Traffic Separation Schemes and COLREG

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Traffic Separation Schemes ; Avoidance of Collisions

Relatively few collisions occur in the open sea. The majority occur in coastal waters, in the approaches to ports, and within ports themselves. This is to be expected given that the risk of collision increases in relation to the frequency of encounter with other vessels.

In areas of high traffic congestion, separation schemes have been introduced in an attempt to split the shipping into identifiable one-way lanes with a substantial separation zone between them, the purpose being to reduce the risk of collision. Many of these traffic separation schemes have been adopted by the IMO. Where traffic separation schemes are shown on Admiralty charts, no distinction is drawn between schemes established by competent national authorities, and those, which have been adopted by the IMO. Admiralty charts contain a note to this effect and advise seafarers to refer to Annual Notice to Mariners No. 17, which lists all chartered schemes and identifies those, which are adopted by the IMO.

Conduct of vessels — COLREG 10

The conduct of vessels in and near traffic separation schemes, which have been adopted by the IMO, is governed by rule 10 of the International Regulations for Preventing Collisions at Sea 1972, as amended. In other schemes local regulations may apply which can modify not only rule 10, but also other provisions in the Steering and Sailing Rules. Care should therefore be exercised to verify the rules, which apply.

Crossing a TSS

Despite these schemes, collisions still occur most commonly when one vessel is crossing a traffic lane. This may be in order to cross the entire scheme, in which case both traffic lanes would have to be crossed, or to gain access to the lane of traffic moving in the direction appropriate to the vessel’s intended route.

It goes without saying that special care is needed when crossing a traffic lane. Particular attention must be paid to the requirements of rules 5 – 8 of the collision prevention regulations. These rules deal with questions of Lookout, Safe Speed, Risk of Collision and Action to Avoid Collision. It is also necessary to remember that the other Steering and Sailing Rules, both in section II (when vessels are in sight of one another), and section III (in restricted visibility), apply within a scheme as they do elsewhere. Vessels using a traffic lane do not have any priority over crossing or joining traffic.

When crossing a traffic lane the following provisions of the International Regulations for Preventing Collisions at Sea are likely to be relevant:-

“Rule 10 Traffic Separation Schemes

  1. A vessel using a traffic separation scheme shall;

i. proceed in the appropriate traffic lane in the general direction of traffic flow for that lane;

ii. so far as practicable keep clear of a traffic separate line or separation zone;

iii. Normally join or leave a traffic lane at the termination of the lane, but when joining or leaving from either side shall do so at as small an angle to the general direction of traffic flow as practicable.

2. A vessel shall so far as practicable avoid crossing traffic lanes, but if obliged to do so shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.

Rule 15 Crossing Situation.

When two power driven vessels are crossing so as to involve risk of collision, the vessel, which has the other on the starboard side, shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.

Rule 16 Action by give-way vessel.

Every vessel, which is directed to keep out of the way of, another vessel shall, so far as possible, take early and substantial action to keep well clear.

Rule 17 Action by stand-on vessel.

a) Where one of two vessels is to keep out of the way the of shall keep her course and speed;

The latter vessel may however take action to avoid collision by her manoeuvre alone as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with these rules.

b) When, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give way vessel alone, she shall take such action as will best aid to avoid collision.

c) A power driven vessel which takes action in a crossing situation in accordance with sub paragraph (a) (ii) of this rule to avoid collision with another power driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.

d) This Rule does not relieve the give way vessel of her obligation to keep out of the way.”

The ability of a vessel crossing a traffic lane to enter the stream of traffic, and to put herself into the position of stand-on vessel under rule 15, cannot generally be criticized provided that she enters the traffic lane with proper regard to the provisions of Rules 1, 2, 5-8 of the collision prevention regulations. She must also cross the lane on a heading, which is, as nearly as practicable, at right angles to the direction of traffic flow. Crossing the lane at right angles minimizes the time that a crossing vessel is in the lane, and results in a distinct mode of encounter with through traffic in the lane. Failure in any of these areas will attract blame in the event of a collision, as in the English Court of Appeal case, the “Century Dawn” ([1996] LLR 125).

In that case 40% of the blame for a collision was imposed on the “Century Dawn” which was crossing a traffic lane in circumstances where she became the stand-on vessel under rule 15. The “Century Dawn” was criticized for her lookout. She should have carefully checked for traffic both visually and by radar before entering the lane. As it was she did not observe the “Asian Energy’, the vessel with which she was later to collide, until the vessels were one mile apart. Criticism also attached to the “Century Dawn” for failing to cross the traffic lane at right angles.

The “Asian Energy” which bore the majority of the claim for the collision, did so on the basis of her equally poor lookout, an alteration of course to port in breach of Rule 15, and the fact that she was in the wrong traffic lane, albeit inadvertently.

When crossing the traffic lane a vessel is required to cross the first lane at right angles, and then to alter course so that it enters the new traffic lane on a course as near as possible to its line and direction. Whilst traffic separation schemes undoubtedly assist the safe navigation of vessels proceeding within them, crossing them requires particular care and attention.

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