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21/02/24: Collision Regulations Need to be Updated for USVs

The 1972 International Regulations for Preventing Collisions at Sea (ColRegs) did not anticipate today's unmanned vessels. It is time to update them, and the United States needs to lead the effort.

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The U.S. Navy envisions an unmanned fleet securing the nation’s global maritime presence. Fifth Fleet Commander Vice Admiral Brad Cooper championed expanding  the unmanned surface vessel (USV) program, stating, “We’ve established a goal to have 100 unmanned surface vessels available for patrol in waters around the Arabian Peninsula by the end of the summer of 2023.”1 Captain Scot Searles, another advocate for the USV program, predicted, “By the middle of this century . . . up to 40 percent of the fleet will be unmanned.”2

Unmanned vessels may enhance force projection, supplement the afloat workforce, and propel the Navy to new horizons. However, they possess a subtle yet important weakness: USVs’ remote piloting configuration does not adhere to the 1972 Convention on the International Regulations for Preventing Collisions at Sea (ColRegs). Foreign adversaries exploit this to seize U.S. vessels.

China and Iran argue unmanned vessels violate admiralty law and threaten mariners’ safety. In December 2016, the People’s Liberation Army Navy (PLAN) seized a U.S. unmanned surveillance vessel; the Chinese Defense Ministry argued the PLAN fulfilled its duty “to prevent the device from causing harm to the safety of navigation and personnel.”3 In 2022, Iran seized a Navy USV using the same reasoning.4 Both vessels ultimately were returned to the United States, but in the Iran case, Navy specialists reported sensitive camera equipment was missing.

As long as unmanned vessels and the ColRegs remain in friction, adversaries will continue to seize USVs. The United States must promote a new framework that places USVs legally within the maritime world.

The Lookout Rule

The international community adopted the 1972 Convention to reduce the likelihood of collisions and maritime incidents, as well as to allow administrative courts to determine fault, cause, and liability in resulting lawsuits. The ColRegs include and oblige mariners to comply with 41 rules related to safety, maritime proficiency, and good seamanship, including the lookout requirement, which stipulates a vessel’s lookout must: (1) be proper, (2) be continuous, and (3) use sight, hearing, and all other available means appropriate.5

The traditional understanding of “proper lookout” is a person specifically designated and trained to identify contacts and report them to the watch officer.6 Several cases provide an understanding of the lookout rule’s requirements and the consequences of a violation:

• In apportioning liability in the 2007 collision of the Samco Europe and MSC Prestige, admiralty judge Justice Nigel Teare opined, “The extensive navigational aids now available to mariners are capable of providing much information, but safe navigation also requires . . . a good visual lookout.”7

• The Ariadne case, an appeal in admiralty arising from a collision between the steamer Ariadne and the brig William Edwards, emphasized the duty of the lookout as of the “highest importance. Upon nothing else does the safety of those concerned so much depend.”8

• Per the 1978 decision in Tug Ocean Prince Inc. v. United States, the physical absence of key bridge personnel will lead to consideration of a ColRegs violation: “The failure to post a lookout when the conditions were such that the same was required was not only negligent and contrary to good practice, it was also a violation of a statutory duty.”9

• In Tillicum, a case involving a collision between the towboat Tillicum and the steamship Rosalie, the court found the towboat lacked a proper lookout during a period of restricted visibility, a violation of the ColRegs. However, because the Rosalie did not navigate with due caution, both vessels were found to have violated recognized rules of navigation, and the claimed damages were equally divided.10

Applying the ColRegs to USVs

Under the ColRegs, USVs fall in the category of vessel, a “watercraft . . . used or capable of being used as a means of transportation on water.”11 Even when no personnel are on board, USVs are capable of marine transportation and therefore are bound by the rules while in international waters. Rule 1(a) states, “These Rules shall apply to all vessels upon the high seas and in all waters connected therewith navigable by seagoing vessels.”12 A similar provision exists in U.S. domestic law, applying the rules to U.S. inland waters.13 USVs must comply with the ColRegs, whether in international or U.S. waters.

The presence of remote lookouts for USVs does not comply with the lookout rule. Although the text of Rule 5 does not plainly require vessels to employ a watchstander on board, the maritime community interprets the “proper lookout” rule to require the physical presence of a lookout.

