《公路线形设计》外文文献(中英对照)

外文文献翻译（含：英文原文及中文译文）文献出处：YHassan.GeometricDesignofHighways[J]AdvancesinTransportationStudies,2016,6(1):31-41.英文原文GeometricDesignofHighwaysYHassanA.AlignmentDesignThealignmentofaroadisshownontheplaneviewandisaseriesofstraightlinescalledtangentsconnectedbycircularcurves.Inmodempracticeitiscommontointerposetransitionorspiralcurvesbetweentangentsandcircularcurves.Thelineshapeshouldbecontinuous,suddenchangesfromflatlinetosmallradiuscurveorsuddenchangeoflonglineendconnectedtosmallradiuscurveshouldbeavoided,otherwiseatrafficaccidentmayoccur.Similarly,arcswithdifferentradiiend-to-end(complexcurves)orshortstraightlinesbetweentwoarcswithdifferentradiiarebadlinesunlessaneasingcurveisinsertedbetweenarcs.Thelong,smoothcurveisalwaysagoodlinebecauseitisbeaut血llylinedandwillnotbeabandonedinthefuture.However,itisnotidealthatthetwo-wayroadlineshapeiscomposedentirelyofcurves,becausesomedriversalwayshesitatetopassthroughcurvedroadsegments.Thelongandslowcurveisusedinthesmallercomers.Ifyouuseashortcurve,youwillseekinks.Inaddition,thedesignoftheflatandverticalsectionsofthelineshouldbeconsideredcomprehensivelyandshouldnotbeonlyone.Nomatterwhich,forexample,whenthestartingpointoftheflatcurveisnearthevertexoftheverticalcurve,serioustrafficaccidentswilloccur.Vehiclesdrivingoncurvedsectionsaresubjectedtocentrifugalforce,andtheyneedaforceofthesamemagnitudeintheoppositedirectionduetotheheightandlateralfrictiontooffsetit.Fromtheviewpointofhighwaydesign,thehighorhorizontalfrictioncannotexceedacertainvalue.Them邸imum,thesecontrolvaluesforacertaindesignspeedmaylimitthecurvatureofthecurve.Ingeneraithecurvatureofac订cularcurveisrepresentedbyitsradius.Forthelineardesign,thecurvatureisoftendescribedbythecurvature,ie,thecentralanglecorrespondingtothe100-footcurve,whichisinverselyproportionaltotheradiusofthecurve.Anormalroadarchissetinastraightsectionoftheroad,andthecurvesectionissettoasuperhigh,andanexcessivelygradualroadsectionmustbesetbetweenthenorn叫sectionandthesuperhighsection.Theusualpracticeistomaintainthedesignelevationofeachmidlineoftheroadunchanged.Byraisingtheouteredgeandloweringtheinneredgetoformasuperhigh,forthelineshapewherethestraightlineisd汀ectlyconnectedwiththec虹lecurve,thesuperhighshouldneverstartonthestraightlinebeforereachingthecurve.Attheotherendofthecurveatacertaindistancetoreachalltheultra-high.Ifthevehicleisdrivingatahighspeedonarestrictedsectionofroad,suchasastraightlineconnectedwithasmallradiuscirclecurve,drivingwillbeextremelyuncomfortable.Whenthecarentersthecurvesection,thesuperhighstartsandthevehicletiltsinward,butthepassengermustmaintainthebodybecauseitisnotsubjectedtocentrifugalforceatthistime.Whenthecarreachesthecurvesection,centrifugalforcesuddenlyoccurs,forcingpassengerstom狄efurtherpostureadjustments.Whenthecarleavesthecurve,theaboveprocessisjusttheopposite.Afterinsertingtherelaxationcurve,theradiusgraduallytransitionsfrominfinitytoacertainfixedvalueonthecirclecurve,thecentrifugalforcegraduallyincreases,andultra-highlevelsarecarefullysetalongtherelaxationcurve,andthecentrifugalforceisgraduallyincreased,therebyavoidingdrivingbumps.Theeasementcurvehasbeenusedonrailwaysformanyyears,butithasrecentlybeenappliedonhighways.Thisisunderstandable.Thetrainmustfollowapreciseorbit,andtheuncomfortablefeelingmentionedabovecanonlybeeliminatedaftertheeasecurveisused.However,thedriverofacarcanchangethelateralpositionontheroadatwill,andhecanprovidearelaxationcurveforhimselfbym咄ingaroundaboutcurve.Butdoingthisinonelane(sometimesinotherlanes)isverydangerous.Awell-designedrelaxationcurvemakestheaboveroundaboutnessunnecessary.Multi-clustersafetyisameasure,androadsarewidelyusedastransitioncUIVes.Foracircularc田vewiththesameradius,addinganeasingcUIVeattheendwillchangetherelativepositionsofthec田veandthestraightline.Therefore,whetherornottouseaneasingcUIVeshouldbedeterminedbeforefinalalignmentsUIVey.ThestartingpointofthegeneralcUIVeislabeledPCorBCandtheendpointislabeledPTorEC.ForcUIVeswithtransitionc田ves,theusualmarkerconfigurationsare:TC,SC,CS,andST.Fortwo-wayroads,theroadwidthshouldbeincreasedatsharpbends.Thisismainlybasedonthefollowingfactors:1.Thedriverisafraidtogetoutoftheedgeoftheroad.2.Duetothedifferenceinthedrivingtrajectoryofthefrontandrearwheelsofthevehicle,theeffectivelateralwidthofthevehicleincreases;3.Thewidthofthefrontofthevehiclethatisinclinedrelativetothecenterlineoftheroad.Forroadsthatare24feetwide,theaddedwidthisnegligible.Onlyifthedesignspeedis30mil/handthecUIVatureisupto2ft.However,fornarrowroads,wideningisveryimportantevenonsmoothcUIVesections.Therecommendedwideningvaluesandwideneddesignsareshownin.Highwaylineardesign.B.LongitudinalslopelineTheverticalalignmentofthehighwayanditsimpactonthesafetyandeconomyofvehicleoperationconstituteoneofthemostimportantelementsinhighwaydesign.Verticallinesconsistofstraightlinesandverticalparabolasorcircularlinescalledverticalslopelines.Whenagradelinerisesgraduallyfromahorizontalline,itiscalledanuphiliandviceversa,itiscalledadownhillslope.Intheanalysisofslopeandslopecontroi如ignersusuallyhave