Intra marketoptimizationforexpresspackagecarrierswithstationtostation travel andproportionalsorting

The flowofpackagesofanexpresspackagecarrierconsistsofpickupsatcostumerlocationsbycouriers and deliveringthepackagestoalocalstationforsorting.Thepackagesarethentransportedtoamajor regionalsortingfacilitycalledtheramp.Attheramp,packagescanbesortedagainbeforedepartingtoa hub. Fromthehubtheyaremovedtothedestinationramp,wheretheentireprocessrepeatsinthe reverse orderuntilultimatedeliveryofthepackagetotheendcustomer.Wefocusontheafternoonand eveningoperationsconcerningstationsandtheramp.Sortingandtransportationdecisionsamongthese locationsareconsidered.Themostimportantdecisionsare:(1)whichpackagestoaggregateatthe stations,and(2)whatisthemostefficienttransportationamonglocationstomeettimedeadlinesat the ramp.Severaloptionsformodelingthesortingprocessatstationsandtheramp,aswellasthe possibilityofvehiclestravelingfromonestationtoanotherstationtoconsolidatevolumebefore proceedingtotherampareconsidered.Wemodeltheseprocessesbymeansofadynamicprogram, wheretimeperiodsrepresenttimeslicesintheafternoonandevening.Theoverallmodelissolvedby approximatedynamicprogramming,wherethevaluefunctionisapproximatedbyalinearfunction. Furtherstrategiesaredevelopedtospeedupthealgorithmanddecreasethetimeneededtofind feasiblesolutions.Themethodologyistestedonseveralinstancesfromanexpresspackagecarrier.The dynamicprogramsolutionsaresubstantiallybetterthanthecurrentbestpracticeandthebestsolutions obtainedfromanintegerprogrammingformulationoftheproblem.