Restricted Visibility

Any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or another similar cause.

In the collision regulations this is a qualitative condition rather than one fixed distance. Darkness alone is not restricted visibility, although it affects what can be seen, and obstruction by a vessel’s own structure is a blind sector rather than the meteorological condition meant by the term.

Vessels operating in or near restricted visibility must apply the relevant rules, including effective lookout, safe speed, engines ready for immediate manoeuvre where required, sound signals and careful use of radar. AIS and electronic charts do not replace detection or collision assessment.