Towing Regulations & Safe Towing Operations

1. Regulatory Framework — CFR Title 46 Subchapter M and Subchapter I

The primary federal regulatory framework for towing vessels in the United States is found in Title 46 of the Code of Federal Regulations (CFR). The USCG administers these regulations through the Office of Commercial Vessel Compliance. Two subchapters are particularly important for the towing endorsement exam: Subchapter M and Subchapter I.

46 CFR Subchapter M — Towing Vessels

Subchapter M (Parts 136 through 144) is the comprehensive regulatory framework specifically for towing vessels. It was finalized by the USCG in 2016 under the Howard Coble Coast Guard and Maritime Transportation Act of 2006, which mandated federal inspection for towing vessels. Prior to Subchapter M, most towing vessels were uninspected vessels subject only to limited USCG oversight.

Subchapter M applies to towing vessels of 26 feet or more in length operating on waters subject to US jurisdiction, with limited exceptions. It covers:

• Vessel design and construction standards (Part 139)
• Fire protection systems and equipment (Part 140)
• Lifesaving equipment and arrangements (Part 141)
• Operations (Part 142) — safety management systems
• Engineering (Part 143)
• Electrical (Part 144)

46 CFR Subchapter I — Cargo and Miscellaneous Vessels

Subchapter I (Parts 90 through 106) governs cargo and miscellaneous vessels. It may apply to certain towing operations where the towing vessel is classified as a miscellaneous vessel rather than strictly a towing vessel, or where the tow itself is an inspected vessel. Subchapter I is also relevant when a towing vessel engages in incidental cargo carriage.

Towing Vessel Definition

Under 46 USC 2101(45), a towing vessel is a commercial vessel engaged in or offering to engage in the service of pulling, pushing, or hauling alongside any other vessel or object. The definition is broad and encompasses tugboats, towboats (river push boats), and assist tugs. It does not include assistance towing vessels operated for recreational vessel rescue, which fall under a separate endorsement category.

Third-Party Organization (TPO) Option

Subchapter M introduced an alternative compliance pathway: vessel operators may use a USCG-accepted Third-Party Organization (TPO) to conduct annual examinations in lieu of direct USCG inspections. TPOs must be accepted by the USCG and follow prescribed examination protocols. This was a major innovation that allows industry classification societies and surveying organizations to participate in the inspection process.

2. Towing Vessel Inspection and the Certificate of Inspection

The Certificate of Inspection (COI) is the foundational document certifying that a towing vessel has been examined by the USCG (or accepted TPO) and meets applicable safety standards. It is the operational license for the vessel.

What the COI Specifies

The COI issued to a towing vessel under Subchapter M specifies:

• Service route or area of operation (e.g., inland rivers, coastal, ocean)
• Minimum crew complement required to operate the vessel
• Maximum number of persons allowed on board
• Required lifesaving and firefighting equipment
• Authorized operating conditions and any operational restrictions
• Expiration date (COIs are typically valid for 5 years)

Inspection Types and Schedule

Towing vessels under Subchapter M are subject to several types of inspections:

• Initial inspection — before a COI is first issued to the vessel
• Annual examination — conducted each year (may be by TPO)
• Periodic inspection — more comprehensive examination at 5-year COI renewal
• Drydock examination — hull and underwater fittings, required periodically based on vessel age and construction
• Spot check — unannounced USCG boarding for compliance verification

Safety Management System (SMS) Requirement

One of the most significant Subchapter M requirements is the Safety Management System (SMS). All towing vessel owners and operators must implement an SMS that documents procedures for:

• Safe vessel operations, navigation, and communication
• Emergency response procedures (fire, flooding, man overboard, grounding)
• Maintenance of the vessel and its equipment
• Reporting and investigation of hazardous conditions and accidents
• Crew training, drill schedules, and competency verification

Exemptions and Exclusions

Not all towing vessels fall under Subchapter M. Excluded categories include:

• Vessels less than 26 feet in length
• Vessels only used for recreational assistance towing (covered by the OUPV towing endorsement, not Subchapter M)
• Public vessels (government-owned and operated)
• Foreign vessels in US waters under international convention arrangements

3. Manning Requirements and Watch Hours

Manning of towing vessels is governed primarily by 46 CFR Part 15 (Manning of Vessels) and the specific COI for each vessel. The USCG determines minimum safe manning based on the vessel's route, size, and operational profile. Failing to maintain the minimum crew specified in the COI is a serious violation.

