Its route covers the municipalities of Basauri and Etxebarri, the city of Bilbao and the left bank of the Nervión river.

The first phase of the line opened on 13 April 2002, with five stations; Gurutzeta/Cruces, Ansio, Barakaldo, Bagatza and Urbinaga.

[4] The Mamariga shuttle, a funicular railway which serves as an access to Santurtzi station, opened in late 2010.

[5] In 2011, the line was extended southwards with two new stations, Ariz opening on 28 February[6] and Basauri on 11 November.

Its opening marked the completion of the line as originally planned.