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Assessment framework for defining safe distances between shipping lanes and offshore wind farms


This practice shows how safety distances can be calculated between areas used for shipping and offshore wind farms.

Application in MSP:
Type of Issue:
Type of practice:
Stage of MSP cycle:
Coherence with other processes:
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Questions this practice may help answer

  • For what purposes does space need to be reserved for shipping in areas with offshore windfarms?
  • How much space must be reserved around offshore windfarms?

Implementation Context

The approach of securing space for navigation in areas with offshore windfarms was developed in the course of the partial review of the National Water Plan (in the Netherlands) in the light of the designation of the Holland Coast areas and the area north of the Wadden Islands for offshore wind energy. It is applied in the maritime spatial plan of the Netherlands.


  • Identify site-specific width of the areas around offshore windfarms that needs to be reserved for shipping.
  • Contribute to the international debate on maritime safety and maritime spatial planning by taking into account requirements form international regulations (COLREGS, GPSR, UNCLOS) as well as the insights of nautical experts and science.


There are three categories of space:

  • A path, i.e. the areas that the ship can use at all times for manoeuvring and for normal avoidance manoeuvres.
  • A safety margin, i.e.  space that is normally not used by shipping, but used in emergency situations. This areas stretches from the Path to the outer limit of the safety zone extending 500 metres around a windfarm
  • Anchoring areas and approach routes of anchoring areas

Elements of a shipping lane, including safety zones

The unit for calculating the size of the path and the safety margin is the standard ship size (L). The standard ship size is defined as the maximum lengths of 98.5% of ships at a given point in time and space.

The width of the path is calculated as the sum of the following elements:

  • Passing and overtaking area
  • Avoidance area

The width of each element is a multiple of the standard ship size (L).

The safety margin is different for port and starboard. The width is calculated by accounting for space for the purposes shown in the figure below, if applicable.

Assessment criteria

The approach was developed in consultation with shipping stakeholders.

Main Outputs / Results

A methodology of identifying site-specific width of space required for navigation next to offshore windfarms.


The methodology can be taken up by other countries for reserving space for shipping in areas used for offshore windfarms.

Contact Person

Joris Brouwers
Specialist Shipping
Rijkswaterstaat (joris[dot]brouwers[at]rws[dot]nl)

Responsible Entity

The Ministry of Infrastructure and the Environment and the Ministry of Economic Affairs of the Netherlands