Beginning at Mersin, on the Mediterranean Sea, the railway corridor stretches inland to Gaziantep, via Yenice, Adana and Osmaniye.
On the eastern side of the railway corridor, the 105 year-old Ayran Tunnel is the only crossing of the Nur Mountains and is a major route connecting Turkey's interior mines to its Mediterranean ports.
In terms of passenger rail, the Mersin-Adana railway is by far the busiest in the region with around 29 daily round-trips between Mersin and Adana at around 45-minute intervals.
[5] Istanbul and Karaman have already been connected with high-speed rail since early 2022 and when the remaining routes are finished, TCDD Taşımacılık will provide direct YHT service from Edirne to Gaziantep, a distance of 1,065 km (662 mi).
The Turkish government greatly neglected its railways from the 1950s onward and the route, which was designed to accommodate steam locomotives, was never upgraded or improved in any significant way, apart from the section between Mersin and Adana which was double-tracked in the 1990s.
The 63 km (39 mi) long section between Toprakkale and Fevzipaşa was electrified with 25 kV AC overhead wire in 1994.
After exiting the tunnel within the Sağlık Plain, the bypass will continue for 3 km (1.9 mi) until joining the Fevzipaşa-Kurtalan railway at Nurdağı.
Just north of Nurdağı station, the Nurdağı-Başpınar railway will branch off with a more direct route to Gaziantep, through the Sof Mountains.