Dream Link for Turkey

First underwater rail link between continents unites Europe and Asia.


Help ease traffic across the Bosphorus in rapidly growing Istanbul

OC Global is part of a team that has linked railway lines on both sides of the Bosphorus with a submerged (immersed tube) rail tunnel crossing the strait.

One of the most important problems in Istanbul is the difficulty of traffic management resulting from the rapid population growth and increase in traffic. The heaviest traffic can be seen on the bridges over the Bosphorus. Two bridges and several ferryboats have been insufficient, resulting in frequent gridlock during the morning and afternoon rush hours.

To address this issue, the government of Turkey initiated the Marmaray Project to provide railway service under the Bosphorus to connect the area between Sarayburnu and Üsküdar.


OC Global has been providing overall consulting services as the lead of the joint venture responsible for project management. We were involved in the basic design and tender assistance to engage construction companies, including preparation of tender documents, evaluation criteria, pre-qualification questionnaires and evaluation criteria, pre-qualification evaluation reports, and technical study reports.

Responsible for the project management plan, we also consulted on the quality assurance system, safety policy, contract management, construction scheduling, and construction supervision and operations management. OC Global also provides special assistance to the employer related to funding arrangements.


The Project is made up of three construction packages:

The Bosphorus Crossing package, including construction of the immersed tube tunnel, bored tunnels on both sides, and four new stations.

The Upgrading of the Commuter Rail package for a distance of 63 km, including installation of a third rail (for power supply to trains), full upgrading of the existing tracks and stations, and new signaling, communication, and fare collection systems along with a new operations control center.

Procurement of New Rolling Stock package, including introduction of 44 sets of 10-car trains.

The Marmaray Tunnel officially opened on 29 October 2013, the Turkish Republic’s 90th anniversary. The Ottoman dream of 150 years ago was realized with the Marmaray link between Europe and Asia, uniting the land masses and the people of the two continents.

Work on the commuter lines is nearing completion.


Japan Construction International Award, 2018
FIDIC Award, 2017
JICA Award, 2014

Official Title
The Engineering and Consulting Services for Gebze-Haydarpasa, Sirkeci Halkali Commuter Rails Upgrading and Railway Bosphorus Tube Crossing Construction (Marmaray)
Project Type
Urban Railway for MRT
General Directorate of Infrastructure Investments (AYGM)
Project Period

2002 – Present

Sustainable Development Goals (SDGs)

Realization of long-term Turkish dream of connecting 2 continents by resilient infrastructure promised Istanbul of easing the rapidly growing traffic resulting from the rapid population growth

“Today we are realizing the dreams of 150 years ago, uniting the two continents and the people of these two continents,”
Turkish Prime Minister Recep Tayyip Erdogan (2013)