rule 08 - action to avoid collision

7/24/2019 Rule 08 - Action to Avoid Collision

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Rule 8 - Action to avoid collisiona) Any action to avoid collision shall be taken in accordance with the

Rules of this Part and shall, if the circumstances of the case admit, bepositive, made in ample time and with due regard to the observance ofgood seamanship.

b) Any alteration of course and/or speed to avoid collision shall, if the

circumstances of the case admit, be large enough to be readily

apparent to another vessel observing visually or by radar; asuccession of small alterations of course and/or speed should be

avoided.

c) If there is sufficient sea-room, alteration of course alone may be the

most effective action to avoid a close-quarters situation provided that

it is made in good time, is substantial and does not result in anotherclose-quarters situation.

d) Action taken to avoid collision with another vessel shall be such as to

result in passing at a safe distance. The effectiveness of the action

shall be carefully checked until the other vessel is finally past and

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Rule 8 - Action to avoid collisione) If necessary to avoid collision or allow more time to assess the

situation, a vessel shall slacken her speed or take all way off bystopping or reversing her means of propulsion.

f) (i) A vessel which, by any of these Rules, is required not to impede

the passage or safe passage of another vessel shall, when required by

the circumstances of the case, take early action to allow sufficient sea-room for the safe passage of the other vessel.

(ii) A vessel required not to impede the passage or safe passage of

another vessel is not relieved of this obligation if approaching theother vessel so as to involve risk of collision and shall, when taking

action, have full regard to the action which may be required by the

Rules of this part.(iii)A vessel the passage of which is not to be impeded remains fully

obliged to comply with the Rules of this part when the two vessels are

approaching one another so as to involve risk of collision.

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Rule 8 - Action to avoid collision

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Rule 8 - Action to avoid collisionKeywords

! Positive

! In ample time

! Observance of good seamanship

!Alteration of course and/or speed

! large enough

!

readily apparent!

avoid small alterations of course and/or speed

!Alteration of course alone

! Close-quarters situation

! Passing at a safe distance

!Action shall be carefully checked! Slacken speed, take all way off (stop)

! Do not impede

!Allow sufficient sea-room

! Not relieved from obligation

!

Comply with the Rules 4


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When shall an action contribute to the avoidanceof a collision

When it :

! avoids risk of collision! avoids a close-quarters situation

! is taken in accordance with the Rules

!is made in ample time

! it is made with the observance of good seamanship

(Rule 8, (a))

!is positive

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When is an action considered positive (Rule 8, (a))

When the action of the give-way vessel does not createany doubt on the stand-on vessel

When the give-way vessel does not create a conflictingsituation with the stand-on vessel

When the give-way vessel communicates her intentionsclearly and appropriately by means of sound signals and/or

VHF

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Rule 8 - Action to avoid collisionIn Ample Time

So that the stand-on vessel should have no

doubt as to the intentions of the give-way

vessel

Small vessels like yachts must not wait until the last minute

to manoeuvre in order to admire the passing ship

Larger ships may not think that they always have the right ofway. Deep draught vessels may, however, make an

exception

(Rule 8, (a))

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General considerations

A difference should be made when vessels are in sight ofone another (Part B, Section II and when vessels are in

restricted visibility (Part B, Section III)

The general principle is : one vessel keeps out of the way(the give-way vessel), the other shall keep her course and

speed( the stand-on vessel) (Rule 17, (a))

There are two exceptions : Head-on situations, when in

sight of one another (Rule 14) and vessels in restricted

visibility (Rule 19)

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According to Rule 16, when vessels are in visual sight of oneanother, the 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.

In that case:

! The stand-on vessel is required to keep course and speedand,

! The stand-on vessel will not be justified in taking action

herself in accordance with Rule 17 (a) (ii)

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In ample time

Enough time to assess the situation clearly

Enough time for the OOW not to have to make a decision

hastily

Enough time so that the OOW can gather enoughinformation

Enough time, not to create any confusion or hesitation onthe stand-on vessel

(Rule 8, (a))

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Rule 8 - Action to avoid collisionIn ample time (Rule 8, (a))

Young OOW, with little experience, have a tendency to wait

too long before they engage in an avoiding action. Thiscreates uncertainty on the other vessel and often causes

dreadful decisions on both vessels leading to a collision

Never forget that not only a collision should be avoided but

also the risk of collision 11


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The colregs are not applicable at long range, when thedistance between the two ships is so big that the risk of

collision does not yet exist:

Both vessels are then free to take any action

What is long range ?

