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1 INTRODUCTION
Collisions have been the second top cause for
shipping casualties and incidents in 2022 [1]. The
Norwegian Maritime Authority – which collects
incident statistics that combine Norwegian vessels
regardlessoflocation,andforeignvesselsoperatingin
Norwegianwaters– reportsthatinevery year since
2011atleast
16collisionshaveoccurred[2].
To prevent collisions from occurring, the
International Maritime Organization (IMO) has
published the International Regulations for
Preventing Collisionsat Sea 1972 (COLREGs). These
rulesapplytoallvesselsuponthehighseasandinall
waters connected therewith navigable by seagoing
vessels [3]. As such,
maritime autonomous surface
ships (MASS) will also be required to follow these
rules.
Having entered into force in 1977 – they were
presumably written without having modern
autonomous cargo vessels in mind. The COLREGs
include various qualitative terms – such as “early”,
“substantial” and “safe” – without providing any
information as
to how these terms could be
understoodinquantitativeterms.Theresultisarule
systemthatreliesheavilyontheinterpretationofthe
navigator. While ambiguity is a desired trait of the
COLREGs (a completely prescriptive and rigid rule‐
systemwouldbeinfinitelycomplicated[4]),ithasled
to
asituationwheretheremaybealargediscrepancy
betweenthelegalinterpretationoftheCOLREGsand
theconventionalwaynavigatorsavoidcollisions[5].
In practice this means that navigators are pressured
bothtofollowconvention,inordertoavoidcollision,
andthelaw,toavoidprosecutionshouldanythinggo
wrong
[5].
Safe Vessel Operations
–
The Tacit Knowledge of
Navigators
L.O.Dreyer
WesternNorwayUniversityofAppliedSciences,Haugesund,Norway
ABSTRACT:Thecollisionregulationsincludeseveralqualitativetermswithoutprovidingguidanceastohow
thesetermscouldbeunderstoodinquantitativeterms.Thesetermsmustthereforebeinterpretedbynavigators,
whichposesaproblemforautonomousships.Extendtheknowledgeofhownavigators
interpretthecollision
regulations,withaspecificfocusonhowtheyinterprettherulecoveringtherequirementtoproceedatasafe
speed.QualitativestudybasedoninterviewsofaconveniencesampleofeightNorwegiannavigators.Datawas
analysedwithsystematictextcondensation.Navigatorscharacterisesafespeedasaspeed
inwhichtheyhave
control.Navigatorsdonotlookatdifferentfactorsmentionedinthecollisionregulationsinisolation,butwithin
thecontextofthesituation.Determiningthesafespeedofavesselismorecomplicatedthanmadeoutinthe
literature. As autonomous ships will have to cooperate with conventional
vessels, their programming must
includetheknowledgeofhowthecollisionregulationsareinterpretedbyhumannavigators.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 17
Number 3
September 2023
DOI:10.12716/1001.17.03.09
580
This distinction between the legal interpretation
andconventionwashighlightedina study byDreyer
[6],whereitwasshownthatvesselspeedspredicted
by legal interpretation of the COLREGs and actual
observed vessel speeds did not align: The idea put
forward by legal scholars that visibility is the most
importantfactorwhenitcomestosafespeed[7‐9]was
notmirroredinthedataofactualshipbehaviours.
Ascollisionavoidancebetweenvesselsisseenasa
game of coordination,where navigators on different
vessels have to independently choose mutually
compatible strategies [5], the control system of a
MASS must not only be aware of the legal
interpretation of the COLREGs, but also of the
conventional way navigators apply the rules in
practice.Indeed,ifMASSare“toostrict”infollowing
thelegalinterpretationoftheCOLREGstheymight–
at times – jeopardize the safety of a ship
encounter
[10].
Asabetterunderstandingoftheconventionalway
navigators apply the COLREGs in practice is
necessary,thisstudyaimstoextendtheknowledgeof
how navigators interpret the rules, with a specific
focus on how they interpret the rule covering the
requirementtoproceedatasafespeed.
2 BACKGROUND
Rule 6 of the COLREGs deals with safe speed. It
requiresthat“everyvesselshallatalltimesproceedat
asafespeedsothatshecantakeproperandeffective
action to avoid collision and be stopped within a
distance appropriate to the prevailing circumstances
and conditions”. To
determine what speed may be
considered safe, the COLREGs provide a number of
factorsthatshallbeamongthosetakenintoaccount,
includingvisibility,trafficdensity,manoeuvrabilityof
the vessel, background light, the state of wind, sea
and current, the proximity of navigational hazards
andthedraught inrelationto
theavailabledepth of
water[11].
