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1、附录A外文翻译A.1原文CONSISTENCYINDESIGNFORLOW-VOLUMERURALROADS3ByClarksonH.Oglesby,H.M.ASCE(ReviewedbytheHighwayDivision)ABSTRACT:The2,000,000milesoflow-volumeruralroadsintheUnitedStatesaredifferentthanthehigh-volumeroadsandshouldbedesigneddifferently.Trafficvolumesonthem
2、arelow,averagingabout110vehicles/dayoraboutonevehicleenteringagivenmilefrombothendseverythreeminutesduringpeakhours.Thiscontrastswithonevehicleeveryfoursecondsatcapacity.Geometriesonmanyoftheseroadshavenotchangedsincetheywerebuiltinthe1920sand1930s.Today,roadimpro
3、vementsshouldbebasedondesignsthatareconsistentandsafe,buteconomical,becauseneedsaregreatandfundsarescarce.Present-daydesignpracticesforhighvolumeroadsrequirethateachoftheirfeaturesmeetastipulateddesignspeedsetbymodernsurfacesandvehicles.Thispracticedoesnotfitthelo
4、w-volumesituationsince,wheneverpossible,driverswillexceedanyaffordabledesignspeed.Theymustbesloweddownwhensituationswarrantit.Aconsistentapproachtodesignwhichrealizescheapbutsafeimprovementstolow-volumeroadsisproposed.Itinvolvesintegratinggeometricdesignandpositiv
5、eguidanceapproaches.Positiveguidanceemploysstriping,signing,andotherdevicesandstrategiestomobilizedrivers'sensessothattheywilldrivesensibly.Selectingthelesscostlybetweengeometryandpositiveguidancetechniqueswillproducesaferroadsmorecheaply.INTRODUCTIONThereareappro
6、ximately3,200,000mile(5,100,000km)ofruralroadsintheUnitedStates.Aroughestimateplacessome2,000,000(3,000,000km)oftheseinalow-volumecategory;thiscommonlyincludesthosewithaveragedailytrafficlessthan400vehicles/dayinbothdirections.Onmostoftheseroadsvolumesareconsidera
7、blylower.Oneestimateplacesthisaverageat110vehicles/dayorapossible20inthepeakhour.Thismeansonevehicleeverythreeminutesenteringagivenmilefrombothends.Incontrast,amajortwo-laneroad,operatingatcapacity,willcarrypossibly1,800vehicles/hoursothatavehiclewillenteragivenmi
8、leeveryfoursecondsor90timesasoften.Themoneyavailabletothoseresponsibleforhigh-volumeroadsisontheorderoftentimesasgreatpermileasforlow-volumeroads.Itfoll
