The Annapolis Book of Seamanship

First Chapter

Chapter 8: Rules of the Road There is a risk of collision every time boats come near each other. Recognizing this, early seamen devised local rules of thumb to guide them out of each other's way. As the sea was internationalized, so were these rules, which came to be called the rules of the road or, more formally, the Navigation Rules. These rules (like those that apply to roads ashore) lay out specific requirements for ways in which boats maneuver near each other and signal each other. These rules apply to all craft -- cruising sailboats, aircraft carriers, personal watercraft, sailboards, seaplanes, rowboats, tankers -- and are enforced by the United States Coast Guard, state and local maritime police, and courts of law. The rules are summarized below. The complete rules are contained in the well-illustrated Coast Guard booklet Navigation Rules: International-Inland, available at many marine stores and from Coast Guard district headquarters. Boats larger than 39 feet are required to carry a copy of the rules.

The Navigation Rules have two very similar parts. One, the Inland Navigational Rules, or Inland Rules, applies to lakes, rivers, and near-coastal waters inside a boundary that is a few miles offshore and is marked on charts.

The other is the International Regulations for Preventing Collisions at Sea -- also known as the International Rules of the Road or COLREGS -- which applies to outer coastal waters and the high seas.

The Inland Rules and COLREGS use the same numbering system and arrangement and are almost exactly the same, with the important exception being different requirements for alerting nearby vessels of your maneuvers using whistle, horn, and light signals.

The rules lay out specific rules for action as well as general guidelines. Caution and forehandedness are essential. For example, Rule 8 instructs us to slow down or stop if a situation is of doubtful safety, and Rule 2 makes it clear that the specific regulations are no substitute for good seamanship. Good seamen know their own and their vessels' capabilities, are alert to nearby vessels, carefully regulate their vessels' speed, keep a lookout in periods of restricted visibility, and are always looking ahead, anticipating trouble. If you have any doubt about another vessel's intentions, call her on radiotelephone channels 6, 9, 13, or 16, or shine a light at her, or make the danger signal (five or more short horn blasts or light flashes) -- or do all three.

Give-Way and Stand-On Vessels. Under the rules, when two or more boats are in a situation that might lead to a collision, at least one of them has to stay out of the way by altering course, speed, or both. A boat that must stay out of another vessel's way is called the give-way vessel. A boat that does not have to get out of the way is called the stand-on vessel. (These terms replace the old "burdened vessel" and "privileged vessel.")

Sometimes under the rules all the boats are give-way vessels (for example when powerboats are headed directly at each other). In that case, every boat involved must alter course. But most of the time there is at least one give-way vessel and at least one stand-on vessel. The give-way vessel must get out of the other vessel's way by altering course and/or speed. The stand-on vessel must continue on her course at her current rate of speed in order not to mislead the give-way vessel. Of course, if the give-way vessel does not get out of the way, then the stand-on vessel must alter course, change speed, or both.

The preferred course alteration is to starboard (the right). However, if a turn to starboard will take you into the path of the other vessel, you may turn to port (the left), or you may stop or back down. There are prescribed signals for announcing actions or intentions.

Size Ranges. The rules sometimes specify different requirements for different size boats. The demarcation is the overall length in meters: 7 meters (23.1 feet), 12 meters (39.6 feet), 20 meters (66 feet), and 50 meters (164 feet). To simplify, we'll use the next smallest whole foot of overall length: 23 feet, 39 feet, 66 feet, and 164 feet, respectively.

The Rules Summary

More maneuverable vessels give way to less maneuverable ones -- that is the broad reasoning behind the rules of the road. This is why a moving boat usually gives way to a stopped boat (like a fishing boat); why a moving powerboat gives way to a sailboat; and why in the tight quarters of a narrow channel all three give way to a big ship. Note: when an auxiliary sailboat's engine is on and in gear, she is a powerboat under the rules of the road.

A Moving Boat and a Boat Not Under Way. The moving boat gives way to the stopped boat. A vessel that is under way usually must stay out of the way of a stationary boat -- for example, an anchored boat or a fishing boat.

