The Gibraltar tunnel, the old dream of a link between Europe and Africa

Summary

Linking Europe and Africa across the Strait of Gibraltar: the idea has fascinated engineers, politicians and maritime geostrategy enthusiasts for more than a century.

Linking Europe and Africa across the Strait of Gibraltar: the idea has fascinated engineers, politicians and maritime geostrategy enthusiasts for more than a century. It dates back to 1869, when the French engineer Laurent de Villedemil already imagined an undersea tunnel linking Spain to Morocco. Since then, many variants have emerged: a 41 km rail tunnel proposed by Jean-Baptiste Berlier in 1895, large steel tubes immersed and anchored to the seabed designed by Garcia Faria, or a twin tunnel imagined in 1908 by Carlos Ibáñez de Ibero. Spain even pushed its investigations as far as drilling to a depth of 400 metres in the 1920s, between Tarifa and Tangier.

It was not until the late 1970s that the project took an official turn. In 1979, King Hassan II of Morocco and King Juan Carlos I of Spain signed an agreement marking their will to link the two countries through shared infrastructure. This cooperation took shape in 1981 with the creation of two dedicated public companies: SECEGSA in Spain and SNED in Morocco, tasked with studying the feasibility of a “fixed Europe-Africa link”. During the 1980s and 1990s, several geological and technical studies were carried out, supported by funds from both states and international partners. These two bodies remain at the heart of the study effort today: on the Spanish side, SECEGSA works notably with the public engineering firm INECO, while on the Moroccan side SNED works under the aegis of the Ministry of Equipment and Water. At the time, the preferred option was rather a giant bridge over the strait. In the mid-1990s, a Californian engineering firm, together with Professor T.Y. Lin, proposed a pharaonic combined suspension bridge: several spans of 5 km each supported by pylons more than 300 metres high, for a total length of about 14 km. The announced cost then exceeded 15 billion dollars, a colossal sum for the time. Other futuristic visions emerged, such as that of architect Eugene Tsui, who imagined in 2004 a hybrid floating structure (a bridge-tunnel on an artificial island). Nevertheless, the feasibility of these mega-bridges was judged too uncertain, given the depth of the water (up to 300 metres) and the strong currents in this strategic passage from the Mediterranean to the Atlantic. As early as 1996, the Moroccan and Spanish authorities turned towards a more realistic solution, an undersea rail tunnel, on the model of the Channel Tunnel inaugurated a few years earlier.

Fostering trade

This project to cross the Strait of Gibraltar comes with an ambitious philosophy: bringing together two continents separated by only 14 km of water at the narrowest point. Economically and logistically, the expected benefits are major. A fixed link would smooth the flow of goods between Europe and North Africa, bypassing the saturated sea route: nearly 100,000 ships pass through the strait every year and its traffic is already congested. With a rail tunnel, more than 13 million tonnes of freight a year are expected to cross the strait in the medium term, along with 12.8 million passengers a year. Rail shuttles could carry cars and lorries between the two shores in under an hour, compared with several hours by ferry today. For Morocco, such a link would boost Tangier’s role as an African logistics hub, connected to European networks. On the Spanish side, Andalusia would benefit from greater openness to the markets of the Maghreb and beyond. The European Union itself sees this corridor as a driver of growth and regional cooperation within its strategy of connectivity with its southern neighbourhood. The geopolitical and cultural repercussions would be just as significant. Symbolically, building a “bridge” between Africa and Europe sends a message of union and partnership, in the spirit of the Channel Tunnel which, in 1994, brought the United Kingdom closer to the European continent. Here, the structure would transcend a maritime frontier that was once that of the mythical “Pillars of Hercules”. Such a project would facilitate tourism (taking the train from Tangier to Madrid or Paris on a continuous route) and business travel. Strategically, the stability and development of the strait’s regions could be consolidated by this direct connection. Some voices point out that North Africa, like Morocco, is experiencing notable economic growth but also migration and security challenges: strengthening ties with Europe through infrastructure of this kind could encourage a better sharing of opportunities and responsibilities alike.

