Design Manual M 22-01 Traffic Barriers November 2006 Page 710-1

Chapter 710 Traffic Barriers

710.01 General710.02 References710.03 Definitions710.04 ProjectRequirements710.05 BarrierDesign710.06 BeamGuardrail710.07 CableBarrier710.08 ConcreteBarrier710.09 Special-UseBarriers710.10 BridgeTrafficBarriers710.11 OtherBarriers710.12 Documentation

710.01 GeneralTrafficbarriersareusedtoreducetheseverityofaccidentsthatoccurwhenanerrantvehicleleavesthetraveledway.However,trafficbarriersareobstaclesthatthevehiclewillencounterandtheymustonlybeusedwhenjustifiedbyaccidenthistoryorthecriteriainChapter700.

710.02 ReferencesDesignGuidanceBridge Design Manual,M23-50,WSDOT

Roadside Design Guide,AASHTO

Standard Plans for Road, Bridge, and Municipal Construction(StandardPlans),M21-01,WSDOT

Traffic Manual,M51-02,WSDOT

710.03 Definitionsbarrier terminal Acrashworthyendtreatmentforlongitudinalbarriersthatisdesignedtoreducethepotentialforspearing,vaulting,rolling,orexcessivedecelerationofimpactingvehiclesfromeitherdirectionoftravel.Barrierterminalsincludeapplicableanchorage.

controlled releasing terminal (CRT) post Astandardlengthguardrailpostthathastwoholesdrilledthroughitsothatitwillbreakawaywhenstruck.

crashworthy Afeaturethathasbeenprovenacceptableforuseunderspecifiedconditions,eitherthroughcrashtestingorin-serviceperformance.

hazard Asideslope,afixedobject,orwaterthat,whenstruck,canresultinunacceptableimpactforcesonavehiclesoccupantsorplacetheoccupantsinahazardousposition.Ahazardcanbeeithernaturalormanmade.

impact attenuator system Adevicethatactsprimarilytobringanerrantvehicletoastopatadecelerationratetolerabletothevehiclesoccupantsortoredirectthevehicleawayfromahazard.

length of need Thelengthofatrafficbarrierneededtoshieldahazard.

longitudinal barrier Trafficbarrierorientedparallelornearlyparalleltotheroadway.Thepurposeistocontainorredirecterrantvehicles.Beamguardrail,cablebarrier,bridgerail,andconcretebarrierarelongitudinalbarriers,whicharecategorizedasrigid,unrestrainedrigid,semirigid,andflexible.Theycanbeinstalledasroadsideormedianbarriers.

shy distance Thedistancefromtheedgeofthetraveledwaybeyondwhicharoadsideobjectwillnotbeperceivedasanimmediatehazardbythetypicaldrivertotheextentthatthedriverwillchangethevehiclesplacementorspeed.

traffic barrier Alongitudinalbarrier,includingbridgerail,oranimpactattenuatorusedtoredirectvehiclesfromhazardslocatedwithinanestablishedDesignClearZone,topreventmediancrossovers,topreventerrantvehiclesfromgoingoverthesideofabridgestructure,or(occasionally)toprotectworkers,pedestrians,orbicyclistsfromvehiculartraffic.

transition Asectionofbarrierusedtoproducethegradualstiffeningofaflexibleorsemirigidbarrierasitconnectstoamorerigidbarrierorfixedobject.

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710.04 ProjectRequirementsThissectionidentifiesthebarrierelementsthatmustbeaddressedaccordingtotheDesignMatricesinChapter325.Removeanybarrierthatisnotneeded(basedonthecriteriainChapter700)orthatposesamoreseverehazardthanthehazarditisshielding.

(1) Barrier Terminals and TransitionsInstall,replace,orupgradetransitionsasdiscussedin710.06(5),TransitionsandConnections.

ImpactattenuatorrequirementscanbefoundinChapter720,ImpactAttenuatorSystems.

Wheninstallingnewterminals,considerextendingtheguardrailtomeetthelengthofneedcriteriain710.05(4)asaspotsafetyenhancement.

Concretebarrierterminalrequirementscanbefoundin710.08(3).Whentheendofaconcretebarrierhasbeenterminatedwithasmallmoundofearth(adesignformerlyknownasaConcreteBarrierBerm),removeandreplacewithacrashworthyterminal,exceptasnotedin710.09.

Redirectionallandforms,alsoreferredtoasearthberms,wereinstalledtomitigatehazardslocatedindepressedmediansandatroadsides.Theywereconstructedofmaterialsthatprovidedsupportforatraversingvehicle.Withslopesintherangeof2H:1Vto3H:1V,theywereintendedtoredirecterrantvehicles.Theuseofredirectionallandformshasbeendiscontinuedasameansformitigatingfixedobjects.Whereredirectionallandformscurrentlyexistasmitigationforafixedobject,ensurethatthehazardtheywereintendedtomitigateisremoved,relocated,madecrashworthy,orshieldedwithbarrier.Landformsmaybeusedtoprovideasmoothsurfaceatthebaseofarockcutslope.

Replaceguardrailterminalsthatdonothaveacrashworthydesignwithcrashworthyguardrailterminals.(See710.06(4),TerminalsandAnchors.)Commonfeaturesofnoncrashworthydesignsincludethefollowing: Nocableanchor Acableanchoredintoconcreteinfrontofthefirstpost

Secondpostnotbreakaway(CRT) DesignAendsection(DesignCendsectionsmaybeleftinplaceseetheStandardPlansforendsectiondetails)

Beamguardrailonbothsidesoftheposts(two-sided)

Buriedguardrailterminalsthatslopedownsuchthattheguardrailheightisreducedtolessthan2feet

Whentheheightofastandardterminalwillbereducedtolessthan26inchesfromthegroundtothetopoftherailelement,adjusttheheighttoaminimumof26inchesandamaximumof28inches.Arailheightof28inchesisdesirabletoaccommodatefutureoverlays.TerminalsareequippedwithCRTpostswithdrilledholesthatneedtoremainatthesurfaceoftheground.

OneterminalthatwasusedextensivelyonWashingtonshighwayswastheBreakawayCableTerminal(BCT).ThissystemusedaparabolicflaresimilartotheSRTandaType1anchor.Type1anchorpostsarewoodsetinasteeltubeoraconcretefoundation.

ReplaceBCTsonInterstateroutes.Onnon-Interstateroutes,BCTsthathaveatleasta3-footoffsetmayremaininplace,unlesstheguardrailrunoranchorisbeingreconstructedorreset.(Raisingtherailelementisnotconsideredreconstructionorresetting.)ReplaceallBCTsthathavelessthana3-footoffset.

Existingtransitionsthatdonothaveacurb,butareotherwiseconsistentwiththedesignsshownintheStandardPlans,mayremaininplace.

Forpreservationprojects,terminalandtransitionworkmaybeprogrammedunderaseparateproject,asdescribedinChapter410.

(2) Standard Run of BarrierInChapter325,theDesignMatricesofferguidanceonhowtoaddressstandardbarrierrunsfordifferentprojecttypes.AStandardRunofbarrierconsistsoflongitudinalbarrierthatisdetailedintheWashingtonStateDepartmentofTransportation(WSDOT)StandardPlans.

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(a) Basic Design Level (B).Whenthebasicdesignlevel(B)isindicatedintheStandardRuncolumnofaDesignMatrixandtheheightofW-beamguardrailisorwouldbereducedtolessthan26inchesfromthegroundtothetopoftherailelement,adjusttheheighttoaminimumof26inchesandmaximumof28inches.Arailheightof28inchesisdesirabletoaccommodatefutureoverlays.

IfType1AlternateW-beamguardrailispresent,raisetherailelementaftereachoverlay.IfType1Alternateisnotpresent,raisetheexistingblockoutupto4incheshigherthanthetopoftheexistingpostbyboringanewholeinthepost.

Overlaysinfrontofsafetyshapeconcretebarrierscanextendtothetopofthelower,near-verticalfaceofthebarrierbeforeadjustmentisrequired.Allownomorethan1foot1inchfromthepavementtothebeginningofthetopnear-verticalfaceofthesafetyshapebarriers.Allownolessthan2feet8inchesfromthepavementtothetopofthesingle-slopebarrier.Allownolessthan2feet3inchesfromthegroundtothetopcableoftheType1cablebarrier,andnolessthan2feet6inchesfortheType2andType3andhightensioncablebarriers.

