High Speed Lines

Leon - Asturias high speed line


A way of making Europe.

The following has been co-funded in the 2000-2006 period:

  • By the European Regional Development Fund (ERDF) through the Castile and Leon Operational Programme and the Integrated Operational Programme of Asturias, the railroad bed works of the Pajares Tunnel, with subsidies which amount to 284.0 and 107,9 million Euros, respectively.
  • By the TETN (Trans European Transport Networks) subsidies, the studies and projects, with subsidies amounting to 3.2 million Euros.

The following will be co-funded in the 2007 - 2013 period:

  • By the Cohesion Fund within the Cohesion Fund-ERDF Operational Programme, the railroad bed works of the La Robla-Pajares tunnel subsection and Pajares - Pola de Lena tunnels subsection, as well as the supply and assembly of the track and installations estimated at 388.9 million Euros

(Information at 31 March 2010)


Inside of the tunnel, site 3

This work will make it possible to link up Leon and Asturias by a high speed line which will hold both passenger and cargo trains and is included, due to its social and economic significance, within the 2005-2020 Strategic Infrastructures and Transport Plan (PEIT) of the Ministry of Public Works. 


For a long time, the Cantabrian Mountain range was an almost impassable frontier between the plateau and the north of the Spanish peninsula, and it has historically been a natural barrier for communications between the Principality of Asturias and the Castile and Leon plateau. Opening a railway crossing to and from Asturias became a priority objective during the second half of the 19th century.

120 years have passed since the opening of the Pajares Pass railway, on 15 August 1884, by King Alfonso XII and Queen María Cristina, but the route continues practically the same, among which the continuous success of tunnels stands out as does the winding nature of the route, with some curves of radius less than 300 metres, and the strong gradients.

Current line information, La Robla (Leon) - Pola de Lena (Asturias, Pajares by-pass section)

  • Distance 83 km
  • Average commercial speed 60 km/h
  • Tunnels 79
  • Maximum speed admitted (depending on train type) 105 km/h


The Pajares By-pass constitutes the main artery of the Leon - Asturias high speed line.

It is has a total length of 49.7 kilometres and also covers, in addition to the construction of two tunnels, between Pola de Gordón (Leon)and Telledo (Asturias), the outer sections towards La Robla and Pola de Lena.

The Pajares Tunnels with an approximate length of 25 kilometres, shall be the sixth longest in Europe and the seventh in the world.

Executing these tunnels makes it possible to overcome the natural wall that the mountain massif of the Pajares Pass has historically meant, and guarantees the high speed connection between Madrid, Castile and Leon and Asturias.

The distance between Asturias and Castile and Leon is reduced 34 kilometres compared to the current railway and trains can reach speeds over 250 km/h.

The crossing time of the new by-pass shall be approximately 15 minutes.

Image of the route.


  • La Robla-Pajares Tunnels (9.4 kilometres)
    It completely runs on a two-road railroad bed. It includes the construction of 6 tunnels, 3 viaducts and a Train Overtaking and Parking Post (Puesto de Adelantamiento y Estacionamiento de Trenes) (PAET) in La Robla, which will serve the safety control post in the Pajares Tunnels. In this section the link with the current Leon-Gijón line is made
  • Pajares tunnels (25 kilometres)
  • Pajares-Sotiello tunnels (6.1 kilometres)
    It runs on two single-track railroad beds. It includes the construction of 1 double tunnel and a viaduct which is also double.
  • Sotiello-Campomanes (4.3 kilometres)
    The initial 2.6 km run along two single-track railroad beds and the remaining on a double track. It includes the construction of 2 tunnels, 3 viaducts and the Train Overtaking and Parking Post (Puesto de Adelantamiento y Estacionamiento de Trenes) (PAET) in Campomanes. On the other hand, at the level of Campomanes the construction has been proposed of the Train Overtaking and Parking Post (Puesto de Adelantamiento y Estacionamiento de Trenes) (PAET), which will also serve as safety control post in the Pajares Tunnels.
  • Campomanes-Pola de Lena (4.9 kilometres)
    It completely runs along a double track railroad bed. It comprises the construction of 2 tunnels and 2 viaducts. In this section the link with the current Leon-Gijón line is made.


Due to the geological and morphological complexity of the mountain massif to overcome, the Pajares Tunnels are a great engineering challenge of similar magnitude to the Guadarrama Tunnels, in the Madrid-Segovia-Valladolid high speed line, of which it is the continuation to the north of the Spanish peninsula.

The heterogeneity of the formations to cross during the execution of the works have made it necessary to design a really wide range of structural elements for the cladding of the tunnels, which have been defined based on the geological-geotechnical studies made to draft the works and bearing in mind the experience in great tunnels that ADIF has.

Leon-side tunnel mouth

Basic tunnel information

  • 2 single track tunnels
  • Distance: 25 km
  • Continuous longitudinal gradient of 16.8 thousandths, descending towards Asturias
  • Circular section: 8.5 m diameter
  • Surface area: 52 m2
  • Connecting galleries: every 400 m.
  • Distance between axis of both tracks: 50 metres inside the massif


Exit to emergency gallery

Worker safety is the most important factor when executing tunnels of this magnitude. From this standpoint, tunnel boring machines have meant great progress in tunnel building.

The work safety plans are articulated through the two operational plans: The Health and Safety Plan, and the Self-protection and Emergency Plan (PAE).

