DrifTec is a collision risk analysis software developed by Tecnitas SAS. It is used to estimate, for a given number of ships navigating on several shipping lanes (routes), the risk of drifting towards a “target” area, as a function of wind, swell, ship type, etc. The software uses the following input data:

- discrete description of the shipping lanes in proximity to the target area, using one or several straight segments for each lane,
- description of the target area (coordinates, size, angular opening),
- discrete data defining the local wind rose (direction/intensity/probability),
- type of ships navigating on each shipping lane, with corresponding drifting coefficients,
- marine traffic data for each of the shipping lanes, and for each type of ship,
- estimated average tug intervention time (delay).

The output provides the risk of collision with the target before tugs intervention, by route and by ship type.

**Route discretization and calculation approach**

The above scheme presents the approach used for meshing the shipping routes (routes → segments → mesh elements) and the definition of the target area (radius, angular opening). The software computes, for each mesh element, the drifting cone towards the target. The probability of a collision is computed as a function of the probability of a having an adverse wind towards the target which is sufficiently strong for the ship to reach the target before tugs can interfere. To this end, critical wind speeds are computed for each route mesh element and for each ship type (note that drifting coefficients are specific to each type of ship).

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