The undersea tunnel: the preferred alternative

Engineers ruled out a road tunnel for cars and lorries because of the ventilation and safety problems linked to exhaust gases. The principle now adopted is that of a rail tunnel, on the model of the Eurotunnel built between France and England: high-speed trains for passengers and freight, and shuttles for vehicles. The route under study would link Punta de Tarifa, in southern Spain in the province of Cádiz, to Cape Malabata, in the Tangier region of Morocco, a distance of 42 km between the terminal stations. According to the official Moroccan documentation of the Ministry of Equipment and Water and the Société nationale d’étude du détroit (SNED), the tunnel would stretch over 38.7 km, 27.7 km of them under the sea, with water depths of up to 300 metres. The same document, however, gives a maximum depth for the structure of up to 475 metres, with at least 175 metres of rock between the tunnel vault and the seabed at the deepest point, and a gradient of 30%, which would make it one of the deepest tunnels ever built. By comparison, the Channel Tunnel lies 115 metres below the seabed, while the future Norwegian Rogfast tunnel will descend to 392 metres beneath the North Sea. SNED describes a twin-tube rail configuration (two single-track galleries) complemented by a pressurised service and safety gallery, linked by cross-passages every 340 metres, as well as a secure stopping area in the middle of the structure. According to experts, building such a structure would require at least 15 years of work, mobilising giant tunnel-boring machines capable of drilling through complex geology. The Strait of Gibraltar lies at the junction of the African and Eurasian tectonic plates, with a seismic fault (the Azores-Gibraltar fault) and areas of unstable clays detected beneath the seabed. The report also highlights a demanding physical environment (intense currents, strong winds, geotechnical variability) and the need to integrate the seismic dimension from the design stage. These technical obstacles call for in-depth studies: as early as 2008, drilling and seismic surveys revealed problematic geological pockets, even suggesting the excavation of an exploratory test tunnel estimated at 1 billion dollars over 8 years.

Work to start by the end of 2030?

After a long pause from the late 2000s, the rail tunnel study was relaunched in 2023 thanks to warmer relations between Madrid and Rabat, sealed by a joint declaration of the transport ministers. Spain allocated new study budgets (1.6 million euros in 2023), with the support of the European Union, which included the project in its strategic recovery plans. At the end of 2024, the Spanish public company SECEGSA commissioned the subsidiary of the German group Herrenknecht (world leader in tunnel-boring machines) to carry out a six-month technical feasibility study. At the same time, seismic sensors were deployed on the floor of the strait to monitor tectonic activity during the studies. The aim is to determine the optimal construction methods for crossing the Camarinal Sill, the shallowest underwater zone of the strait (about 300 metres deep), where the tunnel would pass. On the Moroccan side, the project was relaunched in February 2023, at the 12th Morocco–Spain High-Level Meeting, with the implementation of a joint work plan providing for onshore and offshore investigations, and technical and socio-economic studies including environmental, geostrategic and legal components. SNED’s documents already present the results of numerous investigations: detailed bathymetric surveys, nearly 10,000 km of seismic reflection profiles (mapping of the subsoil using acoustic waves and analysis of the echoes), about 5,000 km of side-scan sonar profiles, underwater inspections and drilling campaigns.

If the ongoing studies prove conclusive, work could start by the end of the decade with the boring, first, of a service tunnel and a first single-track rail gallery, then, in a second phase, a second tube so that the link can operate on two separate tracks, one for each direction. Ultimately, the infrastructure would thus consist of two parallel rail tunnels, complemented by a central emergency gallery, the whole linked by cross-passages at regular intervals. According to projections, the tunnel’s capacity could reach 50 million passengers a year, reflecting the considerable scale of the project.

Between utopia and reality: a dream under way

Long regarded as a perennial pipe dream, the Gibraltar tunnel project is moving from myth to a pre-concrete stage, even though great uncertainties still hang over its financing and profitability. The exact cost of the structure is still not very clear, but recent estimates put it at more than 15 billion euros. That is far more than the 4 to 5 billion euros initially envisaged in the 2000s. This colossal budget would have to be shared between Spain, Morocco and possible international contributors (the European Union, development banks, Arab funds). Beyond the cost, the tunnel’s economic viability will have to be demonstrated: will the revenue from rail tolls and traffic be enough to pay off the structure? The example of the Channel Tunnel, which suffered heavy financial losses in its early years, is often cited by sceptics. Moreover, the sensitive migration context between Africa and Europe raises questions of security and control at the future cross-border crossings. In the official Moroccan-Spanish roadmap, the assessment of socio-economic impact is explicitly listed among the expected deliverables, alongside the environmental, geostrategic and legal assessments, conditioning the move from a preliminary design to a construction decision. The project’s promoters display cautious optimism. Technological advances in civil engineering and underwater works make conceivable what once belonged to utopia. The combination of renewed political will and growing strategic interest also works in the project’s favour. If work began, as has been mentioned, in the 2030s, the first Europe-Africa transcontinental tunnel could see the light of day around 2040, according to the most favourable timetable. By boarding a high-speed train in Tangier, it would then be possible to set foot on Andalusian soil in less than half an hour, fulfilling the age-old vision of a “bridge” between continents. To date, however, no date has yet been set for the start of work: the priority remains the consolidation of the studies, notably the exploration of underground structures and, where appropriate, the construction of an exploratory gallery intended to reduce uncertainties and update costs before an overall budget is drawn up. To be continued…

Bibliographic information

Type

Article

Date

March 2026

Author

Lorenzo Specty

Published in

Marine & Océans, March 2026, “Grands travaux” section, pp. 76-79

Study Centres

ILEB · SMGM

Original language

French

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