The Orhangazi Tunnel within the Gebze-Orhangazi-İzmir Highway Project was opened to traffic a short time ago. The highway will decrease air-pollution resulted due to the stop-and-go in traffic during the transitions between Orhangazi and Yalova, and decrease the traffic jam with time spent in traffic. The Samanlı mountain consisting an important part of the highway was digged and operationalized in 2 years which can be accepted as a record in terms of time. The Orhangazi Tunnel is now the longest operated tunnel in Turkey with its 3 thousand 590 m. length. The tunnel including the earthworks and digs which are nearly 95 thousand truck excavations, a three-lane and double-tube tunnel with a 5,50 m. gabarite height, costed in total 118 million dollars.