Handbook of the Nautical Rules of the Road by Llana & Wisneskey

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Rule 5 -- Lookout



Every vessel shall at all times maintain a proper lookout by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.

Every vessel shall at all times maintain a proper lookout by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.


Rule 5 is a short rule that places a large responsibility on the mariner. Rather than specific duties, equipment, places, times, and number of persons, Rule 5 requires the master to decide how best to maintain a proper lookout. Instead of giving us precise guidance on the adequacy of the lookout, the Rule uses vague terms such as "proper" and "appropriate." Only in this way could the Rule reasonably provide for all vessels at all times. Requirements covering even the most common situations would have been intolerably detailed and complex.

The lookout requirement of Rule 5 relies heavily on common sense and good seamanship. If you are able to comply with the Steering and Sailing Rules (Part B of the Rules) and with Rule 34--all of which depend on lookout information--you will no doubt have met the demands of Rule 5. A proper lookout, therefore, provides all the information needed to comply with those Rules. If the information collected by the lookout is insufficient, then the master must intensify his or her lookout efforts (for example, by turning on the radar) or reduce the need for information (for example, by slowing a fogbound vessel).

The "information gap" that sometimes opens between the amount of information collected and the amount needed to comply with the other Rules is a leading cause of most collisions. Too often vessels collide because they their masters have either ignored the gap or have filled it with assumptions. An appreciation of the lookout requirement will take the mariner halfway toward avoiding collisions.

Definition and Purpose of the Lookout

What is a "lookout"? Perhaps the most common image that leaps to mind is that of a lone seaman wearing yellow foul-weather gear and a navy watch cap, stationed at the very bow of the ship and peering out into the gloom to catch a flicker of light or the moan of a foghorn. This perception is misleading. The term, as used by the Rules, denotes not a person but rather the systematic collection of information.

Responsibility for maintaining a proper lookout lies with the vessel's operator, not with a subordinate designated as "lookout." The vessel's operator--that is, master, watch officer, or person in charge--is the lookout manager. If the operator can keep a lookout personally, then coordinating the collection and analysis of information is relatively straightforward. But if the operator, that is, the decision-maker, must rely on others to gather the information, then management of a proper lookout becomes more complicated. The operator must ensure that information on the vessel's surroundings is detected in a timely manner and promptly communicated, so that he or she can correctly analyze the situation.

The purpose of the lookout is simple, so simple that it can easily be overlooked. As the purpose of the navigation rules is to prevent collisions, it follows that the purpose of the lookout is to collect the information needed to avoid collisions. This fundamental reason for maintaining a proper lookout is something to keep in mind.

Duty of the Lookout

Traditionally, the duty of the lookout was to watch out for vessels, lights, and other objects (such as reefs, shoals, and icebergs) by sight and hearing alone and to report their presence to the vessel's operator promptly. The lookout was allowed some discretion on what to report in crowded waters and would be assigned no other duties that would interfere with this important function.

Although the traditional principles of the lookout are still pertinent, today's mariner has tools available that greatly extend the distance over which information can be detected. Today, a proper lookout is a team effort. Yet the master of the vessel is the one held accountable. For this reason, the master must see to it that each member of the lookout team is competent in the use of equipment and diligent in the performance of that duty.

The master, who knows the vessel's needs for information and who has the authority and the Rule 5 responsibility, should determine the duties of each member of the lookout team. It is the master's duty to ensure that a proper lookout is maintained at all times. That duty cannot be delegated.

Tools of the Lookout

Sight, hearing, and "all available means" are tools of the lookout. While not too long ago "all available means" was limited to the spyglass, modern mariners have a wealth of tools with which to extend the human senses.

Human sight and hearing have, of course, their limitations. Near sightedness may be uncorrected or poorly corrected. Even good eyesight is affected by environmental factors such as ambient light, weather conditions, water spray, or wind. Fatigue can also affect vision, as can moving between extremes of light. Similarly, hearing my be impaired. The noise of wind and wave and ship's machinery may mask the sound you want to hear. The blast from a ship's own whistle blocks out other noises and will temporarily, perhaps permanently, reduce the hearing of the lookout. Hearing testing would be advised.

Fortunately, mechanical means for maintaining a lookout are available. "Available" to Rule 5 means "shall be used" in appropriate circumstances. Some of these "other means" are listed below:

  • Binoculars
  • Radar
  • VHF bridge-to-bridge radiotelephone
  • Automated radar plotting aids (sometimes called collision avoidance radar)
  • Differential GPS (DGPS) satellite navigation equipment
  • Automatic Identification Systems (AIS) radio transponders
  • Vessel traffic services
  • Navigation and piloting instruments

Radar has assumed such importance on modern vessels that Rule 6 (Safe Speed) and Rule 7 (Risk of Collision) discuss it specifically. Most commercial vessels are now fitted with radar, and probably anyone who has seriously ventured out on the water has some concept of what radar is and what it does. Why then are there so many radar-assisted collisions--collisions that occur even though the other vessel was observed on the radar screen? And why are there still night-time collisions when the radar was either not turned on or not observed? As with most tools, radar will not provide any benefit unless used, and used correctly.

A lookout may check an empty radar screen and believe nothing is there because he or she can't see anything. What may have happened, though, is that a weak contact with a small nearby vessel is lost when the radar operator twisted the sensitivity knob to reduce sea-surface clutter. Collisions occur because radar observers rely on capabilities the radar does not have.

