Osman Gazi Bridge

The Osman Gazi Bridge project included the construction of a suspension bridge that forms part of the wider project of the Gebze-Orhangazi-İzmir Motorway. It was built on the Gulf of İzmit, on the easternmost edge of the Sea of Marmara, near the city of İzmit and approximately 50 km southeast of Istanbul. 

The bridge spans a total of 3,300 m and, at the time it was built, it was the sixth-longest suspension bridge in the world (now seventh) in terms of length of the main span, which is 1,550 m long. The bridge is suspended 64 m above sea level, with steel pylons standing at just over 230 m high. Comprising six lanes overall (three going in either direction), its construction has reduced the time to cross the bay from 60 minutes down to a mere six. 

The bridge was built in one of the most earthquake-prone areas in the world and so, to make the bridge as sturdy as possible, the pylons were built on a concrete base which rests on a large bed of gravel, allowing the pylons freedom to slide around in case of severe seismic events.