In Narrow Channels and Traffic Separation Zones. Small boats give way to ships. Ships, ferryboats, tugs with barges, and other large vessels are the stand-on vessels in tight channels and in traffic separation zones (lanes for shipping shown on charts). Boats smaller than 66 feet, boats engaged in fishing, and sailboats must give way in order to allow the ship to continue on in deep water and on a direct course.

Sailboat and Powerboat. Power vessels usually give way to sailboats. Sailing boats are the stand-on vessels, with some exceptions: when overtaking another vessel, when near ships in narrow channels and traffic separation zones, when near stopped vessels, when near fishing boats with nets and lines out, and when near other vessels restricted in their ability to maneuver (such as tows, dredges, and ferries).

Sailboat and Sailboat. Port-tack boat gives way to starboard-tack boat. When boats under sail with their engines off or out of gear are on different tacks, the port-tack boat gives way to the starboard-tack boat.

Windward boat gives way to leeward boat. When sailing boats are on the same tack, the windward boat (the boat upwind of the other) gives way to the leeward boat.

All Vessels. An overtaking vessel gives way to one ahead. The boat behind must stay out of the leading (lead) vessel's way.

Sound and Light Signals. In many situations, the rules require one or more boats under power (including sailboats with their engines on and in gear) to signal their intentions or actions with prolonged (long) or short (one-second) blasts from a whistle or horn. At night, they must also make flashes of a white light in the same pattern. Boats under sail should not use these signals. On boats bigger than 66 feet, the horn must be audible at least 1 mile away (which means a built-in horn), and on 39- to 65-footers, 1Ž2 mile (a hand-held Freon horn should do the job). Smaller boats do not have to carry horn signals, but should.

When leaving dock, sound a long blast.

If you back down, sound three short blasts to announce that your engine is in reverse.

If a collision seems imminent, or if the other crew seems unresponsive to your signals and actions, make the danger signal of five or more short blasts.

When turning, use a sequence of short blasts. Turning to starboard, make one short blast (flash). Turning to port, make two short blasts (light flashes).

Intent-Agreement and Rudder Action. When turning (and in some other maneuvers), the timing of the signals is different in inland waters and international waters. (This difference is one of the few disagreements between the Inland Rules and COLREGS.)

In inland waters (lakes or near-coastal waters), under the Inland Rules, boats exchange signals before a turn is made, using the intent-agreement sequence: signal before making your turn to show your intention and do not turn until the other boat makes the same signal as a sign of agreement with your intention. If the other boat disagrees and her response differs, the signals cross. In that case, sound the danger signal and stop.

In international waters, where COLREGS applies, use the rudder action sequence: make the horn (light) signal as you make the turn.

When a Boat Overtakes Another. The overtaking boat is the give-way vessel. A sailboat or powerboat coming up from astern on another boat must give way to the lead boat. This is the case even if the overtaking boat is under sail and the lead boat is under power.

Sound and light signals in inland waters. Under the Inland Rules, intent-agreement signals are made. The overtaking, give-way boat sounds one short blast (plus a light flash at night) if she intends to pass to starboard, or two short blasts if she intends to pass to port. If the leading, stand-on vessel agrees, she repeats the overtaking vessel's signal, one blast meaning "pass to starboard" and two blasts meaning "pass to port." If the leading vessel's response is a cross-signal (for example, one blast answering the overtaking boat's two blasts), the overtaking vessel should not attempt to pass but should repeat her signal. If the leading vessel sounds the danger signal, the overtaking vessel should not attempt to pass until the leading vessel signals that passage is safe by sounding the correct agreement to the overtaking boat's original intent signal.

Sound and light signals in international open waters, away from narrow channels. Under COLREGS, an overtaking power vessel uses rudder action signals. She sounds one short blast (plus a light flash at night) when she alters course to starboard, or two short blasts (flashes) when altering course to port. If backing down and not passing, she makes three short blasts as she shifts into reverse gear. The leading vessel does not acknowledge these signals, but if she anticipates a collision, she sounds the danger signal (five or more short blasts).

