COLREGS: Crossing, Overtaking, or Head-On? A Decision Guide for the USCG Exam

The Rules of the Road exam is not primarily a test of what give-way vessels do. Every candidate knows the give-way vessel keeps clear. The exam tests whether you can figure out which vessel IS the give-way vessel — which means correctly classifying the encounter first.

Misclassify the situation and every answer you build on top of it is wrong. Classify it correctly and most of the action questions answer themselves. This is the decision guide.

The crossing, overtaking, and head-on comparison page shows these three rules side by side — this article is the decision guide that walks through each in sequence.

Why Classification Matters Before Action

COLREGS Rules 13, 14, and 15 cover three distinct situations: overtaking, head-on, and crossing. Each situation assigns different roles and requires different actions. The rules are written in priority order — overtaking overrides everything, head-on applies when overtaking does not, and crossing applies when neither of those fits. The exam follows the same logic. You work the decision in sequence, not in parallel.

Step 1: Is It Overtaking? (Rule 13)

Rule 13 defines overtaking precisely: a vessel is overtaking when she is approaching another vessel from a direction more than 22.5 degrees abaft the beam of the vessel ahead. In practical terms, this is the zone where the overtaking vessel can see the sternlight of the vessel ahead but cannot see either sidelight.

At night, this is visually clean: if you see only the white sternlight of a vessel ahead, you are overtaking. During the day, the 22.5-degree angle is less obvious, but the principle holds — if you are coming up behind a vessel and would eventually overtake it, you are the overtaking vessel.

The critical Rule 13 fact for the exam: The overtaking rule overrides everything else. Rule 13(a) states that "notwithstanding anything contained in the Rules of Part B, Sections I and II," the overtaking vessel shall keep clear. This means:

• An overtaking sailing vessel must keep clear of a power-driven vessel ahead (even though sailing vessels normally have priority over power-driven vessels under Rule 12).
• An overtaking vessel that is restricted in maneuverability must still keep clear.
• An overtaking vessel that is the "less give-way" type in a different rule must still keep clear.

Rule 13 dominates. If the situation is overtaking, apply Rule 13 and stop — no need to go to Rule 14 or Rule 15.

The doubt rule: Rule 13(d) states that if a vessel is in any doubt as to whether it is overtaking another, it shall assume it is overtaking and act accordingly. Exam questions sometimes create ambiguous geometry — if the approaching angle is unclear, the correct answer is to assume overtaking.

Step 2: Is It Head-On? (Rule 14)

If the situation is not overtaking, ask whether it is head-on. Rule 14 applies when two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision.

The visual identification is specific: both vessels see the other's masthead lights in line or nearly in line AND both sidelights. If you can see both the red and green sidelights of an approaching vessel and both masthead lights appear as one or nearly one, you are in a head-on situation.

Under Rule 14, both vessels are required to alter course to starboard. Neither vessel is a "give-way" vessel in the conventional sense — both alter right. This is the only rule in this set where both vessels take the same action.

The doubt rule: Rule 14(c) states that if a vessel is in any doubt as to whether a head-on situation exists, it shall assume it does and alter course to starboard. Exam questions will sometimes describe conditions where it is unclear whether two vessels are meeting head-on or at a small crossing angle. Assume head-on; alter right.

What disqualifies Rule 14: If the approaching vessel is clearly coming from the side — you can see only one sidelight — it is not head-on. If the angle is clearly not reciprocal, it is not head-on. Head-on requires an essentially end-to-end approach.

Step 3: If Neither, It's Crossing (Rule 15)

If the situation is not overtaking (Rule 13) and not head-on (Rule 14), it is crossing under Rule 15. Two power-driven vessels crossing so as to involve risk of collision: the vessel that has the other on her starboard side is the give-way vessel.

The give-way vessel under Rule 15 shall keep out of the way of the stand-on vessel and, in doing so, shall avoid crossing ahead of the stand-on vessel "if possible." That last phrase appears on the exam. The preferred maneuver is to pass astern of the stand-on vessel.

The stand-on vessel under Rule 17(a)(i) shall maintain course and speed. Under Rule 17(a)(ii) she may take action to avoid collision as soon as it becomes apparent that the give-way vessel is not taking appropriate action. Under Rule 17(b) she must take action if collision cannot be avoided by the give-way vessel alone.

The Rule 15 memory device: "Green to green" (starboard to starboard) means you are the stand-on vessel — the other vessel's green light is on your port side, which means the other vessel has you on her starboard. She is give-way. You maintain course and speed. If you see the other vessel's red light on your starboard side, you are give-way — you have her on your starboard.

The Decision Flowchart

Work these questions in order:

1. Is a vessel approaching from more than 22.5 degrees abaft the beam of the other? If yes — overtaking, Rule 13. Stop here.

1. Are two power-driven vessels approaching on reciprocal or nearly reciprocal courses? If yes — head-on, Rule 14. Both alter to starboard. Stop here.

1. Are two power-driven vessels crossing such that risk of collision exists, and neither of the above applies? If yes — crossing, Rule 15. Vessel with the other on her starboard side is give-way.

1. In doubt between overtaking and anything else: assume overtaking (Rule 13(d)).

1. In doubt between head-on and crossing: assume head-on (Rule 14(c)).

Exam Traps

The Tug-and-Tow Overtaking Question

A tug is towing a barge astern. A vessel approaches the tow from behind. Who is overtaking whom?

The overtaking vessel is the one approaching the composite unit from astern. The composite unit here is the tug AND the tow. The vessel overtaking the barge is also overtaking the tug — the entire tow constitutes the vessel being overtaken. The overtaking vessel must keep clear of the entire composite unit, including the tow.

The exam may ask this from the tug's perspective: "A vessel is overtaking your tow and has come alongside the barge but not yet your tug. What is the situation?" It is still an overtaking situation. The overtaking vessel has not cleared the tow.

What If a Sailing Vessel Is Overtaking a Power-Driven Vessel?

Rule 12 gives sailing vessels priority over power-driven vessels in most encounters. But if a sailing vessel is overtaking a power-driven vessel, Rule 13 applies. The overtaking sailing vessel keeps clear. Rule 13(a) explicitly overrides Rule 12.

This appears on the exam as a trap. The candidate knows sailing vessels usually have priority, applies Rule 12, and gets the wrong answer. The correct sequence: check overtaking first, check head-on second, apply Rule 12 only in crossing situations involving a sailing vessel and a power-driven vessel.

Crossing a Narrow Channel Is Not Rule 15

Rule 9(d) states that a vessel shall not cross a narrow channel or fairway if such crossing impedes the passage of a vessel that can only navigate safely within the channel.

"Shall not impede" is a stronger obligation than "give-way." A vessel that cannot impede a channel-bound vessel must not cross at a time or in a manner that forces the channel vessel to alter course or slow down to avoid collision.

Rule 15 applies in open water between two power-driven vessels. Rule 9 applies in channels and narrow fairways. The two rules are not interchangeable. When the scenario involves a defined channel, apply Rule 9. The "shall not impede" obligation does not depend on which side the channel vessel is on — it applies categorically.

Rule 17: What the Stand-On Vessel Must Do

Once you classify the situation and identify the stand-on vessel, Rule 17 governs her obligations. Three levels apply in sequence:

• Rule 17(a)(i): maintain course and speed.
• Rule 17(a)(ii): may take action to avoid collision by her maneuver alone, as soon as it becomes apparent that the give-way vessel is not taking appropriate action.
• Rule 17(b): shall take action when collision cannot be avoided by the give-way vessel alone.

The exam tests whether candidates understand that a stand-on vessel cannot maneuver freely at will — she is constrained by Rule 17. She maintains until 17(b) applies or until she elects to act under 17(a)(ii). She may not alter course to port toward a give-way vessel on her port side under 17(c), except to avoid immediate danger.

Practice

Classification errors drive most wrong answers on Rules of the Road sections. Drilling scenario classification — without looking at the action yet — isolates the skill. The Rules of the Road practice module runs crossing, overtaking, and head-on scenarios in sequence. Work through those until the decision flowchart above is automatic.