3 3MATERIALSANDMETHODS
3.1 Participants
Apurposivesampleoftwofastferrycaptainsandsix
maritimepilots(eightmen,nowomen)aged33–61
years working in Norway participated in the study.
The lack of gender difference largely reflects the
situationin
themaritimeindustrywherethemajority
ofseafarersaremen[12].Thestrategyforselectingthe
study subjects (purposefully) was influenced by
homogenous sampling (in terms of professional
background) and convenience sampling [13]. The
conceptof saturationwasconsideredwhendeciding
ontheamountofinterviewstoconductinthis
study
[14]. Saturation is achieved “when gathering fresh
data no longer sparks new theoretical insights, nor
reveals new properties of your core theoretical
categories” [15]. Following the eight semi‐structured
interviews that were conducted, saturation was
achieved.
The professional seafaring experience of the
participants ranged from 8 – 38 years. Seven
participantshad21yearsofexperienceormore.
3.2 InterviewProcedure
The author conducted the interviews.One interview
was conducted via the videotelephony software
program Zoom Meetings, one interview was
conducted in a meeting room at the interviewer’s
workplace and the rest of the interviews were
conducted at the homes
of the interviewees. The
interviews lasted from 58 minutes to 2 hours and 6
minutes.Asemi‐structuredinterviewguidewasused
as a tool to obtain detailed descriptions of the
seafarers’ experiences in order to grasp the tacit
knowledge of seafarers that is so important in
ensuring safe vessel operations.
The main questions
were: How do you ensure the safe and smooth
operation of your vessel? What factors go into your
decisionforsettingyourvesselsspeed?Howdoyou
determine safe speed? Could you rank influencing
factorsbyimportance?
Allinterviewswererecordedandtranscribed.
3.3 DataAnalysis
The
data collected in this study was analysed by
means of systematic text condensation [16]. The
approach is described as a four‐step procedure: (1)
reading the transcripts to get an overall impression
and identifying preliminary themes; (2) extracting
meaningunitsfromthetranscriptsandsortingthem
into codes and code groups;
(3) condensing the
meaningwithineachcodegroup;(4)summarizingthe
content into meaningful descriptions [16, 17]. The
author conducted all steps of the analysis. In this
regarditmustbenotedthattheauthor’sbackground
as a navigational watch officer with knowledge and
experiencewithinthefieldhasinfluenced
theprocess
of collecting and interpreting data. As the final
descriptions were developed and refined over time,
the interview transcripts were read repeatedly to
ensure that the constructed descriptions were
groundedintheempiricaldata.
3.4 EthicalConsiderations
TheNorwegiancentreforresearchdataapprovedthe
study.Theintervieweesreceivedan
informationletter
and provided consent to participate. They were
informedthattheycouldwithdrawfromthestudyat
any time (until publication) without providing any
reason. Data was treated confidentially and
informationabouttheseafarersispresentedinsucha
waythattheyarenotidentifiable.
4 FINDINGS
It was
found that navigators predominantly
experienceavesselsspeedtobesafe when they feel
comfortable with the ship and feel that they are in
control.WhileCOLREGrule6–therulecoveringthe
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safe speed requirement – mentions several factors,
andlegalscholarshavepointedtovisibilityasbeing
the most important factor, the navigators had a
different view. Navigators highlight that the factors
affectingsafespeedareverydependentnotonlyone
another,butalsothecontextofthesituation.Indeed,
as
the context is often confused and complicated,
rankingdifferentfactorsbyimportancewilllikelybe
anoversimplificationthatdoesnotcoverallscenarios.
While visibility is seen as an important factor, the
impactvisibilityhason“safe”speeddependsonthe
specificcircumstancesofthesituation.Thesefindings
areelaborated
below.Thefindingsincludeauthentic
illustrative quotations (AIQ), which are not
necessarilydirectcitationsbutdescriptivesynthesized
quotations that aim to grasp the essence of the
opinionsvoicedbyallinterviewees[16,18].
4.1 EnsuringSafeandEfficientNavigation
When asked how they ensure safe and efficient
navigation, interviewees responded by
firstly
mentioning one of the following two concepts:
Comfortableness with the vessel, and knowledge of
the area. How comfortable they are with the vessel
theyareondepends onboththemanoeuvrabilityof
thevesselitself,aswellasoutsidefactorsaffectingthe
vessel. When the navigator is comfortable with
the
vessel,lessattentionisrequiredforkeepingthevessel
oncourse.Thisfreesupmentalcapacitiesthatcanbe
focusedonotherimportanttaskssuchasoverseeing
thetrafficsituation.
