Avoiding Collisions


It's been said; "A collision at sea can ruin your whole day." In order to avoid this, there exists a general set of Federal and International rules of conduct between vessels known collectively as the 'rules of the road'. Part of the rules cover what lights vessels should show which is covered in Navigation Lights. Another part of the rules is meant specifically to guide actions of vessels in close proximity to each other. Just as we stop our car at a red light and go around another car to pass it, there exist maneuvering rules to guide us when we are on the water. To read these rules in their entirety go here: http://www.navcen.uscg.gov/?pageName=navRulesContent

The rules of the road cover every type of water craft from small to large. However, there are situations the rules do not cover. For instance, when three or more vessels converge there are no specific guides to use except common sense. If we know the rules of conduct between two vessels, then we will have a very good idea of how to react when there are more than two vessels meeting or passing.

Throughout the rules caution and anticipation are emphasized. If you aren't sure what's going on you can come to a complete stop, sound the danger signal (5 or more short blasts), or call the other vessel on the VHF radio. Typically, channel 16 is used as the hailing channel for recreation vessels but ships are more likely to be monitoring channel 13. It can be useful and quite reassuring to speak with the freighter coming up from behind in a narrow channel after dark. The ship is probably going at least twice your speed and will be upon you soon. If you communicate to the ship's bridge you intend to stay well to the starboard side of the channel that takes care of the situation. And, the ship's captain will be relieved also; now the captain knows you are aware of the ship, that you are probably competent because you communicated over the VHF with him, and that he can proceed knowing it won't be a dangerous situation.

Stand-on and give-way vessels. The give-way vessel stays out of the way of the stand-on vessel. This does not relieve the stand-on vessel of responsibilities. She is called the stand-on vessel because she must stand-on her course and speed. By doing so, she gives the give-way vessel a way to assess the situation as it develops. What if the give-way vessel does not get out of the way? In that situation the stand-on vessel will have to alter her course and/or speed to avoid danger.

The more maneuverable a vessel is the more likely she is to be the give-way vessel in a close quarters situation. This is why the powerboat is give-way to a sailboat; why a boat that is moving is give-way to a vessel stopped; and why they all give way to a large ship in a narrow channel.

Vessel sizes. All vessels are covered by the rules. The rules are more complicated for larger vessels than smaller ones. Vessels are grouped by their length: Less than 7 meters (23'), 7-12 meters (23'-39'), 12-20 meters (39'-66'), and 20-50 meters (66'-164'). A small vessel (or craft) is less than 20 meters (66') in length.

One note on powerboats and sailboats. A sailboat is a boat that is being propelled by sail alone, if her engine is on and engaged she is considered to be a powerboat even with her sails up.

Sailboats meeting. Here you will need the ability to determine what tack you are on and what windward and leeward mean. You will recall from Points of Sail that our tack is defined as the opposite side on which the mainsail or boom is carried. Below, the boat on the left is port tack while on the right the boat is starboard tack.

Sailboats meeting on opposite tacks.

The sailboat on starboard tack is stand-on while the boat on port tack is give-way. When boats give-way they should, in general, turn to starboard. It's much easier for a sailboat to turn than to slow down or speed up. Ok, so what happens when two sailboats come together on the same tack?

Sailboats meeting on same tacks.

The windward boat keeps out of the way of the leeward boat. The windward boat is the one further upwind, closer to where the wind is coming from. The preferred course is for the windward boat to turn and go behind the leeward boat. The leeward boat takes no action other than to maintain her course and speed. Also, she should be watching the windward boat to make sure she alters course. In this particular case the windward boat alters her course to port which is the easiest way to fall behind the leeward boat.


In most rights of way situations it is best to make an early and substantial change in course. Here substantial would be 20 degrees or more. This action, on the part of the give-way vessel notifies the stand-on vessel that she can proceed on her way without danger.

Powerboats crossing. When two powerboats cross it is a similar situation to Powerboats crossingtwo cars coming to a 4 way stop. The car (boat) on the right has the right of way. The give-way powerboat turns to starboard and passes behind the stand-on vessel. If this were at night the give-way vessel would see a red sidelight on the stand-on vessel meaning she should take early and adequate action. The stand-on powerboat would see green on the give-way vessel meaning it is ok for her to proceed on her course and speed.

Powerboats meeting. When coming straight at each other both powerboats turn to starboard.

Sailboat and powerboat. On open water, not in channels, power gives way to sail. In narrow channels large ships have the right of way.

Vessels overtaking. The overtaking vessel is give-way and must stay out of the way of the vessel being passed. It makes no difference if one of the vessels is power and the other one sail. Whoever overtakes must keep clear. The exception to this is for large (over 20 meters in length) ships in narrow channels. Here, the hard to maneuver ship is stand-on.

Pecking order of vessels. There is a basic order, in the navigation rules, that governs who stays out of the way of whom. Essentially, the hardest to maneuver vessels are stand-on while the easiest give-way to others. In the following list vessels further down stay out of the way of vessels higher up.

Diving. Vessels engaged in dive operations or with anyone in the water. They display the international code flag "A" (alpha) by day; this is a blue/white vertically striped swallow tail. State laws also may call for dive vessels to display the US traditional dive flag (red with a white diagonal stripe). It is important for all other vessels to stay well clear.

Alpha dive flag Dive flag

Fog signals. Vessels underway are required to produce sound signals in restricted visibility; This could be fog, heavy rain, or smoke. All signals are repeated every two minutes or less. A prolonged blast lasts 5 seconds while a short blast is for 1 second.


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