Officer Credentials for Towing Vessels

The master of a towing vessel must hold an appropriate USCG credential. The required credential level depends on the vessel's gross tonnage and route:

• Operator of Uninspected Towing Vessels (OUTV) — a legacy credential for operators of smaller uninspected towing vessels (being phased out as Subchapter M inspects more vessels)
• Master (Towing) — for towing vessels operating on rivers, lakes, and coastal routes; tonnage-rated based on the vessels operated
• Towing Officer Assessment Record (TOAR) — required for the towing endorsement; a logbook of assessed towing tasks supervised by a qualified towing officer

Towing Officer Assessment Record (TOAR)

The TOAR is a USCG-approved logbook documenting that a mariner has been observed and assessed performing specific towing tasks under the supervision of a qualified towing officer. It is required for the towing endorsement on any license (OUPV or Master). TOAR tasks include:

• Making up, adjusting, and breaking towing arrangements
• Vessel maneuvering with a tow in various conditions
• Emergency towing procedures
• Use of capstan, winch, and bitts
• Evaluating the tow for seaworthiness

Watch Hour Limitations

Federal regulations strictly limit watch hours to prevent fatigue-related accidents. Under 46 CFR 15.1111 and Subchapter M operational requirements:

• No officer may stand more than 12 hours of watch in any 24-hour period
• Each officer must receive at least 10 hours of rest in any 24-hour period
• Rest may be split into no more than two periods, one of which must be at least 6 consecutive hours
• Compliance with rest requirements must be documented in a rest-hour log
• The owner, master, and officer share responsibility for compliance

Pilot Rules and River License Requirements

On certain designated waterways — particularly the Mississippi River system, the Ohio River, and other inland rivers — additional state or federal pilotage requirements may apply. Western Rivers licenses are a distinct USCG credential category for masters and pilots operating on the Mississippi, Illinois, Ohio, Arkansas, and related rivers. The Western Rivers route requires demonstrated knowledge of specific river segments, stage readings, bridge clearances, and fleet locations that differ from coastal towing operations.

4. Tow Rigging — Hawsers, Bridles, Pendants, and Hardware

Proper tow rigging is the foundation of safe towing. A failure in the towing arrangement can result in loss of the tow, collision, or capsizing of the towing vessel. Understanding the components, their selection, and their proper use is essential for both safe operations and the towing endorsement exam.

Tow Hawser

The tow hawser is the primary line connecting the towing vessel to the tow. Hawser selection depends on:

• Breaking strength — must significantly exceed the expected load; a safety factor of at least 5:1 (often higher) is standard
• Material — wire rope provides strength and catenary; synthetic fiber rope (nylon, polyester) provides elasticity and is lighter
• Length — longer hawsers allow more catenary and reduce shock loads; typical ocean towing hawsers are 300–1,200 feet or longer
• Condition — hawsers must be inspected regularly for broken wires, kinks, wear, and heat damage

Bridle

A bridle is a V-shaped arrangement where two legs attach to separate points on the tow (typically the forward quarter bits or pad eyes on the bow), converging to a single apex where the towline connects. Bridles distribute the towing load across two attachment points rather than one, reducing stress concentration. They also improve the tow's steering response — a bridle tends to center the tow and reduce yawing. Bridle legs must be equalized in length to ensure even load sharing.

Pendant (Pennant)

A pendant is a short length of wire rope or chain connecting the tow's attachment point (or bridle apex) to the main hawser. Pendants serve multiple functions:

• Chafe protection — the pendant absorbs wear at the tow's chock or fairlead, protecting the main hawser
• Catenary weight — chain pendants add weight near the tow, improving catenary
• Length adjustment — pendants allow the effective tow length to be adjusted without retrieving the full hawser

Catenary and Tow Length

Catenary is the natural sag in a towline resulting from the line's own weight. It acts as a shock absorber between the towing vessel and the tow. Key principles:

• Heavier lines develop more catenary; light synthetic lines develop very little without added weight
• Catenary is reduced as the load increases — a heavily loaded tow straightens the hawser
• Scope (the ratio of hawser length to water depth) matters; more scope generally means more catenary
• In following seas, the tow may overtake the towing vessel — longer scope helps prevent collision
• Tow length affects the tow's tendency to yaw; shorter tows are more maneuverable but harder to control