(b) Full Design Level (F).Whenthefulldesignlevel(F)isindicated,inadditiontotherequirementsforthebasicdesignlevel,thebarriermustmeettherequirementsfoundinthefollowing:

Chapter Subject

700.06 Medianconsiderations710.05(1) Shydistance710.05(2) Barrierdeflections710.05(3) Flarerate710.05(4) Lengthofneed710.05(5) Medianbarrierselectionand placementconsiderations 710.06 Beamguardrail 710.07 Cablebarrier 710.08 Concretebarrier

ExamplesofbarriersthatarenotacceptableasaStandardRunare: W-beamguardrail(excludingtheType31NB4proprietarysystem)with12-foot-6-inchpostspacingand/ornoblockouts.

W-beamguardrailonconcreteposts. Cablebarrieronwoodorconcreteposts. Half-moonorC-shapedrailelements.

(3) Bridge RailWhentheBridgeRailcolumnofamatrixappliestotheproject,thebridgerailsmustmeetthefollowingrequirements:

Useanapproved,crash-testedconcretebridgerailonnewbridgesorbridgestobewidened.TheBridge Design Manualprovidesexamplesoftypicalbridgerails.ConsulttheHeadquarters(HQ)BridgeandStructuresOfficeregardingbridgerailselectionanddesign,andfordesignoftheconnectiontoanexistingbridge.

Anexistingbridgerailonahighwaywithapostedspeedof30milesperhourorlessmayremaininplaceifitisnotlocatedonabridgeoveraNationalHighwaySystem(NHS)highway.WhenType7bridgerailispresentonabridgeoveranNHShighwaywithapostedspeedof30milesperhourorless,itmayremaininplace,regardlessofthetypeofmetalrailinstalled.Allotherbridgerailsmustbeevaluatedforstrengthandgeometrics.(See710.10forguidanceonretrofittechniques.)Thefundingsourceforretrofitofexistingbridgerailisdependentonthelengthofthestructure.Bridgerailretrofit,forbridgeslessthan250feetinlength(oratotalbridgeraillengthof500feet),isfundedbytheproject(PreservationorImprovement).Forlongerbridges,theretrofitcanbefundedbytheI-2subprogram.Contactprogrammingpersonneltodetermineiffundingisavailable.

TheType7bridgerailiscommon.Type7bridgerailshaveacurb,avertical-faceparapet,andanaluminumtoprail.ThecurbwidthandthetypeofaluminumtopraildictatetheadequacyoftheType7bridgerail,asshowninFigure710-1.ConsulttheHQBridgeandStructuresOfficeforassistanceinevaluatingotherbridgerails.

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710.05 BarrierDesignWhenselectingabarrier,considertheflexibility,cost,andmaintainabilityofthesystem.Itisgenerallydesirabletousethemostflexiblesystempossibletominimizedamagetotheimpactingvehicleandinjurytothevehiclesoccupant(s).However,sincenonrigidsystemssustainmoredamageduringanimpact,theexposureofmaintenancecrewstotrafficmightbeincreased.

Concretebarriermaintenancecostsarelowerthanforotherbarriertypes.Deteriorationduetoweatherandvehicleimpactsislimited.Unanchoredprecastconcretebarriercanusuallyberealignedorrepairedwhenmovedfromitsalignment.However,heavyequipmentmayberequiredtorepositionorreplacebarriersegments.Therefore,inmedians,considertheshoulderwidthandthetrafficvolumewhendeterminingtheacceptabilityofunanchoredprecastconcretebarrierversusrigidconcretebarrier.

Drainage,alignment,anddriftingsnoworsandareconsiderationsthatcaninfluencetheselectionofbarriertype.Beamguardrailandconcretebarriercancontributetosnowdrifts.Considerlong-termmaintenancecostsassociatedwithsnowremovalatlocationspronetosnowdrifting.Slopeflatteningishighlyrecommended,evenatadditionalcost,toeliminatetheneedforthebarrier.Cablebarrierisnotanobstructiontodriftingsnowandcanbeusedifslopeflatteningisnotpractical.

WhendesigningabarrierforuseonaScenicByway,considerbarriersthatareconsistentwiththerecommendationsintheassociatedCorridorManagementPlan(ifoneisavailable).ContacttheregionsLandscapeArchitectortheScenicBywaysCoordinatorintheHQHighwaysandLocalProgramsOfficetodeterminewhethertheprojectisonsuchadesignatedroute.Low-costoptions,suchasusingweatheringsteelbeamguardrail(see710.06)orcablebarrier(see710.07),mightbefeasibleonmanyprojects.Higher-costoptions,suchassteel-backedtimberrailandstoneguardwalls(see710.09),mightrequireapartneringefforttofundtheadditionalcosts.Grantsmightbeavailableforthispurposeiftheneedisidentifiedearlyintheprojectdefinitionphase.(SeeChapter120.)

(1) Shy DistanceProvide2feetofadditionalwideningforshydistancewhenabarrieristobeinstalledinareaswheretheroadwayistobewidenedandtheshoulderwidthwillbelessthan8feet.Thisshydistanceisnotrequiredwhenthesectionofroadwayisnotbeingwidenedortheshouldersareatleast8feetwide.

AluminumRailType

CurbWidth9 inches or less

Greater than 9 inches*

Type R, S, or SB

Bridge rail adequate

Bridge rail adequate

Type 1B or 1A Bridge rail adequateUpgrade bridge rail

Other Consult the HQ Bridge and Structures Office* When the curb width is greater than 9 inches,

the aluminum rail must be able to withstand a 5kip load.

Type7BridgeRailUpgradeCriteriaFigure 710-1

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(2) Barrier DeflectionsAllbarriersexceptrigidbarriers(concretebridgerails,forexample)willdeflectwhenhitbyanerrantvehicle.Theamountofdeflectionisprimarilydependentonthestiffnessofthesystem.Vehiclespeed,angleofimpact,andweightalsoaffecttheamountofbarrierdeflection.Forflexibleandsemirigidroadsidebarriers,thedeflectiondistanceisdesignedtopreventtheimpactingvehiclefromstrikingtheobjectbeingshielded.Forunrestrainedrigidsystems(unanchoredprecastconcretebarrier),thedeflectiondistanceisdesignedtopreventthebarrierfrombeingknockedoverthesideofadrop-offorsteepfillslope(2H:1Vorsteeper).

Inmedianinstallations,thedeflectedsystemmustnotbecomeahazardtooncomingtraffic.Usearigidsystemwheredeflectioncannotbetolerated,suchasinnarrowmediansorattheedgeofbridgedecksorotherverticaldrop-offareas.Runsofrigidconcretebarriercanbecastinplaceorextrudedwithappropriatefootings.

Insomelocations,wheredeflectiondistanceislimited,precastconcretebarriercanbeanchored.However,unlesstheanchoringsystemhasbeendesignedtofunctionasarigidbarrier,somemovementcanbeexpectedandrepairsmaybemoreexpensive.UseofanonrigidbarrierontopofaretainingwallrequiresapprovalfromtheHQDesignOffice.

RefertoFigure710-2forbarrierdeflectiondesignvaluestobeusedwhenselectingalongitudinalbarrier.Thedeflectiondistancesforcableandbeamguardrailaretheminimummeasurementsfromthefaceofthebarriertothehazard.Thedeflectiondistanceforunanchoredconcretebarrieristheminimummeasurementfromthebackedgeofthebarriertothedrop-offorslopebreak.

(3) Flare RateFlaretheendsoflongitudinalbarrierswherepossible.Therearefourfunctionsoftheflare: Tolocatethebarrieranditsterminalasfarfromthetraveledwayasisfeasible

Toreducethelengthofneed Toredirectanerrantvehicle

Tominimizeadriversreactiontotheintroductionofanobjectnearthetraveledway

Keepingflareratesasflataspracticablepreservesthebarriersredirectionalperformanceandminimizestheangleofimpact.However,ithasbeenshownthatanobject(orbarrier)closetothetraveledwaymightcauseadrivertoshiftlaterally,slowdown,orboth.Theflarereducesthisreactionbygraduallyintroducingthebarriersothatthedriverdoesnotperceivethebarrierasahazard.TheflareratesinFigure710-3satisfyallfourfunctionslistedabove.Moregradualflaresmaybeused.Flareratesareoffsetparalleltotheedgeofthetraveledway.Transitionsectionsarenotnormallyflared.

