The first three Rules of COLREG set the frame for reading everything that follows.
Rule 1 - Application
The Rules apply to all vessels upon the high seas and in all waters connected therewith navigable by seagoing vessels. Local authorities may make special rules for harbours, rivers and lakes, which should conform as closely as possible to COLREG. There are also special rules for traffic separation schemes.
Rule 2 - Responsibility
Following the Rules to the letter is not an excuse. Nothing in the Rules exonerates a vessel from the consequences of neglecting any precaution required by ordinary practice of seamen, or by the special circumstances of the case. In addition, departure from the Rules is allowed when necessary to avoid immediate danger. This is the "good seamanship" rule that sits above the others.
Rule 3 - General definitions
- Vessel: every description of water craft used or capable of being used as a means of transportation on water.
- Power-driven vessel: any vessel propelled by machinery.
- Sailing vessel: any vessel under sail provided that propelling machinery, if fitted, is not being used.
- Vessel engaged in fishing: fishing with nets, lines, trawls or other apparatus which restrict manoeuvrability.
- Vessel not under command (NUC): unable to manoeuvre as required because of an exceptional circumstance.
- Vessel restricted in her ability to manoeuvre (RAM): restricted by the nature of her work, such as cable laying or diving operations.
- Vessel constrained by her draught (CBD): severely restricted in deviating from her course because of her draught in relation to the available depth of water.
- Underway: not at anchor, made fast to the shore, or aground.
- Vessels in sight of one another: only when one can be observed visually from the other.
- Restricted visibility: any condition where visibility is restricted by fog, mist, falling snow, heavy rainstorms or sandstorms.
Knowing these definitions is the first step to understanding the "who gives way to whom" hierarchy in Rule 18.
The next parts of this series cover the Rules in order.