If you are very comfortable with the vessel, and you
encounter bad weather, then you do not need to use
so
manybraincellsandenergyonthinkingabouthowtoturn
thevessel.
The same principle applies to being comfortable
with the area the navigator is navigating in. Being
well versed in the area includes being aware of the
safe path(s) through the area, navigational aids and
dangers as
well as areas where encountering other
trafficislikely.
If you know the area, the way, the courses, and the
navigational aids, then you can function as a human
sensor: even if there is a technical failure in the vessel’s
navigationequipment,youshouldstillbeabletofindyour
way.
Actively utilising the available navigational aids
means that navigators can traverse an area without
having to constantly check the (electronic)
navigational charts or relying on technical support.
Thisbothintroducesredundancyaswellasitfreesup
mentalcapacitieswhichthenavigatorcanthenfocus
onotherimportanttasks.
4.2
TheMeaningofSafeSpeed
Whenitcomestosafespeed,itwasdifficulttogeta
clear definition of the concept. During some
interviews it seemed as if the interviewees
understandingoftheconceptwasinconsistent.
Safespeedisaspeedwhichallowsyoutostopbeforeyou
get into
a dangerous situation. If something suddenly
appears in front of you, you must be able to stop. This
would mean that you should not be underway when
visibilityissopoorthatyoucannotseepastyourownbow.
Butinreality,safespeedissoindividualthatitis
difficult
todefineproperly.Wegothroughtightwaterwayswithfull
speedbecausewefeellikeweareincontrolofthevessel.So
maybe safe speed really is the speed that you as the
navigatorfeelsafein.
The above AIQ illustrates how the interviewee
initially thought of the legal
understanding of the
term safe speed, and later adjusted the meaning
accordingtohow they applyitin practice. Thisgap
between legal interpretation and the conventional
wayseafarersdeterminesafespeedwas pointedout
specificallybyanotherinterviewee.
Safe speed is quite juridical … I don’t know, but that
term is perhapsvery broad. When I thinkabout setting a
speed that is safe, I don’t usually think about the
COLREGs. What I’m concerned about is that the vessel
steersand movesas Iwant itto, and thatI feelconfident
thatIcannavigatesafely.
The importance of
keeping control of the vessel
and the situation was echoed by the majority of the
interviewed navigators. Factors such as
manoeuvrability of the vessel, traffic situation,
external environmental factors and navigation area
playalargeroleinthisregard.
Themostimportantthingisthatyoufeelincontrolof
the vessel and the situation around you. Going with full
speed reduces your options and means you require more
room to manoeuvre. Reducing the vessels speed generally
increases your manoeuvrability and provides additional
flexibility. It also means that you have more time to
evaluate andexecute thecorrect choices. But be
carefulto
not reduce yourspeed too much – you will sacrifice your
steeringandlosecontrol.
Asthenavigatorstightlycoupledsafespeedtothe
feeling of being in control, they stated that for any
situationthereisnosuchthingastheonecorrectsafe
speed.
Safespeed
isanunclearterm.Inthesamesituationone
navigator may proceed at a safe speed of 10 knots, while
another proceeds at 5 knots. It will be wrong to set any
boundaries,asthatmayforcesomenavigatorstoproceedat
a speed that they do not feel comfortable with
– which
wouldalsobedangerous.Maybethatiswhythetermisa
bitunclear–togivenavigatorssomeleewaytonavigatein
awaythatismostcomfortabletothem.
4.3 StandardSpeedandwhentoDeviate
When setting the vessels speed in practice, the
interviewees unveiled
that full speed ahead is the
default.Thespeedgenerallyonlygetsadjustedwhen
the navigator deems this necessary to stay
comfortableandincontrol.
Ifthereisnotrafficyougowithfull speed.Sometimes
youmeetcaptainswhowanttoreduce incertainareas,and
thatwishgetsrespected.
However, some interviewees shared that a
reductionofspeedmaysometimesbeabureaucratic
processthatmightinvolverepercussions.Asaresult,
they sometimes feel pressured to proceed at speeds
thattheythemselvesdeemunsafe.Examplesofthese
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situations were coupled solely to vessels with
passengersonboard.