(4) Length of NeedThelengthoftrafficbarrierrequiredtoshieldahazard(lengthofneed)isdependentonthelocationandgeometricsofthehazard,direction(s)oftraffic,postedspeed,trafficvolume,andtypeandlocationoftrafficbarrier.WhendesigningabarrierforafillslopeasrecommendedinChapter700,thelengthofneedbeginsatthepointwherebarrierisrecommended.Forfixedobjectsandwaterhazards,Figures710-11aand11bshowdesignparametersfordeterminingthenecessarylengthofabarrierforbothadjacentandopposingtrafficonrelativelystraightsectionsofhighway.

Whenthebarrieristobeinstalledontheoutsideofahorizontalcurve,thelengthofneedcanbedeterminedgraphically,asshowninFigure710-11c.Forinstallationsontheinsideofacurve,determinethelengthofneedasthoughitwerestraight.Considertheflarerate,barrierdeflection,andbarrierendtreatmenttobeusedwhendeterminingthelengthofneed.Whenbeamguardrailisplacedinamedian,considerthepotentialforimpactfromopposingtrafficwhenconductingalengthofneedanalysis.Whenguardrailisplacedoneithersideofobjectsinthemedian,considerwhetherthetrailingendofeachrunofguardrailwillshieldtheleadingendoftheopposingguardrail.Shieldtheleadingendwhenitiswithintheclearzoneofopposingtraffic.(SeeFigure710-11d.)

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BarrierType SystemType DeflectionCable barrier or beam guardrail (Types 20 and 21) on G-2 posts Flexible

up to 12 ft (face of barrier to object)

Beam guardrail Types 1, 1a, 2, 10, 11, 31, and 31NB Semirigid 3 ft (face of barrier to object)

Two-sided W-beam guardrail Types 3 and 4 Semirigid 2 ft (face of barrier to object)

Permanent concrete barrier, unanchored Unrestrained Rigid3 ft(1)

(back of barrier to object)

Temporary concrete barrier, unanchored Unrestrained Rigid2 ft(2)

(back of barrier to object)

Precast concrete barrier, anchored Semirigid 6 inches (back of barrier to object)Rigid concrete barrier Rigid no deflection(1) When placed in front of a 2H:1V or flatter fill slope, the deflection distance can be reduced to 2 feet.(2) When used as temporary bridge rail, anchor all barrier that is within 3 feet of a drop-off.

LongitudinalBarrierDeflection Figure 710-2

PostedSpeed(mph)

RigidSystem

UnrestrainedRigidSystem

SemirigidSystem

70 20:1 18:1 15:160 18:1 16:1 14:155 16:1 14:1 12:150 14:1 12:1 11:145 12:1 11:1 10:1

40 or below 11:1 10:1 9:1

LongitudinalBarrierFlareRatesFigure 710-3

Beforetheactuallengthofneedisdetermined,establishthelateraldistancebetweentheproposedbarrierinstallationandtheitemshielded.Provideadistancethatisgreaterthanorequaltotheanticipateddeflectionofthelongitudinalbarrier.(SeeFigure710-2forbarrierdeflections.)Placethebarrierasfarfromtheedgeofthetraveledwayaspossiblewhilemaintainingthedeflectiondistance.

Iftheendofthelengthofneedisnearanadequatecutslope,extendthebarrierandembeditintheslope.(See710.06(4)(a).)Avoidgapsof300feetorless.Shortgapsareacceptable

whenthebarriersareterminatedinacutslope.Iftheendofthelengthofneedisneartheendofanexistingbarrier,itisrecommendedthatthebarriersbeconnectedtoformacontinuousbarrier.Considermaintenanceaccesswhendeterminingwhethertoconnectbarriers.

(5) Median Barrier Selection and Placement ConsiderationsAswithallbarriers,themostdesirableinstallationusesasystemthatisthemostflexiblesystemappropriateforthelocationandthatisplacedasfarfromthetraveledwayaspracticable.Withmedianbarriers,thedeflectioncharacteristicsandplacementofthebarrierforatraveledwayinonedirectioncanhaveanimpactonthetraveledwayintheopposingdirection.Inaddition,themedianslopesandenvironmentalissuesmightinfluencethetypeofbarrierthatisappropriate.

Innarrowmedians,avoidplacementwherethedesigndeflectionextendsintooncomingtraffic.Inaddition,narrowmediansprovidelittlespaceformaintenancecrewstorepairorrepositionthebarrier.Avoidinstallingdeflectingbarriersinmediansthatprovidelessthan8feetfromtheedgeofthetraveledwaytothefaceofthebarrier.Inwidermedians,theselectionofbarriermightdependontheslopesinthemedian.

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Atlocationswherethemedianslopesarerelativelyflat(10H:1Vorflatter),unrestrainedprecastconcretebarrier,beamguardrail,andcablebarriercanbeuseddependingontheavailabledeflectiondistance.Attheselocations,positionthebarrierasclosetothecenteraspossiblesothattherecoverydistancecanbemaximizedforbothdirections.Itmightbenecessarytooffsetthebarrierfromtheflowlinetoavoidimpactstothedrainageflow.Cablebarrierisrecommendedwithmediansthatare30feetorwider.Inwidemedianswheretheslopesaresteeperthan10H:1Vbutnotsteeperthan6H:1V,cablebarrierplacednearthecenterofthemedianispreferred.Placementofbeamguardrailrequiresthatthebarrierbeplacedatleast12feetfromtheslopebreak,asisshowninFigure710-4.Donotuseconcretebarrieratlocationswheretheforeslopeintothefaceofthebarrierissteeperthan10H:1V.

Atlocationswheretheroadwaysareonindependentalignmentsandthereisadifferenceinelevationbetweentheroadways,theslopefromtheupperroadwaymightbesteeperthan6H:1V.Intheselocations,positionthemedianbarrieralongtheupperroadwayandprovidedeflectionandoffsetdistanceasdiscussedpreviously.Barrierisgenerallynotnecessaryalongthelowerroadway,exceptwheretherearefixedobjectsinthemedian.

Whenbarrierisplacedinamedianasacountermeasureforcrossmediancollisions,designthebarriertobestruckfromeitherdirectionoftravel.Forexample,beamguardrailshouldbedouble-sided(Type3or4).

710.06 BeamGuardrail

(1) Beam Guardrail SystemsBeamguardrailsystemsareshownintheStandardPlans.

StrongpostW-beamguardrail(Types1through4,31,and31NB)andthriebeamguardrail(Types10and11)aresemirigidbarriersusedpredominantlyonroadsides.Theyalsohavelimitedapplicationasmedianbarrier.Installedincorrectly,strongpostbeamguardrailcancausevehiclesnaggingorspearing.Thiscanbeavoidedbylappingtherailsplicesinthedirectionoftraffic(asshown

intheStandardPlans),byusingcrashworthyendtreatments,andbyblockingtherailawayfromthestrongposts.However,avoidtheuseofblockoutsthatextendfromtheposttotherailelementforadistanceexceeding16inches.

W-beamguardrailhastypicallybeeninstalledwitharailheightof27inches.However,therearesomenewerdesignsthatusea31-inchrailheight.Oneisthe31-inch-highWSDOTType31.TheotherisaproprietarysystemcalledtheType31NBsystem.

TheType31systemusesmanyofthesamecomponentsastheWSDOTType1system.However,themaindifferencesarethattheblockoutsextend12inchesfromtheposts,therailheightis31inchesfromtheground,andtherailelementsaresplicedbetweenposts.

ThemaincharacteristicsoftheType31NBsystemarethatitincorporatespostsdesignedtobendonimpact,anditdoesnotuseblockouts,whichpotentiallycanofferadvantagesinapplicationswithnarrowshoulderwidths.Thissystemisalso31inchesmeasuredfromthegroundtothetopoftherailelement,andtherailelementissplicedbetweenposts.CurrentlytheType31NBsystemisnotapprovedfortheuseofcurbwiththissystem.

