A routing measure where vessels must navigate with caution due to converging traffic lanes or hazardous conditions.
Quick facts
Regulation
COLREG Rule 10
In practice
COLREG Rule 10 applies to vessels within precautionary areas that form part of an adopted TSS. While there is no mandatory lane to follow, all COLREG requirements for the conduct of vessels — particularly Rules 5 to 8 on lookout, safe speed, risk of collision, and action to avoid collision — apply with full force. Masters and officers of the watch must reduce speed, post additional lookouts, and plot traffic carefully when navigating through a precautionary area. SOLAS V/10 requires compliance with applicable IMO routeing measures, and the ISM Code requires that SMS procedures address navigation in areas of particular risk, which routinely includes precautionary areas.
Regulatory detail & full definition
A precautionary area is an IMO-designated routing measure identifying a region where vessels must navigate with particular caution and where no specific traffic lanes are prescribed. Precautionary areas are typically established at the junction of traffic separation schemes where traffic converges from several directions, at the mouths of harbours and estuaries, or in areas where navigational hazards, shallow water, or fishing activity create elevated collision or grounding risk. The precautionary area is indicated on official charts.
COLREG Rule 10 applies to vessels within precautionary areas that form part of an adopted TSS. While there is no mandatory lane to follow, all COLREG requirements for the conduct of vessels — particularly Rules 5 to 8 on lookout, safe speed, risk of collision, and action to avoid collision — apply with full force. Masters and officers of the watch must reduce speed, post additional lookouts, and plot traffic carefully when navigating through a precautionary area. SOLAS V/10 requires compliance with applicable IMO routeing measures, and the ISM Code requires that SMS procedures address navigation in areas of particular risk, which routinely includes precautionary areas.