This is not quantified in the colregs

It varies for each vessel according to her manoeuvringcharacteristics and dimensions


Keep in mind that : See also Rule 7, (a)

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Rule 8 - Action to avoid collisionGood seamanshipSeamanship is the art of operating a ship or boat. It involves a knowledge of

a variety of topics and development of specialized skills including:

!navigation and international maritime law

!weather, meteorology and forecasting;

!watch standing;

!ship-handling and small boat handling;

!operation of deck equipment, anchors and cables; rope work and line

handling;

!communications;

!sailing;

!engines; execution of evolutions such as towing;

!cargo handling equipment, dangerous cargoes and cargo storage;!dealing with emergencies; survival at sea and search and rescue; fire

fighting.

The degree of knowledge needed within these areas is dependent upon the

nature of the work and the type of vessel employed by a mariner

However, the practice of good seamanship should be the goal of all. wilkipedia 13


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Observance of good seamanship

Every action shall be taken with due regard to the observanceof the rules of good seamanship, and that means:

! The action shall be effective

! Made in ample time

! Made clearly and positively so as to be sufficiently apparent to the other

vessel

! Due regard shall be paid at all times to the existing dangers of navigation

! The prescribed signals shall be given on the whistle (see Rule 34)

! The new course shall be followed without yawning until all risk of collision

is over! In special circumstances, every action shall be taken with due regard to

ones own knowledge and experience

Failing to do so will inevitably result in a disaster

(Rule 8, (a))

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" In order to assess risk of collision clearly,

the following facts about the stand-on

vessel should be known :# Her course

# Her speed

# Her bearing

# Her distance

# Her CPA

# Her TCPA

# Her bow pass

Most of these elements have been largely discussed in the previous

Rules. They show once more that the use of radar is necessary by day

as well as at night (and in restricted visibility). 15


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Alteration of course and/or speed (Rule 8, (b))

To avoid a collision, the following main actions

may be taken :

!An alteration of course

!An alteration of speed

!An alteration of course and speed

Both must be large enough to be readily apparent

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Alteration of course and/or speed (Rule 8, (b))

By day, at night and in restricted visibility:

! Indirectly: by means of radar plotting

!Almost instantaneously: with the ARPA

By day and clear visibility:

! By visual bearings

! By the silhouette of the vessel (not with air cushion vessels)

At night and clear visibility:

! By visual bearings

! By the respective positions of the navigation lights

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Alteration of course and/or speed Rule 8, (b))

! Made in ample time! Be substantial

In other words:

! In time to be able to properly assess the situation and to

have sufficient time to think

! Large enough to be readily apparent

Usually, alterations of speed are observed less rapidlythan alterations of course

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Alteration of course and/or speed Rule 8, (b))

Alteration of speed alone

!May be required by Rule 6: Save Speed

! When there is too little room to alter your course

! When you need more time to assess the situation

Advantages

Disadvantages

! Unless drastic, not easily apparent from another vessel (especially

on the radar

! They take more time to materialize even when stopping and

applying reverse propulsion

! In the open sea, the engines are not on stand-by19


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Alteration of course and/or speedRule 8, (b))

!if the circumstances of the case admit,!

In some situations, large alterations of course and/or speedcannot be made due to:

! The lack of sea room

! The presence of hazards to the navigation,

! Work being carried out (dredging, working on a navigation mark,!)

! The condition of the vessel (bad stability, small under water

clearance,!

!Bank suction,

! Etc.

Whenever possible, avoid a succession of small alterations

of course and/or speed 20


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Alteration of course alone Rule 8, (c))

This is usually the most effective action to avoid aclose-quarters situation, provided:

! There is sufficient sea-room

! It is made in good time,! It is substantial,

! It does not result in another close-quarters situation.

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Amplitude of course alteration

!Echo trail should turn by at least 20!Alteration of course and speed: at least 30

!Alteration of course alone: at least 60!Preferably and recommended: 90

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Rule 8 - Action to avoid collisionAlteration of course alone Rule 8, (c))

Close-quarters situation

on the radar screen

Ships in the striped area

may be considered as beingpotentially dangerous

In open sea:! 2 3 miles in restricted visibility

depending on size and speed! abt. 1 mile when in sight of one

another

In narrow channels:Vessels will inevitably pass closer to

one another 23

R l 8 A ti t id lli i


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Small course alterations are not readily apparent

Give-way vessel alteredcourse 10 to Sb

Privileged vesseldid not alter course

Consecutive alterations of 10 or

less may seem visible on your

vessel (the give-way vessel) but not

on the other vessel (the privileged

vessel)They will also create a doubt on the

privileged vessel whether the give-

way vessel is really taking sufficient

avoiding action

The privileged vessel will also

hesitate whether to apply Rule 17 (a)

(ii) or (b)

The give-way vessel shows very little

visual action to create a clearavoiding action 24


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Large course alterations (if possible), are the best

avoiding action



Course alterations of 20 or more (if

possible) are clearly visible on both

vessels, by day, at night and on theradar

This is a clear situation and the

privileged vessel now clearly sees

that the give-way vessel has takensufficient avoiding action

It will not have to recourse on Rule

17 (a) (ii) or (b)

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Course alterations at night





At night, the give-way vessel should alter course so that on the privileged vessel,first, both sidelights become visible and finally the red sidelight only

Remark: Shown situations are only examples. Every situation must be consideredin accordance with the actual circumstances.HIC AT NUNC (Here and Now) 26


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A classic maneuver is where the give-

way vessel alters course to pass

astern of the privileged vessel

Both vessels will come on opposite

bows.

