外文文献翻译-铁路隧道的安全

外文文献翻译一铁路隧道的安全1外文文献原文 (1)2外文文献翻译 (2)1外文文献原文SafetyoflongrailwaytunnelsD.Diamantidis"摆,EZuccarellib,A.VVesthauser*

^UniversityofAppliedSciences,Regensburg^Prufeningerstr.58yD・93049,Regensburg^

Germany

bD^AppoloniaS.p.A.yGenova^Italy

cBrennerEisenbahnGmbH,Innsbruck^AustriaReceived10March1999;accepted6September1999AbstractPlanninganddesigningrailwaytunnelswithanexplicitreferencetosafetyissuesisbecomingofutmostimportancesincethecombinationofhighspeed,mixedgoods-passengertrafficandextremelengthofthenewtunnelsunderdesignorconceptevaluation,havesensitivelymodifledtheinherentsafetyoftherailwaytunnel.Althoughtheprobabilityofoccurrenceofaccidentaleventsmaystillbeconsideredratherlow,thepossibleconsequencesofsucheventsinlongtunnelscanbecatastrophic,thereforeraisingtheoverallrisktolevelsthatmaybenomoreacceptable.Thescopeofthispaperistoillustratethestate-of-practicerelatedtoriskanalysisoflongrailwaytunnels.First,ambitioustunnelprojectsarebrieflyreviewed.Theapplicablerisk-analysisproceduresarethendescribedanddiscussed.Theproblemofriskappraisalisaddressedandquantitativetargetsafetylevelsareproposed.Safetysystemsforriskreductionareoutlined.q2000PublishedbyElsevierScienceLtd.Allrightsreserved.Keywords:Railwaytunnels;Riskacceptability;Safetysystems;PassengertrafficIntroductionTherailwayisnowmovingrapidlytowardamodernservicetransportationindustry.HighSpeedRail(HSR)systemsarealreadyoperatinginmanycountriessuchasJapan,England,France,ItalyandGermany.AfurtherdevelopmentofthewholeEuropeanHSRnetworkisplanned.Inordertoachievethedesignvelocityupto300km/h,aconsiderablepartoftheroutesisintunnelswithlengthsgreaterthan10kmandinsomecasesoftheorderof50km.Table1illustratesalistofexistinglongtunnelsworldwide.InthisEuropeancontext,theCommissionoftheEuropeanCommunities(CEC)aimedathomogenizingtheHSRprojectsalsowithrespecttothesafetyissues.However,neithertheCECguidelinesnortheexistingrailwayregulationsandcodesdirectlyaddresstotheproblemofquantitativelyassessingthesafetylevelforrailwaysystems.Thisismostlyduetothefactthatrailwaytransportisconsideredbyrailwayoperatorsandperceivedbythepublicasasafemeanoftransportation.Thisapproachtosafetymightbeapplicabletotraditionalrailwaysystems,whichhaveproventhroughouttheyearstheirperformance;itis,however,notenoughtoguaranteethesafetyofrailwaysystemswhereinnovativeandparticularconditionsarepresent,oroftheexistinglinesthathavetobeupgradedtonewexercisestandards.Forexample,thecombinationofhigh-speedtransit,hightrafficintensity,combinedtransportofpassengersanddangerousgoodsandextremelylongtunnels,mightleadtounacceptablesafetylevels.Therefore,thedesignerhastochoosearailwaysystemconfigurationtogetherwiththepreventiveandmitigativemeasuresofaccidentsthatminimizetheriskandultimatelyshouldverifybvmeansofariskanalysisthattheobtainedsafetylevelisbelowapredefinedtargetlevel.Thescopeofthispaperistoillustratethestate-of-practicerelatedtosafetunneldesignandassociatedrisk-analysisaspectsoflongrailwaytunnels.First,ambitioustunnelprojectsarebrieflyreviewedfromthesafetypointofview.Therisk-analysisproceduresarethendescribedanddiscussed.Theproblemofriskappraisalisaddressedandquantitativetargetsafetylevelsareproposed.Finally,safetysystemsforriskreductionareillustrated.MajortunnelprojectsandtheassociatedriskBasicdesignaspectsinexistingorunderdesignandconstructiontunnelsarebrieflysummarizedinthissection.Table1ListofexistinglongtunnelsworldwideNameCountryLength(km)UndergroundDaischimisuJapan22.2SimplonIIItalv/Switzerland19.8AppenninoItaly18.6RokkoJapan16.2HarunaJapan15.4GotthardSwitzerland15.0NakayamaJapan14.8LolschbergSwitzerland14.5HokurikuJapan13.9PratoTiresItaly13.5LandruckenGermany10.8UnderwaterSeikanJapan53.9EurotunnelUK/France50.0ShinKanmonJapan18.7GreatBeltDenmark8.0SevernUK7.0MersevUK4.9KanmonJapan3.6Thefollowingtunnelsareincluded:theChanneltunnelbetweenEnglandandFrance;theSeikantunnelinJapan;theGotthardtunnelplannedinSwitzerland;theBrennertunnelplannedbetweenItalyandAustria;thenewMontCenis-tunnelplannedbetweenFranceandItaly;thetunnelundertheGreatBeltinDenmark.TheChanneltunnelThetunnelservesrailtrafficandlinksuptheterminalsnearFolkestoneinthesouthofEnglandandCalaisinnorthernFrance.Thetunnelissome50kmlongandcomprisesofthreeparalleltubes,whicharelocatedsome25-45mbeneaththeseabed.Thetrainstravelthroughthetwosingle-trackrunningtunnels,eachofwhichhasaninternaldiameterof7.30m.Bothrunningtunnelshaveacontinuousescapewayinordertoenablepassengersandtrainstafftogetoutofthetunnelquicklyintheeventofanemergency(seeFig.1).Twomaincross-linksconnectthetworunningtunnelssothattrainscanswitchfromonetubetotheotherduringmaintenancework;thesetwomaincross-linksarelocatedinthe37kmlongsectionundertheseabed.Twosmallercross-linksaretobefoundinthevicinityofthetunnelportals.Therunningtunnelsareconnectedat250mintervalsbymeansof2-00mdiameterpressure-relieftunnels.Throughthesecross-cutsthepressurethatbuildsupinfrontofaspeedingtraincanbereducedbydivertingtheairfromonerunningtunnelintotheother.Aservicetunnelwithaninternaldiameterof4.50mislocatedbetweenthetworunningtunnels.Itis,firstandforemost,intendedasanescapeandaccessfacilityintheeventofanaccidentinoneoftherunningtunnels.Inaddition,thisservicetunnelprovidesaccesstothetechnicalcenters,whicharedistributedalongit.Theservicetunnelandthetworunningtunnelsareconnectedtoeachotherviaa3.30indiametercross-cutssetupat375ingapsasescapeways[1].Thetunnelisusedforthefollowingtrainservices:thepassengershuttlesforcarsandbuses;thefreightshuttlesforlorriesaswellas;expressandgoodstrainsbelongingtothenationalrailwaycompanies.Thesignalingsystemincorporatingautomatictrainprotectionisdesignedtominimizetheriskofanytypeofcollisionevenduringsingle-lineoperationwhenmaintenanceisbeingcarriedout.Oneofthemaincriteriaforthedesignoftherollingstockwastherequirementthat,asfaraspracticable,intheeventoffire,ashuttleisabletocontinueonitsjourneyoutofthetunnelsothatfirecouldbetackledintheopen.Toachievethisa30minfireresistancehasbeenspecifiedforthewagonsincludingthefiredoorsandshuttersinthepassengershuttles.ThefireaccidentthatoccurredinNovember1996showedthattheemergencyresponseproceduresrequiredfurtherimprovement.c(a)(D(S)°(£)(£)Fig.2.Investigatedtunnelsystems:AandBwithservicetunnel;Dwithoutservicetunnel.TheSeikantunnelTheSeikantunnelwascompletedin1988andconstitutesthelongesttunnelworldwidewithatotallengthof53.9km.ltisadouble-tracktunnelwithacross-sectionalareaof64m2.Theaveragetrafficis50trainsperday.ThetunnelhastwoemergencystationsandisthusdividedintothreesectionsThemiddlesectionisunderwaterwithalengthof23kmandhasaservicetunneLByprovidingtheemergencystationswithfirefightingsystems,firecanbecopedwithinthesamemannerasconventionaltunnelfires.Incaseoffire,thetrainmustbebroughttoastopatthenearestemergencystationormustbedrivenoutofthetunneLTheGotthardBasetunnelThe57kmlongGotthardBasetunnelisoneofthemainlinksforBahn2000,theSwisspassengertrafficforthenextcentury,andfortherailcorridorofEuropeanfreighttrafficthroughtheAlps[3].ThetunnelrouteisapartoftheZurich-Luganolineandisintendedtocarry150intercity,passengerandfreighttrainsperdayineachdirection.Twotracksareneededforthesetrafficlevelsandthereisamultitudeofdifferenttunnellayouts,whichcanbeconsidered.Possiblenormaltunnelprofilescouldconsistof:adouble-tracktunnelwithaparallelservicetunnel;apairofsingle-tracktunnelwithaservicetunnel;threesingle-tracktunnels;apairofsingle-tracktunnelswithoutaservicetunnel^butwithfrequentinterconnections(seeFig.2).Inadditiontothetraffictunnels,thereisaneedforpossiblytwoovertakingstationstoallowpassengertrainstopassslowerfreightones.Naturallongitudinalflowinthetwotubeswillbethebasisfortheventilationofthetunnel,whichhasanoverburdenof2000morgreater,overmorethan20kmofitslength.Recentlywide-rangingstudieshavebeencarriedoutonthedifferentdesignsoftheGotthardtunnel.Themainparametersthathavebeentherebyinvestigatedare:costsofconstruction;constructiontimeandmethod;operationalcapacityandoperability;maintenance;safetyforthepassengersandthepersonnel.Theperformedsafetystudyhasshownthatthethreesingle-tracktunnelsandthepairofsingle-tracktunnelwithaservicetunnelareassociatedtolowerriskandhigheroperabilitycomparedtothedouble-tracktunnelwithservicetunneLHowevertheassociatedcostsarehigher.BasedontheevaluationofcomprehensivestudiestheconfigurationDhasbeenselected,i.e.apairofsingle-tracktunnelswithoutservicetunnelbutwithinterconnectionsapproximatelyevery325m.Suchinterconnectionscanbeusedformaintenancepurposesandevacuationpurposesincaseofaccidents.TheBrennertunnelOneofthemoststrikingbottlenecksinpassengerandgoodstransitbetweenNorthernEuropeandItalyisthenorth-southconnectionfromMunichviatheBrennerPasstoVerona.Atpresent,onlyone-thirdofthefreightvolumecanbecarriedbyrail,whilsttwo-thirdhastobecarriedbyroadovertheBrennerPass.Thus,itisofgreatimportancethatthemodernrailwaynetworks,whicheitherexistorareintheprocessofbeingcreatedinthecountriesoftheEuropeanCommunitywiththeirhigh-speedsections,areweldedtogethervialongrailwaytunnels,whichcanovercometheAlpsasabarrier.Ifoneconsidersthateachyearuntiltheturn-of-thecentury,ananticipatedtrans-goodsvolumeof150milliontonneshastobecarriedovertheBrennerPass800mabovesea-level,itisthusnotsurprisingthatthecitizensofthesurroundingstateshavecalledfortheremovalofthistrafficbottleneckagainstthebackgroundofenvironmentalconsiderations.TheBrennerBasetunnelisurgentlyrequired.Accordingtothefeasibilitystudy,itconsistsofarailwaytunnelofapproximately55kmlength,connectingInnsbruck,AustriaandFortezza,Italy.TherailtrafficinthetunnelissimilartothatintheGotthardtunnelandwillincludeapproximately340trainsperday,with80%ofgoodstrains,ofwhich10-15%containdangeroussubstances.AflnaldecisionregardingthetunnelconfigurationhasnotbeentakensincetheprojectIsinthefeasibilitystudyphase;however,itappearsverylikelythattwosingle-tracktunnelswithfrequentinterconnectionsasproposedfortheGotthardtunnelwouldbeselected.Asafetystudyhasshownthattheriskofthetunnelduringoperationisacceptableifappropriatesafetymeasuresareapplied[4].MontCe'nistunnel.TheMontCe'nistunnelImprovedtransportlinksthroughtheAlpsareneedednotonlybecauseofthreatenedcapacitybottlenecksbutalsobecauseoftheinsufficientqualityoftheexistingrailwaylinesthroughthemountains.Thelatter,regardedasatechnicalmarvelinthelastcentury,arecircuitouswithmanycurvesandthushavelittlechanceofcompetingwiththefastAlpinemotorwaysofthepresentday.Inadditiontotheplannednorth-southmainrailwaylinesthroughtheAlps,thedelegatestotheWorldcongressforRailwayResearchinFlorencediscussedtheprojectforahigh-speedeast-westraillinktakinginVenice,Milan,Turin,MontCe'nis,LyonandParis.OnesectionofthisprojectisthelinebetweenMontmezlianandTurin,cateringformixedpassengerandgoodstraffic,withabasetunnelof54kminlengthbeneathMontd9Ambin.Thepossibletrafficcapacitiesare:30-40high-speedtrainswithavelocityof220km/h,80goodstrainsofclassicaldesignandcombinedwithavelocityof100-120km/h,50-60cartrainswithavelocityof120-140km/h.Thus,twosingle-lanetunnelshavebeenselectedasthesystemconfiguration(seeFig.3)withaclearanceprofileof43in2each[5].Asaresultofthetopographicalconditionsandwithoutexceedinga1.2%gradientfortheline,anintermediatepointofattackandevacuationpointispossibletothenorthofModane.Consequently,theprojectcouldbeexecutedintheformoftwotunnels,eachlessthan30kmlong.TunnelundertheGreatBeltThetunnelundertheGreatBelthasalengthofca.8kmandconsistsoftwosingle-tracktunnels(centerdistance25m)with30interconnectionsevery250mwhichserveforevacuationandescapeofpeopleincaseofanaccident[6].ConcludingremarksBasedontheaforementionedbriefreviewofexistingorplannedtunnels,thefollowingconclusionswithrespecttotheirdesignandsafetyphilosophycanbedrawn:thedesignphilosophyissomehowdifferentineachoftheaforementionedtunnelprojectsanddependsonthenationalrequirements,thetunnelconfigurationandgeometryandthetunnelcharacteristics(seeTable2);ineachcaseapackageofspecialsafetymeasuresisrecommendedtoreducerisk;cost-benefitconsiderationsareusuallyImplementedtodefinetheoptimumpackageofsafetysystems;geometriesaffectingtheescapeandrescuecapabilitiesvarysignificantlyfromcasetocase(seeTable2).Thebasicaspectaffectingthetunnelsafetyisthetunnelconfiguration.Thefollowingtunnelsystemsaregenerallyconsidered:onedouble-tracktunnel;onedouble-tracktunnelwithservicetunnel;twosingle-tracktunnels;twosingle-tracktunnelswithservicetunnel;threesingle-tracktunnels.Table2Comparisonofrelevantdesignparametersrelatedtosafetyintunnels(TSTT:twosingletracktunnels;ODTT:onedoubletracktunnel)Tunnel(km/h)SystemLength(km)Distanceinterconnect,(m)Widthofescape-way(m)Trafficitrain/day)Freighttrains(%)VelocityMontCenisTSTT54250>1.20160-18044-50220GreatBeltTSTT8.02501.202404010()EurotunnelTSTT503751.1011045160SeikanODTT53.9600-10000-0.64050240GotthardTSTT573250.7530080200BrennerTSTT552501.6034080250SYSTEMRgiatigRrtAVnluao04LOCMJBLETRACKTUNWfiL100ONEDOUBLETHACKTIJMFL•RFRVICFTUNNEL〜80TWOSIMCLCTOACKTUNNFLS50-60QoOTWOSINGLETRACKfUNNELS♦StHviceTUNNEL~40rrintztsingleTRACKTUMNELay40Fig.4.Relativeriskvaluefortunnelsystemscomparedtotheriskofthedoubletracktunnel.Fig.4illustratestherelativeriskpicturefortheaforementionedtunnelsystems.Thevaluesarebasedonresultsfromseveraltunnelriskstudies.Thefinalchoiceofthetunnelsystemdependsnotonlyonsafetyaspects,butalsoonothercriteriasuchascosts(constructionandmaintenancecosts),geologyandlocaltopographyconditions,andoperabilityrequirements,etc.Ingeneralfortunnelswithalengthgreaterthan5kmtheconfigurationoftwosingle-tracktunnelsisrecommendedbecauseofthebettersafetyandoperabilityconditions.RiskanalysisbasisEvaluationofaccidentstatisticsAccidentstatisticsandsafetyInrailwaytransportationhavebeendiscussedinthepastandspecialproblemssuchasthetransportationofdangerousmaterialsorfirepropagationintunnelshavebeenanalyzed[4,6,7].Theprimarycausesofaccidentscanbeclassifiedinto:internalcauses一mechanicalorelectricalfailuresconcerningthecontrolguidesystemaswellasthelogisticandinservicesystems;externalcauses—arthquakes,floods,avalanches^etc.;causesassociatedtohumanaction―peratingfaults,errorsduringmaintenance,sabotages,terroristicattacks.Table3illustratesthemajoraccidentsinrailwaytunnelsduringtheperiod1970-1993. •Basedonacriticalreviewofaccidentalstatisticsinrailwayoperation,thedominatinginitiatingeventsandtheassociatedprobabilitiesofoccurrenceasderivedfortheBrennertunnelstudyareshowninTable4forthetwobasictunnelconfigurations,ieonedouble-tracktunnelandtwosingle-tracktunnels.ThevaluesarebasedonaccidentstatisticsoftheAustrian,GermanandItalianRailways.Norelevantaccidentshavebeentherebyexcludedandapproximatecorrectionfactorshavebeenconsideredtoaccountforthesafetysystemsrelatedtothenewtechnology.Table3TunnelaccidentsinWesternEuropewithfatalitiesduringtheperiod1970-1993DateLocationFatalitiesInitiatingevent22-7-1971Simplon(CH)Derailment516-6-1972Soissons(F)108Hitagainstanobstacle22-8-1973S.Sasso(I)4Collision23-7-1976Simplon(CH)6Derailment....-4-1980Sebadell(E)5tier21-1-1981Calabria(I)5Hitagainstanobstacle9-1-1984ElPais(E)2Collision18-4-1984Spiez(CH)1Collision23-12-1984Bologna(I)15Sabotage26-7-1988Castiglione(I)1Fire14-9-1990Gurtnellen(CH)1Derailment31-7-1993Doniodossola(I)1Collision32AnalysisprocedureTheanalysisofaccidentsinhazardousscenariosisperformedbyusingeventtrees.Theeventtreeapproachrepresentsastraightforwardprocedurefordescribingaccidentalscenariosanditcanincludedifferentvariablesandthenotationoftime.Theprobabilitiesofeventsinthepathsoftheeventtreesareestimatedbasedontheavailabledata,onexpertopinionandonengineeringJudgement.Thecompleterisk-analysisprocedureisshowninFig.5.Onthebasisofthetunneldesignandwithreferencetohistoricalrailwayaccidents,themostimportanthazardousscenariosareidentified.Foreachselectedscenarioaprobabilistieventtreeanalysisisperformedandtheaccidentalscenarioconsequencesintermsofdamagestopassengers,Le.facilitiesareevaluated.Theconsequenceanalysescanbebasedonsophisticatedtoolsthatallowtomodelrelevantaccidentalscenariosinaconfinedenvironment.Theanalysisofthesafetymeasuresconsistsofanevaluationoftheactualsafetyperformanceofeachoneofthem.Suchanevaluationisbased,inmanycases,onsoundengineeringJudgementduetothelackofexperiencewiththenewsafetysystems.33.CasestudyTheaforementionedprocedurehasbeenappliedtocomputethesocietalriskintermsofexpectedfatalitiesbasedontheaccidentalprobabilitiesgiveninTable4.TheobtainedresultsareillustratedintermsofexpectedfatalitiesinTable5・Atypicalapplicationoftheresultsisprovidedfora10kmlongtunnelinTable6fortwotunnelsystems,i.e.twosingle-tracktunnelsandonedouble-tracktunnel.Thefirstsystemis,asexpected,muchsafer;however,inbothcasestheobtainedsocietalriskissmall.Itisnotedthatthemostsignificantcontributortoriskiscollision.Theacceptabilityoftheriskvaluesisdiscussed

