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1 This is he auhor s version of a work ha was submied/acceped for publicaion in he following source: Debnah, Ashim Kumar & Chin, Hoong Chor (2006) Analysis of marine conflics. In Proceedings of he 19h KKCNN Symposium on Civil Engineering, Kyoo, Japan. This file was downloaded from: hp://eprins.qu.edu.au/51380/ c Copyrigh 2006 [Please consul Auhors] Noice: Changes inroduced as a resul of publishing processes such as copy-ediing and formaing may no be refleced in his documen. For a definiive version of his work, please refer o he published source:

2 Please cie his aricle as: Debnah, A.K. and Chin, H.C. (2006) Analysis of Marine Conflics. In: Proc. of he 19 h KKCNN Symposium on Civil Engineering, December 10-12, Kyoo, Japan. Analysis of Marine Conflics *Ashim Kumar Debnah 1 and Chin Hoong Chor 2 12 Deparmen of Civil Engineering, Naional Universiy of Singapore, Singapore ashim@, cvechc@nus.edu.sg ABSTRACT The raffic conflic echnique (TCT) is a powerful echnique applied in road raffic safey assessmen as a surrogae of he radiional acciden daa analysis. I has subdued he concepual and implemenal weaknesses of he acciden saisics. Alhough his echnique has been applied effecively in road raffic, i has no been pracised well in marine raffic even hough his raffic sysem has some disinc advanages in erms of having a monioring sysem. This monioring sysem can provide navigaional informaion as well as oher geomeric informaion of he ships for a larger sudy area over a longer ime period. However, for implemening he TCT in he marine raffic sysem, i should be examined criically o sui he complex naure of he raffic sysem. This paper examines he suiabiliy of he TCT o be applied o marine raffic and proposes a framework for a follow up comprehensive conflic sudy. INTRODUCTION The raffic conflic echnique (TCT) is a sysemaic mehod of analyzing he raffic maneuvers in order o evaluae and compensae any poenial sources of safey hazards. This echnique analyzes he operaional and safey deficiencies by examining he criical vehicle ineracions, sympoms of erraic driving, unsafe maneuvers or near-misses. Before he firs formal proposal of his echnique by McFarland e al. in 1954, radiionally he raffic safey researchers used he acciden saisics as he basis of diagnosing operaional and safey deficiencies. However, as more researchers examined he raffic safey issues, he weaknesses of he acciden saisics as safey assessmen crierion become apparen. In mos cases, occurrence of acciden is an oucome of a complex process of ineracion involving he driver, he vehicle and he road environmen. Hence, i is someimes difficul o pinpoin he causes of accidens us from acciden couns alone. Moreover, he frequency of accidens is segregaed by locaions, ime and ype resuling in low acciden couns a individual sies which could be insufficien for a sound saisical analysis. Moreover, acciden saisics are imprecise, inconsisenly repored and no reliably colleced which could give rise o biased conclusions. The researchers hen considered he conflics or near-misses as a surrogae of he acciden saisics. The main advanage of using he conflics is having a larger daabase wihin a shorer period of ime compared o he acciden saisics. I also solves he ehical problem of waiing for sufficienly larger number of accidens o ake place firs before aking any regulaory measures. Increasing ineres of he researchers in applicaion of his echnique has refined he conceps and implemenaion procedure hrough several conferences, congresses and workshops wih publicaions amouning no fewer han a hundred. Some of hem invesigaed he echnique subecively (Perkins e al., 1967; Campbell e al., 1970; Kruysse, 1991) whereas some reas i obecively (Allen e al., 1978; Balasha e al., 1980; Chin e al., 1997) in order o obain sensibly good resuls. However, use of his echnique in marine raffic safey assessmen has no become popular so far, alhough i has some disinc advanages in he daa collecion and exracion process over he road raffic due o he presence of a real-ime monioring sysem. This paper examines he suiabiliy of he TCT for applying in he marine raffic sysem by idenifying he inheren advanages of he marine raffic operaion sysem over he road raffic. A framework for a follow up marine conflic sudy has been presened hen by examining he difficulies associaed wih he applicaion of his echnique in order o obain meaningful inferences from he analysis. 1 Research Scholar 2 Associae Professor