In the passenger ferry industry, we proceed at high
speeds because we must keep a schedule. People expect to
arriveontime.Thereisaconflictofinteresthere:Wedon’t
wantaccidents,butwealsohaveanobligationto
getpeople
fromAtoBontime.Inpracticethismeansthatyouonly
reduce speed for very special things – and as a result we
don’treducespeedmorethanacoupleoftimesayear.But
you can see the same happening with cruise ships – 300‐
metre‐long vessels going through the fjords at 25 knots,
eveninthemiddleofthenight,justbecausethepassengers
should wake up in a new place the next morning. It’s
completelywild.
Considerationforotherswasalsomentionedasa
reasonforreducingthevesselsspeed.Avesselswake
can cause problems for other vessels, particularly
small craft and moored vessels, and navigators
highlighted that they would reduce their speed in
particularareastoreducethesizeoftheirwake–and
therebykeepanydisturbancetootherstoaminimum.
4.4 SpecificMomentstoConsiderwhenSettinga
Safe
Speed
In the following subsections, different specific
momentsthatnavigatorsconsiderwhensettingasafe
speed will be presented. This illustrates both what
navigators deem important to consider, as well as
highlightwhichconclusionsnavigatorsdrawfromthe
informationtheygather.Whenaskedifthereissome
sortofhierarchy
thatdeterminesthatsomemoments
aremoreimportantthanothers,someinitiallypointed
to a specific moment that they deemed most
impacting. This quickly changed however, and the
interviewees pointed to how the factors are
dependentononeanother,andthattheimportanceof
thedifferentmomentsdependonthe
context.
Fog is worse than anything else. But really this was
back in the day – but nowadays we have such good
equipment.Nowvisibility mightbeimportantin confined
waterswithmuchtraffic,butnotsomuchinopenwaters.
When I think about it all these factors depend on
the
situation, the vesselyou are on and where youaregoing.
Any hierarchy of the factors is changing along with the
conditionsandisnotconstant.
Because of the many dependencies, interviewees
were critical of the possibility of creating a general
safe‐speed‐flowchart, which could be followed to
determinethesafe speedinthatparticular situation.
One interviewed navigator voiced restrained
optimism for the possibility of creating such a
flowchart for one specific vessel in one specific
locationbutalso mentionedthata general flowchart
wouldbecomplicatedasthereissomuchvariancein
howthedifferentfactors
affectwhichspeedwouldbe
safe.
4.4.1 IsSlowerSafer?
As mentioned in 4.2 above, the most important
thingabout safe speed is being in control.So, while
reducing speed gives the navigator more time to
evaluate and execute their options, it also amplifies
theeffectofexternalweatherfactors
–suchaswind
andcurrent–onthevessel.Afterreducingthevessels
speed below a certain point, most vessels will even
lose their ability to manoeuvre. As a result, the
interviewed navigators disagree with the sentiment
that a reduction of speed necessarily leads to a safe
speed. Indeed, examples
of the opposite have been
sharedbymanyinterviewees.
In some of the Norwegian ports there are speed
restrictions limiting speed to 5 knots. For many vessels,
goingataspeedoflessthan5knotsintheseportsisunsafe.
Fast ferries are much easierto steer when going
10 to12
knots,andsomeoftheoldcruiseshipsdonotswing–but
onlygostraightahead–whengoingatlessthan10knots.
Thesameappliesforsomeoftheothermoreconfinedareas–
whenyougotooslow,thewindandcurrenttakesyou
and
yourunaground.Reducingtozerointheseareaswouldbe
lunacy–sopersonallyI liketokeepalittlehigherspeedto
beincontrolofmyownfate.
4.4.2 Visibility
Visibility is mentioned as the first factor to
considerintheCOLREGsandisgenerallyseen
asthe
most important factor for the determination of safe
speedbythelegalcommunity,whereitisstatedthat
isnotsafetogofastwhenvisibilityispoor.Butwhen
is visibility poor? While not all navigators provided
thesamevalues,theyseemedtoagreethatmorethan
1
nautical mile visibility can be considered good,
between5cablesand1nauticalmiletheystarttoraise
their alertness, and below 5 cables they would
consider reducing speed. Additionally, the
interviewees highlighted the following concepts as
important: The size of the vessel you are on, the
amountofnavigable
spacearoundyouandthereason
forthereducedvisibility.
900metrevisibilityiscompletelyfineonavesselthatis
100 metres long, but for a vessel that is 300 metres that
samevisibilitydoes not seemso fineanymore.But it also
dependsontheareayouarein:
Inopenwatersyouhaveso
much room to manoeuvre that a reduction in visibility
reallydoesn’thaveaneffectanymore–especiallysincewe
havesuchgoodequipment.Withradaryoucanseeevenin
thick fog. The only time where radar cannot help you in
reducedvisibilityis
whenyouencounterwetsnow–then
yougetfalseechoesandcannottrusttheradarpicture.
