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Rules of the road decision sheet

A collision-avoidance decision order plus the encounter diagrams worth recognizing instantly.

Decision order before you choose a maneuver

  1. 1. Lookout and safe speedRules 5 and 6 apply continuously. See, hear, and understand the developing situation early enough to retain options.
  2. 2. Decide whether risk existsUse compass bearings, range, radar/AIS where fitted, and systematic observation. If in doubt, assume risk of collision exists.
  3. 3. Check the rules that override the simple hierarchyOvertaking remains overtaking until finally past and clear. Narrow channels and traffic separation schemes can change what a small craft may do.
  4. 4. Classify the encounterThen apply sail-versus-sail, head-on, crossing, or the vessel-responsibility rules. Make action early, substantial, and obvious.
  5. 5. Stand-on is a duty, not immunityInitially keep course and speed, monitor the give-way vessel, and act under Rule 17 when required. Every vessel must avoid collision.

High-yield encounter diagrams

Overtaking, Rule 13A vessel marked STAND ON heads up the page. Behind her, a shaded 135-degree sector spreads from her stern — the arc her sternlight covers, starting 22.5 degrees abaft each beam. An overtaking vessel marked GIVE WAY approaches inside this sector; a curved arrow shows her passing well clear up the overtaken vessel's side.beam22.5° abaftthe beam22.5° abaftthe beam135° sternlight sectorSTAND ONbeing overtakenGIVE WAY — overtakingkeep clear until finally past and clear
Rule 13 — approaching from more than 22.5° abaft the other vessel's beam (inside her 135° sternlight sector, where you'd see only her sternlight at night) makes you the overtaking vessel: keep clear until finally past and clear.
Head-on situation, Rule 14Two power-driven vessels approach bow to bow on reciprocal courses. Both are marked GIVE WAY in amber. Curved arrows show each altering course to her own starboard so they pass port side to port side.A — GIVE WAYalters course to starboardB — GIVE WAYalters course to starboardthey passport to port
Rule 14 — two power-driven vessels meeting on reciprocal courses: neither stands on. Each alters course to starboard and they pass port side to port side.
Crossing situation, Rule 15Your power-driven vessel heads up the page. Another power-driven vessel approaches from your starboard side, heading across your course. You are marked GIVE WAY in amber with a curved arrow turning to starboard to pass astern of her. She is marked STAND ON in green and holds her course and speed.on your starboard bowpass asternYOU — GIVE WAYturn starboard, don’t cross aheadSTAND ONholds course and speed
Rule 15 — power-driven vessels crossing: the vessel that has the other on her own starboard side gives way. Turn to starboard and pass astern — avoid crossing ahead.
Sailing vessels on opposite tacks, Rule 12(a)(i)Wind blows down the page. Two sailboats converge: the left boat has the wind on her port side (port tack, mainsail to starboard) and is marked GIVE WAY in amber, bearing away to pass astern. The right boat has the wind on her starboard side (starboard tack) and is marked STAND ON in green, holding her course.WINDPORT TACKGIVE WAY · wind on portSTARBOARD TACKSTAND ON · wind on starboard
Rule 12(a)(i) — sailing vessels on opposite tacks: the boat with the wind on her port side (port tack) keeps out of the way of the boat on starboard tack.
Sailing vessels on the same tack, Rule 12(a)(ii)Wind blows down the page. Two sailboats sail the same tack on converging courses. The upwind boat, closer to the wind, is marked WINDWARD, GIVE WAY in amber and bears away to pass astern of the other. The downwind boat is marked LEEWARD, STAND ON in green.WINDWINDWARDGIVE WAY · nearer the windLEEWARDSTAND ON · farther from wind
Rule 12(a)(ii) — sailing vessels on the same tack: the windward boat (nearer the wind) keeps out of the way of the leeward boat.
  1. 1NUCNot under command

    exceptional circumstance — cannot maneuver; everything keeps clear of her

  2. 2RAMRestricted in ability to maneuver

    the nature of her work restricts her (dredging, cable-laying, towing that restricts…)

  3. 3CBDConstrained by draftInternational only

    deep draft in shallow, narrow water — avoid impeding her

  4. 4FISHEngaged in fishing

    nets, trawls, or lines that restrict maneuverability — not trolling

  5. 5SAILSailing vessel

    under sail alone — engine on means power-driven

  6. 6POWERPower-driven vessel

    gives way to every vessel above

Rule 18 — the responsibility ladder. Each vessel type gives way to every type above it: power gives way to sail, sail to fishing, fishing to RAM and NUC. “Constrained by draft” exists only under the International Rules. Rules 9, 10, and 13 (channels, schemes, overtaking) outrank this hierarchy; seaplanes and WIG craft keep well clear of everyone.

Learning aid only — not for navigation. Confirm current rules and local requirements with the relevant authority.