A lookout may observe a contact on radar, begin to form a mental pisture of the other vessel, an possibly make a course change. A few minutes later, upon checking the screen, the oberver "confirms" the other vessel's imagined course and speed a not leading to a collision. In making this "confirmation," the radar observer has incorporated a string of assumptions into the process. If the oberver had taken the time to plot the tracks, rether than rely on assumptions, he or she would have seen that the vessels were in fact on a collision course. We cannot emphasize enough how important it is to distinguish between assumption and fact in your decision making. Consciously seek out, do not unconsciously suppress, conflicting evidence. It is very difficult to calculate mentally another vessel's relative course and speed after observing a radar blip two or three times--difficult to the point of impossibility. Assumption making is not one of the "other means" referenced in Rule 5.

If you are fortunate enough to have more advanced (computer-enhanced) radar equipment, your job will be easier; just keep in mind that all aids have their limitations. Do not assume a machine will do your job for you.

Some mariners believe that radar is not necessary on clear nights, yet collisions continue to happen in those conditions. In one such instance, a ship not using its radar ran into a large, newly constructed oil platform in the Gulf of Mexico. The platform was inadequately lighted, but so are many other vessels and objects. Just because you can't see something at night in good visibility doesn't mean it isn't there.

Rule 5 does not require the installation of radar, but if radar is installed it must be used whenever it would contribute to the quality of the lookout. What are your obligations if radar is installed on your vessel but is not working properly? Rule 5 does not require that mafunctioning radar be used. If the problem is temporary, such as signal blockage caused by a heavy rainstorm, the use of radar can be suspended but not abandoned.

Radar can be carried one step further by incorporating a computer to calculate the courses and speeds of other vessels the radar detects. The computer than relates that information to the vessel's own course and speed. The automated radar plotting aid (ARPA) displays position, course, and speed for each target and signals when it detects risk of collision. Some ARPAs will also display the projected future track of each vessel, all against the background of an electronic chart of the area.

Because all of the information on the vessels comes from radar, ARPA's technical limitations are the same as radar's. However easy it is to become overdependent on radar, it is much easier to relinquish the lookout function, including decision-making, to the magic-box ARPA. A poor understanding of this very useful tool may lead the unwary mariner into extremis.

Automatic Identification Systems (AIS) have been implemented in some areas to advance the state of the art even further. AIS uses radio transponders in much the same way as the mandatory aircraft T-CAS collision avoidance system uses Mode-S radar transponders to transmit encoded information from each aircraft to other aircraft in the area and to air traffic controllers. In the case of the shipborne AIS, this information can include vessel identification, GPS/DGPS position, course, speed, navigation status, dimensions, or cargo. Combined with a display capability, AIS presents critical navigation and vessel traffic information to the bridge team. AIS systems at present are limited and have not been standardized, although an international standard is being actively pursued, and it seems likely that carriage requirements for such equipment will follow adoption of an international standard.

In many situations the best way to find out if other vessels are in the area is to ask. A blind call on the radiotelephone may elicit an answer from an undetected vessel, or a call about traffic to a known vessel may produce useful information, such as any planned course changes. In a number of heavily trafficked areas the mariner can call a vessel traffic service (VTS) for advisory information. The VTS operators keep track of all major vessels' positions, course, and speeds, as well as accumulate information on navigation hazards. This service will be discussed in more detail with Rule 10.

The tools available to aid the mariner in maintaining a lookout will continue to develop. The use of shipboard radar transponders in conjunction with ARPAs and radiotelephones, for example, is being explored. The continued exploitation of microprocessor technology will make available new means for maintaining a proper lookout. Whatever changes the future will bring, Rule 5 will continue to require that the person directing the movement of the vessel know the benefits and limitations of any new devices and be able to use them. Continuing education is part of the navigation rules.

Prevailing Circumstances and Conditions

A proper lookout is that which is sufficient to prevent a collision, without any allowance for good luck, in the prevailing circumstances and conditions. Tp give substance to this definition, we offer more specific observations:

  • A lookout in the open ocean can be less intense than one in coastal or inland waters. It cannot, however, be abandoned--midocean collisions do occur.
  • A lookout on a vessel at anchor is required, with the level of effort depending upon the location of the anchorage, depth of water, type of ground tackle, wind, currents, waves, and so forth. The lookout should determine whether the anchor is dragging and should warn other vessels of the anchored vessel's presence.
  • The means and methods for maintaining a lookout vary with night and day. At night, lookouts should make greater use of binoculars and radar. Masters should post observers away from the vessel's own lights so as not to impair the night vision of the lookout. During the day and in good visibility, a vessel can be seen at a much greater distance , as indicated by the fact that a masthead light for the largest vessel need be visible for only six miles and for the smallest vessel, only two miles. During daylight, and under the most favorable conditions, the watch officer on a large vessel may perform the lookout alone.
  • The size and arrangement of a vessel have a direct bearing on the effort required to maintain a proper lookout. On small vessels where there is an unobstructed all-around view and where there is no impairment of night vision, the craft's operator may both steer and keep the lookout. Unobstructed view, simple controls, no distractions, and high maneuverability are important here.
  • Visibility is generally the key factor in maintaining a proper lookout. As the visibility decreases, the level of effort to maintain a proper lookout increases tremendously. Sight needs to be augmented by hearing, radar, and radiotelephone. Unless you are in the open ocean, you should seek precise navigational information. In the case of low-lying fog, at least one person should be positioned high enough to see over the fog.

Full Appraisal of the Situation and Risk of Collision

These last words restate the purpose of Rule 5. It is this broad objective that you should keep in mind when managing the lookout. If there is not enough information to assess the situation, you should tap all your resources to gather more. If you are still unable to acquire the information you need, then you should take steps immediately to reduce your requirement for information--for example, by slowing or stopping. Otherwise, you are violating Rule 5. This is not one of those circumstances where doing more with less is a virtue.

Although it is true that the determination of a proper lookout is left to the mariner, it is also true that courts of law assign as a contributory fault the lack of a proper lookout in a very large proportion of collision cases.


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