Precautionary Area
The routeing measure marking where traffic converges or crosses, the conduct it requires, and the COLREG duties that attach inside it.
A precautionary area is a routeing measure marking an area within defined limits where ships must navigate with particular caution and within which the direction of traffic flow may be recommended. It is used where traffic converges, where routes cross, and at the junctions between traffic separation schemes.
Unlike a traffic lane, a precautionary area does not establish a direction of travel that ships must follow. It signals that the ordinary assumptions about traffic flow do not hold, which is why crossing duties bite hardest inside one. In the Straits of Malacca and Singapore the Rules extend the duty to avoid impeding a vessel constrained by her draught, applying COLREG Rule 18(d), at every precautionary area rather than only in the approaches to Raffles Lighthouse.
Seven precautionary areas accompany the eight traffic separation schemes in the Strait of Malacca and Singapore Strait routeing system, including Off Port Klang at One Fathom Bank and Off St John’s Island and Pulau Sambu. The full article will cover the definition and adoption of the measure, the conduct it requires, its relationship to traffic separation schemes and vessel traffic services , and the principal areas in force.