Sound and light signals in international waters in a narrow channel. Under COLREGS, if the leading vessel must alter course to make way for the overtaking vessel to pass, an overtaking power or sail vessel sounds two long blasts followed by one short blast to indicate that she plans to pass to starboard; or two long blasts followed by two short blasts to indicate that she plans to pass to port. The leading vessel must acknowledge this signal. If the leading vessel agrees with the overtaking vessel's intentions, she sounds one long, one short, and one long, which is the International Code signal for "Charlie" or "affirmative." She must then make way for the overtaking boat. But if the leading vessel disagrees with the overtaking boat's plan, she sounds the danger signal (five or more short blasts). The overtaking vessel must not attempt to pass until the leading vessel agrees.

When Powerboats Meet. Both boats must give way, preferably by turning to starboard. Vessels meet when they approach each other on reciprocal or nearly reciprocal courses, bow to bow or nearly so. Both vessels here are give-way vessels. Both must alter course, preferably to starboard so that they pass port side to port side (although the rules make a provision for starboard side to starboard side passage). "Show her your port side" is the rule of thumb.

Sound and light signals in inland waters. Under the Inland Rules, intent-agreement signals must be made if two powerboats are passing within 1/2 mile of each other. These signals are one short blast for course alteration to starboard, two short blasts for course alteration to port, or three short blasts for backing down. (At night also show light flashes.) When one vessel hears the other vessel's signal, she either sounds the same signal to indicate agreement or sounds the danger signal (five or more short blasts) to indicate disagreement. If there is disagreement, both vessels slow or stop. If they agree, the vessels turn to starboard (or port) in order to make safe passage. If the signals cross -- for example, if one boat sounds three blasts and the other sounds one blast -- both boats should sound the danger signal and take appropriate precautionary action.

When meeting, if you have any doubts about the safety of a situation:

1. Assume that you are meeting the other vessel.
2. Sound one blast 1Ž2 mile from the other vessel.
3. Listen carefully for her response.
4. If there is agreement, turn to starboard well to the side of the other vessel.
5. If there is disagreement, sound the danger signal and stop.

Sound and light signals in international waters. Under COLREGS, if a port side to port side passage can be safely made, no signals are required. But if a collision is possible, each vessel must make a rudder-action signal as she turns: one short blast for turning to starboard or two short blasts for turning to port. If a vessel is forced to back down, she makes the backing-down signal of three short blasts.

When Powerboats Cross. The boat to the left is the give-way vessel. Boats that converge without either meeting or overtaking are crossing. The one on the other boat's port side is the give-way vessel.

Sound and light signals in inland waters. Under the Inland Rules, intent-agreement signals are exchanged by vessels in a crossing situation. If the left-side, give-way vessel intends to turn to starboard and go astern of the right-side, stand-on vessel, she sounds one short blast. When the stand-on vessel indicates her agreement with one short blast, the give-way vessel makes her turn (usually slowing down as well). If the give-way vessel intends to turn to port, she makes two short blasts. (Thoughtless skippers sometimes make two or more blasts to announce that they are barging across the stand-on vessel's bow, regardless of the rules of the road.) It's always safer for the give-way vessel -- the one to the port of the other vessel -- to sound one short blast, and when the stand-on boat echoes it, to turn hard to starboard and pass well astern. If signals cross, the stand-on vessel should make the danger signal and stop or slow down. Again, at night, light flashes are made simultaneously with sound signals.

Sound and light signals in international waters. Under COLREGS, the left-side, give-way vessel sounds one short blast as she turns to starboard (toward and astern of the stand-on vessel), two short blasts if she turns to port (but not into the stand-on vessel's projected course), or three short blasts if she backs down to allow the stand-on vessel to pass ahead. But if the give-way vessel intends to slow down or stop, she makes no signal. The right-side, stand-on vessel neither signals nor alters course unless a collision is imminent. If a collision threatens, the stand-on vessel sounds the danger signal (five or more short blasts) and takes appropriate action, usually by stopping, backing down, or turning to starboard, carefully making the appropriate signals.

In Restricted Visibility. The more restricted the visibility, the slower the speed. The Inland Rules and COLREGS both require that every vessel "at all times proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions." Each vessel is required to maintain a lookout for lights and sounds such as foghorns or the wash of other vessels -- no matter what the visibility. Lookouts must be especially attentive to the bearings on approaching vessels. If the bearings do not change as the boats converge, there will be a collision. If the bearings do change, one boat will pass astern of the other.

