Excavation works on the Sarıyer–Kilyos Tunnel in Istanbul have reached a major landmark with the completion of TBM-driven tunnelling, marking one of the most significant achievements to date on this strategic highway project. The General Directorate of Highways has confirmed that this is the first time a tunnel boring machine has been deployed under its responsibility, underscoring a new phase in Turkeys adoption of mechanised tunnelling for large‑scale infrastructure.
The project uses Turkeys third‑largest TBM, a 13.65‑metre‑diameter earth pressure balance machine developed by China Railway Engineering Equipment Group (CREG). The TBM, known as CREC 1294, was assembled on site following a 70‑day cavern installation period and is designed to operate at depths of up to 172 metres while navigating tight horizontal curves.
A total of 4,800 metres of excavation has now been completed, representing a substantial portion of the planned tunnel works. The full Sarıyer–Kilyos Tunnel will extend approximately 7 kilometres and is designed as a twin‑tube connection linking Maslak and Levent to the Northern Marmara Motorway, Istanbul Airport and the Yavuz Sultan Selim Bridge.
Officials emphasise that once operational, the tunnel will reduce a 35‑minute journey to just 5 minutes, significantly improving mobility between Istanbul’s northern districts and major transport hubs. The project is expected to deliver annual economic savings of 4 billion TL through reduced congestion, lower fuel consumption and improved logistics efficiency. Completion is targeted for 2026.
The successful completion of TBM excavation marks a critical step toward final lining, systems installation and commissioning, positioning the Sarıyer–Kilyos Tunnel as one of Turkey most transformative urban transport investments.
Project Fact Box
Project: Sarıyer–Kilyos Tunnel
Location: Istanbul, Türkiye
Implementing Authority: General Directorate of Highways
TBM Supplier: China Railway Engineering Equipment Group (CREG)
TBM Type: EPB TBM, CREC 1294
TBM Diameter: 13.65 metres
Tunnel Length: Approx. 7 km (twin‑tube)
Excavation Completed: 4,800 metres (TBM section)
Maximum Depth: 172 metres
Horizontal Curve Radius: Minimum 190 metres
Purpose: Connect Sarıyer, Maslak and Levent to Northern Marmara Motorway, Istanbul Airport and Yavuz Sultan Selim Bridge
Travel Time Reduction: 35 minutes to 5 minutes
Annual Savings: 4 billion TL
Scheduled Completion: 2026
The original tender for the Sarıyer–Kilyos Tunnel does not appear to be publicly available. What is clear from available information is that: The project is being delivered under the authority of the General Directorate of Highways (KGM). It forms part of the wider Northern Marmara Motorway / Yavuz Sultan Selim Bridge access network.
Financing for the Sarıyer–Kilyos Motorway Tunnel was secured through a US$405m bond issuance by ICA, the operator of the Yavuz Sultan Selim Bridge and Northern Ring Motorway. This confirms that the project is structured as a motorway PPP, but the tender documentation itself is not referenced. 07/26.