3 RELEVANCE OF TCT TO MARINE TRAFFIC I has been examined ha he TCT is a useful ool for safey diagnosis of he road raffic ineracions. In he process of implemening i efficienly and effecively, difficulies arisen regarding he daa collecion and analysis procedure. These difficulies someimes resric he use of his echnique o some exen. However, hese difficulies could easily be handled in order o use his echnique effecively in marine raffic sysem, which in urn proves is suiabiliy for his raffic sysem. These issues are elaboraed in he following secion. Suiabiliy of TCT o marine raffic In order o examine he raffic ineracions for safey sudies, vehicle kinemaic informaion is necessary for a quaniaive analysis of he conflics. Usually, in road raffic sysem, hese daa are gahered by recording vehicle movemens for a cerain ime period using he ime-lapse camera or he video echnology. This mehod of recording vehicle movemen pahs has resriced he sudy area and he sudy ime period o an exen. Moreover, he exracion procedure of he required informaion from he recorded media is ime consuming and labor inensive. However, marine raffic has a grea advanage over he road raffic in erms of he availabiliy of vessel kinemaic daa due o he presence of a monioring sysem. The radar based Vessel Traffic Informaion Sysem (VTIS) is he ship monioring sysem, which provides real-ime navigaional informaion abou he ships plying wihin he range of he sysem. In his inegraed sysem, sensors from differen locaions rack he vessel movemens and oupu heir signals o a cenral locaion where he operaors monior and manage vessel raffic movemens. Due o he involvemen of several sensors for a arge ship he accuracy of hese informaions is quie good enough. This daabase can be a good source of vessel ineracion daa as well as he oher geomeric and operaional daa for a marine conflic analysis. In road raffic sysem, he exraced vehicle kinemaic daa could be erroneous due o he manual exracion process from he recording media, whereas in he marine raffic sysem hese daa is accurae enough due o he involvemen of several radar sensors. Moreover, i is hard o obain he geomeric daa (e.g., lengh, widh) of he vehicles from he recorded films. On he oher hand, from he VTIS daabase i is possible o obain hese vessel geomeric daa (e.g., lengh, widh, heigh, and draf) as well as he oher possibly required informaion (e.g., ship onnage, ship s and pilo s ideniy, speed, and direcion of sailing ec.). These varieies of informaion could enable he TCT o pinpoin he main causes of shipping collisions effecively. Due o he absence of such a monioring sysem in he road raffic sysem, vehicle ineracions can no be recorded over a larger sudy area for a longer ime period. Therefore, he facors induced from he geomeric and operaional differences beween differen road secions as well as he ime-dependen facors (e.g., seasonal variaions, visibiliy) canno be aken ino accoun easily for a conflic sudy o make i generalized over he road secions and differen ime periods. However, in marine raffic sysem a comprehensive conflic sudy can be conduced considering all of hese facors due o he presence of he VTIS, which can provide required daa of a larger sudy area for a longer ime period. Moreover, he variaions in wind, curren and idal forces can also be aken ino accoun for a longer sudy period. Hence, i can be concluded ha availabiliy of he monioring sysem could make he implemenaion of his echnique easier and more effecive for he marine raffic sysem. Furhermore, he vehicle movemen process of he marine raffic is more complex han ha of he road raffic. The former one is faciliaed by he Navigaional Assisance Service (NAS) provided by he VTIS, which enables he ship-crews o obain real-ime navigaional advice from he por operaors. Therefore, ship maneuvering process becomes a complex process of ineracion involving he ship, her pilos and crews, he por operaors and he marine environmen. I is herefore no surprising ha approximaely 80% of he shipping accidens