In poor visibility, vessels are required to reduce speed to a minimum when their lookouts hear another vessel's fog signal from forward of the beam. This is an indication that the boats are approaching each other, and such an approach should be made at the lowest possible speed until all are certain that there is no danger of a collision. There are several required fog signals, each for a different situation. The signals must be made with bells or whistles by vessels 39 feet or longer. Smaller boats are not required to, but should, sound fog signals in periods of restricted visibility.

Sound Signals in Fog. Whistles and bells used as fog and other signals are in both COLREGS and the Inland Rules. Below is a summary.

On vessels that are under way, the following whistle or horn signals are made at intervals of 2 minutes or less:

Sailboats, vessels engaged in fishing, towing, or pushing, and vessels either not under command or restricted in their maneuverability: one long blast followed by two short blasts (long-short-short).
Powerboats making way through the water: one long blast (long).
Powerboats under way but stopped: two long blasts (long-long).
A vessel being towed: one long blast followed by three short blasts (long-short-short-short).
(Under COLREGS only) A powerboat whose room to maneuver is constrained by her deep draft: one long blast followed by two short blasts (long-short-short).

On vessels that are not under way, these signals are made in periods of limited visibility:

Vessel at anchor: if shorter than 328 feet, a bell forward is rung rapidly for 5 seconds every minute; if longer, a bell forward and a gong aft are rung rapidly for 5 seconds every minute; in addition, an anchored vessel may sound her horn in a pattern of one short blast, one long blast, and one short blast (short-long-short) at intervals necessary to alert approaching vessels.
Vessel aground: if shorter than 328 feet, the vessel every minute sounds three distinct bell strokes, then rapidly sounds a bell forward for 5 seconds. If longer, that sequence is followed by the rapid sounding of a gong aft for 5 seconds. A vessel aground may also sound the whistle code signals "F" (short-short-long-short, meaning "I am disabled; communicate with me"), "U" (short-short-long, "You are running into danger"), or "V" (short-short-short-long, "I require assistance") at necessary intervals.
(Under the Inland Rules only) An anchored vessel engaged in fishing or restricted in her ability to maneuver: one long blast followed by two short blasts (long-short-short) at an interval of 2 minutes.
A vessel moored at the end of a pier: make any noise with a horn, bell, or gong.

Other Sound Signals. A vessel about to round a bend in a river or channel where the other side of the bend is obstructed must sound one long blast, to be acknowledged by any vessel approaching the bend on the other side.

The signal for requesting the opening of a drawbridge is one long blast followed by one short blast (long-short), to be echoed by the bridge tender within 30 seconds if the draw is to be opened immediately. If there is a delay, the response is five short blasts -- the danger signal. If the skipper, for reasons of emergency, must pass immediately, she then makes the danger signal. When approaching an open bridge, the vessel should make the long-short signal. The bridge tender will not respond unless he plans to close the span before the vessel passes through. If the skipper requests an opening over the radiotelephone, she should not make a horn signal.

Special Circumstances. Both the Inland Rules and COLREGS allow for special circumstances -- situations when for one reason or another the rules don't quite cover all possibilities. In those cases there is no stand-on vessel, and all boats involved are to consider themselves give-way vessels regardless of their original evaluation of the situation. There may, for example, be a third vessel that due to damage cannot comply with the rules or that has been thrust into the scene. Or a stand-on vessel in a crossing situation suddenly realizes that the give-way vessel to port is attempting to inch across her bow regardless of the signal she gave.

Navigation Lights

All vessels that are under way or at anchor must show (or be prepared to show) at least one navigation light at night and in restricted visibility. Each type of vessel carries a specified combination of navigation lights (running lights) in order to make it easier for other boats to identify her. Here is a description of the lights that most boats must carry (and some day signals, called day shapes, as well):

Sidelights, red for the port side and green for the starboard side, are shown when the vessel is under way. They cover from dead ahead to 112.5° off to each side of the bow (or from 12 o'clock to almost 4 and 8 o'clock).

