It will provide a direct link between northern Germany and Lolland, and from there to the Danish island of Zealand and Copenhagen, becoming the world's longest road and rail tunnel.

[9] The tunnel will replace a heavily travelled ferry service from Rødby and Puttgarden, currently operated by Scandlines, a route known in German as the Vogelfluglinie and in Danish as Fugleflugtslinjen.

[12][13] However, in late 2010, after further feasibility studies, the Danish project planners declared that an immersed tunnel would instead present fewer construction risks and would cost about the same.

[19][20][21] In June 2015, €589 million of EU funding was awarded to Denmark by the European Commission under its Connecting Europe Facility (CEF) scheme, allowing the tunnel project to go ahead.

According to a report released on 30 November 2010 by Femern A/S (a subsidiary of the Danish state-owned Sund & Bælt Holding A/S), the company tasked with designing and planning the link between Denmark and Germany, the corridor for the alignment of the link has now been determined and will be sited in a corridor running east of the ferry ports of Puttgarden and Rødbyhavn.

Additionally, there are ten service elements with a length of 85.7 metres but both wider and higher with a subfloor (basement) to house technical equipment.

The Fehmarn Belt Fixed Link will be financed by state-guaranteed loans, which will be paid by the road and train tolls.

[36] The Schleswig-Holstein State Government announced in 2013 it envisioned the construction of a new Fehmarn Sound link or an upgrade of the current Fehmarn Sound Bridge, since it considered the current bridge – with two lanes for road traffic and one track for rail traffic – to be a bottleneck for the German hinterland connection.

[37] On 3 March 2020, the German Federal Ministry of Transport, the State of Schleswig-Holstein and Deutsche Bahn announced that a new 1.7 km long immersed Fehmarn Sound Tunnel (German: Fehmarnsundtunnel) with four road lanes and two rail tracks, costing approximately 714 million euros, is planned to be built by 2028, while the current bridge will be preserved for pedestrians, cyclists and slow road traffic.

Immersion involves dredging a trench across the seafloor, laying a foundation bed of sand or gravel, and then lowering precast concrete tunnel sections into the excavation and covering it with a protective layer of backfill several metres thick.

On 30 November 2010, Denmark's Femern A/S project manager announced it had selected immersed tunnel design submitted by the Ramboll, Arup, and TEC consortium.

The proposed tunnel would be 17.6 kilometres (10.9 mi) long, 40 metres (130 ft) deep below the surface of the sea and would carry a double-track railway.

An interim agreement was reached in Berlin between the Danish and German authorities on 29 June (represented by their transport ministers) to proceed with the construction of the fixed link.

[17] On 3 September, the ministers of transportation from Denmark and Germany, Carina Christensen and Wolfgang Tiefensee, signed the treaty for the construction of the Fehmarn Belt Fixed Link at a ceremony held in Copenhagen.

According to a report in Der Nordschleswiger, German Traffic Minister Peter Ramsauer decided to reduce planned government investment in new infrastructure in Germany by 25 per cent due to the economic crisis.

It expected that two further years would be spent in court processes, since political objectors had stated they would appeal the authority approval.

[59] DB Netz AG submitted a document to the BMVI detailing variants of the rail connection to the tunnel later that same month.

[60] In March, Femern A/S decided on a Government request to start large preparatory work on land, such as building a factory for concrete tunnel elements,[61] in anticipation of a positive German court decision later.

On 3 March, the German Federal Ministry of Transport, the State of Schleswig-Holstein and Deutsche Bahn announced that a new 1.7 km long immersed Fehmarn Sound Tunnel (German: Fehmarnsundtunnel) with four road lanes and two rail tracks, costing approximately €714 million, is scheduled to be built by 2028, while the current Fehmarn Sound Bridge, which was at risk of becoming a bottleneck, would be preserved for pedestrians, cyclists and slow road traffic.

[38] On 30 April, it was announced by Femern A/S that work was scheduled to begin on 1 January 2021, although it was possible that this would be delayed due to the effects of the COVID-19 pandemic[according to whom?].

Sabine Leidig (Die Linke) commented: "The ecological effects and the burden upon the neighbours of this giant project are much too large, compared to its small utility.

[64] On 18 January, the German Federal Administrative Court in Leipzig imposed a construction freeze on the areas near protected reefs, while it considered legal challenges from a group opposed to the project.

Although times have changed and Europe has been politically and economically reshaped in the meantime, the plans for the Fehmarn Belt Fixed Link have stayed the course.

Despite an offer to help offset the costs of the tunnel by the Danish Cyclists' Federation, it is not planned to include a cycle path.

[75] There have been objections from local people on the German side, both from those fearing the loss of jobs in connection with the present busy ferry traffic, and from environmental protectionists who believed that wildlife would suffer from the construction of the originally conceived bridge.

[76] At the same time, employment connected to construction works would be only short-term, while residents would suffer from the increase in traffic, especially with the planned freight trains which would move from the present Jutland-Great Belt Fixed Link route.

Furthermore, it is claimed that the project might be economically unjustified, as predictions of passenger traffic and goods transport may be overestimated and there is a considerable risk that the investment will not be recouped.

[77] The European Court of Auditors has criticized the planning of the German land connection for letting costs rise uncontrolled.

[78] In 2019, the Bundesrechnungshof commented that "in view of the current traffic forecasts, it is questionable whether the benefits of the project will increase to such an extent that the expected costs are justified under economic aspects".

[80] This made train travel, for example from Stockholm to Brussels, impossible unless one night is spent in a hotel en route.