The railway was originally constructed to be the northern terminus of the Irmak-Zonguldak railway, since Ereğli had a larger port than Zonguldak; The story of Eregli's incomplete railway (in Turkish) however the cost of bridging the 22 kilometers gap between Armutçuk and Kozlu (the terminus of the Irmak-Zonguldak railway) proved to be too expensive, due to the mountainous terrain.