If you don't see another vessel's sidelights, you are astern and may be overtaking. If you see a red light, her port side is turned toward you. If you see her green light, her starboard side is turned to you. If you see both the red and green lights, she is headed directly at you. Sidelights may be placed on either side of the bow, in the shrouds, in a single lantern on the bow, or (in sailboats smaller than 66 feet) in a tricolor light at the top of the mast (see below).

The stern light is a white light showing aft from the stern through 67.5° on either side, or an arc of 135°. Like the sidelights, it is turned on only when the boat is under way.

The masthead (steaming, bow) light, which when lit indicates that the boat is under power, is a white light located not at the top of the mast, as the name suggests, but partway down. (On small power vessels it may be placed at the top of a short vertical spar). On most sailboats it's about a third of the way down from the actual masthead. Showing over the same arc as the sidelights, it is turned on only when the boat is under power.

The tricolor, a three-in-one light at the top of the mast, may take the place of the stern light and sidelights -- but only on a boat smaller than 66 feet when she is under sail. Because it is high up and uses only one bulb, it both provides the greatest range of visibility and saves electricity. When the engine is turned on and in gear, the tricolor is turned off and the normal sidelights and stern light are lit with the masthead light. The reason for this is that the sidelights and stern light are required by the rules to be lower than the masthead light in order to indicate clearly that the boat is under power. If the tricolor is on when the boat is under power, other vessels cannot accurately read her status under the rules of the road.

An all-around light is any light shining through 360°. An all-around fixed (not flashing) white light hung in the rigging or at the top of the mast indicates that the boat is at anchor. A flashing strobe light at the top of the mast warns off nearby ships.

Navigation lights help mariners identify the type, size, and heading of vessels they see at night. This helps crews understand the situation and determine the course of action they should take. Here is a brief summary of the rules on navigation lights, which must be shown between sunset and dawn and at other times of restricted visibility. The complete rules are contained in the Coast Guard booklet Navigation Rules: International-Inland.

Under Sail. A boat longer than 23 feet that is under sail or being rowed must display red and green sidelights and a white stern light. A boat under sail between 23 feet and 66 feet may show these lights in a tricolor combined light at the top of the mast.

A boat shorter than 23 feet that is under sail or being rowed should display sidelights and a stern light. But if these lights are not displayed, a boat in this category must carry a flashlight or lantern that can be quickly lit and displayed in time to prevent a collision.

Under Power. An auxiliary sailboat that is under power must observe the same rules that all powerboats observe except that during the day a sailboat under sail and being propelled by her engine must display a black cone point down (the Inland Rules do not require this of boats smaller than 39 feet). The basic rule for powerboats is that only the masthead (steaming) light, the sidelights, and the stern light must be lit, with the steaming light above the sidelights. An option for a power-driven boat shorter than 39 feet is a pattern of sidelights and an all-around white light. If this optional pattern is displayed, the stern light and masthead light must not be lit.

A vessel longer than 164 feet must show a second masthead (steaming) light abaft of and higher than the forward one.

Under COLREGS only, a power-driven boat shorter than 23 feet that has a maximum speed of 7 knots or less may show an all-around light.

Large Vessels and Tows. Other types of lights are specified for larger powerboats and for fishing boats, tow boats and tows, and other vessels with limited maneuverability. In general:

A yellow aft-facing light indicates a tow. It is placed just above the stern light on a tug or other boat that is towing or pushing another. A flashing forward-facing yellow light is on the bow of a barge being pushed. Barges show sidelights and stern lights, each barge being considered a separate vessel. The day shape for a towed vessel is a black diamond.

Two or more forward-facing white lights one above the other indicate that the vessel is towing or pushing one or more other vessels.

A red or green all-around (360°) light indicates a working or other boat with poor maneuverability. It can be found on a fishing boat, dive boat, or other work boat that is restricted in her ability to maneuver. Often these boats have nets or equipment to the side or astern. If there are no sidelights showing, the vessel is stopped. If there are sidelights, she is moving ahead slowly and with poor maneuverability.

Range lights (two forward-facing white lights on separate masts, one lower than the other) indicate a large vessel's course. The lower mast is the forward one. When the lights are one above the other, the vessel is headed at you.