The above AIQ highlights how navigators can –
underspecificcircumstances–deemavisibilityrange
of 900 metres as completely fine. The interviews
highlighted that the importance of visibility is not
independent, but
instead depends on the context as
well. Only when other safetymargins are reduced –
suchasnavigatinginanarrowchannelorinanarea
ofhightraffic–wouldnavigatorsstarttoadjusttheir
speed. If, however, they encountered reduced
visibility in open waters with no other traffic,
they
wouldcontinueproceedingattheirnormalspeed.In
general, the interviewed navigators mentioned
visibilitylesswithregardstocollisionavoidance,but
more with regards to keeping the vessel on track.
Theyvoicedtheircontentwithboththeavailableand
plannedaidstonavigationalongtheNorwegiancoast
and stated that
they used classical i.e., visual
navigation methods as their preferred way of
navigating along the coast. A reduction in visibility
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would mean that they would need to switch to
technicalnavigationmethodsinstead.
Youcanobviouslyusethechartandradartosailinthis
area,butwemostlyusethesetoolstocheckforothertraffic.
Thenavigationhappensmostlybyeye:Weusetheaidsto
navigationthat
wehavealongthecoast,asforexamplethe
sectorlights.Thatisaverypleasantwayofnavigating.But
when visibility is poor, we must switch to technical
navigation. Then we must allocate more time to utilizing
those tools and have less time for looking outside the
window.
The
danger of not being able to detect another
vessel in poor visibility was not generally seen as
great enough to warrant a reduction of speed no
matter the context. Furthermore, it was pointed out
thatitisgenerallysmallerpleasurecraftthataremost
atriskofnotbeingdiscoveredin
badweather–and
thatthesewouldgenerallynotbeoutonthewaterin
badweather.
But this is a type of risk assessment. When it isdark,
visibility is low and there are gale force winds that mean
thatIhaveabitofwaveclutteronthe
radar,thenIdonot
expect small vessels to be out on the water. And then I
don’treducespeed justbecauseoftheoff chancethatthey
couldbethere.
The above AIQ highlights the kind of risk
assessmentthattakesplace.Whileinthatinstanceit
washighlightedwhy
areductionofspeedmaynotbe
necessaryitwasalsohighlightedbynavigatorsthatif
they pass areas where they know the likelihood of
encountering small vessels to be larger, they would
eithertrytotakeadifferentrouteorreducespeedpre‐
emptively.
4.4.3 Traffic
Whilethereis
generallylesstrafficinNorwaythan
inotherpartsoftheworld,trafficwasmentionedas
animportantfactorthroughouttheinterviews.
The interviews showed that dense traffic is a
somewhat vague concept, that depends on a lot of
otherfactors.Firstly,notonlythenumberofvesselsin
the area
is important, but also how they are
positioned and how they are manoeuvring. Traffic
that is organised in a way that encounters are
minimized – as for example in a traffic separation
scheme–wouldbeconsideredlessdensethantraffic
that is unorganized. Additionally, navigators
described that – when
compared to open waters –
fewer vessels were required in confined waters for
themtofeelasthoughtrafficwasdense.Thetypesof
vesselsencounteredalsoinfluencestheperceptionon
thedensityoftraffic–leisurevesselsareseenasless
predictableandthereforemoredifficulttocollaborate
with than
vessels with professional crew on board.
Finally,trafficisdenseornotdenseinrelationtothe
vessel you are on yourself. If you experience
numerousvesselencountersfromdifferentdirections,
the manoeuvrability of your vessel will determine
how constrained you will feel. As a result, traffic
densityinthe
samesituationmightbeconsideredlow
when steering a highly manoeuvrable vessel, and
high when steering a vessel that is hardly
manoeuvrableatall.Overall,trafficisnotconsidered
tobedenseiftheyfeelcomfortableintheirabilityto
keepclearfromallvessels.Themoredifficultitgetsto
understand and react to other traffic, the more
navigatorsfeelthattrafficisbecomingdense.
I feeltraffictobecome dense whenI feelthat I cannot
steer away from the different vessels with my standard
speedinapropermanner.
Interestingly,theissueoftrafficwasgenerallynot
discussed
intermsofwhattodowhenyouencounter
dense traffic, but more in the way of how you can
actively avoid getting into situations with dense
trafficandnumerousclosequarterssituations.
