It turns out there’s a bottleneck right through the heart of one of the world’s most active cities, and until recently, it was hard to see any solutions besides patience. All freight trains moving across the European/Asian border of Trkiye are presently forced through the Bosphorus’s Marmaray tunnel, a facility designed predominantly for metro transit service by commuters and only able to handle about three million tonnes of cargo annually. For a nation whose Twelfth Development Plan has as its explicit goal the role of Trkiye as connector between Europe, Asia, and the Middle East, sitting as it does on the Western end of the Middle Corridor’s rising trade route, three million tonnes is just an estimate. On Tuesday, the Asian Development Bank sanctioned a loan of pound 645.83 million as the next piece in an arrangement expected to be one of the largest multilateral infrastructure investments worldwide this decade.
Istanbul North Rail Crossing (also known as the INRAIL project) is a 127-km-long greenfield railway that will run without passing through the Istanbul metro area. Specifically, INRAIL will connect Gebze on one side of the Bosphorus to Halkali on another side of the water passage via a newly constructed railroad bridge, namely the Yavuz Sultan Selim Bridge. It is planned that roughly half of the distance (61 km, in 44 tunnels) will be underground, constructed by using a twin-tube tunneling machine, NATM and cut and cover techniques. The total cost of the project amounts to $8.27 billion, funded by $6.75 billion loaned from six international financial institutions: the World Bank, the Asian Development Bank, the Asian Infrastructure Investment Bank, the European Bank for Reconstruction and Development, the Islamic Development Bank, and the OPEC Fund for International Development.
Financing coalition
World Bank has disbursed anchor financing of $2 billion on March 31, 2026, which has been the largest individual tranche, while other funding agencies have made up for the rest of $6.75 billion funding for the project. Asian Development Bank has also disbursed pound 645.83 million (about $750 million) on June 9, 2026, as part of the ADB-World Bank Full Mutual Reliance Framework (FMRF); this is the first of two tranches from ADB, the second tranche of which would be released in 2028. Asian Infrastructure Investment Bank is contributing to the $6.75 billion funding as well, representing China-led financial institution supporting a project designed to reinforce a corridor in order to provide an alternative to the Russian corridor. European Bank for Reconstruction and Development has contributed $6.75 billion as it is in line with EBRD’s mandate supporting countries under transition within the context of the Middle Corridor. Furthermore, Islamic Development Bank and OPEC Fund for International Development have both contributed their shares to this funding effort; this can be attributed to Trkiye’s position as part of OIC and hydrocarbon-based finance of non-hydrocarbon projects.
The World Bank and the EBRD stand for the Western-led multilateralism. The AIIB is the leading alternative organization created by China with the explicit intention of serving as the counterpoint to the former multilateral system. The Islamic Development Bank and the OPEC Fund stand for the capital of the Gulf and the OIC countries. The unusual convergence of those six different organizations to finance one single railway project in Trkiye, under the “Full Mutual Reliance Framework” specifically designed in order to ensure more effective cooperation between the ADB and the World Bank in the preparation stage, occurs only due to the fact that the underlying rationale behind such financing is beyond discussion. Each of those institutions has its own reasons to be interested in the development of the Middle Corridor, which vary from the EBRD’s task of assisting the transition economies to the role of the AIIB as the organization involved in ensuring connectivity in the non-Russian Eurasia.
Perhaps the capacity transformation in this equation is the most important part. Current capacity is 3mt post INRAIL Project is expected to rise around 50mt. That is more than 15-teen fold potential increase. Turkish Transport Minister Abdulkadir Uraloglu stated that the line, upon its completion, is supposed to cater to 33 million passengers as well as 30 million tons of cargo per year. The explanation of the World Bank highlights exactly those corridors that are going to benefit from the project: the Trans-Caspian Transport Corridor known as the Middle Corridor, the Iraq Development Road, and the Turkish-EU corridor; all these corridors are constrained by their capacities precisely when it comes to the point of INRAIL relief. A bottleneck that is constraining each of these corridors when crossing the Bosphorus will no longer limit them once INRAIL starts functioning.
Possible implications on the Middle Corridor
Speaking of non-Russian, Eurasion corridor, this year, there have been abundant records on the trajectory of growth in the Middle Corridor: an increase in the volume of cargo five times in seven years to reach 4.5 million tonnes; transit time reduced from 28 to 32 days to 13 to 17 days; and forecasts by the World Bank that the figure would be around 11 million tonnes by 2030. Virtually every analysis of the trajectory of growth in the Middle Corridor has highlighted one common threat: the possibility that the investment in infrastructure in Central Asia and over the Caspian – such as improvements in the ports of Kazakhstan, the China-Kyrgyzstan-Uzbekistan railway, and the expansion projects in BTK and Alat Port in Azerbaijan – would overtake the capacities of the corridor’s western end.
The INRAIL solution eliminates that limitation in an overall time frame that is not an urgent one, but which corresponds to the growth plans for the corridor itself, and which, in any case, will take realistically a decade in view of the required tunnelling. The capacity of the BTK rail line was increased only last week to five million tonnes per year. The Alat Port expansion aims for 25 million tonnes per year. If the throughput of the Bosphorus crossing is limited to 3 million tonnes per year and everything else is moving towards 10 or 25 million, growth bottlenecks for the corridor arise right in Istanbul.
One aspect of INRAIL which should not go unnoticed due to the lack of coverage from the freight numbers deserves attention – this is the first time ever that a rail connection will be established between Istanbul Airport in Europe and Sabiha Gökçen Airport on the other side of the Bosphorus. Istanbul Airport transported more than 80 million passengers in 2025 and is currently one of the busiest airports by international traffic in the world; Sabiha Gökçen is its counterpart located on the Asian side. Establishing a connection through rail to the national rail network, as well as between both airports, will create a multimodal transport capacity that few megacities around the globe can offer: two international airports, a heavy rail freight route, and passage over the Bosphorus in one corridor. This will be especially beneficial for air cargo transported to further rail transportation over the Middle Corridor route and for passengers who would need to transfer between both airports without enduring Istanbul’s notorious road traffic.
The bidding process for the construction of INRAIL should be completed before 2026, with construction beginning immediately thereafter, implying that any freight benefits will come slowly over the period between 2027 and 2035 and not immediately. This timeline is important to keep in mind while assessing the project. What is relevant here is that INRAIL is not a response to the current demand for Middle Corridor transit; it is an attempt to secure capacity in advance of anticipated demand in the 2030s, at a time when growth in the corridor is accelerating further, and six different development banks with different strategic considerations agree that making this bet is worthwhile. As ADB puts it, the project will enhance Trkiye’s position as “a vital transport and logistics hub connecting Europe and Asia,” not as one that it might become but as one that has already been firmly established.