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Very few people have actually heard of it, and yet this project could profoundly transform the way we travel between Northern Europe and the rest of the continent. It’s called the Fehmarn Belt Tunnel. About 18 kilometers long, it will eventually connect Germany and Denmark under the Baltic Sea, allowing travelers to cross the strait in just seven minutes by train. Originally scheduled for 2029, the project now aims to open starting in 2031, following a delay caused by the complexity of its construction.
Today, Europe is fairly well connected by rail. The major capitals are linked, particularly thanks to high-speed lines that are increasingly shaping the landscape and crossing borders. But there are still a few geographical barriers that slow down traffic. One of the most notable is located between Hamburg and Copenhagen.
If you take a train today from Paris to Copenhagen, the journey proceeds without any major difficulties as far as Hamburg. But between Germany and Denmark lies a strait about 18 kilometers: the Fehmarn Belt. On a map, this strait may seem almost insignificant. In reality, it has long been a strategic bottleneck which hinders trade between Scandinavia and Central Europe. It is precisely this barrier that the Fehmarn Belt Tunnel aims to eliminate.
The Fehmarn Belt Tunnel will connect Germany and Denmark under the Baltic Sea via an underwater tunnel approximately 18 km, the longest of its kind in the world.
This project in 10 billion euros, funded primarily by Denmark, will connect From Hamburg to Copenhagen in about 2 hours and 30 minutes and to cross the strait in 7 minutes by train, strengthening the European rail corridor Scandinavia–Mediterranean.
But the construction project is also causing environmental controversies, with some NGOs warning about the impacts of seabed dredging and the risks to biodiversity in the Baltic Sea.
Between Hamburg and Copenhagen lies a relatively short strait: the Fehmarn Belt. It separates the German island of Fehmarn on the Danish island of Lolland.
But despite its narrow width, this passage has long been a major logistical obstacle along the route connecting Scandinavia to Central Europe.
This bottleneck slows down trains, complicates the flow of goods, and limits the smooth flow of travel between the north and south of the continent.
For a long time, there was a rather unusual way to cross this strait. Trains would drive directly onto a ferry, which would cross the Baltic Sea in about 40 minutes before continuing on its route on the Danish side.
An ingenious—but also fragile—system. The crossing depended heavily on the weather, which dictated the schedules and could disrupt traffic in the event of inclement weather.
Crossing the Baltic Sea to connect Hamburg and Copenhagen: a real challenge
This ferry system has died in 2019. Since then, trains have had to bypass the strait by traveling through northern Denmark. This detour adds about 160 kilometers to the journey. As a result, the trip from Hamburg to Copenhagen now takes nearly five hours, even though the two cities are separated only by less than 300 kilometers as the crow flies.
In other words, the last major rail barrier between Scandinavia and Central Europe is still in place.
Because this section is located along a major economic corridor: the Scandinavia-Mediterranean Corridor. If you draw a nearly vertical line between Stockholm and Milan, you get one of the continent’s major economic corridors. This corridor is part of the TEN-T network, the European program designed to connect and modernize transportation infrastructure.
The goal is simple: to enable Europe to function as a cohesive economic area, free of technical barriers and geographical obstacles. And that is precisely what the Fehmarn Belt Tunnel aims to achieve.
The Fehmarn Belt Tunnel will be approximately 18 kilometers. It will host two electrified railroad tracks and a highway with two lanes in each direction. And above all, he will become the world's longest underwater road and rail tunnel.
This is an important distinction: unlike the Channel Tunnel, this one will not be dug deep beneath the sea.
The Channel Tunnel was built using massive tunnel-boring machines that dig through the rock beneath the seabed. The Fehmarn Belt Tunnel takes a completely different approach. Here, engineers are digging a wide trench in the Baltic Sea seabed, then laying the tunnel sections in it before covering them. In other words: instead of boring a tube under the sea, the tunnel is laid directly on the seabed.
The first phase of the project involved dredging the seabed. Specialized vessels sucked up sand and sediment to dig a massive trench under the sea. In total, approximately 15 million cubic meters of sand and clay were extracted. These materials were then reused to extend the shoreline near Lolland, in Denmark, to create new natural and recreational areas.
The tunnel will consist of 89 concrete segments: 79 standard segments and 10 special segments for technical equipment. Each standard segment is approximately 217 meters long, 42 meters wide, and weighs more than 73,000 metric tons.
These giant blocks are manufactured in a massive factory built specifically for the project. Once completed, they are floated like enormous concrete ships and then towed to their final positions. A special platform then slowly lowers them into the trench, about 40 meters below the water’s surface, before securing them together. And it is this submersion phase—which requires precision to within half a centimeter—that has proven more complex than anticipated and led to the postponement of the schedule announced by the Danish project owner.
A method often compared to a giant LEGO set: assembling giant pieces to create a continuous structure 18 kilometers long.
The Fehmarn Belt Tunnel is a natural extension of the network Trans-European Transport Network (TEN-T). This program aims to connect the continent's major economic regions in order to facilitate trade and bridge geographic divides.
Along this north-south axis, Scandinavia remains relatively peripheral despite its political integration into the European Union. Yet Sweden and Finland export large quantities of goods to Germany and Central Europe, particularly wood, steel, and industrial products.
The B1M - © OpenStreetMap contributors
Today, most freight trains between Germany and Sweden travel through the Storebælt Bridge, in the heart of Denmark. However, these freight trains are extremely long and heavy, which creates a bottleneck on the Danish rail network.