At night a different sidelight should be

visible

Afterwards, the give-way vessel

gradually turns back until the original

course is resumed

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4

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2

3

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General considerations Rule 8 (b) & (c)

Small alterations of course and/speed are less visible (especially on the radar)and must be avoided

Small alterations of course and/or speed may even increase the risk of collisionand end in a close-quarters situation

A change of course is usually more effective:

!For a vessel sighted ahead or fine on the bow

! For a vessel approaching on Sb at a reasonable distance

! To avoid an overtaking vessel which fails to keep out of the way! Small alterations of course may be confused with the yawning of the vessel

A change of speed is usually more effective:

!

If it is a radical alteration! For a vessel approaching from abeam or near the beam (thus far from the

bow)

A change of course and speed are usually necessary:

! For vessels close to one another

EVERY SITUATION IS DIFFERENT, SO, STRICT RULES CANNOT BE GIVEN

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Passing at a safe distanceRule 8 (d)

The term Safe Distance depends on the circumstancesand conditions such as:

!High seas

! Channels

! Traffic density

! Visibility

! Navigational hazards

! Characteristics and maneuverability of own vessel! The avoiding action one is taking

! Etc.

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In the open sea, with good visibility:

! One mile or more can generally be considered as a safe

distance!At night one mile may not be sufficient

In restricted visibility when observing by radar:

!The closest point of approach (CPA) should be between 2

and 3 miles

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Passing at a safe distance Rule 8 (d)

In order to pass astern of a vessel, itis not uncommon to alter course on

the stern of the other vessel. The

course is being kept on her stern,

gradually coming back to the

original course

THIS MANEUVER IS EXTREMELY

DANGEROUS BECAUSE:! Vessels will pass too close to each

other

! Vessels will find themselves in a close-

quarters situation

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Theeffectiveness of the action shall be carefully checkeduntil the other vessel is finally past and clear

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In this situation, risk of collision isreal and effective.

Action is necessary to avoid a

collision

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Always carefully check the effectivenes of the action

Risk of collisionremains until the

other vessel is past

and clear

An appreciablechange of bearings

may not be sufficient

to establish that the

other vessel will pass

clear (especially withlarge vessels)

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Slackening of speed Rule 8 (e)

According to Rule 6, every vessel is required to proceed at asafe speed at all times

A reduction of speed may also be required:!

To avoid a collision! To allow more time to asses the situation

If necessary, take all way off:! By stopping or

!Reversing the means of propulsion

According to Rule 19 (b) and (e) a vessel in restricted

visibility shall also proceed at a safe speed or take all herway off

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To reduce the speed of a vessel:

!Reduce the number of revolutions of propeller!Stop engines

!Reverse the means of propulsion

Usually, engines are less powerful when running asternthan running ahead

With some engines it may be dangerous to apply a crashstop (from full ahead to full astern)

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Rule 8 - Action to avoid collisionSlackening of speed Rule 8 (e)

When a crash stop has to be applied on a vessel proceeding at full

speed, the engines can become immobilized by reversing too rapidly

It is better to reverse the engines to full astern once the vessels speed

has been reduced

The best procedure to reverse engines (and to avoid acute cavitation is):

1)

To stop the engines

2)

After a few minutes to give slow astern

3)

Then give half astern

4)

Finally give full astern

Seek advise with the Chief Engineer and consult the enginesmanual

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Too often officers hesitate or take too long to carry out an engine action

On most vessels moving at full speed ahead, a certain time will elapse

before the engines may be reversed. Vessels with variable pitch propellers

are an exception

On a vessel of abt. 50.000 dwt, and a speed of abt. 15 knots:

! When the engines are stopped, she will still cover abt. 26 miles

! When the engines are reversed she will still cover abt. 10 miles

A tanker of abt. 200.000 dwt at 16 knots may need:

! 20 minutes to halve her speed after stopping the engines

! One hour to stop the vessel with engines stopped

!Abt. 25 minutes to stop the vessel with engines full astern 38


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Slackening of speedRule 8 (e)

DO NOT FORGET:

That the frictional resistance of the hull in the water, is directly

proportional to the square of the speed

This means that the last miles will take much longer than the first miles to

bring the vessel to rest

When carrying out a crash stop

! The rudder looses its effect when the engines are stopped

!Your ship will have swung abt. 90

You can also stop your ship with a Rudder Cycling Stop

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Keep the following characteristics of your vessel in mind:

!The stopping time

!The stopping distance

!The turning circle

These characteristics must be at the disposal of the OOW and

the pilot and any other person engaged in the maneuver of theship

They must be exposed in a visible spot on the bridge

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IMO Recommandations on navigational watch

The OOW should bear in

mind that the engines are

at his disposal and heshould not hesitate to use

them in case of need .

