Under Rule 19, a vessel that detects by radar alone another vessel forward of the beam and cannot avoid a close-quarters situation shall, so far as possible:

Explanation

Rule 19(d) says a vessel detecting another by radar alone must determine if a close-quarters situation/risk is developing and take avoiding action in ample time; if that action is a course change, she should avoid altering to port for a vessel forward of the beam (except one being overtaken), and avoid altering toward a vessel abeam or abaft the beam.

Authority: Navigation Rules, Rule 19(d)