Althoughsomewhatdifferent,bothsystemsoffertolerancesforfutureHMAoverlays.TheType31systemallowsa4-inchtolerancefrom31inchesto27incheswithoutadjustmentoftherailelement.TheType31NBsystemoffersatolerancefrom31inchesto29inches.

(2) W-Beam Barrier Selection and Placement Existingrunswithrailheightat27inchesareacceptabletoleaveinplaceandcanbeextendedifthedesignheightof27inchesismaintainedintheextendedsection.Wherefutureoverlaysareanticipated,extendwithType1alternateorthe31-inchdesign.

Forexistingrunsbelow26inches,adjustorreplacetherailtoaheightof26inchesminimumto28inchesmaximumorreplacetherun.

Usethe31-inch-highguardraildesignfornewruns.

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1.Forexistingroadwayswheretheshoulderwillnotbewidenedandtheshoulderisgreaterthan4feet,usetheType31system.Theexistingshoulderwidthmaybereducedupto4inchestoaccommodatethe12-inchblockoutwithoutprocessingadeviation.

2.Forexistingroadwayswheretheshoulderwidthis4feetorless,theType31NBsystemcanbeused.

ForcurrentlyavailableplansforType31,refertotheHQDesignStandards(PlanSheetLibrary)atthefollowingwebsite:http://www.wsdot.wa.gov/eesc/design/designstandards/psl/default.htm

Sometransitionsandconnectionsarecurrentlyunderdevelopmentandwillbeaddedtothissiteassoonastheyarecompleted.PlanswillbehousedatthislocationuntiltheyaretransitionedintotheStandardPlans.

(3) Additional GuidanceWeakpostW-beamguardrail(Type20)andthriebeamguardrail(Type21)areflexiblebarriersystemsthatcanbeusedwherethereisadequatedeflectiondistance.Thesesystemsuseweaksteelposts.Theprimarypurposeofthesepostsistopositiontheguardrailvertically,andtheyaredesignedtobendoverwhenstruck.Thesemoreflexiblesystemswillresultinlessdamagetotheimpactingvehicle.Sincetheweakpostswillnotresultinsnagging,blockoutsarenotnecessary.

Keeptheslopeoftheareabetweentheedgeoftheshoulderandthefaceoftheguardrail10H:1Vorflatter.Onfillslopesbetween6H:1Vand10H:1V,beamguardrailmustnotbeplacedwithin12feetofthebreakpoint.Donotplacebeamguardrailonafillslopesteeperthan6H:1V.Foradditionalguidanceonbeamguardrailslopeplacement,refertoFigure710-4.

Onthehighsideofsuperelevatedsections,placebeamguardrailattheedgeofshoulderpriortotheslopebreak.

Forguardrailinstalledatorneartheshoulder,2feetofshoulderwideningbehindthebarrierisgenerallyprovidedfromthebackoftheposttothebeginningofafillslope.Iftheslopeis2H:1Vorflatter,thisdistancecanbemeasuredfromthefaceoftheguardrailratherthanthebackofthepost.(SeeFigure710-12,Case1.)

Onprojectswherenoroadwaywideningisproposedandtheminimum2-footshoulderwideningbehindthebarrierisnotpracticable,longpostinstallationsareavailableasshowninFigure710-12,Cases3,4,5,and6.Whenguardrailistobeinstalledinareaswheretheroadwayistobewidened,theuseofCases4,5,or6requiresadesigndeviation.

Railwashersonbeamguardrailarenotnormallyused.Ifrailwashersarepresent,theyarenotrequiredtoberemoved.However,iftherailelementisremovedforanyreason,donotreinstallrailwashers.Inareaswhereheavysnowaccumulationsareexpectedtocausetheboltstopullout,specifysnowloadpostandrailwashersinthecontractdocuments.(Snowloadpostwashersareusedtopreventtheboltsfrompullingthroughtheposts,andsnowloadrailwashersareusedtopreventtheboltheadfrompullingthroughtherail.)Inotherinstallations,itisnormaltohavetherailpullloosefromtheboltheadwhenimpacted.Railwashersarenevertobeusedwithinthelimitsofaguardrailterminal,exceptattheendpostwheretheyarerequiredforanchorageoftherail.

Theuseofcurbinconjunctionwithbeamguardrailisdiscouraged.Ifacurbisnecessary,the3-inch-highcurbispreferred.Ifnecessary,the4-inch-highextrudedcurbcanbeusedbehindthefaceofrailatanypostedspeed.The6-inch-highextrudedcurbcanbeusedatlocationswherethepostedspeedis50milesperhourorless.Whenreplacingextrudedcurbatlocationswherethepostedspeedisgreaterthan50milesperhour,use3-inch-highor4-inch-highcurb.(SeetheStandardPlansforextrudedcurbdesigns.)

Whencurbisusedinconjunctionwith31-inch-highType31W-beamguardrail,itisacceptabletoplacea6-inch-highcurbata7-inchoffsetfromthefaceoftherail.

Currently,curbisnotapprovedforusewiththeType31NBsystem.

Beamguardrailisusuallygalvanizedandhasasilvercolor.Itcanalsobeprovidedinaweatheringsteelthathasabrownorrustcolor.AlongScenicByways,HeritageTourRoutes,statehighwaysthroughnationalforests,orotherdesignatedareas,considerusingweatheringsteel

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guardrail,weatheringsteelterminals,andwoodenpoststominimizethebarriersvisualimpact.(See710.05.)

(4) Terminals and AnchorsAguardrailanchorisrequiredattheendofarunofguardrailtodeveloptensilestrengththroughoutitslength.Inaddition,whentheendoftheguardrailissubjecttohead-onimpacts,acrashworthyguardrailterminalisrequired.(SeetheStandardPlans.)

Theburiedterminal(BT)isdesignedtoterminatetheguardrailbyburyingtheendinabackslope.TheBTisthepreferredterminalbecauseiteliminatestheexposedendoftheguardrail.

TheBTusesaType2anchortodevelopthetensilestrengthintheguardrail.DesignthelengthofneedbeginningatthepointwheretheW-beamremainsatfullheightinrelationtotheroadwayshoulder,usuallybeginningatthepointwherethebarriercrossestheditchline.ThebacksloperequiredtoinstallaBTmustbe3H:1Vorsteeperandatleast4feetinheightabovetheroadway.Flaretheguardrailintothebackslopeusingaflareratethatmeetsthecriteriain710.05(3).Providea10H:1Vorflatterforeslopeintothefaceoftheguardrail(andupto4H:1VintheditchsectionoftheType2buriedterminal),andmaintainthefullguardrailheighttotheforeslope/backslopeintersection.Thismightrequirefillingditchesandinstallingculvertsinfrontoftheguardrailface.TheentireBTcanbeusedwithinthelengthofneedforbackslopesof1H:1Vorsteeperifthebarrierremainsatfullheightinrelationtotheroadwayshoulder.

Ifthebackslopeisflatterthan1H:1V,provideaminimum75-foot-longclearareaonthebacksideofthebarrierpriortothemitigatedhazard.

(a) Flared Terminal. IfaBTcannotbeinstalledasdescribedabove,consideraflaredterminal.(SeeFigure710-13.)Therearecurrentlytwoacceptablesolesourceproprietarydesigns:theSlottedRailTerminal(SRT)andtheFlaredEnergyAbsorbingTerminal(FLEAT).Bothofthesedesignsincludeananchorfordevelopingthetensilestrengthoftheguardrail.Thelengthofneedbeginsatthethirdpostforbothflaredterminals.

1.TheSRTusesW-beamguardrailwithslotscutintothecorrugations,andwoodbreakawayandcontrolledreleaseterminal(CRT)poststhataredesignedtobreakawaywhenhit.TheendoftheSRTisoffsetfromthetangentguardrailrunbytheuseofaparabolicflare.Whenstruckheadon,thefirsttwopostsaredesignedtobreakaway,andtheparabolicflaregivestherailanaturaltendencytobuckle,minimizingthepossibilityoftheguardrailendenteringthevehicle.Thebucklingisfacilitatedbytheslotsintherail.TheCRTpostsprovidestrengthtothesystemforredirectionanddecelerationwithoutsnaggingthevehicle.TheSRThasa4-footoffsetofthefirstpost.

