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The Danish Straits are an important part of the route from the North Sea to the Baltic Sea for ships. The waters around Denmark have a number of well established passages but careful planning is required when navigating them because of traffic levels, narrow routes, local regulations and diverse navigational conditions.

Being aware of the key requirements before entering Danish waters can help ship operators prepare their crews for a smoother and safer passage. Here are five important things to think about when planning a transit of the Danish Straits.

Why Are the Danish Straits Important for Commercial Shipping?

The Great Belt and the Sound are among the main routes for commercial vessels passing through Danish waters. By sea, these routes are very busy. The Danish Maritime Authority reports that every year more than 26,000 ships pass through the Great Belt and about 35,000 ships pass through the Sound.

For the operators this means that the choice of route through the Danish Straits is not just a question of choosing the shortest passage. The most suitable route can be affected by the dimensions and draft of the vessel, its cargo, applicable requirements and traffic conditions.

What Should Operators Know About Traffic and Reporting Requirements?

Traffic management is an important part of navigating Danish waters. The Great Belt and the Sound have established vessel traffic services and compulsory ship reporting systems, called BELTREP and SOUNDREP, respectively.

 Vessels with such systems must provide the required information when operating in the relevant reporting areas. SOUNDREP applies to ships of 300 gross tonnage and above in its operational area. Accordingly, ship operators are to ensure that the bridge team is aware of the reporting requirements for the transits. Being prepared with the right information can make communicating with the relevant VTS authority easier.

When Is Pilotage Recommended or Required?

Pilotage is another important consideration in planning a voyage through the Danish Straits. Danish rules specify the conditions under which some ships are to be piloted. These include ships carrying oil, chemicals or gases, ships with more than 5,000 tonnes of bunker oil onboard and ships carrying highly radioactive materials. There are also IMO recommendations concerning pilotage for certain transits. For example, DanPilot says that the IMO recommends the use of pilots for vessels with a draft of 11 meters or more transiting the Great Belt. There are also particular recommendations for some tankers and other vessels transiting the Sound.

Pilotage requirements can depend on vessel type, cargo, draft and route. Operators should check the current regulations well in advance of departure rather than relying on general assumptions.

How Do Vessel Size and Draft Affect Route Planning?

Vessel size can have a large impact on transit planning. The Danish waters include narrow passages, designated traffic routes and areas where the available depth may influence the choice of route. DanPilot currently lists multiple transit routes through Great Belt and Sound by vessel draft. For example, its normal Great Belt transit information shows a maximum draft of 15 meters for one route, but its listed Sound routes are of lower draft limits.

Hence the special importance of accurate information on the vessel. When planning the voyage, operators should take into account the actual draught of the vessel, the expected speed, cargo, manoeuvring characteristics and any other relevant limitations. What works for one vessel may not work for another vessel. Planning ahead gives operators and masters the opportunity to spot possible constraints and to plan for appropriate support where required.

Why Is Voyage Preparation Important in Danish Waters?

Good preparation is especially useful in areas with high commercial traffic. The Danish Maritime Authority says that in Danish waters traffic separation systems have been developed to help manage ship movements and to reduce the risk of dangerous encounters. Ship operators should prepare by reviewing current navigational information, checking reporting requirements, confirming pilotage arrangements where applicable, and ensuring the bridge team is familiar with the planned route.

Weather, currents, traffic density, vessel characteristics and operational conditions may also influence the practical conduct of a voyage. Knowing about these things helps the crew make decisions during the transit.

What Should Ship Operators Check Before Transit?

Operators may find it useful to have a clear pre-transit checklist to work through before a vessel enters Danish waters. This may include verification of:

• Planned route and applicable navigation requirements
• Draft of the vessel and other dimensions of interest
• Pilotage requirements or recommendations
• Reporting Responsibilities for BELTREP or SOUNDREP
• Current navigation and safety information
• VTS communication protocol
• Requirements related to cargo
• Arrangements for pilot boarding, if applicable

The Danish Maritime Authority publishes current maritime regulations, notices and guidance for Danish waters. Pilotage providers publish information about routes and pilotage requirements. Regulatory changes are also worth a look before each voyage. In May 2026, the IMO adopted amendments to BELTREP and SOUNDREP which will in future include the reporting of relevant insurance certificate information when the amendments enter into force.

Preparing for a Safe and Efficient Danish Straits Transit

The Danish Straits are well-established shipping lanes, but transit can be successful not only by following a charted passage. When preparing for a voyage in Danish waters, the ship operators shall take into account vessel characteristics, traffic management, reporting obligations, pilotage and current information on navigation. Planning ahead before departure can help operators liaise better with the vessel’s master and bridge team, VTS authorities and pilotage providers. For vessels that operate in the region on a regular basis, keeping abreast of current Danish maritime requirements is an important part of responsible voyage planning. For professional maritime operations and services in Denmark, visit North Sea Agency.