IwillalwaystrytoavoidgettingintosituationswhereI
will experience multiple vessel encounters. Instead, if
I
noticethatIamrunningintosuchasituation,Iwillrather
reducespeedahead oftime,wait forthesituationtoclear,
andthencontinuewithnormalspeed.IfIweretocontinue
and then reduce when encountering the dense traffic, my
reductionofspeedintroducesnewdangers,
suchasdrift.In
an areawherethere islittlespace and maybecurrentthis
introduces a new danger in itself – and the last thing I
wanttodoinanalreadydifficultsituationistoaddmore
distractingfactors.
Lookingaheadlikethismeansthatnavigatorslook
attraffic
densitynotonlyreactively,butproactively.
Theyproactivelylookoutforsituationswheredense
trafficmay occur, and try to either not get into that
situation, or come prepared. This tendency for
proactivitywasalsohighlightedbynavigatorsstating
thattheywillnotonlyconsidertrafficthattheyhave
observed,
butalsotrafficthathasnotbeenobserved
yet.
There are areas where the likelihood of encountering
other traffic is just so much higher. In open waters we
encounterfewervesselsthanwhenpassingportsandcities.
Andthentherearetimeswhereweknowthatmorepleasure
craftwillbe
onthewater–suchasthenationalday.
4.4.4 Area
Fortheareamoment,boththeproximitytoshore
orother navigationalhazards andavailabledepthof
water was combined. The most important aspect of
the area is that the navigator must be comfortable
navigating in it. Furthermore, the
area plays a large
roleinprovidingcontext:Theeffectofbothvisibility
and other traffic were enhanced when they were
takingplaceinaconfinedarea.
The interviewees working onboard fast ferries
basically did not see proximity to shore or other
navigational hazards as problematic and stated that
theywould
proceedatfullspeedevenwhencloseto
shore.
Therearetimeswherewehaverocksandshorewithin5
metres of the side of the vessel, but we still go with full
speed. Tight spaces by themselves do not warrant a
reductioninspeed.
This is likely due to
the generally supreme
manoeuvrability of the fast ferries employed in
Norway. The maritime pilots who work on many
differenttypesof vesselshad a morenuanced view.
ThepilotshighlightedthesuperiorityofaU‐turnover
a stopping manoeuvre when encountering a
dangerous situation. As a result, the consensus was
that the border between open and confined waters
584
waswherethevesselcouldsafelyexecuteaU‐turn.A
differentiation between open and confined waters
therefore depends on the manoeuvrability of the
vessel involved. However, from experience, the
maritime pilots stated that most vessels below 140
metres in length, having 5 cables of water around
them, would be
navigating in what they would
considertobeopenwater.
Whenitcomestotheeffectthedepthofwaterhas
onsafespeed,thefastferrynavigatorsstatedthatthe
watersofftheNorwegiancoastaregenerallysodeep
that it does not have an effect. While some of
the
maritime pilots highlighted the increase in turning
circle and stopping distance in shallow water, the
intervieweesindicatedthattheywouldreducespeed
in shallow areas with the sole intention of reducing
the effect of squat and the resulting possibility of
touchingthebottom.
4.4.5 Wind,WavesandCurrent
Interviewees stated
that wind is a factor of great
importance,that needs betaken into account during
nearlyalloperations.Thisincludesnotonlythewind
speed, but also the wind direction. Wind is seen as
moreproblematicwhenblowingperpendiculartothe
vessels course, and less problematic when blowing
parallelto
thevesselscourse.Theeffectofwindspeed
onsafevesselspeedisgenerallyseentobeinverted,
i.e.highwindspeedsrequirehighvesselspeeds.This
is because the drift inducing effect wind has on a
vessel is larger at lower speeds, and less at higher
speeds.
Itiswind
thatwestrugglewiththemost.Windcauses
you to drift, and if you then reduce speed you drift even
more.Thatiswhyyouneedhighspeedinhighwinds.
Reductionofdriftisimportantforseveralreasons.
If you are in a tight space, the introduction of drift
makesthespaceeventighterastherequiredleeway
angle to keep the vessel on course means that the
vesseltakesmorespaceinthewaterway.Theleeway
angleincreaseswithincreaseddriftorreducedvessel
speed,uptoapointwherethevesselwillnotbeable
to keep on
track and risks being pushed aground.