With the Fehmarnbelt Tunnel, some of this traffic will be able to take a more direct route. As a result, traffic will flow more smoothly and more capacity will be freed up for passenger trains.
For travelers, the impact could be very tangible. Today, the trip Hamburg – Copenhagen takes about 4:30 to 5:00. With the tunnel, it could drop to about 2 hours and 30 minutes.
A transformation that is changing the very nature of the relationship between the two cities: two and a half hours is a trip that can be made in a single day for a business trip.
This new accessibility could also transform the way people travel around the country. Once you arrive in Copenhagen, it becomes much easier to continue by train to other Danish destinations such as Aarhus, the country's second-largest city.
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A city known for its intimate atmosphere, internationally renowned museums, and vibrant culinary scene. Thanks to the rail network and short distances, it’s easy to explore the region and its natural areas.
In practical terms, who's footing the bill? The Fehmarn Belt Tunnel is financed primarily by the Denmark, which has chosen to finance the project through a public company tasked with managing it. The Danish government guarantees the loans taken out to finance the project, while the infrastructure will be paid off gradually over several decades.
How? Thanks to the road tolls and rail fees paid by tunnel users. This financing model is not unprecedented: it is part of a very long-term approach to infrastructure, in which revenue generated by future traffic is used to repay the investments made today.
It should be noted that while Denmark is financing the tunnel itself, Germany is responsible for the access improvements on the German side, including the modernization of the railroad and road infrastructure in Schleswig-Holstein.
This model is part of a very specific Danish tradition: that of “fixed links.” For several decades, the country has been investing in permanent infrastructure—such as bridges and tunnels—to gradually replace the ferries connecting its islands to the mainland.
Two flagship projects illustrate this strategy:
These projects have profoundly transformed the country’s economic geography. Where people once had to wait for a ferry, travel has become continuous and much faster. The Fehmarn Belt Tunnel is part of this trend: transforming a sea crossing into a permanent connection with continental Europe.
On the one hand, as the European Union seeks to drastically reduce its greenhouse gas emissions, transportation appears to be a major challenge. The sector accounts for nearly one-quarter of European emissions, with road travel accounting for the vast majority.
By strengthening rail connectivity between Northern and Central Europe, the Fehmarn Belt Tunnel could promote a shift in transportation modes toward rail. It won't eliminate trucks or regional flights, but it could reduce their competitive advantage on certain routes.
Source: European Environment Agency
On the other hand, the project has also sparked numerous environmental controversies. The Fehmarnbelt Strait is, in fact, a sensitive marine ecosystem, located in a Baltic Sea Protected Area and home to several species important to local biodiversity.
Among the concerns raised by NGOs and researchers are:
Dredging, in fact, represents the construction project's most significant environmental impact, because sediment dispersion can temporarily disrupt marine ecosystems and benthic habitats.
Some environmental organizations, such as the German NGO NABU, have also criticized the project, arguing that its environmental benefits could be limited, particularly due to the presence of traffic lanes in the tunnel, which will continue to accommodate vehicle traffic.
© FermernAS
In fact, legal challenges have been filed in Germany by local associations and groups opposed to the project, citing, in particular, the risks to biodiversity and the impacts on Natura 2000 sites.
As with any mega-infrastructure project, the issue of profitability is a subject of debate. The business model is based on a simple assumption: Traffic will gradually increase over the coming decades, driven by economic exchanges between Scandinavia and Central Europe.
But some observers remain cautious. In Germany, the Federal Court of Auditors in particular, expressed reservations about the traffic forecasts. If the number of vehicles or trains using the tunnel turned out to be lower than estimated, it could take longer than expected.
Another source of uncertainty is competition from Existing ferry routes between Germany and Denmark, which might adjust their rates to remain competitive.
Added to this is a more political criticism: unlike the Channel Tunnel, which created an entirely new link between two major markets, the Fehmarn Belt upgrades an existing line rather than creating a new one. Its impact will therefore depend largely on how transportation flows evolve over the coming decades.
Ultimately, the Fehmarnbelt Tunnel tells a story that goes far beyond its 18 kilometers of concrete. It is the story of a Europe striving to connect its regions across borders and build a more cohesive rail network across the continent. The project has now entered a decisive phase.
Following the symbolic inauguration of the first section by King Frederik X in 2024, the project has now entered its most spectacular phase: the submersion of the gigantic concrete sections that will form the tunnel. It is precisely this operation—which has proven far more complex than anticipated—that led the project owner to postpone the opening from 2029 to 2031. This additional delay serves as a reminder of just how extraordinary this project is, yet its potential to transform rail connections between continental Europe and Scandinavia remains intact. Stay tuned...
Issue du monde de la communication et des médias, Sophie est Responsable éditoriale chez HOURRAIL ! depuis août 2024. Elle est notamment derrière le contenu éditorial du site ainsi que La Locomissive (de l'inspiration voyage bas carbone et des bons plans, un jeudi sur deux, gratuitement dans ta boîte mail !).
Convaincue que les changements d’habitude passent par la transformation de nos imaginaires, elle s’attache à montrer qu’il est possible de voyager autrement, de manière plus consciente, plus lente et plus joyeuse. Son objectif : rendre le slow travel accessible à toutes et tous, à travers des astuces, des décryptages et surtout, de nouveaux récits.
