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Strait road tunnel, Istanbul

5.4km long tunnel under the Bosphorus Strait, connecting Europe to Asia

The Istanbul Strait Road Crossing project is a new crossing of the Bosphorous Strait that connects the European and Anatolian regions of Turkey, relieving congestion on the two existing Bosphorus Bridges.

The new tunnel was constructed between the areas of Kazlicesme and Goztepe, along a 14.6-km route. The route features a 5.4-km twin-deck tunnel that crosses the Bosphorus beneath the seabed, with the aim to alleviate İstanbul’s traffic pressure.

The project also included the construction of an additional 10km of access roads, two toll plazas and the operations buildings for the tunnel. The project is expected to reduce the travel time between Kazlicesme and Goztepe from 100 minutes to just 15 minutes.

Project Summary


10,000 vehicles per day

75minsreduction in travel time

106mbeneath sea level

Eurasia Tunnel Eurasia Tunnel

A team effort and the world's first intercontinental tunnel

We began working on the award-winning project in 2009, providing technical advisory, environmental monitoring and traffic audit services to the institutions funding the project during the procurement and construction stages. 

The tunnel is a first to bring two continents together, by linking Europe with the motorway network on the Asian side.

It represents a truly international effort with investors from Turkey and South Korea, tunnel materials provided from Germany and operation, surveying and maintenance assisted by France, Italy, Netherlands and the UK.

Major consultancy services

We also advised the funding institutions on the technical requirements for the project, including a review and commentary on the design, the traffic models and economics, the construction and operation proposals, the environmental impact and stakeholder consultations; as well as the review of construction costs, contract documents and analysis of the project risks including seismic risk.

The tunnel opened to the public in December 2016

The finished tunnel stands about 1km south of the undersea train tunnel Marmaray and marks another success for Turkish infrastructure.

While significantly improving commuting times for citizens and businesses in Istanbul, the tunnel also reduces air and noise pollution in the city.