Southern Metropolitan By-Pass - Phase 1b

Phase 1 of the Southern Metropolitan Bypass (VSM) begins in Santurtzi (past the Ugadelbieta service area) and reaches Venta Alta (Arrigorriaga). It is divided into two sub-phases::

  • Phase 1a, between Santurtzi and Larraskitu, began in May 2007 and has been in service since September 2011.
  • Phase 1b: from Peñascal to Venta Alta, started in January 2019, and entered into service in spring 2023.

Phase 1b characteristics

Phase 1b consists of the connection of the Southern Metropolitan Bypass VSM from the Peñascal junction to the AP-68 motorway at Venta Alta. Its implementation fulfils the main objective of Phase 1: The creation of a functional and safe road alternative to the most congested section of the A-8 motorway, which is the section between the Port link and the AP-68 motorway. The general objectives of the Bizkaia Road Plan are also achieved.

  • To optimise the functioning of the Metropolitan Road Network.
  • To respect the environment and nature at a level that ensures that ensure quality of life by reducing congestion times and pollution and noise levels.
  • To reduce the accident rate by eliminating accident hot spots.
  • And to provide a new approach for demand management and traffic control.

The work has been divided into two sections:

The first is Section 9A, Peñascal-Bolintxu. The second is Section 9B, Bolintxu-Venta Alta, which in turn is subdivided into two subsections:

  • Subsection 9B-1, Bolintxu-Venta Alta junction
  • Subsection 9B-2, Seberetxe Tunnel

Section 9a Peñaskal-Bolintxu runs entirely within the municipality of Bilbao. It essentially consists of the trunk road of the Southern Metropolitan Bypass between the adjoining sections 8a, Peñaskal-Larraskitu (already in service), and 9b, Bolintxu-Venta Alta (under construction).

It starts at the Peñascal junction and continues inside the cut-and-cover tunnels built under the area where vehicles leaving the VSM in the direction of the A-8 via the Larraskitu tunnels are charged a fee. From the cut-and-cover tunnels, the excavation and support of the Arnotegi tunnels has been carried out until reaching the Bolintxu valley, where the section ends.

The total length of the section is 2,180 metres. The standard section of the trunk road is two (2) lanes in each direction, each 3.5 metres wide.

The entire section runs virtually inside the Arnotegi tunnels, with the length of the underground carriageway (including the cut-and-cover tunnels already built) being 1,916 and 1,933 metres for each tube.

The execution of the works has generated a total cuttings volume of 513,132 m3, and a total embankment volume of 33,013 m3, which has meant the need for 527,800 m3 of surplus disposal volume. This surplus material has been taken to the Peñaskal surplus site, a former quarry that was partially filled during the works of phase 1a.

In the Bolintxu area, all the work has been influenced by the environmental importance of the surroundings. In this regard, the opening at Bolintxu has been resolved with several anchored micro-pile screens (front and side) to minimise the volume to be dug in this unique spot.


The Arnotegi tunnels have been built with the following geometric characteristics:

  • Standard section: two pavements of 0.75 m + 1.00 m hard shoulder + two lanes of 3.50 m + 2.50 m hard shoulder.
  • eight galleries between tunnels, of which six are pedestrian galleries and two are vehicle galleries with lateral lay-bys.

The total lengths of the tunnels, including cut-and-cover tunnels and tunnels in mines, are 1,916 m for Axis-1 and 1,933 m for Axis-2.


The Peñascal junction connects the VSM with the A-8 motorway and with the Miribilla junction through the Larraskitu tunnels. The works have included its refurbishment, adapting its drainage networks and channelling, as well as its surfacing, signposting, and lighting. All open areas have been finished off with appropriate re-vegetation and environmental restoration work.

Vegetation restoration and landscape integration measures have been carried out on all areas affected by the works. It is particularly worth mentioning the recovery and morphological restoration of the Peñaskal quarry, where the planting of species typical of the oak wood and the restoration of the surrounding waterways with riverside species will make it possible to re-establish the previously existing habitats and ecological connectivity, enhancing the biodiversity of the surroundings.

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