
296
cautionarea)thatproposedbyKiyoshiHara(Hara&
Nagasawaetal.1990,Hara&Nakamura1995).
We employed only three subjects who had
onboardexperienceascaptainsinpreviousstudy,so
theextentofdataaboutSAinnavigatorswaslimited
in the previous study (Nishizaki & Takemoto 2016).
Therefore,thepurposeofthisstudyistoconfirmthe
validityoftheriskcategoryof“attentionarea”using
additionaldataontheSAinnavigators.
Inthecurrentstudy,foursubjectsemployedwere
different from previous studies. They were
interviewedabouttheirinformallookoutusingsame
listofquestions
asinpreviousstudies,andtheSAin
navigators was measured using SAGAT under the
sameexperimentalconditionsasinpreviousstudies.
The“attentionarea”wasdefinedbya functionof
distance and rate of bearing change of other ships.
Because 3 subjects employed in previous study put
emphasis on them
in determining priority level.
Therefore, in current study, through the interview
questions, it was reconfirmed that navigators
emphasized distance and rate of bearing change of
othershipsindeterminingprioritylevel.
Inaddition,itbecameobviousfromthesimulator
experiments with SAGAT in this study, that the
“attentionarea”covered
shipswithhighprioritylevel
innavigators’SAasinthisstudy.As theresults,the
validityofthe“attentionarea”wasconfirmed,andit
became obvious that there was a limit line covered
ships with high priority level. Furthermore, it was
evident that the “attention area” can assist in
detecting
ships with high priority level around the
timewhenthecollisionavoidancewasperformed.
Inthispaper,themethodsemployedinsimulator
experimentswithSAGATareexplainedinSection2.
Subsequently, the experimental conditions and
scenariosaredescribedinSection3.Theresultsofthe
interviews and simulator experiments are
presented
in Section 4. Based on these results, discussions are
explainedinSection5.Weprovidetheconclusionsof
thisstudyarehighlightedinsection6.
2 METHODFORMEASURMENTOF
NAVIGATORS’SITUATIONAWARENESS
SAGATisaneffectivemethodtomeasurenavigators’
SAs in the simulator experiments. The original
SAGATwas
developedandproposedtomeasurethe
SA of aircraft pilots in cockpits, and the procedural
standardsofSAGATwereestablished(Endsley1988).
ThroughtheuseofSAGAT,itispossibletomeasurea
pilot’s situation awareness directly, independent of
their memory of the experiments after these
experimentsareover.
In
order to maintain the continuity of the
simulation,theinterruptiontimeshouldbeselectedto
be as short as possible. However, there are
ambiguities in the oral reports about all ships in a
congestedseaarea,anditisdifficulttoaccountforall
recognizedshipsinashortinterval.
In
order to measure the situation awareness of
ship navigators, we adopted the method where
subjectsfillinrecognizedshipsonaradarchart.This
method was proposed as an evaluation method for
marinepilottrainees(Okazaki&Ohya2012).Weset
interruptiontimeasoneminutetoenabletestsubjects
toanswerbasedonradarwatchinformationbyuseof
theradarchart.A sample report based on the radar
chartisshowninFigure1.
Figure1.ExampleofareportforSAGAT.
3 EXPERIMENTS
3.1 BridgeSimulator
Thepurposeofthesimulatorexperimentsistoobtain
dataonnavigators’SAinkeepingwatchbytheuseof
SAGAT.ExperimentswithSAGATwereconductedin
the ship maneuvering simulator of the National
MaritimeResearchInstitute.Withinthebridgeofthe
simulator, general navigational equipment
were
installed,suchasacompass,pairofbinoculars,radar,
ECDIS, and steering stand. It is possible to record
behaviors of the subject in response to navigational
orders and other ships situations using behavioral
analysissystemsinthesimulator.
3.2 Subjects
Inthisstudy,foursubjectsdifferentfromtheprevious
study and with onboardexperience wereemployed.
The informationof subjects in a previousstudy and
thatinthisstudyareshowninTable1.
Table1. Comparison between the previous and current
studyonsubjectinformation.
_______________________________________________
Experimental
SeasonSubjectIDAppointment
_______________________________________________
Previousstudy Sub.ACaptain
Sub.BCaptain
Sub.CCaptain
Currentstudy Sub.DChiefOfficer
Sub.E2ndOfficer
Sub.F3rdOfficer
Sub.GChiefOfficer
_______________________________________________