Restricted in Ability to Manoeuvre
Abbreviation: RAM
Vessel which from the nature of her work is restricted in her ability to manoeuvre; shows ball-diamond-ball / R-W-R lights.
In practice
RAM vessel signals its status via lights/shapes; other vessels keep clear. Common: dredgers, cable layers, fishing during operations.
Regulatory detail & full definition
Vessel Restricted in Ability to Manoeuvre — defined in COLREG Rule 3(g) as a vessel which from the nature of her work is restricted in her ability to manoeuvre as required by the Rules and is therefore unable to keep out of the way of another vessel. Examples include vessels laying or recovering navigational marks, dredging or surveying, replenishment underway, launching aircraft, mineclearance, and towing operations that severely restrict manoeuvrability. RAM vessels show by day a ball-diamond-ball; by night red-white-red all-round lights vertically. RAM has priority below NUC under Rule 18.
Authoritative source: COLREG 1972 ↗
Related
Source: COLREG 1972 Rule 3(g)
High confidence
Editorial confidence: how we grade.