However, timely notice of

intended variations ofengine speed should be

given where possible

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Advantages of reducing speed

!More time to assess the situation!Better chances of manoeuvring

!In case of collision, less damage

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It is imperative to reduce speed

!In restricted areas where a helm action is

impossible!When other vessels or hazards prevent a helmaction

!When visibility is restricted

!In some crossing situations

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Rule 8 Action to avoid collision


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Rule 8 - Action to avoid collisionDo not impede the passage

Not to impede the passage means that a vessel shall not hamper, hinderor obstruct the passage of another vessel

Some vessels like vessels proceeding in a narrow channel, sailing vessels,

fishing vessels, deep draught vessels, etc. often cannot maneuver at liberty

or take avoiding action and hence, they should not be impeded in theiractivities or in their conditional status

Not to impede may not be confused with keep out of theway because not to impede is required long before a risk of

collision begins to exist

Not to impede can also be described as stay away, and dont bother the

other vessel. In fact, allow her sufficient sea-room

Rule 8 (f) (i)

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Do not impede the passage Rule 8 (f) (i)

Difference between keep out of the way and not to

impede

Keep out of the way only applies when risk of collision

exists and one of the two vessels has to take decisiveaction to avoid it

Not to impede.Risk of collision does not yet exist and theconcerned vessel is, in effect, being asked to take early

actionto avoid such a risk developing

For more details regarding the terms: Close-quarters situation,

Risk of Collision, Not to Impede and Keep Out of the Way,

see Complexity of some Terms after the Rule 19 slides 45



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Rule 8 - Action to avoid collisionDo not impede the passage Rule 8 (f) (i)

Where does the expression not to impede appear! Rule 8f: Action to avoid collision

! Rule 9b: Narrow channels sailing vessels less than 20m

! Rule 9c: Narrow channels fishing vessels

! Rule 9d: Narrow channels crossing vessels

! Rule 10i: Traffic Separation fishing vessels

! Rule 10j: Traffic Separation sailing vessels less than 20m

! Rule 18d: Responsibilities between vessels constrained

by draught

In fact, not to impede should also apply to: vessels not under command,

vessels restricted in their ability to maneuver (dredgers, buoying ships, cable

layers, etc), 46



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Do not impede the passage Rule 8 (f) (i)

Rule 8 (f) applies in all conditions of visibility

Thus :

!By day

! At night

! In restricted visibility

! Whether vessels are in sight or not

!Whether a vessel is only detected on radar

! Etc.

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Do not impede the passage Rule 8 (f) (ii)

The obligation not to impede the passage or safe passage of another

vessel, remains even if a risk of collision already exists

In other words:

If risk of collision has developed between a not to impede vessel andanother vessel, the not to impede vessel will not automatically become a

stand-on vessel and the other vessel a give-way vessel

The not to impede vessel will not be relieved of her obligation to keep out

of the way. Any stand-on action required by any other Rule will be

overridden

The not to impede vessel will not be relieved of her obligation to

also take the necessary action to allow sufficient room for the

passage or safe passage of the other vessel

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Rule 8 - Action to avoid collisionDo not impede the passage Rule 8 (f) (iii)

When a not to impede vessel and a not to be impededvessel, have approached one another so as to involve risk of

collision, the not to be impeded vessel must obey the Rules

of Part B of the Steering and Sailing Rules

Both vessels are now expected to take action and to makean alteration

This was already underlined in the last part of Rule 8 (f) (ii)which clearly states that the not to impede vessel (e.g. a

crossing vessel) shall, when taking action have full regard to

the action which may be required by the Rules of this Part

(of the not to be impeded vessel)

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" Do not impede the passage

# Take early action to allow sufficient sea-room

# Obligation remains if risk of collision exists

# Take into account the action the other vessel

may take

# If risk of collision exist, the Rules of Part B

must be applied

Summary

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" This implies that action

# Shall be effective

#

Made early# Be apparent to the other vessel

# With regard to existing dangers to navigation

# That the necessary signals shall be given

# The new course shall be followed without

yawing

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"Always:

Avoid a collision, but also

The risk of collision

rule 08 - action to avoid collision

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