Finally, large drift may lead other traffic to become
uncertainaboutyourintentions,asillustratedbythe
AIQbelow:
Our own leeway angle can, in some places, create
uncertainty with regards to my intentions. So that if I
compensatefordrift withadjustingmy
course,itcanlook
like Iʹm steering straight towards someone –eventhough
Iʹmnot.Iwanttoavoidcreatingwrongsignals‐orsignals
thatcanbemisunderstood–atalltimes.
The effect of waves on safe speed was generally
notconnectedtocollisionavoidance,butratherto
the
reduction of forces that may cause damage to the
vessel. Interviewees therefore mentioned that high
waveswouldcauseareductioninspeedtoreducethe
chanceofdamagestotheownvessel.
Interviewees did not mention current as a factor
thatinduces drift but were more focusedon current
that sets either in the same, or opposite directionto
the vessels course. In this regard the navigators
highlighted that current that sets opposite to the
vessels course is generally seen as having a positive
influenceoncontroloverthevessel,whilecurrentthat
sets with the vessel has a negative
influence on
control over the vessel. Vessels that proceed against
thecurrentmight beabletoreducetheirspeedover
ground to zero, while maintaining enough speed
through water to maintain manoeuvrability. On the
otherhand,itisvirtuallyimpossibletocometoastop
when the current sets in
the same direction as the
vessel, as the vessel will loose steering due to low
speedthroughthe water before evercomingtozero
speed over ground. With this being said, navigators
stillstatedthatinpracticecurrentonlyhasanimpact
ontheiralertness,andnotontheirselectionof
speed.
4.4.6 BackgroundLight
Background light had two meanings for the
interviewees – it could come from both inside and
outsidethenavigationalbridge.Inanycase,itisseen
as a disturbance and – where possible – steps were
beingtakentoreducetheiroccurrence.Thisincludes
asking others
on the bridge to switch off any
background light on the bridge, as well as a case
where navigators took contact with a quay to ask
themtomodifyanewlyinstalledfloodlightinaway
thatitbecomeslessinterfering.
Navigators stated that the disturbing effect of
background light is
largest when navigating in
unknownareas,andissignificantlyreducedbyboth
modern support technology such as radar and AIS
andwhenanavigatorsknowstheareasowellthathe
isabletoquicklyfilteroutbackgroundlightandfocus
onthelightsthatareimportantforsafenavigation.
In practice this means that background light
influences safe speed only when the navigator does
notfeelcomfortablewiththesituation.
In a normal setting when experiencing background
light,theradarimagegivesmesuchagoodpictureofwhere
I am, where I am going, where I am going to
turn, and
whichboatsarearoundthatitdoesnotaffectmysetspeed.
5 DISCUSSION
Theresultspresentedaboveshowthatthereal‐world
problemofdeterminingsafespeedistoocomplexto
be adequately captured by overly simplistic
descriptions. The interviews show that the different
factors affecting safe
speed cannot be looked at in
isolation,butwithinthecontextinwhichtheyoccur
onthewater. Navigatorsthereforedonot determine
safespeedbyfollowingrule6oftheCOLREGsword
forword,takingintoaccounteachfactorinorder,but
instead interpret it as a goal‐based rule.
Navigators
equate the requirement of proceeding at a speed
wheretheycantake proper and effectiveactiontoa
speed where they feel in control and adjust their
speed accordingly. Importantly, navigators do not
onlyfocusonbeingincontrolinthecurrentsituation,
butalsointheforeseeablefuture.
Thisunderstanding
is exemplified by navigators mentioning reducing
speed in open waters and good conditions to avoid
meeting other vessels in confined waters with
possiblylessfavourableconditions.
585
5.1 TheGapBetweenWork‐as‐DoneandWork‐as‐
Imagined
Thiswayofdeterminingsafespeedisincontrastwith
the way legal scholars approached this problem,
takingeachfactorforitselfandinterpretingitseffect
on the safe speed in isolation. This indicates a
difference between the work
‐as‐done by the
navigatorsandthework‐as‐imaginedbytheoristsand
legal scholars and is in line with the findings of a
study, where the speeds of vessels in different
visibility conditions was analysed [19]. That study
found that contrary to the legal understanding of
“safespeed”,vessels
didnotsignificantlyreducetheir
speedinpoorvisibility.Alargedistancebetweenhow
work is imagined, and how work actually is done
indicates an ill‐calibration at the blunt end to the
challengesandrisksencounteredatthesharpendof
realoperations[20].Thisdistancemightbeattributed
to
legalscholarshavingaworldviewwheresafetyand
compliancewithrulesaretheonlyfactorsthataffects
speed. In reality, it is widely known that “human
behaviorinanyworksystemisshapedbyobjectives
andconstraintswhichmustberespectedbytheactors
for work performance to be successful”
[21]. These
objectivesandconstraintscanoftenbecontradictory.
