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1 DECISIONSUPPORTINGSYSTEMS
Thedevelopmentofinformationandcommunication
technologies (IT and ICT) creates increasing
opportunities for acquiring, processing and sharing
information. The need for improvement and
extensionof navigationalequipmentandsystemson
shipsandinland‐based centersresultsfromthefact
that the safe navigation and vessel t
raffic
management require access to relevant information
anditsproperuse.Navigationalsystemsanddevices
are systematically supplemented with new
functionalities. On the one hand, the
operator/navigator acquires additional information,
on the other hand, excess information makes the
selection of relevant information more difficult and
consequently hampers making the correct decision.
For thi
s reason, greatemphasis is placed on human
centereddesignofsuchsystems.
Currently used navigational systems and devices
increase the scope of support in decision‐making
processesbyusingpredictionalgorithmsorstatistical
tools.Moreandmoreattentionispaidtonavigation
decision support systems that additionally allow to
generatesolutionstoanavigationsituation,including
collision situations. Thesesolutions are presented to
the navigator or operator. This is part
icularly
important in complex decision‐making situations in
difficult conditions: storm, restricted visibility, high
traffic. NAVDEC is an example of the navigational
decision support system on seagoing ship
(Pietrzykowski & Borkowski & Wołejsza, 2012). The
systemenables,int
eralia,analysisandassessmentof
thenavigationsituation,andgenerationofavoidance
manoeuvres in collision situations. Proposed
solutionsshouldbe effective, legal andrational.The
third requirement relates to navigators/operatorsʹ
preferences resulting from their knowledge and
experience(Pietrzykowski& Magaj&Maka,2014).
This is very import
ant because the collision
regulations leave a certain margin for interpretation
andaction.Thecreationofarationalsystemrequires
the application of complex models and computing
algorithms. The automatic generation of solutions is
particularly important in encounter situations in
dense traffic areas. These areas, mainly port
a
pproaches and frequently used shipping routes,
are often restricted (limitation of one of three
dimensions). There is a whole range of constraints
Navigators’ Behavior in Traffic Separation Schemes
Z.Pietrzykowski,P.Wołejsza&J.Magaj
M
aritimeUniversityofSzczecin,Poland
ABSTRACT: One of the areas of decision support in the navigational ship conduct process is a Traffic
SeparationScheme. TSSsareestablishedinareaswithhightrafficdensity, often near the shore and in port
approaches.Themainpurposeoftheseschemesistoimprovemaritimesafetybychannelingvesselt
rafficinto
streams.TrafficregulationsaswellasshipsbehaviorinrealconditionsinchosenTSSshavebeenanalyzedin
ordertodevelopdecisionsupportalgorithms.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 9
Number 1
March 2015
DOI:10.12716/1001.09.01.15
122
which restrict ship maneuvers: shipʹs dimensions,
shipmaneuverability,shapeanddepthofthewater
area, obstacles and navigational dangers, legal
regulations , other sea‐going vessels, drilling
platforms,windfarmsandother.
The use of decision support systems in areas
whereTSSsareestablishedrequiresthatsuchsystems
should
take into consideration general and TSS‐
specificregulationsaswellasnavigatorsʹexpertise:
experience and knowledge needed for analysis and
assessmentofthesituationandforthedetermination
of safe maneuvers, i.e. calculation of a safe ship
trajectory. One of the possibilities is presented in
(Szlapczynski,2012).
2 TRAFFICSEPARATION
SCHEMES
TSScanbedescribedas atraffic‐managementroute‐
system ruled by the IMO where the traffic lanes
indicate the general direction of the traffic flow.
IMOʹsresponsibilityforshipsʹ routing is set forth in
SOLASChapterV,whichrecognizestheOrganization
as the only international body for establishing
such
systems.Shipsʹroutingsystemscontributetosafetyof
lifeatsea,safetyandefficiencyofnavigationand/or
protectionofthemarineenvironment.Rule10ofthe
COLREGs(COLREGs,1972)prescribestheconductof
vessels when navigating through traffic separation
schemes adopted by the IMO. However, this in no
way
relieves vessels from compliance with other
COLREGsrules.Itshouldbenotedthattherearealso
TSSnotgovernedbytheIMO.
ThetrafficlanesinTSSaredemarcatedbyvirtual
boundaries.Thismeansthatboundaryviolationdoes
not imply directly a risk of grounding or collision
with the shore. In
many cases vessels simply sail
acrossaTSS.Insuchsituations,theshipshallcross
onaheadingʹasnearlyaspracticableatrightangles
to the general direction of traffic flowʹ. The
regulationsalsoallowashiptojoinorleaveatraffic
laneattheterminationof
thelane, butwhenjoining
or leaving from either side shipsʹshall do so at as
smallanangletothegeneraldirectionoftrafficflow
aspracticableʹ.
Such wording leavesroom for interpretation
(tolerance range) by decision‐makers. Both the
navigator and the decision support system should
take such
interpretation margin into account in the
analysis and assessment of the situation and in
determiningamaneuvertosolveacollisionsituation.
