For almost 40 years, we have supported Administrador de Infraestructuras Ferroviarias (ADIF) in the development of one of the world’s largest high-speed rail networks.
As Spain’s network expanded to more than 3,000 kilometers and connected more than 60 cities, ADIF faced a succession of challenges: delivering new high-speed corridors across complex terrain, integrating those corridors into busy urban environments without disrupting existing services, and increasing capacity and interoperability across a growing network. From early planning studies through detailed design and construction supervision, we have helped ADIF address these challenges while supporting its long-term vision for a connected national rail system.
Over four decades, Spain’s high-speed rail (HSR) program has progressed through distinct phases of development. Each stage brought different technical, operational and strategic challenges for ADIF, the Spanish Railway Infrastructure Administrator.
Throughout this evolution, we have contributed across all project stages, including feasibility studies, preliminary design, detailed design and construction supervision. This experience spans new corridor development, urban integration programs and network enhancement projects, supporting ADIF through successive phases of Spain’s HSR expansion.
Map of the Spanish High-Speed Rail network.
Extending high-speed rail across difficult terrain
ADIF’s first challenge was establishing entirely new high-speed corridors capable of operating at speeds of 300 to 350 km/h while crossing Spain’s diverse geography. These new routes required specialized alignment design, major structures and extensive tunneling to connect major metropolitan areas, regional capitals and international gateways. The resulting network includes the South corridor, North-East corridor, South-East/Levante corridor and North-West corridor, which together form the backbone of Spain’s HSR system.
We supported corridor delivery across many of these routes. Our involvement ranged from early route development studies for the 200-kilometer Madrid-Segovia-Valladolid corridor to design and supervision services for the Madrid-Barcelona-French Border corridor, and major engineering packages on the Madrid-Levante, North-West and Basque Y corridors. One example is the Arroyo del Valle Viaduct on the Madrid-Segovia-Valladolid line. Measuring 1,749 meters in length and rising 80 meters above the valley floor, the structure enabled the route to traverse challenging terrain while maintaining the geometric precision required for high-speed operations.
Across Spain’s broader HSR program, we have contributed to the design of more than 185 structures and 45 viaducts, as well as more than 25 HSR tunnels totaling 38 kilometers. These assets helped ADIF extend high-speed rail into regions that would otherwise present significant physical barriers to network development. This phase has contributed to the development of the national HSR network that now stretches more than 3,000 kilometers and connects more than 60 cities across Spain.
Integrating high-speed rail into operating cities
As the national corridor network expanded, ADIF faced a different challenge: bringing high-speed rail into dense urban environments without disrupting critical railway services. Early HSR development relied largely on existing stations. As demand grew, new urban integration projects became necessary to reshape how high-speed rail interacted with cities through new stations, reconfigured track layouts, relocated railway infrastructure and complex underground works.
In Barcelona, we delivered preliminary and detailed design for high-speed and affected commuter rail infrastructure, workshops and station access works, alongside works management responsibilities for the 4.2-kilometer corridor, La Sagrera. This corridor required railway integration within a highly constrained urban environment. Geometric limitations, temporary diversions of operating railway lines and the construction of multi-cut-and-cover tunnels all had to be carefully planned and staged to maintain railway operations during construction.
La Sagrera illustrates the shift in ADIF’s priorities from expanding the national network to integrating that network successfully into major cities. Similar challenges were also addressed in the Girona arrival tunnel, the integration of high-speed rail in Miranda de Ebro and Toledo access works featuring the 918-meter Tajo River viaduct, helping ADIF expand HSR accessibility within urban centers while maintaining continuity of service on existing rail networks.
La Sagrera demonstrates the complexity of bringing high-speed rail into a dense urban environment.
Increasing capacity and interoperability
With a mature national network in place, ADIF’s focus has increasingly shifted toward improving connectivity between corridors, expanding operational flexibility and making better use of existing infrastructure. Rather than constructing entirely new standalone routes, many of today’s projects concentrate on linking corridors and upgrading conventional lines to support faster services and greater interoperability. These programs often involve working within heavily constrained railway environments where operational, geometric and structural limitations are significant.
We supported this strategy through the design of the 11.3-kilometer link between the Madrid-Barcelona and Madrid-Seville corridors and the design of the Madrid-Barcelona to Madrid-Levante connection, which is intended to enable future through-running via the Atocha-Chamartín tunnel. We have also monitored major Mediterranean Corridor connection projects and more recently, supported ADIF’s approach of adapting existing infrastructure for high-speed operation. The 27-kilometer Fuente Santa-Almería upgrade includes alignment improvements, structural and tunnel enhancements, increased load capacity and new 25 kV electrification requirements. Designed to help complete a circular high-speed route in southeastern Spain, it also improves compatibility with the wider HSR network.
Our work continues across key corridors, including the Burgos-Vitoria section, with a 1,850-meter twin-bore tunnel and five viaducts; the Sevilla-Huelva section, with six viaducts and a 3-kilometer conventional line diversion; and the Murcia-Cartagena railway integration program, which includes a new HSR station, three viaducts and 500 meters of cut-and-cover tunnel. Together, these projects are designed to support additional capacity, improved regional access and greater interoperability across Spain’s evolving rail system.
The Arroyo del Valle Viaduct enabled the Madrid-Segovia-Valladolid high-speed line to cross challenging terrain while maintaining high-speed alignment requirements.
Supporting ADIF’s next chapter
Over nearly 40 years, ADIF’s priorities have evolved from building new high-speed corridors, to integrating rail into complex urban environments, and now to strengthening connectivity across a mature network.
Throughout each phase, we have adapted our support to meet the challenges of each stage, from major corridor infrastructure and urban integration to network enhancements. Today, we continue to help shape the long-term evolution of one of the world’s most extensive high-speed rail networks.