To maintain the greatest level of safety, the tunnels will have interconnecting galleries every 40 metres, which will facilitate the maintenance tasks and evacuation if necessary.

During the excavation works, one of every three galleries has been excavated simultaneously with the excavation of the second tube, for the safety of the workers.

There is a preferred stoppage point which serves so that if a train had any incident (breakdown, power supply, etc...) it stops at said point so that travellers can transfer to another train, or be evacuated to the outside of the access gallery to Buiza.

The safety control centres for the Pajares Tunnels are located in La Robla (Leon) and Campomanes (Asturias).

Tunnel boring machines

Tunnel boring machines in the tunnel mouth

Another of the most characteristics elements in this type of works is the use of mechanized excavation machines with full section (T.B.M. "Tunnel Boring Machine").

TBM have been used to execute the Pajares Tunnels.

These machines have the singularity of their use for hard rock but within it there are different technologies according to the manufacturers to give solutions to each land.

Safety is a fundamental advantage and priority in this type of machines since the excavation and support of the tunnel take place within the protective shield. It also makes it possible to place the definitive tunnel cladding. In this way, with the placement of the prefabricated reinforced concrete dowels the tunnel structure is totally finalised on passage of the tunnel boring machine.


During all works, environmental protection actions shall be carried out which aim to procure the greatest possible integration of the railway in the environment.

In this sense, to safeguard the natural riches of the territory which crosses the Pajares By-pass an environmental protection policy has been applied which constitutes one of the strategic aims of the Railway Infrastructure Administrator (Adif).

Projecting and executing a base tunnel with 25 km length involves, from the outset, a clear commitment to the minimization of environmental impact that can be caused by a high speed railway line. The impacts in this case are reduced around the mouths, in the materials resulting from the excavation and the implementation of auxiliary systems of the work.

The most outstanding actions in this environmental aspect have been as follows:

  • Waste control.
  • Transport of materials along a conveyor belt to the Controlled Inert Waste Deposit (DCRI) to avoid heavy truck traffic in the area.
  • Protection of River Huerna according to parameters of the North Hydrographic Confederation.
  • Treatment and protection of hydrological systems: drinking water treatment, waste water purification, industrial installation of water treatment, flood tanks.
  • Reduction of contaminating atmospheric emissions.
  • Environmental regeneration and improvement of the mouth and DCRI area.
  • Environmental Integration and Compensation Measures according to the Environmental Impact Statement: spreading of topsoil, hydroseeding, seeding.
  • Planting of native species: hazels, chestnut trees, oaks, poplars, willows, birches, lime trees, rowans, holly trees (main food of the grouse) and cherry trees (main food of the brown bear).
  • Fauna protection: Collaboration programme between Adif and the Brown Bear Foundation for the tracking, control of conservation and protection measures of the natural habitat where the Iberian brown bear (ursus arctos) lives in the vicinity of the Pajares Tunnels.
  • Geological surveys respectful for the grouse roosting places.


Site 1 La Pola de Gordón (Leon)-Folledo (Leon): East tunnel (9.8 km) and West tunnel (11.0 km)

It is the section between La Pola de Gordón (Leon) and Folledo (Leon). The initial 300 metres are open air. In addition to the main tunnels, the project includes the construction of an intermediate access gallery of 2 km in length. This gallery starts from the town of Folledo and with a 13% gradient it links to the route of the main tunnels and at its kilometre point 7.8. It also includes the execution of the connecting galleries every 400m.

  • Awardee: UTE FCC-ACCIONA
View of the West Tunnel

Site 2 Folledo (Leon)-Viadangos (Leon): East tunnel (4.4 km) and West tunnel (3.2 km).

It includes the central section of the base tunnels between Folledo and Viadangos. To access the tunnels, the project designs the execution of an access gallery 5.5 kilometres in length with a 6.13% gradient. In this section a Preferred Stoppage Point has been executed which consists of connecting the two tunnels with the Buiza access gallery by two galleries.

  • Awardee: UTE Dragados-Obras Subterráneas.

Site 3 Viadangos (Leon)- Telledo (Asturias) East tunnel: a 10.3 km tunnel.

It comprises the execution of the East tunnel, from Telledo (Asturias), where the north mouth is located and Viadangos (Leon), where it links with the tunel executed by Site 2.

This site will build the access viaduct to the tunnels over River Huerna.

  • Awardee: UTE Ferrovial-Agroman-Sacyr-Cavosa

Site 4 Viadangos (Leon)-Telledo (Asturias) West tunnel: a 10.3 km tunnel

It includes execution of the section of the East Tunnel from Telledo (Asturias), where the north mouth is found and Viadangos (Leon), where it links with the tunnel executed by site 2.

This site will build the access viaduct to the tunnels over River Huerna.

  • Awardee: UTE Ferrovial-Agroman-Sacyr-Cavosa

It comprises the execution of the East tunnel, from Telledo (Asturias), where the north mouth is located and Viadangos (Leon), where it links with the tunel executed by Site 2.

It will also build the connecting galleries between the tubes of Site 3 and 4.

  • Awardee UTE Copcisa-Hispánica Constructores-Brues and Fernández Construcciones-Azvi.

Related links

  • Video: La excavación de los Túneles de Pajares
    The video includes the main phases of one of the most significant Spanish engineering works: the construction of the Pajares tunnels, a historical challenge in the improvement of communications in our country. The technicians that participated in the excavation and the construction faced these challenges due to the great complexity of the works.