In this connection, the authors have analyzed
vessel traffic in selected regions of the Baltic Sea
where TSSs are established: TSS Adlergrund, TSS
Bornholmsgat,TSSNorthofRügen
andTSSSłupska
Bank(Figures1‐4).TheanalysismakesuseofAIS
data registered during one day in June 2011.
Individualshipencountersituationsandvesseltraffic
flowshavebeenanalyzed.
The analysis is aimed to develop and test the
methodologytobeusedinfurtherresearch.
Figure1.TSSNorthofRügen
Figure2.TSSAdlergrund
Figure3.TSSBornholmsgat
Figure4.TSSSłupskaBank
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3 NAVIGATORSBEHAVIOUR
This section provides examples of proper and
improper conduct of ships in Traffic Separation
Schemes(TSS).
The case study was performed using two shipsʹ
passages in TSS Bornholmsgat. In both cases ship
encountersituationswithothertargets aretakeninto
consideration and are presented graphically. The
examined
shipisplacedinthecenterofthescreen.
Case1.Thechosenshipheadingsouthcameinto
south‐west traffic lane of Bornholm TSS at a slight
angle(Figure5),whichisinaccordancewithrule10
(TrafficSeparationSchemesofCOLREGs,pointb/iii:
b/Avessel
usingatrafficseparationschemeshall:
iii/ normally join or leave a traffic lane at the
termination of the lane, but when joining or
leavingfromeithersideshalldosoatassmallan
angle to the general direction of traffic flow as
practicable.
Figure5.Joiningatrafficlane.
The ship sailed almost the entire length of the
trafficlane,butthedirectionofitsmotionwasnotin
linewiththedirectionofthelane.Meanwhile,Rule10
pointb/ireads:
b/avesselusingatrafficseparationschemeshall:
i/ proceed in the appropriate traffic lane in the
generaldirectionoftrafficflowforthatlane.
Afterabout80minutesthevesselreacheditsport
sideofthelane,andthenenteredaseparationzone
(Figure6),breakinganotherrule:
b/Avesselusingatrafficseparationschemeshall:
ii/ so far as is practicable keep clear of
a traffic
separationlineorseparationzone.
Figure6.Enteringaseparationzone.
The crossing of the zone at this point is not
allowed.Thisisstatedinpointe/:
e/ a vessel, other than a crossing vessel or a vessel
joining or leaving a lane shall not normally enter a
separationzoneorcrossaseparationlineexcept:
i/ in cases of emergency
to avoid immediate
danger;
ii/toengageinfishingwithinaseparationzone.
The conditions described in the section i/ and ii/
are not applicable in this situation, so another rule
wasbroken.
Meanwhile,thevesselcontinuestotravelthrough
the separation zone on a course close to the zone
direction,subsequentlyenteringtheoppositelaneand
cuttingitatasmallangle,whichisnotinaccordance
withRule10pointc/:
c/avessel,shallsofaraspracticable,avoidcrossing
traffic lanes but if obliged to do so shall cross on a
headingasnearlyaspracticableat
rightanglestothe
generaldirectionoftrafficflow.
Inaddition,theruleofpointb/i/isbroken:
b/avesselusingatrafficseparationschemeshall:
i/ proceed in the appropriate traffic lane in the
generaldirectionoftrafficflowforthatlane;
The vessel brings about(Figure 7)
a collision
situation(CPAlessthan1NmandTCPAlessthan10
minutes)withtwotargetsthatproceedontheproper
lane,inaccordancewiththerules.
Figure7.Collisionsituation.
After passing at a distance of about 0.6 Nm and
leavingthelane, the shipmovesaheadof two other
shipsandcomestooclosetoanothership(Fig.8).
124
Figure8.Closequarterssituation.
Case 2. The examined ship (in the middle of the
screen)headingnorth‐eastenteredandfollowed(Fig.
9)theeastlaneinaccordancewithrule10pointb/i/:
b/avesselusingatrafficseparationschemeshall:
i/ proceed in the appropriate traffic lane in the
generaldirectionof
trafficflowforthatlane.
Figure9.Propertargetcourseonthetrafficlane.
The vessel went through the first section of the
traffic separation scheme in the normal direction.
Thensheproceededtoovertakeslowershipsleaving
alltargetsonherportside(Figure10).
Figure10.Overtaking.
After about3hours, the vessel left the systemin
theproperplace(Figure11),inaccordancewithpoint
b/ii(seecase1): she leaves fromonesideatasmall
angletothegeneraldirectionoftrafficflow.
Figure11.Leavingtrafficlane
4 TRAFFICFLOWS
Vessel traffic in the chosen Baltic Sea TSSswas
analyzed using AIS data recorded within one day.
TheshipstrajectoriesareshowninFigures12‐15.