inSection4.Table4Inputaccidentalfrequenciesperonemilliontrainkilometers(ODTT:onedoubletracktunnel;TSTT:twosingletracktunnels)InitiatingeventTSTTODTTDerailment0.001Collision0.0002Hitagainstanobstacle0.006Fire0.00090.0010.00030.0060.0009Table5Societalrisk,i.e.expectedfatalitiesper1milliontrainkilometers(ODTT:onedoubletracktunnel;TSTT:twosingletracktunnels)InitiatingeventTSTTODTTDerailmentCollision 0.025(46%)0.017(55%)0.012Hitagainstanobstacle 0.011(20%)0.003(10%)Fire 0.006(11%)0.006(19%)Total 0.054(100%)0.031(100%)

RiskperceptionconsiderationsBackgroundBothindividualriskandsocietalriskareconsidered.TheacceptableindividualriskisafunctionoftheindhdduaPsinvolvement;differentacceptablelevelsshouldbedefinedforactivitieswheretheindividualvoluntarilyexposeshimselftothehazardwithrespecttoaninvoluntaryparticipation[8]«Forvoluntaryrisk,anupperlimitofprobabilityofdeathperyearequalto1022hasbeendefined;whereasfortheinvoluntaryrisk,thefollowingvalueshavebeensuggested:P>10^一notacceptable;10'6<p<ICT1一tolerable;p<IO"6一acceptable.Table6ODTTSocietalriskfortheexampletunnel(100trainsperday;10kmlong)expressedinexpectedfatalitiesperyear(ODTT:onedoubletracktunnel;TSTT:twosingletracktunnels)InitiatingeventTSTT ODTT0.00390.0017Derailment0.00390.0017Collision0.0056Hitagaistanobstacle0.0010Collision0.0056Hitagaistanobstacle0.0010FireTotal0.01030.00830.00360.00200.00200.0178Forsocietalrisk,theacceptabilitycriteriaarebasedonthedefinitionofanacceptableprobabilityrangeforeventsofgivenconsequences.Ofcourse,theseverestconsequencesareassociatedwiththelowestvaluesoftheacceptableprobability.SafetystandardsforotherindustrialactivitiesAbriefreviewoftheacceptabilityriskcriteriaproposedoradoptedbydifferentindustrialsectorsisprovided[9].Table7summarizesthetypeofapproachfollowedbytheseindustriestodefinesafetytargets.42LRoadtransportRoadaccidentshavebeenextensivelyanalyzedandseveralstatisticalsyntheseshavebeenpresented.Nevertheless,roadwayregulationsdonopresentanyquantitativeevaluationofthepresentrisklevelfortheroadwaysystemanddonotproposeacceptablelimitsontheoccurrenceofaccidentalevents.AirtransportRiskacceptabilitycriteriahavebeendefinedforairtransportbysomerulesandregulations,however,nouniquecriterionexistsyet.Atpresent,onecanconsiderthattheacceptablerisklevelis1027accidentswithfatalitiesperhourofflight,correspondingtoapproximately2£10210accidentsperkilometerofflight.TOC\o"1-5"\h\zTable7 'RiskacceptabilitycriteriaforvariousindustrialactivitiesIndustry Qualitative SemiquantitativeQuantitative\o"CurrentDocument"Roadtransport X XAirtransport XChemical XNuclear XOffshore XChemicalindustryChemicalindustriesareexposedtohazardsthatincludefires,explosions,toxicreleases;riskanalysesinthechemicalindustryisthereforeastrongtradition.Quantitativecriteriaforthedefinitionofsocietalacceptablerisklevelshavebeenpresented[10].NuclearpowerplantsSafetyisobviouslyamajorconcernfornuclearpowerplants.Duringdesign,accidentaleventswithaninsignificantprobabilityofoccurrenceareusuallynottakenintoaccount.Severalstudiesperformedforsomeplantsconcludedthattheprobabilityofcoremeltisoftheorderof1024-1025occurrencesperyear[11].OffshoreproductionplatformsSeveralstudieshaveaddressedthedefinitionoftargetsafetylevelsforsocietalriskfortheoffshoreIndustry.InCanada,forexample,safetycriteriahavebeendefined,basedoncost-benefitconsiderationsandcomparisontootherindustrialrisks[12],thatindicateanannualprobabilityof1025forcatastrophicconsequences,1023forsevereconsequencesand1021forminorconsequences.MethodologicalapproachThebasiccriterionforthedefinitionofatargetsafetlevelforarailwaysystemistoassumethatthesafetyinherentinthetraditionalrailwaysinthepasttwoorthreedecadesisacceptable.Thesafetytargetis,thereforederivedbyanalyzingtherecentriskhistoryoftherailwaysintermsofthefrequencyofoccurrenceofaccidentsandtheextentoftheirconsequences.Theproceduregenerallyusedtoestimatetheriskassociatedtorailwaytransportisbasedontheanalysesofthefrequencyofoccurrenceofgivenconsequencesforagivenaccident;theriskRifortheithtypeofaccidentisthereforegivenby:&-RG (1)wherepiistheprobabilityofoccurrenceoftheithtypeofaccidentandCiistheexpectedconsequenceoftheithtypeofaccident.Globally,thegenericriskRtisdefinedas:%=£pg ⑵ITheconsequencesCiaregenerallyclassifiedaccordingtothreelevelsofgravity:“medium”,“severe”and“catastrophic”.Toeachoftheseclassesithasbeenassociatedameannumberofvictims:mediumconsequences:3victims;severeconsequences:30victims;andcatastrophicconsequences:300victims.

10TheevaluationoftheprobabilitypicanbeperformedassumingthataccidentaleventsoccuraccordingtoaPoissonprocess;thismeansthataccidentaleventsareindependent[13].Theprobabilityofhavingnaccidentaleventsoftype/duringthetimeTisgivenby:10Pi(n/T}=e-uT(uTytln\ (3)whereinisthefrequencyofoccurrenceoftheaccidentalevents;whereastheprobabilityofhavingatleastoneaccidentaleventnointhesametimeisgivenby:r(〃o/t)=i-戒 (4)Foraccidentsassociatedtocatastrophicconsequencesonly,afeweventsoccurredandthereforestatisticaldataarenotsufficienttoprovidereliableestimates.FortheseeventsitisthereforerecomniendedtouseaBayesianapproach.TheprobabilityofhavingatleastoneaccidentduringthetimeTo,havingobservedneventsinatimeinterval7\isgivenby:p(m，〃，r)=i-i/[i+7；/Tr+,(5)TheaforementionedmethodologyhasbeenappliedondataofrecordedaccidentsoftheItalian,AustrianandGermanrailways.TheresultsarepresentedinFig.6inadiagramwheretheconsequences,intermsofexpectedvictims,areplottedagainsttheannualprobabilityofhavingatleastoneaccidentthatleadstotheseconsequences.ResultsareconsideredvalidforafirstdeflnitionofanacceptablesafetylevelforWesternEuroperailwaysystemsandarecomparabletothecomputedvaluesforvarioustunnelprojects.tolerableandnegligibleFrcqvcntInto^rabbyiO-1Prebath jy.W4CccaaionaltolerableandnegligibleFrcqvcntInto^rabbyiO-1Prebath jy.W4Cccaaionaly.安Rog。 -•n■yW**lrnpmhank>lo«at)*ey10”intredibte ■:二.NettieScalingFarters-....0.1,1,10..-CatMirophhCWSceiMarginalSafetyHazardSovertfUr/vlx.10-1引0°RISKCLASSIFICATOICCRHazardProbeWlVLsclofrisk

matrix:ofFig.7.Principleclassificationclassificationintolerable,undesirable,x.104•eventsofmediumconsequencesareassociatedwithanannualprobabilityof10M(pertrain-kilometer);•eventsofsevereconsequencesareassociatedwithanannualprobabilityof10'10(pertrain-kilometer);and•eventsofcatastrophicconsequencesrailwaysystems,inparticular,p-Cconditionsthatfallbelowthecurveareassociatedtoacceptablesafetylevels.areassociatedwithaprobabilityof10'11railwaysystems,inparticular,p-Cconditionsthatfallbelowthecurveareassociatedtoacceptablesafetylevels.(pertrain-kilometer).ThecurveofFig.6,therefore,definestheacceptabilityconditionsforthestudiedSuppose,forexample,thattoatunnelofapproximately50kmlengt