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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.Trafficvolumesonthemarel
2、ow,averagingabout110vehicles/dayoraboutonevehicleenteringagivenmilefrombothendseverythreeminutesduringpeakhours.Thiscontrastswithonevehicleeveryfoursecondsatcapacity.Geometriesonmanyoftheseroadshavenotchangedsincetheywerebuiltinthe1920sand1930s.Today,roadimprovementss
3、houldbebasedondesignsthatareconsistentandsafe,buteconomical,becauseneedsaregreatandfundsarescarce.Present-daydesignpracticesforhighvolumeroadsrequirethateachoftheirfeaturesmeetastipulateddesignspeedsetbymodernsurfacesandvehicles.Thispracticedoesnotfitthelow-volumesitu
4、ationsince,wheneverpossible,driverswillexceedanyaffordabledesignspeed.Theymustbesloweddownwhensituationswarrantit.Aconsistentapproachtodesignwhichrealizescheapbutsafeimprovementstolow-volumeroadsisproposed.Itinvolvesintegratinggeometricdesignandpositiveguidanceapproac
5、hes.Positiveguidanceemploysstriping,signing,andotherdevicesandstrategiestomobilizedrivers'sensessothattheywilldrivesensibly.Selectingthelesscostlybetweengeometryandpositiveguidancetechniqueswillproducesaferroadsmorecheaply.INTRODUCTIONThereareapproximately3,200,000mil
6、e(5,100,000km)ofruralroadsintheUnitedStates.Aroughestimateplacessome2,000,000(3,000,000km)oftheseinalow-volumecategory;thiscommonlyincludesthosewithaveragedailytrafficlessthan400vehicles/dayinbothdirections.Onmostoftheseroadsvolumesareconsiderablylower.Oneestimateplac
7、esthisaverageat110vehicles/dayorapossible20inthepeakhour.Thismeansonevehicleeverythreeminutesenteringagivenmilefrombothends.Incontrast,amajortwo-laneroad,operatingatcapacity,willcarrypossibly1,800vehicles/hoursothatavehiclewillenteragivenmileeveryfoursecondsor90timesa
8、soften.Themoneyavailabletothoseresponsibleforhigh-volumeroadsisontheorderoftentimesasgreatpermileasforlow-volumeroads.Itfoll
