Collision Regulations - Clarification of the term “rigidly connected in a composite unit”

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Table of Contents

• Collision Regulations
• Collision Regulations (continued)
• Issue - What is Rigidly Connected?
• Issue (continued)
• US - Interpretation
• Previous CMAC Proposal Tug and Barge Working Group (April 2010)
• Standing Committee on Navigation and Operations (November 2010)
• Safety
• New Proposal
• Advantages of New Interpretation
• Comments

Collision Regulations

Rule 24 – Towing and Pushing
Rule 24(b)

• When a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit they shall be regarded as a power-driven vessel and exhibit the lights prescribed in Rule 23.

Rule 35(f) - Sound Signals in Restricted Visibility

• Requires a pushing vessel and a vessel being pushed ahead, when rigidly connected in a composite unit, to give the same signals as a power-driven vessel instead of the signals of a vessel engaged in towing or pushing another vessel.

Collision Regulations (continued)

Responsibility Between Vessels:

• Under the Rule 18 of the Collision Regulations, there is no distinction made between a power-driven vessel and a vessel pushing another vessel.
• Therefore the difference in light arrangements between a power-driven vessel and a vessel pushing another vessel does not impact on one vessel's responsibility to keep clear of the other.

Issue - What is Rigidly Connected?

• A Marine Safety Tug and Barge Working Group, formed to examine the status of Tug and Barge operations and regulations in Canada reported in 2005…

“It is recommended by the WG that a common definition of terms be used nationally. Such terms as articulated, integrated, combination, rigidly connected etc has led to misunderstandings and confusion.”

• CMAC discussions on clarifying the term “rigidly connected in a composite unit” dates back to 2006

Issue (continued)

• There is a wide variety of connection methods used for tug and barge pushing operations, ranging from simple to very complex systems.
  • Connection using winches, hawsers and/or chains.
  • Some with a special bracket or designed with a stern notch to help hold the tug in position.
  • Notches vary considerably in their depth relative to the tug length and in their design.
  • Mechanical means: use of clamps, hydraulic rams or pins that apply pressure, engage holes, teeth or notches and various other solid mechanical connections.
• Almost all are designed to allow some relative movement between the tug and the barge i.e., independent pitching.
• Without a common understanding, the navigation lights exhibited by vessel engaged in pushing operations will continue to be inconsistent.

US - Interpretation

US Navigation Rules Interpretation:

• A “composite unit” is interpreted to be a pushing vessel that is rigidly connected by mechanical means to a vessel being pushed so they react to sea and swell as one vessel. “Mechanical means” does not include the following: a) lines, b) hawsers; 3) wires; 4) chains.
  
  Pushing vessel and vessel being pushed: Composite Unit: - 33CFR 82.3. and 90.3.

Previous CMAC Proposal
Tug and Barge Working Group (April 2010)

• The term “rigidly connected” when determining whether or not an integrated tug/barge unit is a “composite unit” means that, a Push mode or Dual Mode Integrated Tug Barge, when manoeuvring, does so as a single vessel, without “perceptible relative motion” between the tug and the barge.
• “Perceptible relative motion” should be read to mean relative between the tug and barge in the athwartship direction of the horizontal plane such that a meeting vessel would be mislead as to the relative heading between itself and the approaching composite unit.
• To take into account practical and operational considerations, it would be necessary to deviate from the regulations with respect to the placement of the forward masthead light and sidelights.

Standing Committee on Navigation and Operations (November 2010)

Comments on the April 2010 T/B WG proposal:

• Interpretation may not provide sufficient clarity such as, the term “perceptible”, leading to further inconsistencies
• Would not be consistent with U.S. interpretation for “composite unit”
• Most ATBs exhibit lights of a tug pushing a barge, not as “composite unit”
• Proposal would require in many cases deviations from Collision Regulations technical requirements due to practical considerations (i.e., forward masthead light height, vertical separation and position in relation to the sidelights).

Safety

• There does not appear to be any compelling safety advantage for a tug and barge pushing combination to exhibit one set of lights over the other.
  • Exhibiting lights of a single power-driven vessel, with its two mast head lights, might be considered more readily identifiable to some, or that it provides a greater indication of the vessel's aspect.
  • However, being able to differentiate between a tug pushing a barge from a single vessel provides useful additional information to other vessels in the area.
  • To persons familiar with the Collision Regulations, both light arrangements facilitate vessel detection and collision avoidance.

New Proposal

• The term "rigidly connected" in the Collision Regulations means that the connection results in there being no relative motion between the pushing vessel and the vessel being pushed ahead.

Advantages of New Interpretation

• Consistent with the U.S. interpretation.
• Consistent with common industry practice where ATBs are not considered rigidly connected.
• Easier to implement without creating additional regulatory exemptions from the Collision Regulations.
• Clearer interpretation resulting in greater consistency.
• Ensures correct positioning of lights, in accordance with positioning and technical requirements of Annex 1, Collision Regulations.
• No relative movement or misalignment of navigation lights during the voyage.
• Tug/Barge arrangements that have such a connection will almost certainly have similar operating characteristics of a power-driven vessel in all circumstances.

Comments

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