Day shapes (black diamonds or ball-diamond-ball sequences) hung in the rigging of a tug towing one or more barges indicate limited maneuverability.

Fishing Vessels. While fishing, if stopped they do not show sidelights and stern lights, but they do show them while under way. In both cases they show all-around red-over-white lights at the masthead, and if their gear extends more than 492 feet to one side, an all-around white light. Day shapes for fishing boats are two black cones with their points together or, for vessels shorter than 66 feet, a basket plus a black cone whose point aims toward outlying gear.

Trawlers dragging nets do not show sidelights and stern lights when they're stopped, but while moving they show sidelights. In either case they show a green-over-white all-around light. Trawlers show the same day shapes as fishing boats, but do not have indicators of outlying gear.

Vessels Not Under Command. In the circumstance that she cannot be steered or make way, a vessel shows two all-around red-over-red lights in a vertical line where they are best seen, and if she's underway, sidelights and a stern light. Her day shape is two black balls in a vertical line.

Pilot Vessels. Vessels that carry pilots out to arriving ships display sidelights, stern lights, and an all-around white-over-red light at the masthead when they are under way. At anchor they light the white-over-red light and the proper anchor lights; during the day they show one black ball for their day shape.

All Vessels at Anchor or Aground. When anchored, a boat smaller than 164 feet shows an all-around white light where it is best seen, unless she is anchored in a Coast Guard­approved special anchorage (see chapter 15), when she need not display an anchor light. The 360° light at the top of a sailboat's mast serves as an anchor light unless it is a strobe, which indicates distress; so does a lantern hung off the headstay. Large vessels show two anchor lights, one forward and one aft. The day shape for an anchored vessel is a ball. If aground, the vessel shows her anchor light or lights plus an all-around red-over-red light where it is best seen.

Other Lights. Law enforcement vessels usually show a flashing blue light. Moored barges carry two white lights. Partially submerged vessels or objects under tow in inland waters carry an all-around white light at each end if less than 82 feet wide, four all-around white lights if wider, and, if very large, all-around white lights no more than 328 feet apart. Submarines in the United States Navy carry normal navigation lights plus a flashing yellow light that flashes once per second for 3 seconds and then is off for 3 seconds.

Maneuvering in Collision Situations

If you are converging with another vessel, take compass or relative bearings on her every 30 seconds. If the bearings move forward, she'll cross ahead of you; if aft, she'll cross behind you. But if they don't change, you are certainly on a collision course. "Constant bearing, closing range" is the rule of thumb. You must take immediate action. Slow down or speed up and take more bearings. Better yet, turn radically toward her wake, let her pass ahead, then turn back on your original course. Whatever you do, you can't afford to wait until the last moment. Converging courses are especially hard to judge if the other boat is at a great distance and going much faster than you are. Large commercial vessels offer a particular challenge because while they seem to be moving slowly, they're actually going twice or three times your speed.

On a bow-to-bow reciprocal course with another vessel, alter course hard to starboard -- at least 20°. "Show him your port side." The closer the boats are to each other, the greater the alteration should be. If the other boat confusedly alters course to her port, into your new path, you can steer hard to port for a starboard side to starboard side passing, you can stop and let her pass, or you can keep going to starboard. Watch her like a hawk. In this situation, taking bearings won't tell you much about the chances of evading collision.

When near a personal watercraft (PWC, Jet Ski), be especially defensive. The noise and quickness of the machine may well overwhelm whatever interest the operator has in observing the rules of the road. These little power vessels are notoriously prone to accidents. For example, in Florida in 1996, personal watercraft comprised 8 percent of registered boats but were involved in 37 percent of the state's boating accidents. Most PWC accidents involved collisions with other vessels, and almost half the drivers had less than 20 hours' experience in PWCs.

At low speeds or in high waves or strong winds, your boat has limited maneuverability and will be blown sideways downwind. Stay far upwind of other vessels.

Near Ships. The so-called "gross tonnage rule," an informal advisory, says that small boats should always stay out of the way of big boats, no matter what the Navigation Rules say. Not only are big vessels unmaneuverable, but they will blanket your wind, and their large wake can pull a boat into their hulls, tow lines, or a barge. Never attempt to sail across a tow line; it's shallower than you think.

