Collision Course

A relative approach on which two vessels will collide if neither changes its movement.

A steady bearing accompanied by decreasing range is a classic indication that another vessel may be on a collision course. The bearing may be observed visually or by suitable instruments, but small changes can be difficult to detect and uncertainty increases at long range or in poor conditions.

Risk should be assessed early using all available information and rechecked as the situation develops. Even when the bearing changes, close-quarters risk may remain, particularly with a large vessel, a nearby target or an alteration of course by either vessel.