The Osmangazi Bridge or Izmit Bay Bridge is the fourth longest span suspension bridge in the world, built between Dilovasi Dil Cape and the Altinova Hersek Cape with a total length of 5 meters and a total length of 1.550 meters.
Within the scope of the Gebze-Orhangazi-İzmir Highway project, 384 kilometers of motorway including Osman Gazi Bridge and 49 kilometers of connection roads are constructed. By using only the bridge, the gulf crossing will take from 2 hours to 6 minutes, and when the whole project is completed, the Istanbul-Izmir journey, which takes an average of 8 hours, will decrease to 3,5 hours. The savings made by using the bridge crossing instead of the new highway to be built and 95 kilometers shorter than the existing state road and approximately 1,5 kilometers with the bridge taking 88 hours are the main reasons that reduce the travel time. As the current state road passes through many city centers, highway speed rules cannot be applied.
When the project is completed, 650 million dollars of national savings will be achieved annually. The cost of the bridge was $ 1,2 billion. The entire cost of the bridge and the highway is 6,9 billion dollars, all of which will be covered by Otoyol A.Ş.
In the tender announcement of the Gebze - İzmir highway project, published at the beginning of 2008, a three-way, three-turn-lane highway (six-lane in total) and a one-way-one-way-two railway line plans were included on the Izmit Bay bridge. However, in August 2008, the railway lines were abolished with the "Addendum No.1" and on September 27, 2010, the contract for the Gebze - Izmir highway with the railway-free Körfez bridge was signed.
On March 21, 2015, one of the guide cables, called Catwalk, which will carry the main cables on the bridge, broke. The broken rope was assembled between 31 May and 4 June. Japanese engineer Kishi Ryoichi, who held himself responsible for the breaking of the rope, described the accident as a matter of honor and committed suicide.  8000 workers worked during the construction phase.
The bridge was opened on the evening of June 30, 2016, with a ceremony attended by Turkish motorcycle pilot Kenan Sofuoğlu, president Recep Tayyip Erdoğan and his prime minister Binali Yıldırım.
Within the first ten days following its opening to traffic, at least 95% of the bridge traffic was first class vehicles. During the period when the bridge was free, an average of 1 vehicles served daily, while an average of 100.000 vehicles used the bridge during the period when the paid service started. The average weekly cost to the state of less vehicle transit than committed is $ 6.000 million.
The bridge was opened to traffic on 1 July 2016. (Free until 11 on 07.00 July) After it was opened to traffic;
- 1 on 2016 July 49.942
- 2 on 2016 July 83.147
- 3 on 2016 July 83.170
- 4 on 2016 July 75.650
- 5 on 2016 July 108.74
- 11-26 July 2016 100.932 vehicles used the bridge.
Vehicle pass guarantee
The equivalent of 14,6 million cars per year is guaranteed. In case of fewer passes, the difference will be paid by the government.