2.TheFLEATusesW-beamguardrailwithaspecialendpiecethatfitsovertheendoftheguardrailandwoodbreakawayandCRTposts.TheendoftheFLEATisoffsetfromthetangentguardrailrunbytheuseofastraightflare.Whenstruckheadon,theendpieceisforcedovertherail,bendingtherailandforcingitawayfromtheimpactingvehicle.

TheFLEATisavailableintwodesignsbasedonthepostedspeedofthehighway.Forhighwayswithapostedspeedof45milesperhourorgreater,useaFLEAT350thathasa4-footoffsetatthefirstpost.Forlower-speedhighways(apostedspeedof40milesperhourorless),useaFLEATTL-2thathasa1-foot-8-inchoffsetatthefirstpost.

Whenaflaredterminalisspecified,itiscriticalthatembankmentalsobespecifiedsothattheareaaroundtheterminalcanbeflattenedasshownontheStandardPlans.Foreveryfootofheightoftheembankment,13cubicyardsofembankmentarerequired.

Nosnowloadrailwashersareallowedwithinthelimitsoftheseterminals.

TheFHWAhasgrantedapprovaltousethesesolesourceproprietaryterminalswithoutjustification.

Traffic Barriers Design Manual M 22-01 Page 710-10 November 2006

TrafficBarrierLocationsonSlopesFigure 710-4

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-11

(b) Nonflared Terminal.Wherewideningtoprovidetheoffsetforaflaredterminalisnotpracticable,consideranonflaredterminal.(SeeFigure710-13.)Therearecurrentlytwoacceptablesolesourceproprietarydesigns:theETPLUSandtheSequentialKinkingTerminal(SKT).BothofthesesystemsuseW-beamguardrailwithaspecialendpiecethatfitsovertheendoftheguardrailandwoodbreakawayandCRTposts.Whenhitheadon,theendpieceisforcedovertherailandeitherflattensorbendstherailandthenforcesitawayfromtheimpactingvehicle.

Bothoftheseterminalsincludeananchorfordevelopingthetensilestrengthoftheguardrail.Thelengthofneedbeginsatthethirdpostforbothterminals.

Bothoftheseterminalsareavailableintwodesignsbasedonthepostedspeedofthehighway.Theprimarydifferenceinthesedesignsisthelengthoftheterminal.Forhighwayswithapostedspeedof45milesperhourorgreater,usethe50-foot-longETPLUSTL3orSKT350.Forlower-speedhighways(apostedspeedof40milesperhourorless),usethe25-foot-longETPLUSTL2orSKT-TL2.

Whiletheseterminalsdonotrequireanoffsetattheend,aflareisrecommendedsothattheendpiecedoesnotprotrudeintotheshoulder.Theseterminalsmayhavea1-footoffsettothefirstpost.Fourfeetofwideningisrequiredattheendpoststoensurethatthesystemisproperlyanchored.Foreveryfootofembankmentheight,3cubicyardsofembankmentarerequired.

Nosnowloadrailwashersareallowedwithinthelimitsoftheseterminals.

TheFHWAhasgrantedapprovaltousethesesolesourceproprietaryterminalswithoutjustification.

(c) Terminal Evolution Considerations.Someapprovedterminalshavebeeninserviceforanumberofyears.Duringthistime,therehavebeenminordesignchanges.However,theseminorchangeshavenotchangedthedevicesapprovalstatus.Allpreviousdesignsfortheseterminalsmayremaininplace.Ifquestionsariseconcerningthecurrentapprovalstatusofadevice,contacttheHQDesignOfficeforclarificationwhenreplacementisbeingconsidered.

(d) Other Anchor Applications. UsetheType1anchortodevelopthetensilestrengthoftheguardrailontheendofguardrailrunswhereacrashworthyterminalisnotrequired.UsetheType4anchortodevelopthetensilestrengthoftheguardrailonthetrailingendofguardrailrunsalongone-wayhighways.UsetheType5anchorwiththeWeakPostIntersectionDesign.(See710.06(6),Cases12and13.)UsetheType7anchortodeveloptensilestrengthinthemiddleofaguardrailrunwhentheguardrailcurvesandweakpostsareused.(See710.06(6),Cases9,12,and13.)

TheoldType3anchorwasprimarilyusedatbridgeends.(SeeFigure710-5.)Thisanchorconsistedofasteelpipemountedverticallyinaconcretefoundation.Bridgeapproachguardrailwasthenmountedonthesteelpipe.Onone-wayhighways,theseanchorswereusuallypositionedsothatneithertheanchornorthebridgerailposedasnagginghazard.Inthesecases,theanchormayremaininplaceifastiffenedtransitionsectionisprovidedattheconnectiontothepost.Ontwo-wayhighways,theanchormaypresentasnagginghazard.Inthesecases,installaconnectionfromtheanchortothebridgerailiftheoffsetfromthebridgerailtothefaceoftheguardrailis1foot6inchesorless.Iftheoffsetisgreaterthan1foot6inches,removetheanchorandinstallanewtransitionandconnection.

Locationswherecrossroadsanddrivewayscausegapsintheguardrailrequirespecialconsideration.Eliminationoftheneedforthebarrieristhepreferredsolution.Otherwise,abarrierflaremightberequiredtoprovidesightdistance.Iftheslopeis2H:1Vorflatterandtherearenohazardsonoratthebottomoftheslope,aterminalcanbeusedtoendtherail.PlacetheanchorofthisinstallationascloseaspossibletotheroadapproachradiusPC.Ifthereisahazardatornearthebottomoftheslopethatcannotbemitigated,thentheWeakPostIntersectionDesign(see710.06andtheStandardPlans)canbeused.Thissystemcanalsobeusedatlocationswhereacrossroadorroadapproachisneartheendofabridgeandinstallingabridgeapproachguardrailplacement(includingguardrailtransitionandterminal)isnotpossible.

Traffic Barriers Design Manual M 22-01 Page 710-12 November 2006

(5) Transitions and ConnectionsWhenthereisanabruptchangefromonebarriertypetoamorerigidbarriertype,avehiclehittingthemoreflexiblebarrierislikelytobecaughtinthedeflectedbarrierpocketanddirectedintothemorerigidbarrier.Thisiscommonlyreferredtoaspocketing."Atransitionstiffensthemoreflexiblebarrierbydecreasingthepostspacing,increasingthepostsize,andusingstifferbeamelementstoeliminatethepossibilityofpocketing.

Whenconnectingbeamguardrailtoamorerigidbarrierorastructure,orwhenarigidobjectiswithinthedeflectiondistanceofthebarrier,usethetransitionsandconnectionsthatareshowninFigures710-6and710-10anddetailedintheStandardPlans.Thetransitionpayitemincludestheconnection.

ForcurrentlyavailabletransitionsandconnectionsforTypes31and31NB,refertotheHQDesignStandards(PlanSheetLibrary)atthefollowingwebsite:http://www.wsdot.wa.gov/eesc/design/designstandards/psl/default.htm

Sometransitionsandconnectionsarecurrentlyunderdevelopmentandwillbeaddedtothissiteassoonastheyarecompleted.PlanswillbehousedatthislocationuntiltheyaretransitionedintotheStandardPlans.

OldType3AnchorFigure 710-5

Condition ConnectionUnrestrained concrete barrier ARigid untapered safety shape bridge rails or barriers(1)

B

Bridge rails with curbs 9 inches or less in width

B

Bridge rails with curbs between 9 and 18 inches wide

C

Vertical walls or tapered safety shape barrier(1)

D

(1) New safety shape bridge rails are designed with the toe of the barrier tapered so that it does not project past the face of the approach guardrail.

GuardrailConnectionsFigure 710-6

(6) Guardrail Placement CasesTheStandardPlanscontainsplacementcasesthatshowallofthebeamguardrailelementsrequiredfortypicalsituations.Followingisadescriptionofeachcase:

Case 1isusedonlywherethereisone-waytraffic.ItusesacrashworthyterminalontheapproachendandaType4anchoronthetrailingend.

Case 2 isusedwherethereistwo-waytraffic.Acrashworthyterminalisusedonbothends.Whenflaredterminalsareusedonbothends,aminimumof25feetofguardrailisrequiredbetweentheterminallimits.