Capstan and Winch Operations

The towing winch (or capstan) is the primary mechanical device for paying out and retrieving the tow hawser. Safe operation requires:

• Understanding of winch brake holding capacity — the brake must hold the maximum anticipated tow load
• Never standing in the bight of a line under tension
• Controlled payout when making up the tow to prevent surging
• Regular inspection of winch brakes, drums, and warping heads for wear
• Automatic towing winches adjust scope automatically; operators must understand the tension control settings

Bitts, Chocks, and Fairleads

Towing bitts are the primary attachment points on the towing vessel where the hawser is secured when the tow winch is not in use. They must be rated for the expected tow load and properly secured to the vessel's structure. Chocks and fairleads guide the hawser and must be smooth and well-maintained to prevent chafe. The towpost (kingpost) or towing hook is an alternative fitting used on some river towboats where the tow is made fast to a single strong point.

5. Towing Lights and Shapes — COLREGS Rule 24

COLREGS Rule 24 governs the lights and shapes required for towing and pushing vessels and their tows. This rule is heavily tested on the captain's license exam. Understanding Rule 24 requires knowing not only what lights a towing vessel shows, but what the tow itself shows, and how the arrangement changes based on the tow's length and configuration.

Towing Astern — The Standard Arrangement

When a vessel is towing another vessel or object astern (behind on a hawser), COLREGS Rule 24(a) requires:

• Two masthead lights in a vertical line if the tow is 200 meters or less
• Three masthead lights in a vertical line if the tow exceeds 200 meters (hawser + tow length)
• Sidelights (red to port, green to starboard)
• Sternlight (white, 135-degree arc aft)
• Yellow towing light — directly above the sternlight, same arc as the sternlight (135 degrees aft)

The Tow Itself — Required Lights

Under Rule 24(e), the tow (the vessel or object being towed) must show:

• Sidelights (if a vessel)
• A sternlight
• If the tow exceeds 200 meters, a diamond shape by day

Pushing Ahead and Towing Alongside

Under Rule 24(b), a vessel pushing ahead or towing alongside shows:

• Two masthead lights in a vertical line (forward)
• Sidelights
• Sternlight
• Note: No yellow towing light is shown when pushing ahead or towing alongside

The vessel being pushed ahead, if not part of a composite unit, shows sidelights at its forward end. A composite unit (tug and barge rigidly connected so they maneuver as one vessel) is treated as a single power-driven vessel and shows the lights of such.

Towing in Restricted Visibility — Rule 35

In restricted visibility (fog, rain, snow), COLREGS Rule 35 governs sound signals. A towing vessel underway must sound:

• One prolonged blast followed by two short blasts, at intervals of not more than 2 minutes
• The tow (if manned) sounds one prolonged blast followed by three short blasts, at intervals of not more than 2 minutes
• These signals distinguish a towing vessel and its tow from other power-driven vessels (one prolonged blast every 2 minutes)

In restricted visibility, speed must be reduced to safe speed (Rule 6) and additional lookouts posted. The towing vessel must navigate with extreme caution — the tow may not respond to course changes as quickly as the towing vessel, and the overall length of the towing arrangement must be accounted for in all maneuvers.

Inland Towing Lights — Differences from COLREGS

The US Inland Navigation Rules generally mirror COLREGS Rule 24, but with one important distinction for pushing ahead: when a vessel is pushing ahead or towing alongside and the tug and tow are a composite unit, the lights shown are those of a single power-driven vessel. The Inland Rules also specifically address the Western Rivers, where special arrangements apply for certain commercial towing operations.

6. Inland and River Towing

River and inland towing — particularly on the Mississippi River system — involves a distinct set of terminology, procedures, and regulatory requirements compared to coastal and ocean towing. The exam frequently tests inland towing concepts because Western Rivers operations are a specialized and historically significant part of US commercial maritime industry.

