In 2009, Denmark and Germany together resolved to build a fixed route across the Fehmarnbelt. Alongside a bridge, the possible plans for a tunnel as a crossing option were explored. The final decision was in favour of a tunnel. It is designed to have a length of 18.1 km and to be built as an immersed tunnel. The individual tunnel segments would be manufactured with a rectangular cross section and five cells – each the equivalent of one of the five tunnel tubes – to be floated into position and then lowered to the seabed. Two tunnel tubes will serve the motorway and two for rail transport, while the fifth will be the maintenance and supply tunnel. The segments will have a cross section of 43 × 10 metres. The land-end access will feature connecting ramps with the tunnel portals and several hundred metres of cut-and-cover tunnel. The design for the tunnel relies on ultramodern construction methods and state-of-the-art rules for ventilation and safety. Thanks to the use of the latest methods for manufacturing the individual immersed tube elements, it has proved possible to optimize key parameters such as scheduling, costs and quality.