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Unit7EconomicsandTransportationEngineering
Text

Aneconomicanalysisshouldnotbecarriedoutasallafterthought.Itshouldbeusedaspartofacontinuousprocess，startingwiththeobjectivesoftheproposedtransportationproject(cantheseobjectivesbesatisfiedinanyotherway?)，runningthroughtheentireplanninganddesignprocess，andonlyending，asafinalsummingup，withtheoverallevaluation.Itshouldconsiderthefollowingquestions：
①Projectidentification.Whichprojectsorpoliciesshouldbeconsideredaspossiblesolutionstoaparticulartransportneed?
②Establishingroughpriorities．Whichprojectsandpoliciesshouldbeconsideredindetail?
③Detailedevaluation．Whichcostsandbenefitsarerelevanttotheevaluation，howshouldtheybemeasured，andhowcantheybestbepresentedasanindexofpriority?
④Projectselection．Shouldthisprojectbeselected，shoulditberejected，orshoulditbepostponed?
Economicsisoftenoverlookedasanaidtotransportationplanninganddesign．Yetanytransportationengineeringprobleminvolvesawholeseriesofessentiallyeconomicdecisions．Intheareaofdesign，forexample，thetransportationengineermustchoosematerials，selectanoveralldesignconcept，andthencombinethecomponentpartsoftheschemeintoaneffective，andeconomical，whole．Arivercrossingcouldthusbebyferryboat，causeway，orbridge．Inthelattercaseitcouldbeinsteel，concrete，ortimber．Itcouldbesuspended，arched，orsimplysupported．Whatshouldtheengineerchoose?
Therangeofchoiceisnotusuallyaslargeasthis．Somesolutionswillbephysicallyinfeasible(e.g.，bylackofsuitablefoundationsforanarchedbridge),butimportantchoiceswillremain．Intheabsenceofarigorouseconomicanalysis，thedesignermaymakethesechoicesonthebasisof：
①Experience，whichmayormaynotcoveranadequaterangeofoptions．
②Preconceptionsastowhatisdesirable(e.g.,onesolutionuseslessmaterial)．
③Aninnateviewofmathematicalorstructuralelegance(e.g.，anarchisamoreelegantstructuralform)．
Economicsavoidstheneedforthesearbitraryrulesbyprovidingatangiblecriterion-costforchoosingbetweenalternativesolutions.Inmanycasesthiscanbedonequitesimplybydrawingenvelopesofcostcurvesof,forexample,steelg