Case 3isusedatrailroadsignalsupportsonone-wayortwo-wayroadways.Aterminalisusedontheapproachend,butusuallycannotbeusedonthetrailingendbecauseofitsproximitytotherailroadtracks.Forone-wayroadways,aType4anchorisusedonthetrailingend.Ontwo-wayroadways,aType1anchorisusedonthetrailingend.Ifthereisahistoryofcrossoveraccidents,consideradditionalprotection,suchasanimpactattenuator.

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-13

Case 4isusedwhereguardrailontheapproachtoabridgeistobeshiftedlaterallytoconnectwiththebridgerail.Aterminalisusedontheapproachendandatransitionisrequiredatthebridgeend.Acurveintheguardrailisshowntoshiftittothebridgerail.However,thelengthofthecurveisnotcriticalandtheonlyrequirementistoprovideasmoothcurvethatisnotmoreabruptthantheallowableflarerate.(SeeFigure710-3.)

Case 5isatypicalbridgeapproachwhereaterminalandatransitionarerequired.

Case 6isusedonbridgeapproacheswhereopposingtrafficisseparatedbyamedianthatis36feetorwider.Thiscaseisdesignedsothattheendoftheguardrailwillbeoutsidetheclearzonefortheopposingtraffic.

Cases 7and 8areusedwithbeamguardrailmedianbarrierwhenmedianhazardssuchasbridgepiersareencountered.Atransitionisrequiredontheapproachendforeachdirectionandtheflareratemustnotbemoreabruptthantheallowableflarerate.(SeeFigure710-3.)

Case 9 (A, B, and C)isusedonbridgeapproacheswhereopposingtrafficisseparatedbyamedianlessthan36feetwide.Thisdesign,calledaBullNoseTerminal,treatsbothbridgeendsandtheopeningbetweenthebridges.Thenoseisdesignedtocollapsewhenstruckheadon,andtheribbonstrengthoftherailbringsthevehicletoacontrolledstop.Type7anchorsareinstalledoneachsideofthenosetodeveloptheribbonstrength.

Sinceanimpactingvehiclewillpenetrateintothesystem,itiscriticalthatnofixedobjectbelocatedwithinthefirst30feetofthesystem.

Case 10 (A, B, and C)isusedatroadsidehazards(suchasbridgepiers)when3feetormoreareavailablefromthefaceoftheguardrailtothehazard.Theapproachendisthesameforone-wayortwo-waytraffic.Case10Aisusedwithtwo-waytraffic;therefore,aterminalisrequiredonthetrailingend.Case10Bisusedforone-waytrafficwhenthereisnoneedtoextendguardrailpastthebridgepierandaType4anchorisusedtoendtheguardrail.Case10Cisusedforone-waytrafficwhentheguardrailwillextendforadistancepastthebridgepier.

Case 11 (A, B, and C)isusedatroadsidehazards(suchasbridgepiers)whentheguardrailistobeplacedwithin3feetofthehazard.Sincethereisnoroomfordeflection,therailinfrontofthehazardmustbeconsideredarigidsystemandatransitionisnecessary.ThetrailingendcasesarethesameasdescribedforCase10.

Cases 12 and 13arecalledWeakPostIntersectionDesigns.Theyareusedwhereanintersectionrequiresagapintheguardrailorthereisnotadequatespaceforabridgeapproachinstallationthatincludesatransitionand/orterminal.Theseplacementsaredesignedtocollapsewhenhitatthenose,andtheribbonstrengthoftherailbringsthevehicletoastop.AType7anchorisusedtodeveloptheribbonstrength.ThesedesignsincludeaType5transitionforconnectionwithbridgerailandaType5anchorattheotherendoftherail.TheType5anchorisnotabreakawayanchorand,therefore,canonlybeusedonlow-speedsideroadsanddriveways.

Sinceanimpactingvehiclewillpenetrateintothesystem,itiscriticalthatnofixedobjectbelocatedwithintheclearareashownontheStandardPlan.The25feetalongthesideroadarecriticalfortheoperationofthissystem.

Thesedesignsweredevelopedforintersectionsthatareapproximatelyperpendicular.Evaluateinstallationonskewedintersectionsonacase-by-casebasis.UsetheCase22placementifitisnotfeasibletoinstallthisdesignaccordingtotheStandardPlan.

Case 14showstheapproachraillayoutforaServiceLevel1bridgerailsystem.Type20guardrailisusedontheapproachandnotransitionisrequiredbetweentheType20guardrailandtheServiceLevel1bridgerailsincetheyarebothweakpostsystems.AType6transitionisusedwhenconnectingtheType20toastrongpostguardrailoraterminal.

Case 15isusedtocarryguardrailacrossaboxculvertwherethereisinsufficientdepthtoinstallstandardpostsformorethan17feet8inches.Thisdesignusessteelpostsanchoredtotheboxculverttosupporttherail.Newerdesigns,Cases19,20,and21,havereplacedthisdesignforshorterspans.

Traffic Barriers Design Manual M 22-01 Page 710-14 November 2006

Cases 16 and 17aresimilartoCases1and2,exceptthattheyflaretherailandterminalasfarfromtheroadaspossibleandreducethelengthofneed.

Case 18isusedonthetrailingendofbridgerailonaone-wayroadway.Notransitionisnecessary.

Case 19 (A and B)isusedwhereitisnotpossibletoinstallapostatthe6-foot-3-inchspacing.Thisdesignomitsonepost(resultinginaspanof11feet6inches,whichisconsistentwithapostspacingof12feet6inches)andusesnestedW-beamtostiffentherail.Thecasesdifferbythelocationofthesplice.Nocuttingoftherailoroffsettingofthesplicesisnecessaryordesirable.

Case 20 issimilartoCases19Aand19B,exceptthatitallowsfortwopoststobeomitted(whichresultsinaspanconsistentwithapostspacingof18feet9inches).

Case 21 hasasimilarintentasCases19A,19B,and20inthatitallowsfortheomissionofpoststospananobstruction.ThisdesignusesCRTpostswithadditionalpostblocksforthreepostsbeforeandaftertheomittedposts.Thedesignallowsforthreepoststobeomitted(whichresultsinaspanconsistentwithapostspacingof25feet).

Case 22istheStrongPostIntersectionDesignthatprovidesastiffbarrier.ThisdesignisonlytobeusedasalastresortatcrossroadsorroadapproacheswhereabarrierisnecessaryandthereisntaclearareabehindthenoseorminimumdistancesforaWeakPostIntersectionDesign.(SeeCases12and13.)

Case 23 theplacement/connectionofgenericcablebarriertoW-beamflaredterminals.

Case 24 theplacement/connectionofgenericcablebarriertoW-beambullnoseapplications.

Case 25theplacementofgenericcablebarrieratthriebeambullnoselocations.

Case 26 thegenericcablebarriertoW-beamshieldingatredirectionallandformlocations.

Case 27theplacementofgenericcablebarrierforshieldingatredirectionallandformlocations.

710.07 CableBarrierCablebarrierisaflexiblebarriersystemthatcanbeusedonaroadsideorasamedianbarrier.Theprimaryadvantageofcablebarrieristhatitprovideseffectivevehiclecontainmentandredirectionwhileimposingthelowestdecelerationforcesonthevehiclesoccupants.Italsohasadvantagesinheavysnowfallareasinthatithasminimalpotentialtocreatesnowdrifts.Inaddition,itdoesnotpresentavisualbarrier,whichmaymakeitdesirableonScenicByways.(See710.05.)

Maintenanceisaconsiderationbecauseroutinemaintenanceisnecessarytokeeptensioninthecables,andacomparativelylongrunofcablebarrierwillhavetoberepairedafteranimpact.However,theeffort(timeandmaterials)requiredtomaintainandrepaircablebarrierismuchlessthantheeffortrequiredforaW-beamsystem.

Therearecurrentlytwomaintypesofcablebarrierinuse.Thefirstisthegenericcablebarriersystem,whichisdetailedintheStandardPlans.Thesecondistheproprietaryhigh-tension(H.T.)cablebarriersystems(availablefromseveralmanufacturers).

Fornewinstallations,thehigh-tensioncablebarriersarethefirstchoice.However,itisacceptableforthegenericsystemtoremaininplaceortobeinstallednew,ifneeded.

