The Halkalı–Kapıkule railway project covers approximately 231 kilometres between the Istanbul area and the Bulgarian border. It is divided into two main sections: Halkalı–Çerkezköy and Çerkezköy–Kapıkule. Construction of the latter, which is 153 kilometres long, is co-financed by the European Union and Turkey.

According to official project information, the line is designed as a double-track railway for passenger and freight services, with a design speed of up to 200 km/h. These technical specifications apply to the project as a whole and should not automatically be taken as a guaranteed operating speed for every train along the entire route.