The Bilbao Metropolitan Southern Bypass was included in the Bizkaia Special Accessibility Plan 2003, approved by the General Assemblies.

The Metropolitan Southern Bypass is an alternative route to the A-8 motorway between the Pobeña Viaduct (Muskiz) the Kortederra zone, on the municipal boundary between Galdakao Amorebieta. It is 36 km long.

In principle, three implementation phases are planned. Phase 1A will run the Santurtzi hub to the Larraskitu hub, by the current Eastern Bypass link road. It will be a total of 16 km long. This first phase is seen as the solution to the existing regular traffic problems in the section of A-8 between Sestao the Bilbao exit at Sabino Arana.

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.

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 natural values at levels 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.