(1) WSDOT Generic Cable BarrierTheWSDOTGenericSystemconsistsofthreesteelcablesmountedtosteelposts(weakposts).Themaximumspacingforthesteelpostsis16feetontangentsectionsandcurveswitha700-footradiusorgreater.Adeflectionof11feet6inchesisanticipatedwiththispostspacing.Asmallerspacingisrequiredonradiilessthan700feet.Fortangentsectionsandlargeradiuscurves,thedeflectioncanbereducedto7feetbyreducingthepostspacingto4feet.

Ateachendofthebarrierrun,thecableisturneddownandanchoredtoconcreteblocks.Acoilspringandturnbucklearerequiredoneachcabletomaintaintensiononthesystem.

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-15

(2) High-Tension Cable BarrierInadditiontothegenericcablebarriersystemdescribedabove,proprietaryhigh-tension(H.T.)cablebarriersystemsarenowavailablefromafewdifferentmanufacturers.Potentially,thesesystemsoffersomeadvantagesovertheWSDOTGenericCableBarrierSystem.Forexample,thesesystemsdeflectlessthanthestandardWSDOTdesign.Dependingonthesystemandpostspacing,deflectiondistancesrangefrom6feet8inchesto9feet3inches.Inaddition,whenimpacted,theH.T.systemsalsoresultinlessdamagetothebarrier.Inmanycases,thecablesremainattheproperheightafteracollisionhasdamagedseveralposts,whichofferssomemaintenancebenefits.(SeeFigure710-14forplacementdetails.)

(3) Cable Barrier PlacementCablebarriercanbeinstalledupto1footinfrontofsideslopesassteepas2H:1V.Cablebarrieristheonlybarrierthatcanbeplacedonasideslopesteeperthan10H:1Vwithinthe12-footareaimmediatelybeyondthebreakpoint.Donotplacethisbarrieronasideslopesteeperthan6H:1V.Figure710-14showstheplacementofcablebarrier.

Narrowmediansprovidelittlespaceformaintenancecrewstorepairorrepositionthebarrier.Wheneversightconditionspermit,provideatleast14feetofclearancefromtheadjacentlaneedgetothecablebarrier.

Whencablebarrieristobeconnectedtoamorerigidbarrier,atransitionsectionisrequired.(SeetheStandardPlansorcontacttheHQDesignOfficeforfurtherdetails.)

710.08 ConcreteBarrierConcretebarriersarerigidorunrestrainedrigidsystems.Theyarealsousedasshoulderbarriers.Thesesystemsarestifferthanbeamguardrailorcablebarrier,andimpactswiththesebarrierswilltendtobemoresevere.

Lightstandardsmountedontopofconcretemedianbarriermustnothavebreakawayfeatures.(SeetheStandardPlansfortheconcretebarrierlightstandardsection.)

Wheredrainagemightbeaproblem,contacttheHQHydraulicsBranchforguidance.

(1) Concrete Barrier ShapesConcretebarriersuseasafetyshape(NewJerseyshapeand,onbridges,theF-Shape)orsingle-slopedfacetoredirectvehicleswhileminimizingvehiclevaulting,rolling,andsnagging.AcomparisonofthesebarriershapesisshowninFigure710-7.

TheNewJerseyshapefaceisusedonprecastconcretebarrier.

Thesingle-slopebarrierfaceisrecommendedwhenseparatingroadwayswithdifferentelevations(steppedmedians).Thesingle-slopebarrierfacecanbeusedforbridgerails(medianoroutside)whenitistobeusedonanyapproachtoabridgeandanexistingbridgerailistobereplaced.

NewJerseyShape(Type2)

F-Shape Single-SlopeConcreteBarrier

ConcreteBarrierShapesFigure 710-7

TheF-Shapefaceisusedonallotherbridgerailsandoncast-in-placebarrierwheretheNewJerseyandsingle-slopefacearenotappropriate.WhentheF-Shapefaceisusedandprecastbarrieristobeusedontheapproaches,acast-in-placetransitionsectionisrequiredsothatnoverticaledgesofthebarriersareexposedtooncomingtraffic.FordetailsontheF-Shapebarrieroranyofthebridgeraildesigns,seetheBridge Design Manual.

Foraestheticreasons,avoidchangesintheshapeofthebarrierfacewithinaprojectorcorridor.

Traffic Barriers Design Manual M 22-01 Page 710-16 November 2006

(a) New Jersey Shape Barrier. TheNewJerseyshapefaceisprimarilyusedonprecastconcretebarrier.

ConcretebarrierType2(seetheStandardPlans)isaprecastbarrierthathastheNewJerseyshapeontwosidesandcanbeusedforbothmedianandshoulderinstallations.Thisbarrieris2feet8inchesinheight,whichincludes3inchesforfuturepavementoverlay.

The cost of precast Type 2 barrier is significantly lessthanthecostofthecast-in-placebarriers.Therefore,considerthelengthofthebarrierrunand the deflection requirements to determine whethertransitioningtoprecastType2barrierisdesirable.IfprecastType2barrierisusedforthemajorityofaproject,usetheNewJerseyfaceforsmall sections that require cast-in-place barrier, suchasforalightstandardsection.

ConcretebarrierType4isalsoaprecast,single-facedNewJerseyshapebarrier.Theseunitsarenotfreestandingandmustbeplacedagainstarigidstructureoranchoredtothepavement.IfType4barriersareusedbacktoback,considerfilling any gap between them to prevent tipping.

ConcretebarrierType5isaprecastbarrierthathasasingleNewJerseyfaceandisintendedfor use at bridge ends where the flat side is highlyvisible.BothType2andType5designsarefreestanding,unanchoredunitsconnectedwithsteelpinsthroughwireropeloops.Forpermanentinstallation,thisbarrierisplacedonapavedsurfaceanda2-foot-widepavedsurfaceisprovidedbeyondthebarrierforitsdisplacementduringimpact.(SeeChapter640.)

Precastbarriercanbeanchoredwhereamorerigidbarrierisdesired.(AnchoringmethodsareshownintheStandardPlans.)TheType1andType2anchorsarefortemporaryinstallationsonarigidpavement.Type3anchorscanbeusedintemporaryorpermanentinstallationsonanasphaltpavement.ConsulttheHQBridgeandStructures Office for details when anchoring permanentprecastconcretebarriertoarigidpavement.

Precastbarrierusedontheapproachtobridgerailmustbeconnectedtothebridgerailbyinstallingwireropeloopsembedded1foot3inchesintothebridgerailwithepoxyresin.

Placeunrestrained(unanchored)precastconcretebarrier, on foundation slopes of 5% or flatter. In difficult situations, a maximum slope of 8% may beused.Keeptheslopeoftheareabetweentheedge of the shoulder and the face of the traffic barrier as flat as possible. The maximum slope is10H:1V(10%).

(b) Single-Slope Barrier.Thesingle-slopeconcretebarriercanbecastinplace,slipformed,orprecast.Themostcommonconstructiontechnique for this barrier has been slipforming, butsomeprecastsingle-slopebarrierhasbeeninstalled. The primary benefit of using precast barrieristhatitcanbeusedastemporarybarrierduringconstructionandthenresetintoapermanentlocation.

Thisbarrierisconsideredarigidsystemregardlessoftheconstructionmethodused.Fornewinstallations,theminimumheightofthebarrierabovetheroadwayis2feet10inches,whichallows2inchesforfutureoverlays.Theminimumtotalheightofthebarriersectionis3feet6inches,withaminimumof3inchesembeddedintheroadwaywearingsurface.Thisallowsforuseofthe3-foot-6-inchbarrierbetweenroadwayswithgradeseparationsofupto5inches.Agradeseparationofupto10inchesisallowed,asshownintheStandardPlans.Thebarrier must have a depth of embedment equal toorgreaterthanthegradeseparation.Contactthe HQ Bridge and Structures Office for grade separationsgreaterthan10inches.(SeetheStandardPlans.)

(c) Low Profile Barrier. Low profile barrier designsareavailableformedianapplicationswherethepostedspeedis45milesperhourorless.Thesebarriersarenormallyusedinurbanareas.Theyaretypically18to20incheshighandoffer sight distance benefits. For barrier designs, terminals,andfurtherdetails,contacttheHQDesign Office.

