Chelonia Limited Cetacean Monitoring Systems 

Collisions model 

Collisions between fast vessels and large cetaceans have emerged as a problem since speeds above 14 knots became common. The free program Collision.exe (325 KB) provides a simple 2 dimensional model of maximum possible collision rates based on vessel size and track lengths, plus whale size, population density and mean surface time.
The basis of the model is: Assume:
Specify or measure:
Then: The whale as a horizontal linear target at random orientation to the ferry's line of travel will present an average 'target size' of 0.64 * whale's length. The whale could be viewed as a point and half the 'target size' of the whale can then be added to both sides of the 'damaging width' of the ferry to give a 'collision strip width' of W + 1.27L. From the length of the ferry transect a 'collision area' can then be derived  (W+ 1.27L)*D/1000 sq km. With the number of transects per year and the density of whales at risk this gives: Annual collisions = (W + 0.64L)*D/1000*Y*T*P Sources of ErrorErrors in estimating L, T, W and P could be significant, as could errors in the assumptions above:

