Rule 34 — Maneuvering and Warning Signals (Inland)

TL;DR — On inland waters, whistle signals are intent signals exchanged between power-driven vessels in sight of one another within half a mile; one blast means "I intend to leave you on my port side," two blasts means "I intend to leave you on my starboard side," and the vessel receiving the signal must agree or sound the doubt signal. 33 CFR §83.34

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What the Rule Says

Applicability

Inland Rule 34 applies to all vessels upon the inland waters of the United States, and to vessels of the United States on the Canadian waters of the Great Lakes to the extent there is no conflict with Canadian law. 33 CFR §83.01 The signals described below are triggered when power-driven vessels are in sight of one another — meaning one can be observed visually from the other — and are meeting or crossing at a distance within half a mile of each other. 33 CFR §83.34 33 CFR §83.03

Maneuvering Signals — Meeting and Crossing (§83.34(a))

When a power-driven vessel underway is maneuvering as authorized or required by the Rules in a meeting or crossing situation within half a mile, she shall indicate that maneuver by whistle: 33 CFR §83.34

| Blasts | Meaning | |--------|---------| | 1 short | "I intend to leave you on my port side" | | 2 short | "I intend to leave you on my starboard side" | | 3 short | "I am operating astern propulsion" |

Upon hearing a one- or two-blast signal, the receiving vessel shall, if in agreement, sound the same signal and take the steps necessary to effect a safe passing. If the receiving vessel doubts the safety of the proposed maneuver, she shall immediately sound the doubt/danger signal (paragraph (d)) and each vessel shall take appropriate precautionary action until a safe passing agreement is made. 33 CFR §83.34

Overtaking Signals (§83.34(c))

When in sight of one another, a power-driven vessel intending to overtake another power-driven vessel shall signal her intention: 33 CFR §83.34

| Blasts | Meaning | |--------|---------| | 1 short | "I intend to overtake you on your starboard side" | | 2 short | "I intend to overtake you on your port side" |

The vessel about to be overtaken shall, if in agreement, sound a similar signal. If in doubt, she sounds the doubt signal under paragraph (d). 33 CFR §83.34

Note carefully: in the meeting/crossing context, one blast means the signaling vessel will pass leaving the other on her own port side. In the overtaking context, one blast means the overtaking vessel will pass on the other vessel's starboard side. The frame of reference shifts — this is a frequent source of exam errors.

Doubt / Danger Signal (§83.34(d))

When vessels in sight of one another are approaching and either vessel fails to understand the intentions or actions of the other, or doubts whether sufficient action is being taken to avoid collision, the vessel in doubt shall immediately sound at least five short and rapid blasts on the whistle. This signal may be supplemented by a light signal of at least five short and rapid flashes. 33 CFR §83.34

Bend Signal (§83.34(e))

A vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction shall sound one prolonged blast. Any approaching vessel within hearing around the bend or behind the obstruction shall answer with a prolonged blast. 33 CFR §83.34

Departure from Dock or Berth (§83.34(g))

When a power-driven vessel is leaving a dock or berth, she shall sound one prolonged blast. 33 CFR §83.34

Multiple Whistles (§83.34(f))

If whistles are fitted on a vessel at a distance apart of more than 100 meters, one whistle only shall be used for giving maneuvering and warning signals. 33 CFR §83.34

VHF Agreement Exception (§83.34(h))

A vessel that reaches agreement with another vessel in a head-on, crossing, or overtaking situation — for example, by using the radiotelephone as prescribed by the Vessel Bridge-to-Bridge Radiotelephone Act — is not obliged to sound the whistle signals prescribed by this Rule, but may do so. If agreement is not reached, whistle signals shall be exchanged in a timely manner and shall prevail. 33 CFR §83.34

Supplemental Light Signals (§83.34(b))

Whistle signals may be supplemented — not replaced — by light signals using an all-round white or yellow light: 33 CFR §83.34

• 1 flash = "I intend to leave you on my port side"
• 2 flashes = "I intend to leave you on my starboard side"
• 3 flashes = "I am operating astern propulsion"

Each flash duration shall be about 1 second. The light shall be visible at a minimum range of 2 miles, synchronized with the whistle, and shall comply with Annex I (33 CFR part 84). 33 CFR §83.34

Maneuvering Light Position (§84.18)

The maneuvering light shall be placed approximately in the same fore-and-aft vertical plane as the masthead light(s). Where practicable, it shall be at a minimum height of one-half meter vertically above the forward masthead light, and shall be carried not less than one-half meter vertically above or below the after masthead light. On a vessel carrying only one masthead light, the maneuvering light, if fitted, shall be carried where it can best be seen, not less than one-half meter vertically apart from the masthead light. 33 CFR §84.18

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Why It Matters on the Exam

Rule 34 is one of the highest-yield topics on the OUPV and Master 100 GT written examinations. Expect multiple questions in each sitting. The examiners test:

1. Intent vs. action. Inland whistle signals are intent signals — a vessel signals what she intends to do before doing it, and the other vessel must agree. This is the most fundamental concept. A vessel does not simply act and then signal; she signals first and waits for agreement. 33 CFR §83.34