are caused by human errors in he design and operaion sages (Soares e al., 2001). On he oher hand, he road raffic is operaed simply by he udgmen of he drivers according o he surrounded road environmen. Therefore, he marine raffic maneuvering process is more complex han ha of he road raffic. Since he TCT has been proven effecive in examining he causes of accidens for he complex road raffic ineracions, i can be reasonable o use his echnique o pinpoin he corresponding causes of he shipping collisions for he more complex marine raffic sysem insead of using he acciden saisics alone. Difficulies in applying TCT o marine raffic Due o he presence of a monioring sysem he marine raffic has some disinc advanages over he road raffic. However, here are some difficulies which could arise in he applicaion of he TCT o he marine raffic. The maor shipping acciden ypes consiue grounding, collision, foundering, and fire/explosion. Among hese only he ype collision incorporaes wo or more ships in an acciden even. The res are caused mainly due o mechanical failure, fire or hiing obecs oher han a ship. Hence, he kinemaic informaion may no be sufficien enough o pinpoin he causes of hese acciden ypes. The characerisics of he marine environmen, he vessel sysem, and he aiude of he operaors, crews and pilos may become imporan facors acing behind hese accidens. Moreover, a collision beween wo ships may ake place due o several reasons: insufficien or lae reacion by he pilos and he por operaors; poor visibiliy; insufficien space o maneuver; poor maneuverabiliy of he ships; srong wind, curren and idal forces; meeing or crossing of ships a relaively narrow channels or a channel bends. Therefore, in order o use he TCT for diagnosing he safey deficiencies,

4 he conflics should reflec he whole range of he possible causes of hese acciden ypes. Moreover, nearby he por areas usually a large number of ships remain anchored for loading/unloading purposes or simply for parking. These ships ac as saionary obecs in he collision process wih anoher ship which is sailing. In such cases, he conflic even is acually single vessel ineracion alhough he collision akes place beween wo ships. Therefore, for he complex raffic ineracion process involving he human facors as well as he vessel sysem and environmenal facors i is necessary o examine he TCT criically before implemening i for safey assessmen. A framework of a marine conflic sudy is discussed here which would be able o miigae he difficulies associaed wih he implemenaion of his echnique in marine environmen. Course of ship Course of ship i v i Probable poin of collision v θ (x i, y i ) Ship i l i θ i Ship (x, y ) w i PROPOSED FRAMEWORK FOR A CONFLICT STUDY Fig. 1. A collision even beween wo ships In he proposed framework, he conflics will be analyzed in such a way ha hey are obecively defined, quaniaively measured, and applied suiably. These are elaboraed in he following secions. Conflic definiion The conflics should be defined in such a way ha hey can be evaluaed quaniaively. Represening conflics as nearness o collision by using he ime or space proximiy beween he involved ships is a good approach of defining i quaniaively. By considering he conflic even, as shown in Fig. 1, he conflic measure is a funcion of kinemaic condiions and he ship aribues. This can be represened mahemaically in he following way: C, = f { ( xi, y x, y, vi, v, θ θ ), ( l wi, l, w ) } (1) Kinemaic daa; changes wih ime Ship Aribues; fixed wih ime where C, is he measure of conflic for ship i and a ime ; x i, y i, x, y are he corresponding posiions of he ships a ime ; v i, v are he ship velociies a ime ; θ i, θ are he bearing angles of he ships a ime ; and, l i, w i, l, w are he lenghs and widhs of he ships i and respecively. The mos criical value of his measure (C cr ) will be obained a he closes poins of approach of he ships. I is he minimum or he maximum value over ime for he ships i and, based on he naure of he measure. Mahemaically, i can be derived as follows: C = Min C } or Max C } ; cr {, {, (2) Moreover, he conflics should be such defined ha he definiion reflecs he inended purpose of he corresponding sudy. If he purpose is o diagnose he safey problems and esablishing remedial measures for he problems involved, hen i should be relaed o he common causes of he corresponding safey hazards. For example, if he sudy is inended o analyze he causes of shipping collisions, hen he definiion should be relaed he common causes of hese collisions. On he oher hand, if he purpose is o esablish rules for a safe navigaion clearance in he ailgaing siuaions, hen i should be defined in erms of relaive ime and space separaions beween he ships. I is herefore more appropriae o choose definiions ha need no rely on he observed evasive acions aken by he pilos since a conflic siuaion may arise wihou showing any sign of evasive acions or hese acions may no be easily observed. Moreover, he pilo s habi of aking evasive acions also varies from one o anoher. This process of defining conflics can be able o pinpoin he main causes of he

5 collisions. However, i would no be sraigh forward o idenify he causes of he oher acciden ypes unless he conflics can be defined in erms of he corresponding causes of hese accidens. Conflic measuremen The conflics should be measured quaniaively according o he definiions raher han using any subecive scale of measuremen. The subecive measuremen procedure could produce biased resuls due o he udgmenal error of differen observers. For measuring he conflic measures quaniaively, he kinamic informaion as well as he ship aribues is required. The VTIS can be a good source of such informaion. By employing he quaniaive measuremens he saionary ships can be aken ino accoun in he conflic process if hey are considered as fixed obecs, i.e., he siuaion is like ha a moving ship is colliding on o a fixed obec. Suiable applicaion Besides being well defined and properly measured, he conflic measures mus produce meaningful inferences from he analysis. In order o obain such resuls, he conflics should reflec correcly he corresponding causes of he examined safey hazards ha are discussed earlier in he definiion secion. For exracing meaningful inferences from he analysis, Chin e al. (1997) showed a comprehensive way of evaluaing he serious conflics by separaing hem from he oher conflic observaions. By employing a suiable hreshold value of he corresponding conflic measure, he serious conflics are disinguished from he nonserious ones, as shown in Fig. 2. From he probabiliy funcion of he conflic measure he proporion of criical conflics can be deermined by evaluaing he area under he curve beyond he hreshold value. CONCLUSION The TCT is a powerful echnique applied in he road raffic safey assessmen as a surrogae of he radiional acciden daa analysis procedure. This echnique is promising for he marine raffic safey analysis having some disinc advanages in he daa collecion and exracion process over he road raffic. I would be possible o exrac meaningful inferences from he conflic analyses wih he proposed framework where he conflics are defined obecively, measured quaniaively and applied suiably. As a follow up o his he mehodology will be applied o he exising mariime daa for he Por of Singapore. REFERENCES Frequency of conflic evens Low risk conflics Threshold value Serious conflics Measure of conflic Fig. 2. Hypohesized frequency disribuion of conflic evens Allen, B.L., Shin, B.T. and Cooper D.J. (1978) Analysis of raffic conflics and collisions. Transporaion Res. Bd. TRR Rec. 667, Balasha, D., Hakker, A.S., Livneh, M.A. (1980) A quaniaive definiion of he near-acciden concep. Suppl. Rep. 557, Transpor and Research Laboraory, Crowhorne, England. Campbell, R.E. and King, L.E. (1970) The raffic conflics echnique applied o rural inersecions. Acciden Analysis and Prevenion, Vol. 2, Chin, H.C., Quek, S.T. (1997) Measuremen of raffic conflics. Safey Science, Vol. 26(3), Kruysse, H.W. (1991) The subecive evaluaion of raffic conflics based on an inernal concep of dangerousness. Acciden Analysis and Prevenion, Vol. 23(1), McFarland, R. and Moseley, A.L. (1954) Human Facors in Highway Transpor Safey, Harvard School of Public Healh, Boson, Mass. Perkins, S.R. and Harris, J.I. (1967) Traffic Conflic Characerisics: Acciden Poenial a Inersecions. General Moors Corporaion, Warren, MI. Soares, C.G, Teixeira, A.P. (2001) Risk assessmen in mariime ransporaion. Reliabiliy Engineering and Sysem Safey, Vol.74,