In Farwell’s Rules of the Nautical Road, Craig Allen Sr. and Craig Allen Jr. argue electronic means of contact detection “in no way . . . obviate the requirement for vessels to maintain a lookout capable of detecting other vessels by visual and auditory means.” They define a lookout as a watchstander supplemented by—not replaced by—electronic means of detection, such as “closed circuit television cameras, and . . . sound detection and amplification equipment.”14 In The Watch Officer’s Guide, authors James Stavridis, Robert P. Girrier, and Jeff Heames warn against neglecting “older and more reliable means of safeguarding a ship” for contact detection.15 British marine investigators have argued, “The human eye is still the most effective watch keeping aid.”16 U.S. destroyers and cutters still implement a lookout watch rotation.

These examples show the standard for a proper lookout is a physically present, proficient watchstander. Thus, USVs violate the rule when using a remote operator as a lookout.

Even if cameras and microphones could meet the “proper lookout . . . by sight and hearing” rule, USVs cannot meet the “always maintain” requirement. Current electronics and satellite equipment are not reliable enough to maintain a constant, stable connection between hardware and operator. The Navy realizes this and plans to staff skeleton crews to maintain essential equipment on board USVs and intervene when necessary.17 At this time, remote lookouts do not provide the same quality and consistency as a watchstander.

Modern electronics and detection technology provide a vital means of contact detection and avoidance, but the lookout watch, adequately manned by professional mariners, provides the required legitimacy for a lookout.

Collision Avoidance and Liability

A USV’s remote crew also constrains its ability to avoid collision. In a traditional bridge watch structure, the watch officer uses radar, the designated lookout, and his or her maritime proficiency to identify and respond to contacts. The watch officer also will contact the other vessel when necessary to determine proper action. In contrast, USV operations rely on a stable satellite connection and information delivery to a remote operator. The operator must act in a time-sensitive situation in which the delivery of information and command execution could be delayed. In a situation involving a USV, a traditionally crewed vessel determined to be the stand-on will not have a human counterpart on the opposing vessel.

In such a situation, under which ColRegs designation would a USV fall? The answer depends on the vessel. Most USVs are propelled by machinery and so would fall under the “power-driven vessel” designation. Smaller surveillance USVs tend to be sail-powered and may qualify as “sailing vessels” when using only sail for propulsion.18

Unmanned vessels do not qualify as “not under command” in their standard mode of operation. To be not under command, a vessel must be unable to maneuver due to an unexpected circumstance.19 The normal delay in command execution because of remote piloting would not qualify, although the “not under command” designation could apply in the event of an equipment malfunction.

Finally, USVs do not immediately qualify as “restricted in their ability to maneuver.” Vessels in this category are unable to maneuver in collision situations because of the nature of their work.20 The remote piloting system is the USV’s means of navigation, not its work. The Navy intends to use USVs for transport and surveillance, work that would not prevent them from taking action to avoid collision.

Thus, most unmanned vessels are power-driven vessels and, as such, must conduct themselves accordingly in collision situations and will face the consequences should a collision occur.

The unconventional crew configuration of USVs makes the Navy vulnerable to incurring liability in the event of a collision. Rule 2(a) of the ColRegs stipulates the rules will not absolve vessel owners, master, or crew from the consequences of failing to adhere to the rules or the ordinary precautions of seamen.21 U.S. naval vessels may be subject to torts; the Public Vessels Act allows people to file suit in admiralty for damages caused by a public vessel or counterclaim a suit brought by the government.22 The Navy faces liability for damages should its unmanned vessels be involved in a collision. As the Ariadne case showed, the absence of a proper lookout likely will incur causative fault unless the vessel can prove its violation was not a causative factor in the collision.

The configuration of USVs, absent all other circumstances, disadvantages the Navy in a potential collision case. Thus, the Navy has a liability risk when operating unmanned vessels in maritime zones with potential for collisions.

Reconciling with the Rules

The Navy has several routes to reconcile the USV remote crew configuration with the ColRegs:

Man the Unmanned

The Navy could supplement the USVs with lookout watchstanders. Rear Admiral Casey Moton, former program executive officer for unmanned and small combatants, noted a skeleton crew would “handle those things that are just not quite there with maneuvering critical situations.”23 This statement is ambiguous on whether the crews will staff a lookout watch, but if so, they would fulfill the lookout requirement by adding the key human element to contact detection and collision avoidance. However, this also would thwart the design of unmanned vessels and the goals of the Navy. Rear Admiral Moton added, “We don’t want there to be this crutch that we’re just going to fall back on the crew.” Manning an unmanned vessel defeats its purpose, and the Navy likely would not adopt such a proposition.