Essential River Towing Terminology

Right-of-Way on Western Rivers

The Inland Navigation Rules include specific provisions for vessels on Western Rivers (the Mississippi River and its tributaries above the Huey P. Long Bridge, and the Red River of the North). Key rules:

• Inland Rule 9(a)(ii) applies in narrow channels — vessels less than 20 meters or sailing vessels shall not impede passage of a vessel that can navigate only inside the channel
• On Western Rivers, a downbound vessel (going with the current) has right-of-way over an upbound vessel in a meeting situation — downbound vessels are harder to maneuver and stop
• The downbound vessel proposes the passing arrangement via radio; the upbound vessel acknowledges or proposes an alternative
• Bridge-to-bridge radio communication (VHF Ch. 16 or Ch. 13 on inland waters) is required for vessels of 26 feet or more

Inland Rules — Whistle Signals for Towing

Unlike COLREGS where passing arrangement signals are informational, Inland Rules use a maneuvering signal system where the signal proposes an agreement and the vessel must receive an affirmative answer before maneuvering:

• One short blast — I intend to leave you on my port side (pass starboard to starboard)
• Two short blasts — I intend to leave you on my starboard side (pass port to port)
• Three short blasts — I am operating astern propulsion
• Five short blasts — Danger signal; doubt about the other vessel's intentions
• Agreement signals are repeated back by the other vessel

Bridge and Lock Procedures

Navigating a large river tow through bridges and locks requires precise positioning and communication. Large tows may exceed lock chamber dimensions, requiring the tow to be broken apart. Pilots must know the bridge clearances for their pool at the current stage, and must account for the overhead clearance consumed by the towboat's wheelhouse, exhaust stacks, and radar mast.

7. Towing Vessel Stability and Safety Operations

Towing vessels face unique stability challenges that do not affect most other commercial vessels. The high freeboard of the tow, side forces from the hawser, and the dynamic loads of towing operations can all adversely affect a towing vessel's stability. Understanding these risks is essential for safe operations and is tested on the captain's license exam.

Girting (Girded)

Girting (or being girded) is one of the most dangerous hazards in towing. It occurs when the tow overtakes or swings to the side of the towing vessel so that the towline comes abeam or forward of the beam. The side force exerted by the towline can capsize the towing vessel by rolling it toward the tow before the crew can react. Girting most commonly occurs:

• When towing in following seas and the tow surges forward
• When turning at excessive speed or with too short a towline
• When a crosscurrent or wind pushes the tow laterally
• When the towpoint is too high on the towing vessel (raises the effective towpoint, reducing stability)

Free Surface Effect in Towing Vessels

Towing vessels often operate with partially filled fuel and ballast tanks. Free surface effect — the reduction in effective metacentric height (GM) caused by liquid sloshing in partially filled tanks — can significantly reduce stability. Operators must be aware of:

• Keeping tanks either full or empty where possible to minimize free surface
• The stability booklet requirements under Subchapter M that vessels must carry and crew must understand
• Load line and draft marks — towing vessels must not be overloaded

Emergency Towing Procedures

Emergencies during towing operations require practiced, methodical responses:

• Parted hawser — immediately slow the towing vessel, account for the free end, approach the tow with caution, and re-establish the tow as conditions permit
• Tow taking on water — assess the tow's condition; a sinking tow creates extreme hazards and may need to be cast off in a safe location
• Man overboard from tow — coordinate rescue between the towing vessel and any crew on the tow; hawser management is critical
• Towing vessel machinery failure — anchor the tow immediately if in navigable channel; notify USCG and Vessel Traffic Service (VTS) as required

Environmental and Pollution Requirements

Towing vessels must comply with MARPOL Annex I (oil pollution) and applicable US regulations under 33 CFR Parts 151 and 155. Key requirements:

• Oil Record Book must be maintained for towing vessels over 400 GT or those certified to carry more than 200 cubic meters of oil in bulk
• Discharge of oil or oily mixtures within US waters is prohibited
• Hazardous material tows (tank barges) are subject to additional requirements under 33 CFR Subchapter O
• Reporting of oil spills to the National Response Center is mandatory (33 CFR Part 153)

Notification Requirements for Towing Operations

Certain towing operations require advance notification to the USCG or Vessel Traffic Service:

• Tows exceeding certain dimensions (length, width, or draft) may require a USCG permit under 33 CFR Part 162 or applicable VTS rules
• Navigating through a VTS area with an oversized or hazardous tow requires advance notice
• Towing operations in or near bridges may be subject to bridge administration requirements under 33 CFR Part 117
• Hazardous material tows may require notice under 33 CFR 160.204 (advance notice of arrival)

8. Frequently Asked Questions

Exam Preparation — What to Focus On

The USCG towing endorsement exam and the towing sections of the OUPV/Master exam test a predictable set of concepts. Focus your preparation on these high-frequency topics: