The high-speed connection with Asturias, via the Pajares Bypass, is one of the most complex engineering works in Europe and the world: 80% of its 50 km route goes through 12 tunnels that, together with its 10 viaducts, cross the Cantabrian Mountains and the considerable difference in altitude between Asturias and the Meseta (500 m).

The Pajares tunnel (25 km) is the seventh longest railway tunnel in Europe and its execution has been an unprecedented challenge: Up to 5,000 people and five tunnel boring machines worked at the same time on the construction of this infrastructure, which runs at a depth of 1 km.

The electrified double track has the most advanced railway signaling system (ERTMS level 2) and can reach a maximum speed of 275 km/h.

Its route cuts the length of the current section through the Puerto de Pajares - which dates back to the 19th century - by 37 km and has a lower altitude and slope, which facilitates winter maintenance work.

The Pajares Bypass is one of the most versatile railway lines in Spain, as it will be used by passenger trains, running on Iberian gauge and, in the future, on standard gauge, and freight trains. It therefore represents an unprecedented advance in railway connections: Travelers will see their train travel time between Asturias and Madrid reduced by more than an hour. And freight trains will be able to transport up to 15% bigger loads and be longer.

• 4 billion investment
• 50 km long
• 12 tunnels and 10 viaducts
• 5 tunnel boring machines as tall as the Eiffel Tower and weighing 2,000 tons each worked simultaneously on its construction
• It takes between 10 and 15 minutes for the train to pass through the Pajares Tunnel
• The #Pajares twin-bore tunnel is as long as Manhattan Island

During its design, planning and construction phases, environmental protection measures were implemented in this unique natural environment. These measures included environmental restorations and of tunnel mouths; waste management; the use of 3 km of conveyor belts to transport excavation material, significantly reducing heavy truck traffic; the protection of the Huerna River and agreements for the protection of the brown bear.

The Asturias connection gives new impetus to the development of the high-speed rail network in Spain, which exceeds 4,000 km and is now established as the largest in Europe and the second largest in the world.