Narrow channels and traffic separation schemes

A narrow channel and a traffic separation scheme are different things. One relates navigation to a narrow channel or fairway; the other organises traffic in a scheme adopted by the Organization. Both can make a duty not to impede relevant, but with different subjects and conditions. The illustration separates fictional geometries without depths, positions or tracks. Identifying space, scheme status and vessel capabilities comes before any conclusion about an encounter. A charted route does not automatically have the legal status of an IMO-adopted scheme.

Rule 9(a) requires keeping as near as safe and practicable to the outer limit lying on the vessel’s starboard side. Safe and practicable matter: the rule does not prescribe touching the edge or ignoring draught. Under paragraph (b), a vessel under 20 metres or a sailing vessel must not impede one that can safely navigate only within the channel. This is not simply “larger beats smaller”; inability to navigate safely outside the channel is a specific condition. Both vessel status and the actual navigable space belong in the analysis.