in 1938, the railway is a busy main line of standard track gauge 1,435 mm. The Trans-Iranian Railway combines spectacular mountain settings with sustained steep mountain grades less than 3.0%, which is today considered the maximum practical mountain railway grade. Railways with grades steeper than 3% have proven problematic to operate. The property’s mountain railway design hits the critical design balance point between the outstanding and the impractical. Its exceptional mountain railway scale is also exhibited by the proliferation of major engineering structures en route namely: 174 large bridges, 186 smaller bridges, 224 tunnels, including 11 spiral tunnels and 89 train stations. These structures are distinguished by the high quality of their 1930s construction, which has enabled them to survive to the present day in as-built condition. The Trans-Iranian Railway represents the expansion of the modern state power in the 20th century in a specific non-colonised Asian context within active involvement of national capital and stakeholders. The role of the railway industry in the social, economic, industrial and cultural growth of Iran and the region, as well as in international trade and transactions, is undeniable. Not only has this railway boosted the economy and trade by speeding up transportation, but it has also made…