Pre-disaster investmentdecisionsforstrengtheningahighwaynetwork

We addressapre-disasterplanningproblemthatseekstostrengthenahighwaynetworkwhoselinks are subjecttorandomfailuresduetoadisaster.Eachlinkmaybeeitheroperationalornon-functional after thedisaster.Thelinkfailureprobabilitiesareassumedtobeknownapriori,andinvestment decreasesthelikelihoodoffailure.Theplanningproblemseeksconnectivityforfirstresponders between variousorigin–destination(O–D)pairsandhencefocusesonuncapacitatedroadconditions. The decision-maker’sgoalistoselectthelinkstoinvestinunderalimitedbudgetwiththeobjectiveof maximizingthepost-disasterconnectivityandminimizingtraversalcostsbetweentheoriginand destinationnodes.Theproblemismodeledasatwo-stagestochasticprograminwhichtheinvestment decisionsinthefirststagealterthesurvivalprobabilitiesofthecorrespondinglinks.Werestructurethe objectivefunctionintoamonotonicnon-increasingmultilinearfunctionandshowthatusingthefirst order termsofthisfunctionleadstoaknapsackproblemwhosesolutionisalocaloptimumtothe originalproblem.Numericalexperimentsonreal-worlddatarelatedtostrengtheningIstanbul’surban highwaysystemagainstearthquakeriskillustratethetractabilityofthemethodandprovidepractical insightsfordecision-makers.