2. The agreement requirement. Unlike some other rules, Inland Rule 34 requires the receiving vessel to respond with the same signal if she agrees. Silence is not agreement. If the receiving vessel doubts the maneuver, she sounds the doubt signal. 33 CFR §83.34

3. The overtaking signal reversal. In meeting/crossing, one blast = "I will pass leaving you on my port side." In overtaking, one blast = "I intend to overtake you on your starboard side." The frame of reference is the other vessel's side in the overtaking context. Exam writers exploit this distinction. 33 CFR §83.34

4. The VHF exception. If VHF agreement is reached, whistle signals are not required — but if VHF agreement is not reached, whistle signals shall be exchanged and shall prevail. 33 CFR §83.34

5. The bend and departure signals. Both use one prolonged blast, but for different purposes. The bend signal requires an answering prolonged blast from any vessel within hearing. The departure signal requires no answer. 33 CFR §83.34

6. The maneuvering light specifications. Color (all-round white or yellow), range (2 miles minimum), flash duration (about 1 second), and the requirement that it be synchronized with the whistle are all testable. 33 CFR §83.34 33 CFR §84.18

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Common Pitfalls

Pitfall 1 — Confusing Inland and International signals. On the high seas under the International Regulations, one short blast means "I am altering course to starboard" and two short blasts means "I am altering course to port" — these are action signals. On inland waters under 33 CFR §83.34, the signals are intent signals with different meanings. The exam will present scenarios that require you to identify which body of water applies. 33 CFR §83.01 33 CFR §83.34

Pitfall 2 — Assuming silence equals agreement. The rule is explicit: the receiving vessel shall sound the same signal if in agreement. A vessel that does not respond has not agreed. The doubt signal must be sounded if safety is in question. 33 CFR §83.34

Pitfall 3 — Applying Rule 34 outside its trigger conditions. Rule 34(a) applies only when vessels are in sight of one another AND within half a mile AND meeting or crossing. "In sight" means visually observable — not radar contact. 33 CFR §83.03 33 CFR §83.34

Pitfall 4 — Misidentifying the maneuvering light color. The light may be all-round white or yellow — not red, not green. Candidates sometimes confuse this with other all-round lights. 33 CFR §83.34

Pitfall 5 — Forgetting the departure signal. A power-driven vessel leaving a dock or berth sounds one prolonged blast. This is a standalone requirement unrelated to meeting or crossing situations. 33 CFR §83.34

Pitfall 6 — Misreading the overtaking signal frame of reference. When the overtaking vessel signals two short blasts, she means she intends to overtake on the other vessel's port side — not her own. Read the rule text carefully: "I intend to overtake you on your port side." 33 CFR §83.34

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Quick Check

Q1 — You are on a power-driven vessel on inland waters. Another power-driven vessel approaching from ahead sounds one short blast. What does this signal mean, and what must you do if you agree?

The other vessel is signaling "I intend to leave you on my port side." If you agree, you must sound one short blast in return and take the steps necessary to effect a safe passing. Silence is not agreement. 33 CFR §83.34

Q2 — A power-driven vessel intends to overtake another power-driven vessel on the vessel's starboard side. What whistle signal does the overtaking vessel sound?

One short blast, meaning "I intend to overtake you on your starboard side." 33 CFR §83.34

Q3 — You are approaching a blind bend in a channel. What signal is required, and what response should you expect?

Sound one prolonged blast. Any vessel within hearing around the bend or behind the obstruction shall answer with one prolonged blast. 33 CFR §83.34

Q4 — Two power-driven vessels on inland waters reach a passing agreement via VHF radio. Are whistle signals required?

No. A vessel that reaches agreement via radiotelephone as prescribed by the Vessel Bridge-to-Bridge Radiotelephone Act is not obliged to sound whistle signals, but may do so. However, if VHF agreement is not reached, whistle signals shall be exchanged and shall prevail. 33 CFR §83.34

Q5 — What are the specifications for the supplemental maneuvering light under Inland Rule 34?

The light shall be an all-round white or yellow light, visible at a minimum range of 2 miles, with each flash lasting about 1 second, synchronized with the whistle. It shall comply with Annex I (33 CFR part 84). 33 CFR §83.34

Q6 — Where must the maneuvering light be positioned on a vessel with two masthead lights?

In approximately the same fore-and-aft vertical plane as the masthead lights. Where practicable, at a minimum of one-half meter vertically above the forward masthead light, and not less than one-half meter vertically above or below the after masthead light. 33 CFR §84.18

Q7 — A power-driven vessel is getting underway from a berth. What signal is required?

One prolonged blast on the whistle. 33 CFR §83.34

Q8 — You are in doubt about whether another vessel's actions are sufficient to avoid collision. What signal do you sound, and how many blasts minimum?

The doubt/danger signal: at least five short and rapid blasts on the whistle. This may be supplemented by at least five short and rapid flashes of the maneuvering light. 33 CFR §83.34