Finished in 2029: World's longest underwater road and rail tunnel

The Fehmarnbelt Tunnel is a monumental infrastructure project connecting the Danish island of Lolland with Germany's Fehmarn Island beneath the Baltic Sea.

The Fehmarnbelt Tunnel will rely on natural ventilation, with vehicle movement creating a piston effect that continuously pulls fresh air into the tunnel. This system can be enhanced by mechanical ventilation, powered by large ceiling-mounted fans, but will only activate in exceptional circumstances, such as unusually slow traffic or accidents causing a standstill. Photo: femern.com

Once completed in 2029, it will be the world's longest underwater road and rail tunnel, significantly enhancing connectivity between Scandinavia and central Europe.

Recent developments

In February 2025, DEME Group announced a significant milestone: the first two massive tunnel elements, each weighing 73,500 tons, were successfully floated from the skidding beams in Upper Basin A to Lower Basin A. This achievement resulted from meticulous planning and collaboration across multiple teams.

Earlier, in January 2025, the first two completed elements were moved from the tunnel factory in Rødbyhavn, Denmark, into the adjacent basin, marking a pivotal step toward the tunnel's completion.

The Fehmarnbelt Tunnel will connect Denmark and Germany for road and rail traffic. With a travel time of only seven minutes by train and ten minutes by car, this construction project provides a rapid rail connection between Scandinavia and Central Europe. Michael B. Christensen, CEO of Femern A/S

On the German side, preparations for the tunnel portal near Puttgarden are underway. The temporary retaining dyke that previously enclosed the northern part of the tunnel is being removed, allowing for the construction of the tunnel entrance.

Once the Fehmarnbelt Tunnel is completed, the journey between Rødbyhavn and Puttgarden will take just seven minutes by train and 10 minutes by car. Travelers will save about an hour each way compared to the current ferry crossing. Unlike ferries, the Fehmarnbelt Tunnel will operate 24/7, unaffected by wind or weather, ensuring reliable and efficient travel at all times. Photo: femern.com

Project overview

Spanning approximately 18 kilometers, the tunnel will feature a four-lane motorway and a dual-track railway. This direct link is set to drastically reduce travel times; what currently takes over 45 minutes by ferry will be shortened to seven minutes by train and ten minutes by car.

Engineering innovations

The tunnel's construction employs an innovative approach, utilizing 89 precast segments, each weighing 73,500 tons and measuring 217 meters in length.

These segments are constructed on land and will be submerged 40 meters into the Baltic Sea, where they will be joined to form the tunnel. This method minimizes marine disturbance and showcases remarkable engineering prowess.

Expected tolls

The expected tolls for the Fehmarnbelt Tunnel are not yet finalized, but estimates suggest that the cost for a single car trip could be around €50-€60 (approximately $55-$65 USD) one-way. For trucks, the tolls would likely be higher, with estimates around €100-€120 (about $110-$130 USD) for each trip.

These fees are designed to cover the costs of construction and future maintenance of the tunnel. The exact toll rates will be set closer to the tunnel's completion in 2029. A new financial analysis from Femern A/S shows that the repayment period for the Fehmarnbelt project is 32 years.

Projected impact

Beyond improving travel efficiency, the Fehmarnbelt Tunnel is expected to bolster economic ties between Denmark and Germany by facilitating smoother trade and tourism. The project also emphasizes environmental considerations, promoting electric rail transport over air travel to reduce carbon emissions.

Fehmarnbelt Tunnel: Key facts

Project start date The Fehmarnbelt Tunnel project officially commenced in 2020, with preparatory work beginning in Denmark in 2019. The groundbreaking for the tunnel was marked by the start of construction on both the Danish and German sides. The tunnel is expected to be completed by 2029.

Owner and operator The tunnel is owned and operated by the Danish company Femern A/S. This state-owned company is responsible for the financing, construction, and operation of the tunnel. It is a subsidiary of the Danish Ministry of Transport.

Project cost The total cost of the Fehmarnbelt Tunnel is estimated at approximately €7 billion (around $7.7 billion USD). This is one of Europe's largest infrastructure projects, with the cost covering both the construction and the technology involved in building the tunnel and surrounding infrastructure.

Entrepreneurial vision The project is seen as a bold vision for the future of European connectivity. It has been driven by Femern A/S, working with several international contractors, including DEME Group and other engineering firms, who bring extensive experience in large-scale tunneling and offshore construction.

Size and design The tunnel will be an 18-kilometer-long (11-mile) subsea tunnel, making it the longest of its kind in the world. It will consist of a four-lane motorway and a dual-track railway. The tunnel will be built using 89 precast tunnel elements, each weighing 73,500 tons, which will be submerged 40 meters below the Baltic Sea.

Daily and yearly capacity

• Car Traffic: The Fehmarnbelt Tunnel is designed to handle up to 6 million vehicles per year, with an expected 10,000 vehicles crossing daily.

• Rail Traffic: The tunnel will accommodate up to 1 million trains per year, which will enable about 300 trains to pass through daily.
  

Travel time savings:

• The tunnel will drastically reduce travel times between Denmark and Germany. For instance, travel that currently takes more than 45 minutes by ferry will be cut down to 10 minutes by car and 7 minutes by train.

• The tunnel will improve the direct connection between central Europe and Scandinavia.
  

Environmental considerations The Fehmarnbelt Tunnel has been designed with environmental sustainability in mind. It aims to reduce carbon emissions by encouraging the use of electric trains over air travel. The tunnel’s construction process uses environmentally friendly methods, including minimizing disruption to the surrounding marine ecosystem.

Economic and political impact The tunnel is expected to boost trade, tourism, and economic activity between Denmark and Germany. It is anticipated to strengthen the European Union's internal market by providing faster and more efficient transportation across the Baltic region. It will also facilitate greater mobility for both goods and people between the Scandinavian Peninsula and central Europe.

Financing and funding The tunnel project is primarily financed through a public-private partnership (PPP), with the Danish government covering a significant portion of the funding, while private investors and international financial institutions are also involved.

Construction technology The tunnel is being built using a process known as the «Immersed Tunnel Method.» This method involves prefabricating massive tunnel sections on land, then floating them into position and sinking them to the sea bed where they are connected to form the tunnel.

Expected completion date The tunnel is scheduled for completion in 2029, though delays or adjustments in the timeline are always a possibility for such large infrastructure projects.

Economic significance Once completed, the Fehmarnbelt Tunnel is expected to provide a major boost to the economies of both Denmark and Germany by fostering greater trade and travel. It will be part of the Scandinavian-Mediterranean Corridor under the Trans-European Transport Network (TEN-T), strengthening connections between northern and southern Europe.

Political support The tunnel is supported by both the Danish and German governments. It is seen as a flagship project for European integration, improving infrastructure links and fostering stronger economic ties between the two countries.

The Fehmarnbelt Tunnel is not only a critical piece of infrastructure but also a statement of Europe's commitment to advancing sustainable, efficient transportation networks.