Rules for Boats in Traffic Separation Schemes

The courses for most ocean races today pass through or near one or more Traffic Separation Schemes, warranting a deeper understanding of the rules.
Racing near commercial boats
Traffic Separation Schemes keep commercial and recreational mariners safe while transiting or racing in high-traffic areas. François Van Malleghem/DPPI

If you race near a major commercial port, you’ve probably encountered a Traffic Separation Scheme. A TSS is essentially a two-lane highway for maritime traffic. A TSS enhances safety and allows commercial shipping to function alongside recreational boating. A TSS is not delineated by buoys, but charts show its two lanes and the direction of travel within each. There is a separation zone, or sometimes just a ­separation line, between the lanes.

Most TSSs are administered by a Vessel Traffic Service. The VTS serves a role for the TSS similar to that of air traffic control for an airport. The U.S. Coast Guard is usually responsible for organizing and staffing the VTS in domestic waters and use an Automatic Information System, which enables all vessels are equipped with AIS to view the locations and motions of other vessels in the AIS on a digital chart.

Traffic schemes are established in international waters by the International Maritime Organization. In the International Regulations for Prevention of Collision at Sea, Rule 10, Traffic Separation Schemes, sets requirements that apply to any vessel within or near a TSS adopted by the IMO. For a TSS in the inland waters of the United States, Rule 10 in the Inland Rules applies. Rule 10 in the Inland Rules is identical to Rule 10 in the IRPCAS, which requires a sailboat using a TSS to proceed in the appropriate traffic lane in the general direction of traffic flow for that lane; to keep clear of a separation line or zone; when joining or leaving a lane, to normally do so at as small an angle to the direction of flow as practicable; when obliged to cross a lane, to do so as nearly as practicable at right angles to the general direction of ­traffic flow in the lane; when not using the TSS, to avoid it by as wide a margin as is practicable; and, most importantly, not to impede the safe passage of a power-driven vessel following a traffic lane.


The Coast Guard and local law ­enforcement agencies enforce the IRPCAS and the Inland Rules. By law, any sailboat, racing or not, is subject to Rule 10. In The Racing Rules of Sailing, Rule 48.2 requires a boat that is racing to comply with IRPCAS Rule 10 and, for that reason, a boat racing can be disqualified for breaking that rule.

The preamble to Part 2 of the racing rules states that, when a boat sailing under the racing rules meets a vessel that is not governed by the racing rules, she shall comply with the IRPCAS or government right-of-way rules. Given that, you might ask why we need both the preamble to Part 2 and Rule 48.2.

The answer is simple: only the sixth requirement in IRPCAS Rule 10 (listed above) applies when a boat sailing under the racing rules meets a vessel that is not. All of the other five requirements apply to a single boat in or near a TSS whether there are other vessels near her or not.


Any sailboat, racing or not, is subject to Rule 10. Rule 48.2 requires a boat that is racing to comply with IRPCAS Rule 10 and, for that reason, a boat racing can be disqualified for breaking that rule.

Why does any of this matter? Traffic Separation Schemes serve an important safety function that everyone on the water in any boat should recognize and applaud. However, the presence of a TSS that boats racing must, or might, pass through during a race can create safety issues for large, difficult-to-maneuver vessels using the TSS lanes that must contend with a fleet of boats. The Coast Guard requires any organization hosting sailboat races to obtain permits to conduct such races. If boats in a yacht club race create unsafe situations for large commercial or naval vessels in a TSS, the host club, or maybe all clubs in the area, might have trouble securing permits to run future races. For this reason alone, and for the obvious reason of safety, it’s important the leaders of our sport take great care to deal prudently and cooperatively with the authorities involved in enforcing IRPCAS Rule 10 or the identical Inland Rule 10.

Also, Rule 10 presents a few knotty issues of interpretation for protest committees. If you study Rule 10’s requirements listed above, you will see several imprecise or “fuzzy” terms, including “practicable,” “general direction” and “normally.” These terms make it difficult for protest committees to make consistent decisions regarding Rule 10.

Rule 10 is not a rule that any of us involved in sailboat races can simply change. Changing it would require an international agreement negotiated between governments. Race officials, therefore, can’t just rewrite Rule 10 with a sailing instruction to make it clearer. However, IRPCAS Rule 1(b) does permit local authorities to make “special rules” and such rules could modify Rule 10. One club, the St. Francis YC, has negotiated with the local VTS to use a special sailing instruction for races held right off their clubhouse on San Francisco Bay just east of the Golden Gate Bridge. St. Francis has a challenging situation for its racecourse. Any race it might conduct in front of its clubhouse would most likely require boats to sail across a narrow stretch of water frequently used by larger ­commercial vessels.


The following two paragraphs summarize the St. Francis YC’s sailing instruction:

Commercial Traffic: The race ­committee may deploy boats on the racecourse equipped with signal flag V. If a race committee member in one of these boats signals a racing boat to change course—by making a sound with a horn or whistle and pointing flag V at her—that boat shall promptly comply unless compliance would create an unsafe condition. If the boat fails to comply, the race committee shall protest her. The protest committee shall assume that the course change would not have created an unsafe condition, and the protested boat shall have the burden of proving otherwise.

Also, if a commercial vessel makes five short, rapid blasts on its whistle (a danger signal, see IRPCAS Rule 34(d)) at a boat that is racing, and/or the vessel or the Coast Guard is subsequently able to identify the offending boat, that boat may be protested; if so, the protest committee shall assume that she has impeded the commercial vessel’s passage or otherwise violated Rule 10, and the protested boat shall have the burden of proving otherwise. If the protest is upheld, the boat shall be scored DNE: disqualification that is not excludable. St. Francis YC shall cooperate with and provide relevant information to the Coast Guard or other governmental authority regarding investigations of boats impeding ship traffic or violating the Inland Rules.


Other organizations have adopted a much simpler way of dealing with a TSS in or near the racing area. For example, the sailing instructions for the Fastnet Race simply designate several TSSs as obstructions—as permitted by the definition Obstruction—and state that boats shall not enter areas designated as obstructions. Of course, this approach is feasible only if it is possible for boats to sail the course without entering any of the separation schemes.

There are now more than 100 TSSs and the racecourses for most ocean races pass through or near one TSS—or, sometimes several. For this reason, World Sailing has established a committee to make a proposal for dealing more comprehensively with TSSs in The Racing Rules of Sailing. The committee is chaired by Stan Honey, Chairman of the World Sailing Oceanic and Offshore Committee, and, in writing this article, I have benefited from research that Stan has done on TSSs.

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