Continue without Notice

The Navy may choose to continue the USV program, discontinue manned crews, and disregard the implications of a ColRegs violation. The rules do allow deviation when necessary to avoid immediate danger, and commanding officers have and will continue to balance full compliance with the ColRegs against operational necessity.24 If the Navy applies this mindset to USVs, foreign nations, especially the nation’s adversaries, could use the ColRegs against U.S. naval forces, which will erode force projection in key maritime zones. In addition, the United States’ credibility could be hurt if the international community views the Navy’s USV development as a gross violation of the ColRegs.

Promote New Rules for a New Future

The better solution is for the United States to spearhead the creation of new international rules that standardize the requirements for USV use. The aviation community has done it for aerial drones. In 2019, the European Union established “detailed provisions” to regulate unmanned aircraft operations, personnel requirements, and the parameters within which they may operate.25 The United Kingdom released a similar “drone code,” the Air Navigation Order Amendment, that regulates the certification of drone users and the manner in which they may operate their aircraft.26

The maritime world could create a similar framework to fold USVs into the global maritime infrastructure. Such rules would codify safety standards, avoidance system requirements, and operating zones for USVs. For example, it could require all USVs to possess an all-round camera with infrared capabilities and a microphone able to detect sound signals at the frequencies prescribed in the ColRegs. The rules also could establish how an unmanned vessel and a crewed vessel shall operate when risk of collision exists.

This solution would provide the greatest benefit to the Navy because it would allow USVs to operate in the maritime domain legally, alongside manned vessels. The United States should be at the forefront of this development so the regulations align with the nation’s vision of the future maritime domain. Otherwise, as former Supreme Court Justice Stephen Breyer remarked, “The world will follow someone else’s example . . . we may find ourselves not well served by.”27

Why It Matters

The United States and its military must respect and abide by international maritime rules. To ignore them would degrade efforts to maintain a rules-based international order. The controversy surrounding USVs will only grow as foreign adversaries use the ColRegs as a legal precept to seize U.S. military equipment and property. The United States must realign itself with the longstanding principles of professional mariner conduct and lead initiatives to fit USVs in the maritime framework.


1. Sam LaGrone, “Navy Wants 100 Unmanned Ships Monitoring Middle East Waters by Next Year,” USNI News, 11 October 2022.

2. Sam LaGrone, “CNO: Navy to Finalize Large Unmanned Surface Vessel Requirements Later This Year,” USNI News, 5 April 2023.

3. Mark J. Valencia, “U.S.-China Underwater Drone Incident: Legal Grey Areas,” The Diplomat, 12 January 2017.

4. CDR Clay Robinson, USN (Ret.), “Protect Unmanned Surface Vessels in the Gray Zone,” U.S. Naval Institute Proceedings 149, no. 1 (January 2023).

5. Convention on the International Regulations for Preventing Collision at Sea (ColRegs), Rule 5, 1972, 28 U.S.T. 3459, T.I.A.S. No. 8587, 1050 U.N.T.S. 16, entered into force 15 July 1977.

6. British Columbia Mills Tug and Barge Co. v. Myrolie, 259 U.S. 1 (1922).

7. The Samco Europe and MSC Prestige (2011) 2 Lloyd’s Rep 579.

8. The Ariadne, 80 U.S. (13 Wall.) 475, 479 (1872).

9. Tug Ocean Prince, Inc. v. United States, 584 F. 2d 1151 (2d Cir. 1978).

10. The Tillicum, 217 F. 976 (W.D. Wash. 1914).

11. ColRegs, Rule 3.

12. ColRegs, Rule 1(a).

13. 33 C.F.R. § 83.01 (2022).

14. Craig H. Allen Sr. and Craig H. Allen Jr., Farwell’s Rules of the Nautical Road, 9th ed. (Annapolis, MD: Naval Institute Press, 2020).

15. ADM James Stavridis and RADM Robert P. Girrier, USN (Ret.), and CAPTs Tom Ogden and Jeff Heames, USN, The Watch Officer’s Guide, 16th ed. (Annapolis, MD: Naval Institute Press, 2020).

16. U.K. Marine Accident Investigation Branch Safety Digest 01/98, Case No. 4.

17. LaGrone, “Navy to Finalize Large Unmanned Surface Vessel Requirements.”

18. ColRegs, Rule 3.

19. ColRegs, Rule 3.

20. ColRegs, Rule 3.

21. ColRegs, Rule 2(a).

22. 46 U.S.C. § 31102 (2006).

23. LaGrone, “Navy to Finalize Large Unmanned Surface Vessel Requirements.”

24. ColRegs, Rule 2(b).

25. Commission Implementing Regulation (EU) 2019/947.

26. Air Navigation Order (Amendment) 2019 No. 261.

27. Stephen G. Breyer, The Court and the World: American Law and the New Global Realities (New York: Vintage Books, 2016).

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