Figure12.VesseltrafficinTSSNorthofRügen
Figure13.VesseltrafficinTSSAdlergrund
125
Figure14.VesseltrafficinTSSInBornholmsgat,
Figure15.VesseltrafficinTSSSłupskaBank
On this basis, a more detailed analysis of traffic
flowshasbeencarriedoutforeachoftheTSS(Tables
1and2).
The analyzed data includedthe number of
vessels entering the system, the number of ships
crossing the TSS and their direction, the number of
vessels joining or leaving
a traffic lane at the
terminationofthelane.
Ships which violated the regulations were
identified‐some of them violated the separation
zone.
Table1.VesseltrafficflowsinanalyzedTSS.Part1
_______________________________________________
Noof Noofmaneuvers
_________________________
TSSships speedcrossingTSS/
changes* angle[]
_______________________________________________
Rügen9311/24
Adlergund19‐1/64
Bornholmsgat
Mainpart 5633/53,38,98
Westpart 95‐‐
South‐westpart 571‐
SłupskaBank
Westpart 301‐
Eastpart 25‐‐
_______________________________________________
*speedchangemorethan3kn
Table2.VesseltrafficflowsinanalyzedTSS.Part2
_______________________________________________
Noofjoinor Noofintersec‐ proceeding
TSS leaveatraffic tiosoftraffic inopposite
lane/angle[] separationzone direction
_______________________________________________
Rügen‐2‐
Adlergund2/17,30‐‐
Bornholmsgat
Mainpart 2/18,812*
Westpart‐‐‐
South‐westpart‐‐‐
SłupskaBank
Westpart 2/26,2111
Eastpart 1/24‐3*
_______________________________________________
*fishingvessels
Additionally,thedensitydistributionsofshipsfor
eachoftrafficlaneswerecalculated(Fig.16).
Figure16. TSS North of Rügen. Traffic density in traffic
lanesandadjacentareas.
5 CONCLUSIONS
Trafficseparationschemesarevirtualareas,generally
marked by buoys. Our investigation has established
thatmost ships proceed in accordance with
regulationsconcerningTSSs.Despiterelativelydenser
trafficintheseareas,thereexistsincreasednavigation
safety resulting from high predictability of the
navigatorsʹ(ships)behavior.
Ifthevesseltraffic
controlsystemisnotrestrictive,
ordoesnotexist,thereareoftenviolationsofthelaw,
aswasthepassageofvesselanalyzedinCase1.The
reasonforsuchbehaviorofthenavigatorcouldbethe
factthatthetrafficseparationsystemimpedesvoyage
planning,therefore,itwasignored
bythenavigator.
On the other hand, the provisions of Rule 10 are
notstrict,thustheirinterpretationmayvary.Pointb/
is an example of this: ʹa vessel using a traffic
separation scheme shallʹ [...] followed by
recommendations,expressedbytheword“should”in
thetextofthispoint.
Another suchʺimpreciseʺ wording is a provision
on ships joining or leaving from either side of the
track.Rule10referstoamaneuveratapossiblysmall
angletothegeneral direction of movement, without
specifying the size of the angle, which can lead to
divergentinterpretations.
126
Thisimprecisewordingmayalsoincludethetexts
ofpointsi/orj/,referringtofishingandsailingships.
Thepointsincludingthe phraseʺnotimpedingʺsafe
passageofapower‐drivenshipsusetheverbʺshould
notʺ, which is frequently used by fishing or sailing
shipstoforce
actionbymotordrivenshipsthatgoon
therightlane.Suchwordingshouldbeavoidedas
muchaspossible.Also,thereisneedtotraincrewsof
shipsengagedinfishingoperationsorsailingshipsin
thecorrectinterpretationofrelevantCOLREGs.
This article presents research into traffic flows
in
selectedBalticSeaTSSs.Theideabehindtheresearch
is to develop methodology for the identification of
navigators behavior in TSSs in real conditions and,
further, to develop decision support algorithms for
TSSareas.
REFERENCES
COLREGs‐Convention on the International Regulations for
Preventing Collisions at Sea [with amendments 2009],
IMO1972
Pietrzykowski,Z.,Borkowski,P.,WołejszaP.2012.Marine
integrated navigational decision support system,
Telematicsinthetransportenvironment,12thInternational
ConferenceonTransportSystemsTelematics.TST2012,
Katowice‐Ustroń,Poland, October10‐
13, 2012.Selected
papers. Ed. Jerzy Mikulski. Berlin, CCIS nr. 329,
Springer:284‐292.
Pietrzykowski Z., Magaj J., Maka, M. 2014. Safe Ship
Trajectory Determination in the ENC Environment,
Telematics Support for Transport, 14th International
ConferenceonTransportSystemsTelematics.TST2014,
Katowice/Kraków/Ustroń, Poland, October 22‐25, 2014.
Selected
papers.Ed.JerzyMikulski.Berlin,CCISnr.471,
Springer:130‐136.
Szlapczynski, R. Evolutionary sets of safe ship trajectories
within Traffic Separation Schemes2012. Journal of
Navigation66:65‐81.
