2.1 Narrow channels and the keep-to-starboard requirement:
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2.1 Narrow channels and the keep-to-starboard requirement:

Narrow channels and fairways constrain the navigation of vessels by offering less space to manoeuvre and bringing vessels in closer proximity than what is usually desirable for safe navigation.(1) Craig H. Allen Sr. & Jr., Farewell’s Rules of the Nautical Road, p. 227.Shorter distances between vessels and the higher probability of denser traffic reduces the time available for vessels to assess situations and take appropriate actions. Moreover, the ‘narrow’ width of such channels, coupled with the often limited water depth, leaves vessels with fewer possibilities for course alterations, not forgetting that the effects of hydrodynamic interactions both between vessels, as well as between vessels and the physical characteristics of the channel, such as banks, can create an added layer of complexity and danger to navigation.(2) Nicholas J. Healy, Joseph C. Sweeney, The Law of Marine Collision, (Centreville, Maryland: Press, Inc., 1998), 145-146.All of these factors contribute to an increase in the risk of collision.(3) Craig H. Allen Sr. & Jr., Farewell’s Rules of the Nautical Road, p. 227.

By way of organizing the flow of traffic, rule 9(a) of the COLREGS regulates the navigation of vessels in stretches of water where navigation is restricted by boundaries on each side, in order to mitigate the risk of collision.(4) The problem of defining what is a narrow channel is a complex one that deserves to be treated separately. Thus, it is not considered here.In principle, the rule has the effect of dividing any such bordered stretches of water, which can qualify as a narrow channel or fairway, into two distinct lanes.(5) Certain channels or fairways are too narrow to accommodate bi-directional navigation. The flow of vessels in these areas will usually be restricted to a single direction. In certain cases, the question of whether navigation within the waterway is open to vessels proceeding in both directions may depend on the size and characteristics of the vessels transiting through the area. When required by the circumstances, both-ways traffic can be halted and the channel can be momentarily converted into a one-way waterway to allow vessels above a certain size to navigate safely. See Craig H. Allen, “Taking Narrow Channel Collision Prevention Seriously To More Effectively Manage Marine Transportation System Risk,” Journal of Maritime Law & Commerce Vol. 41, No. 1 (2010): 6. Although also subject to a Traffic Separation Scheme, the Strait of Istanbul is a good example of such an organization. See Ece J.N, Sözen A, Akten N, Erol S, “The Strait of Istanbul: A Tricky Conduit for Safe Navigation,” European Journal of Navigation, 5, 1 (2007): 46-55.In each lane, vessel traffic is supposed to flow in a single direction only. The organization and direction of traffic in this way aims to mitigate or even eliminate, in theory at least, the risk of collision between vessels that are following the course of the narrow channel, but in opposite directions. Provided they remain in their respective lanes, the chances of vessels meeting end-on, i.e. on reciprocal or nearly reciprocal courses, are significantly reduced.(6) Craig H. Allen, “Taking Narrow Channel Collision Prevention Seriously To More Effectively Manage Marine Transportation System Risk”, Journal of Maritime Law & Commerce Vol. 41, No. 1 (2010): 30.

The main duty of vessels navigating in narrow channels is thus fairly clear and straightforward. Rule 9(a) dictates that any “vessel proceeding along the course of a narrow channel or fairway shall keep as near to the outer limit of the channel or fairway which lies on her starboard side as is safe and practicable”. In other words, vessels following the natural course of the narrow channel are required to keep to the starboard side. By remaining on their respective starboard side, a safe port-to-port passing is ensured with vessels proceeding in opposite directions. Moreover, by specifying that vessels should remain as close as possible to the outer edge of the narrow channel, the rule also aims to increase the passing distance between vessels. For the sake of simplicity and clarity, we shall borrow the appellation used by Craig H. Allen and refer to this obligation as the “keep-to-starboard” requirement.(7) Craig H. Allen, “Narrow Channel Collision Prevention,” 18.

In The Canberra Star,(8) The Canberra Star, [1962] 1 Ll. Rep. 24.a decision of the English admiralty court, the keep-to-starboard requirement was applied so as to also affect the navigation of vessels that were entering a narrow channel. These vessels were said to have a duty to enter the narrow channel in such a manner so as to ensure that they find themselves on the starboard side of it upon entering(9) The Canberra Star, [1962] 1 Ll. Rep. 24, 28 col. 2(Fig. 1). The idea is that a vessel which is entering a narrow channel that lies on her starboard side (“inbound vessel”) would be able to pass safely port-to-port with any vessel which is leaving that same narrow channel (“outbound vessel”). The keep-to-starboard requirement is thus a concern for more than just those vessels which are within the confines of a narrow channel. The duty also affects the navigation of inbound vessels as they enter into the channel. Such extension(10) In my opinion, a strict interpretation of the words in rule 9(a), or rule 9 in general, does not point towards the application of its provisions outside the narrow channel. This brings to the forefront an interesting discussion on the scope of application of rule 9(a) and the reasoning behind its extension to vessels which have not yet entered, but are in the course of entering. We will not discuss this point further in this article, but I would point out that the case law appears to indicate that compliance with rule 9(a) is a matter of good seamanship. See The Canberra Star, [1962] 1 Ll. Rep. 24, p. 28 col. 2; A. N. Cockcroft and J. N. F. Lameijer, A guide to the Collision Avoidance, 49. However, this solution does not really offer a good solution to encounters between outbound and inbound vessels when the latter is approaching an entrance which is on her port side. This was also pointed out by the UK supreme court in The Alexandra I. See The Alexandra I (SC), [2021] 1 Lloyd’s Rep 299, para 144.of the application of rule 9(a) to inbound vessels holds true at the very least as long as the entrance of the narrow channel lies on the starboard side of the said inbound vessels (Fig. 1). This therefore explains the position of the vessel Alexandra I. She intended to enter the narrow channel, and therefore in her view she was bound by rule 9(a) to keep-to-starboard, in the same vein as the Ever Smart which was leaving it. From this point of view, it may appear reasonable to hold the Ever Smart at fault after it was established that she was staying in the middle of the narrow channel and not keeping-to-starboard from at the very least 11 minutes before the collision. This view satisfied the admiralty court and the court of appeal, but failed to convince the UK supreme court as we shall see (infra, 2.3).

Fig. 1. Vessel entering the narrow channel while keeping to starboard