| Mount Bolu Tunnel | |
| Location: | Mount Bolu |
| Coordinates: | 40.746°N 31.4552°W |
| Start: | Kaynaşlı, Düzce |
| End: | Yumrukaya, Bolu |
| Startwork: | 1993 |
| Operator: | General Directorate of Highways |
| Traffic: | automotive |
| Length: | 3014m (9,888feet) (east bound) 3125m (10,253feet) (west bound) |
| Lanes: | 2 x 3 |
| Speed: | 70km/h |
| Hielevation: | 860m (2,820feet) |
| Lowelevation: | 810m (2,660feet) |
| Width: | 2 x 17m (56feet) |
| Grade: | 1,7% |
Mount Bolu Tunnel (Turkish: Bolu Dağı Tüneli) is a 3.1adj=midNaNadj=mid highway tunnel constructed through the Bolu Mountain in Turkey between Kaynaşlı, Düzce and Yumrukaya, Bolu.
The tunnel is part of the Gümüşova-Gerede Highway
O-4 / E80 within the Trans-European Motorway project, which was carried out by the Turkish Bayındır and Italian Astaldi joint venture since April 16, 1993. The total cost of the tunnel is about US$300 million. It has twin 17adj=midNaNadj=mid bores carrying three lanes of traffic in each direction.The tunnel crosses the North Anatolian Fault. The November 12, 1999 Düzce earthquake (MW=7.2) caused substantial damage to the tunnel and viaducts, which were under construction at the time of the earthquake.
On September 4, 2005 the excavation of the tunnel in the Istanbul-Ankara direction was finished. The excavation for the tunnel in the Ankara-Istanbul direction was completed by the beginning of August 2005.
The Istanbul-Ankara direction (3014m (9,888feet)) was opened to traffic on January 23, 2007 by the Turkish Prime Minister Recep Tayyip Erdoğan and Italian Prime Minister Romano Prodi. Four months following the initial opening, on May 7, the Ankara-Istanbul direction (3125m (10,253feet)) became operational.
Speed in the tunnel is limited to 70km/h. Dangerous goods carriers are not permitted to use the tunnel.