Izmit Bay Bridge 2016

Izmit Bay Bridge 2016

© Ozkan Ulucam

The Bridge

Following the successful construction of the Second Bosphorus Bridge (Fatih Sultan Mehmet Bridge), which opened in 1988, the Turkish Ministry of Works commissioned Bill Brown to design long span suspension bridge schemes across Izmit Bay and Canakkale Straits. In 1994 he presented his Izmit Bay Bridge: a 1,540m single span with an aerodynamic box girder deck.

In 2009 the project was revisited by the Turkish Ministry with an increased desire to see the project realised and improve Turkish infrastructure. Japanese company, IHI, who had built the Second Bosphorus Bridge, won the tender to construct the superstructure of the bridge. They commissioned Danish firm, COWI, as consulting engineers working alongside architects Dissing+Weitling. They followed the Severn-type bridge design that Bill had originated and a 1,550m single span bridge began construction in 2013. The overall length was 2,682m and it was designed with expansion joints and towers on gravel beds to resist a powerful earthquake. On opening in 2016 it was named the Osmangazi Bridge.

Izmit Bay Bridge

Also known as the Osmangazi Bridge

Key Facts

The longest bridge in Turkey

The sixth-longest suspension bridge in the world by the length of its central span


Dilovası/Altınova, Turkey

Across the Gulf of Izmit

Part of the Istanbul-Izmir expressway

Designers / Engineers

IHI Corporation

COWI (Consulting engineers)

Dissing+Weitling (Architects)

Dr William Brown (preliminary design)


Suspension bridge

1,550m main span

2,682m total length

Main contractors



Began 30 March 2013

Open 1 July 2016

Longer bridge spans

Bill Brown had been constantly refining his bridge deck designs following his breakthrough innovation in 1960 of the streamlined box girder for the Severn Bridge. In the 1990s he was focussing on designs that would increase the distance that could be spanned. He carefully considered the aerodynamics with the aid of his own wind tunnel and the latest computer software, but it was his vast bridge engineering experience and creative mind that forged the design concepts. The preliminary design for Izmit was presented with visualisations.

The Turkish road network would be significantly developed around the bridge and two decades later Turkey would have a significant improvement in its connectivity between Istanbul and Izmir, east of the Sea of Marmara.

Long-span bridges in Turkey