complexity of some terms

7/24/2019 Complexity of Some Terms

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Part B of the Colregs may well be the most difficult and complex part

where some terms and expressions are used that may create somemisunderstanding and/or doubt in the neophyte or young OOW.

The terms that need to be understood without any ambiguity are:

1.

Close-quarters situation2.

Risk of Collision

3.

Keep out of the way.

4.

Not to impede

All these term may or may not be used in connection with each other.

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The term close-quarters situation has been defined and describe, iIn its

simplest form, in Rule 7.

(See Presentation, slides 7/27, 19/32).

In the figure of next slide, the following statements can be made: It is

obvious that vessels A and B represent a greater potential danger than

vessesl C, D and E. Further, vessel A is a greater danger to the own vessel

(as stand-off vessel) than vessel B (as give-way vessel) (Rule 15).

Vessel C is also a stand-on vessel but vessels D and E who are overtakingvessels, are definitely give-way vessels.

The minute a close-quarters situation is developing with another vessel

whether in sight or not there is a potential risk of collision and the

necessary action needs to be taken to get safely out of this situation. Once

a close-quarters situation has been cleared, risk of collision is theoreticallyalso cleared and any vessel outside the close-quarters zone must be

closely monitored until all risk of collision is finally passed.

The rule of thumb should be:

As far as possible, avoid any vessel to enter the close-quarters zone. 2


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In narrow channels:

Vessels will inevitably pass closer to

one another

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C

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Close-quarters situation

The distance of a close quarters situation is difficult to measure in miles.

It depends upon a number of factors:

-

Size and manoeuvring characteristics of the vessels

-

The speed of the vessels-

The traffic density

-

Experience and judgement of the Master and/of the OOW

-

Etc.

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Distances of 2 to 3 miles are usually suggested, being the range of

visibility of the sidelights or the range of audibility of large vessels.

According the local circumstances, distances of less than 2 miles may

be sufficient (slow speed, overtaking, passing clearly astern, etc. 4


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In its simplest form, risk of collision may start to develop when two

or more vessels have approached one another so close, that if no

action is taken by one or all vessels, a collision would almost be

inevitable.

Risk of collision has been dealt with in Rule 7 and 8.

(See Presentation, slides 7/17, 7/19, 7/20, 7/21 and 8/12.)

As a general rule one could admit that when vessels approach one

another at a distance of 3 to 4 miles or less a potential risk of

collision is developing.

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Risk of Collision (Rule 7, (a))

It is difficult to define "risk of collision", but,the view of A.N. Cockcroft is, that "risk may

be considered to begin when two vesselshave approached so close to one another

that a departure from the rules by either

would bring danger of collision" 6


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Factors determining Risk of Collision :

! The bearing of the vessel(s)

! Distance between two vessels

! Speed of approach

! Do courses cross one another

!The number of vessels in the vicinity

If there is any doubt such risk shall be deemed to exist

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Some of the main difficulties in the Colregs are :

How far apart must vessels be before there is

risk of collision

When is a stand-on vessel obliged to keep

course and speed

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At a distance of 14,76 miles,

there is no risk of collision;

hence, the Colregs do not yet

apply


Risk of collision does not apply to vessels at great distances and with a

low speed of approach

Example

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On the open sea, a distance of

6 miles or less and with a high

speed of approach, risk of

collision may start to develop;

hence, the Colregs do apply


Example

In rivers, narrow channels, canals and harbours, risk of collision applies

at relative shorter distances

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Keep out of the Way

When there is risk of collision between two vessels one of them musttake avoiding action (or keep out of the way) to avoid a possible

collision. There are some exceptions such as Head-on situations,

permissive actions, last minute actions and Dual actions.

(See also the relevant slides which deal with this subject).

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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

Rule 8 - Action to avoid collision

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

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Every 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.

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Not to impede may well be the most difficult term used in the Colregs. It

is also the term which is least understood by students and young OOW.

Not to impede the passage means that a vessel shall not hamper,

hinder or obstruct the passage of another vessel.

Some vessels like vessels proceeding in a narrow channel, sailingvessels, fishing vessels, deep draught vessels, etc. often cannot

maneuver at liberty or take avoiding action and hence, they should not

be impeded in their activities or in their conditional status.

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

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

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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

their draught

In fact, not to impedeshould also apply to vessels not under

command, vessels restricted in their ability to maneuver (dredgers,

buoying ships, cable layers, etc),

(See also the relevant slides which deal with this subject).

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Y$ /$, -96&7& ,A& 6*%%*D& Rule 8 (f) (i)

Difference between keep out of the wayand 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 the

concerned vessel is, in effect, being asked to take earlyactionto 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 17


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Keep out of the way applies as soon asrisk of collision between two ships starts to materialize

Not to impede applies before

risk of collision appears

! when there is a risk of collision

!the give-way vessel must take action to avoid it

! the vessel takes action so that"! no risk of collision starts to develop

Rule 16 - Action by give-way vessel

Do not confuse keep out of the way with not to impede

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Y$ /$, -96&7& ,A& 6*%%*D& 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 impedevessel andanother vessel, the not to impedevessel will not automatically become a

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

The not to impede vesselwill 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 impedevessel 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 19


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R l 17 A ti b t d l


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THE FOUR STAGES IN A COLLISION SITUATION

1. At long range/ Action not yet compulsory but permitted:

Before risk of collision exists both vessels are free to

take action

2. Risk of collision begins to apply:

The give-way vessel must take actionThe stand-on vessel must keep course and speed

3. When it becomes apparent that give-way vessel is

not taking appropriate action:

The stand-on vessel gives the required whistle signal R34(d)and takes action to avoid collision by her manuvre alone

4. Collision cannot be avoided by the give-way vessel

alone:

The stand-on vessel is required to take action to contribute

to the avoidance of collision

Rule 17 - Action by stand-on vesselGeneral considerations

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R l 17 A ti b t d l


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Action not yetcompusory

but permitted

Keep course andspeed

Action permittedSignal required

Action required

The distances at which the variousstages apply will vary considerably:

! Great for high speed vessels in

crossing situation

! In open sea, crossing situation

between power-driven vessels:

a)

outer limit to keep course and speed is

about 5 to 8 miles

b)

outer limit for permissive action is

about 2 to 3 miles



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R l 17 A ti b t d l


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Action not yetcompulsory

but permitted

Keep course andspeed

Action permittedSignal required

Action required

Between 5

and 8 miles

About 2 to

3 miles


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Summary

Less than 1 mile

E l N Ch l


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Example Narrow Channel

1068 4 2 A

B

C

DE

F

G

H

B: Oncoming vessel 5; Must

keep Sb of channel

A: Own vessel - VLCC

C: Sailing vessel 9,5

May act freely.

No risk of collision

D: Vessel fishing 6

Not impeding.

No risk of collision

E: Yacht < 20 m. 3,6

Impeding + Risk ofcollision

F: Power-driven vessel

Impeding + risk of collision

G: Power-driven vessel 8Not impeding + No risk of collision yet24


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Conclusion

The previous slides are only guidelines and examples to determine atwhich distance vessels may or must take action to avoid risk of

collision or indeed a collision.

Vessels come in such a variety of sizes, speeds, manoeuvring

characteristics, etc. that strict guidelines are impossible to be given.

Special circumstances may also have their importance such as narrowchannels, hazards to navigation, the degree of visibility visibility, force

and direction of the wind, etc.

The experience of the Master and the OOW play of course a

predominant role in judging when and how to take an avoiding action.

It is consequently important to judge each situation separately and

always act according to good seamanship,

HIC AT NUNC

(Here and now)25

complexity of some terms

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