The prohibition notice follows an accident on the Great Belt Bridge on January 2, when a Danish State Railways (DSB) passenger train was struck by debris from a passing freight train, killing eight passengers and injuring 16.

Police and accident investigators believe the accident was caused by one or more road trailers not being securely fastened to the type Sdggmrs 'pocket wagons' they were being carried on, with the 'king pin' used to secure them found to be either loose or working loose in transit. Tests carried out on undamaged trailers showed similar issues. Investigators are working on the assumption that the extreme high winds at the time of the accident, which disrupted land and sea transport across much of northwest Europe, may have led the loose trailer to partially obstruct the path of the oncoming passenger train.

Similar 'pocket wagons' are widely used across Europe and rely on the road trailer being mounted to the wagon via a system that replicates the arrangement for road movement, with the pin securing the connection between trailer and lorry tractor unit.

The DB Cargo-operated freight train involved in the incident carries curtain-sided semitrailers loaded with empty beer crates up to 30 times a week and has been operating for several years without any previous problem. DB Cargo announced immediate suspension of the Carlsberg 'beer train' following the accident saying it would not run again until the cause was identified and resolved.

In addition to domestic traffic such as the Carlsberg 'beer train' multiple transit freight trains cross Denmark daily from Germany to Sweden and Norway, some of which utilise pocket wagons.

The Great Belt fixed link between the islands of Zealand and Funen opened in 1998 and comprises two bridges totalling 13.4km and an 8km rail tunnel. The link is the main rail connection between Copenhagen and Jutland and a key artery for freight traffic between Scandinavia and Germany.

Trafikstyrelsen has introduced new operating rules for freight trains using the route, restricting them to 80km/h in strong winds and prohibiting the operation of high-sided freight vehicles if wind speeds exceed 39 knots. All freight operations will be suspended if wind speeds exceed 49 knots.