Exploit your range of visibility, or the distance to the horizon. Someone standing on the deck of an average cruiser-racer, with eyes 10 feet above the water, sees about 3 1/2 nautical miles (4 statute miles) in clear weather. Of course, ships, with their high sides and bridges, will be visible many miles farther away, assuming clear weather. The range of visibility from the deck of our cruiser-racer to a barge with 50 feet of freeboard is about 11 miles. (We will describe range of visibility calculations in the next chapter.) Since barges move slowly, you'll have plenty of time to take evasive action.

Compare that with the sighting of a 20-knot tanker. The range to its bridge, 100 feet above the water, is about 15 miles. Since the tanker is making a mile every 3 minutes, the two vessels will meet in no more than 45 minutes. If they are moving toward each other, a collision situation may develop in only half an hour. Once the two vessels are within a couple of miles of each other, the ship will be helpless to avoid collision, assuming she even sees your boat, which may not be visible to the crew way aft in the bridge. Even if they did see you, it takes 1­2 miles to stop the ship.

Therefore it is crucial to begin to track large ships as soon as you see them. Once you spot a tanker or freighter, assign a crew member with good eyesight and judgment to lookout duty. Nothing should distract this person from looking at and taking bearings on the ship until it's clearly ahead. While the ship may seem to be moving slowly, do not be fooled. A large vessel at high speed makes very little wake. The best indicator of its speed is how quickly the vessel grows larger and higher as it races toward you.

Do not anticipate that the ship will alter course for you. Unless you're absolutely sure that you'll cross its bow at least 1 mile ahead, alter course so that the ship crosses your bow. Chances are that it's on autopilot, with the deck watch preoccupied with various chores. If the wind were to die or your engine to poop out, there would be nothing to stop the ship from running you down.

Night Sailing. At night, judging the other boat's position, course, speed, and intentions is especially difficult since you have only her navigation lights to go by. You may not be able to distinguish them from her cabin lights or flashlights, or high waves may obscure them.

You must identify the other vessel as soon as possible. If she shows range lights, she's a large power vessel moving faster than first appears. If you see a yellow light, there is a tow. A single masthead light indicates a boat under power -- if it's high up, she's probably a sailing auxiliary, which means she's slow. If you don't see any masthead lights, that means only one thing: she's a sailboat under sail, and her maneuverability and crew's visibility probably are limited.

If the only sidelight you see is the red light, alter your course to starboard (if necessary) to "show her your red" and pass port side to port side. If you see the green light, make whatever adjustments are necessary to clear her at a safe distance, preferably port side to port side but, if necessary, starboard side to starboard side. If both sidelights are visible, she's heading directly at you on a collision course. Alter course hard to starboard until you see only her red light, sail on a little farther to be safe, then turn back to your original course. If you see a white light down low, it's probably a stern light and you're overtaking.

Since red and green have about 25 percent less visible range than white, you often see masthead lights, stern lights, and ranges well before the sidelights appear, especially on large ships. If you can't see the sidelights, study the range lights. If they're in line, she's heading at you; if the range light is to the right of the masthead light, she's heading to your port; if the range light is to the left, she's heading to your starboard. If neither light is visible, she's powering away from you. Since many collisions and near-collisions involve large power vessels and smaller boats, don't allow a pair of range lights to appear on the horizon without analyzing which way the ship under them is sailing.

Always keep a lookout, and don't assume that the other crew sees you. Make your boat as visible as possible. At night, show navigation lights in the proper combination. Someone who does see you will be able to predict your future position if you steer a steady course at a steady speed. In fog, use a radar reflector, but don't assume that you will appear on every ship's radar scope. The ship's long deck, islands, and larger boats may screen you, as may rain or rough waves. At close ranges, a ship's radar may not notice you because the vessel may be rolling.

If a collision seems likely and the other crew obviously doesn't know you're there, do everything you can to make your boat visible. Carry a bright hand-held light to shine on your sails or at the oncoming vessel's bridge. If that doesn't do any good, fire off flares or turn on a strobe light to attract the other crew's attention to your location.

Copyright © 1999 by John Rousmaniere