In practice, the interviewees have shared how the
objectivetoproceedatasafespeedmayclashwiththe
objectivetofollowtherules (as with the case where
some speed restrictions in pla ce in Norway would
requirenavigatorstoproceedat
unsafeslowspeeds),
or with the economic objectives of the shipping
company (as with the case where navigators are
pressuredtoproceedathigh speedsinordertostay
onschedule).
With collision avoidance being a game of
coordination, where navigators on different vessels
have to independently choose mutually compatible
strategies [5], it is feasible to predict that MASS
designedaccordingtohowworkisimaginedandnot
howworkisdonewillhavetroublecoordinatingwith
conventionalvessels.Furthermore,asinformalwork‐
systemsandadaptationsoftendevelopwhenhumans
comeintocontactwithsystemsdesignedaccordingto
work‐as‐imagined
[22], one can expect seafarers on
othervesselstodevelopnewwaysofinteractingwith
MASS that are designed according to work‐as‐
imagined.Thesenewhabitsmaybedegradingsafety
andcausingnewtypesofhazardoussituationsinthe
shippingroutesandfairways[23].
Astheabilitytoelicit
andrepresenttheknowledge
ofexpertsisagrowingconcerninsystemsdesign[24,
25], the results of this paper can be seen as an
exchange of knowledge between navigators and the
designers of MASS, hopefully contributing to
bridging the gap between work‐as‐imagined and
work‐as‐done.
5.2 Limitations
The findings and generalisability of this study must
be seen considering some limitations. The informant
groupismadeupofalimitednumberofnavigators
that were selected as part of a convenience sample.
Only Norwegian navigators were included in the
study,leavingthepossibilitythatnavigatorsofother
countries
interpret the rules in a different way.
Exploringthepossibilityofdifferentinterpretationof
the COLREGs by navigators educated in different
countries is something that could be looked at in
future research. However, considering the
internationalnatureofthe maritime industry,where
navigatorsworkwithinternationalcolleaguesandare
subject to
international regulation, the conclusions
drawnmaystillhavebroadrelevanceandshouldbe
further investigated to find whether they resonate
withthenavigatorsingeneral.
6 CONCLUSION
The objective of this study was to extend the
knowledgeofhownavigatorsinterprettherules,with
a specific focus on how they
interpret the rule
coveringtherequirementtoproceedatasafespeed.
Although a small‐scale qualitative study, valuable
insight into the tacit knowledge of navigators and
how they interpret the requirement to proceed at a
safespeedwasobtained.
It was found that the most important aspect for
navigatorswith
regardstosafespeedwasthefeeling
of being in control. The major factors impacting this
feelingwasthenavigator’scomfortablenesswithboth
thevesselandtheareatheyarenavigatingin.
The navigators’ interpretation of the factors
mentionedinCOLREGsrule6showshownavigators
mustdeterminethesafe
speedinarealworldthatis
complex, and where each factor must be seen in
relation to the context of the overall situation. This
breakswiththeviewofhowlegalscholarsapproach
this problem, where each factor is analysed in
isolation. While legal scholars conclude that it is
unsafe
to proceed at high speeds in low visibility,
navigatorshavenoproblemwithproceedingthrough
fogathighspeeds,giventhattheyareinopenwaters
withnoothertrafficaround.
Interesting take‐aways include the fact that a
slowervesselspeedisnotsaferbydefault.Indeed,a
too
lowspeed canalsobe an unsafespeed. Another
interestingtake‐awayisthatnavigatorsincludefuture
situationsintheir determination of safespeedinthe
present. Navigators are aware of situations where a
change in speed does not affect the safety of
navigation in the present but has an impact
of the
safety of navigation in the future. An example here
would be navigators reducing their vessels speed in
openwatersaheadofaconfinedwaterway,withthe
intentionoflettinganothervesselleavethewaterway
beforeenteringthewaterwaythemselves.
Theconclusionofthispaperisthatdetermininga
safevesselspeedismorecomplicatedthanmadeout
intheliterature.AstheMASSofthefuturewillhave
to collaborate with conventional vessels, it is
importanttoensurethatMASSarenotprogrammed
with only work‐as‐imagined in mind, but also by
consideringthework‐as‐donein
practice.
586
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