Most of it provides one driving lane per direction and it is planned to be superseded or replaced in all sections by either motorways, or expressways.

[4] Road I-1 runs through the centre of Mezdra and then it bypasses Botevgrad before making connection with Hemus motorway (A2).

Through the Balkan Mountains road I-1 runs parallel to Hemus motorway and climbs via the Vitinya Pass.

Close to Pernik, at Dragichevo interchange, road I-1 merges into Struma motorway (A3) to the village of Dolna Dikanya.

After bypassing Sandanski, between Melnik interchange and the village of Marino pole, road I-1 was demolished and replaced by a section of Struma motorway, which entered in service in 2015.