資源描述：
《美國道路線型設(shè)計規(guī)范AASHTO—Geometric Design of Highways and Streets.pdf》由會員上傳分享，免費在線閱讀，更多相關(guān)內(nèi)容在行業(yè)資料-天天文庫。
1、CHAPTER4CROSSSECTIONELEMENTSGENERALToassureconsistencyinthispolicy,theterms“roadway”and“traveledway”aredefinedbyAASHTOasfollows:Roadway:Theportionofahighway,includingshoulders,forvehicularuse.Adividedhighwayhastwoormoreroadways(seeExhibits4-1and4-2).Traveledway:Theportionoftheroadwayforthe
2、movementofvehicles,exclusiveofshoulders(seeExhibits4-1and4-2).PAVEMENTSurfaceTypeTheselectionofpavementtypeisdeterminedbasedonthetrafficvolumeandcomposition,soilcharacteristics,weather,performanceofpavementsinthearea,availabilityofmaterials,energyconservation,initialcost,andtheoverallannua
3、lmaintenanceandservice-lifecost.Thestructuraldesignofpavementsisnotincludedinthispolicy,butisaddressedintheAASHTOGuideforDesignofPavementStructures(1).Importantpavementcharacteristicsthatarerelatedtogeometricdesignaretheeffectondriverbehaviorandtheabilityofasurfacetoretainitsshapeanddimens
4、ions,todrain,andtoretainadequateskidresistance.High-typepavementsretaintheirshapeanddonotravelattheedgesifplacedonastablesubgrade.Theirsmoothnessandpropercross-slopedesignenabledriverstosteereasilyandkeeptheirvehiclesmovingintheproperpath.Attheotherextreme,low-typesurfaceshaveatendencytowa
5、rdraveling,whichreducestheireffectivewidthandrequiresgreatersteeringefforttomaintainacorrectpath.Accordingly,low-typesurfacesareusedwheretrafficvolumeislight.Whiletheselectionofdesignspeedisdependentonmanyfactorsotherthanpavementsurfacetype,high-typesurfacesprovideforhigheroperatingspeedst
6、handolow-typesurfaces.Therefore,thesurfacetypeprovidedshouldbeconsistentwiththeselecteddesignspeedforthehighway.CrossSlopeUndividedtraveledwaysontangents,oronflatcurves,haveacrownorhighpointinthemiddleandacrossslopedownwardtowardbothedges.Unidirectionalcrossslopesacrossthe309AASHTO—Geometr
7、icDesignofHighwaysandStreetsExhibit4-1.TypicalCrossSection,NormalCrown310CrossSectionElementsExhibit4-2.TypicalCrossSection,Superelevated311AASHTO—GeometricDesignofHighwaysandStreetsentirewidthofthetraveledwaymaybeutilized.Thedownwardcrossslopemaybeaplaneorrou
