The Ballonti Route is the alternative to the A-8 for mobility and accessibility amongst the municipalities of the Left Bank. It takes much of the traffic that would otherwise use the N-634 road and the A-8 motorway on the one hand, and the estuary road (BI-3739) on the other. The El Carmen-Galindo stretch runs through the municipality of Sestao.
The project consisted of excavating a 230 m. - long tunnel. 12.850 m3 was excavated by tunnelling and 18.900 m3 by trench excavation.
The Artxanda Tunnels are a varied road system with three routes forming a triangle. Two of them, La Salve-Txorierri and Ugasko-Txorierri (toll fee) join the centre of Bilbao to Dual carriageway BI-637 (Txorierri corridor) speeding up access to the airport of Bilbao and the municipal districts on the right hand bank of the Nervión River. The third, Ugasko-La Salve, is a by-pass to the city of Bilbao between the quarters of Begoñ
The construction of this road facilitates the connection of the roads N-634 and BI-632 and reduces traffic on roads BI-3333 and BI-3323 and in the town of Durango caused by vehicles using the Iurreta-Kanpazar-Gipuzkoa route through BI-632.
The work consists in the construction of a new road parallel to the existing one between the links of Padura and Aranguren, 5,800 m. long, over the partially executed excavations with the first road to convert it into a Dual carriageway. In addition, the Aranguren link is remodelled to adapt it to the situation of double road and the links of Padura, Artxube and southern to Zalla are made.