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-17

(2) High Performance Concrete BarrierHighPerformanceConcreteBarrier(HPBarrier)isarigid42-inch-highbarrierdesignedtofunctionbetterduringheavy-vehiclecollisions.Thistallerbarriermayalsooffertheaddedbenefitsofreducingheadlightglareandreducingnoiseinsurroundingenvironments.HPBarrierisgenerallyconsideredsingle-slopebarrier.However,othershapesareavailable.(SeetheStandardPlansforbarrierdetails.)

UseHPBarrierinfreewaymediansof22feetorless.Also,useHPBarrieronInterstateorfreewayrouteswhereaccidenthistorysuggestsaneed,orwhereroadwaygeometricsincreasethepossibilityoflargertruckshittingthebarrieratahighangle(suchason-rampsforfreeway-to-freewayconnectionswithsharpcurvatureinthealignment).

ConsidertheuseofHPBarrieratotherlocations,suchasnearhighlysensitiveenvironmentalareas,neardenselypopulatedareas,overornearmasstransitfacilities,oronverticallydividedhighways.

(3) Concrete Barrier TerminalsWheneverpossible,burytheendoftheconcretebarrierinthebackslope.Thebacksloperequiredtoburytheendmustbe3H:1Vorsteeperandatleast4feetinheightabovetheroadway.Flaretheconcretebarrierintothebackslopeusingaflareratethatmeetsthecriteriain710.05(3).Providea10H:1Vorflatterforeslopeintothefaceofthebarrierandmaintainthefullbarrierheighttotheforeslope/backslopeintersection.Thismightrequirefillingditchesandinstallingculvertsinfrontofthebarrierface.

The7-foot-longprecastconcreteterminalendsectionforConcreteBarrierType2maybeused: OutsidetheDesignClearZone. OnthetrailingendofthebarrierwhenitisoutsidetheDesignClearZoneforopposingtraffic.

Onthetrailingendofone-waytraffic. Wherethepostedspeedis25milesperhourorless.

AnotheravailableendtreatmentforType2barriersisaprecastorcast-in-placetaperedterminalsectionhavingaminimumlengthof48feetandamaximumlengthof80feet.Itisusedinfrequentlyforspecialapplicationsandcanonlybeusedforpostedspeedsof35milesperhourorless.Fordetails,contacttheHQDesignOfficeorrefertothePlanSheetLibraryatthefollowingwebsite:http://www.wsdot.wa.gov/eesc/design/designstandards/psl/default.htm

WhentheBarrierTerminalsandTransitionscolumnofadesignmatrixappliestoaproject,existingsloped-downconcreteterminalsthatarewithintheDesignClearZonemustbereplacedwhentheydonotmeetthecriteriaabove.

Whentheendofaconcretebarriercannotbeburiedinabackslopeorterminatedasdescribedabove,terminatethebarrierusingaguardrailterminalandtransitionoranimpactattenuator.(SeeChapter720.)

(4) Assessing Impacts to WildlifeTheplacementofconcretebarriersinlocationswherewildlifefrequentlycrossthehighwaycaninfluencetrafficsafetyandwildlifemortality.Whenwildlifeencounterphysicalbarriersthataredifficulttocross,theyoftentravelparalleltothosebarriers.Withtrafficbarriers,thismeansthattheyoftenremainonthehighwayforalongerperiod,increasingtheriskofwildlife/vehiclecollisionsorvehicle/vehiclecollisionsasmotoristsattemptavoidance.

Traffic-relatedwildlifemortalitymayplayaroleinthedeclineofsomespecieslistedundertheEndangeredSpeciesAct.Toaddresspublicsafetyandwildlifeconcerns,seeFigure710-8toassesswhetherconcretebarrierplacementrequiresanevaluationbytheEnvironmentalServicesOfficetodetermineitseffectonwildlife.Makethisevaluationearlyintheprojectdevelopmentprocesstoallowadequatetimefordiscussionofoptions.

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710.09 Special-UseBarriersThefollowingbarriersmaybeusedondesignatedScenicBywayandHeritageTourroutesiffundingcanbearranged.(See710.05andChapter120.)

(1) Steel-Backed Timber GuardrailSteel-backedtimberguardrailsconsistofatimberrailwithasteelplateattachedtothebacktoincreaseitstensilestrength.Thereareseveralvariationsofthissystemthathavepassedcrashtests.Thenonproprietarysystemsuseabeamwitharectangularcrosssectionthatissupported

Willthebarrierbeleftwithinthesamemilepostlimitsforgreaterthan60days?

YES

NO

NO

NO

NO

YES

YES

Istheprojectlocatedentirelywithinadevelopedurbanarea?(ConsultHighwayLog.)

Isrightofwayfencedwith6-footorhigherchainlinkorwiremeshfence?

NO

YES YES

YES

Willthebarrierbeinstalledonanelevatedstructure(bridge,overpass,viaduct,etc.)?

NO

NO

NO

Willthebarrierbeinstalledadjacenttoastream,river,wetland,lake,orpond?

Willthebarrierbeinstalledinaknownwildlifecrossingarea(sectionofhighwaywithwildlifecrossingsignsorlinedwithdeerreflectors)?

WillthebarrierbeinstalledonoradjacenttolandsadministeredbytheForestService,BureauofLandManagement,Military,orTribalEntities?

YES

Does the project propose to use a concrete barrier?

Contact Region or Headquarters EnvironmentalServices Office

for Assistance in Determining the Effect of Barrier

Placement

No Contact Necessary

YES

ConcreteBarrierPlacementGuidance(AssessingImpactstoWildlife)Figure 710-8

byeitherwoodorsteelposts.Aproprietary(patented)systemcalledtheIronwoodguardrailisalsoavailable.Thissystemusesabeamwitharoundcrosssectionandissupportedbysteelpostswithawoodcoveringtogivetheappearanceofanall-woodsystemfromtheroadway.TheIronwoodguardrailcanbeallowedasanalternativetothenonproprietarysystem.However,specifyingthissystemexclusivelyrequiresapprovalbytheAssistantStateDesignEngineerofapublicinterestfindingfortheuseofasolesourceproprietaryitem.

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-19

Themostdesirablemethodofterminatingthesteel-backedtimberguardrailistoburytheendinabackslopeasdescribedin710.06(4).Whenthistypeofterminalisnotpossible,theuseofthebarrierislimitedtohighwayswithapostedspeedof45milesperhourorless.Ontheselower-speedhighways,thebarrierscanbeflaredawayfromthetraveledwayandterminatedinaberm.

Fordetailsonthesesystems,contacttheHQDesignOffice.

(2) Stone GuardwallsStoneguardwallsfunctionlikerigidconcretebarriersbuthaveanappearanceofnaturalstone.Thesewallscanbeconstructedofstonemasonryoverareinforcedconcretecorewallorofsimulatedstoneconcrete.Thesetypesofbarriersaredesignedtohavealimitedprojectionofthestonesthatwillnotaffecttheredirectionalcharacteristicsofthebarrier.Themostdesirablemethodofterminatingthisbarrieristoburytheendinabackslope,asdescribedin710.08(3).Whenthistypeofterminalisnotpossible,theuseofthebarrierislimitedtohighwayswithapostedspeedof45milesperhourorless.Ontheselower-speedhighways,thebarriercanbeflaredawayfromthetraveledwayandterminatedinaberm.

Fordetailsonthesesystems,contacttheHQDesignOffice.

710.10 BridgeTrafficBarriersBridgetrafficbarriersredirecterrantvehiclesandpreventthemfromgoingoverthesideofthestructure.(SeetheBridge Design Manualforinformationregardingbridgebarrieronnewbridgesandreplacementbridgebarrieronexistingbridges.)

Formostnewbridgerailinstallations,usea2-foot-8-inch-highsafetyshape(F-Shape)bridgebarrier.AtransitionisavailabletoconnecttheNewJerseyshape(Type2ConcreteBarrier)andtheF-Shapebridgebarrier.(SeetheStandardPlansforfurtherdetails.)Thesingle-slopebridgebarrierthatis2feet10incheshighcanbeusedtobeconsistentwiththeheightsofconnectingsingle-slopebarrier.(See710.08(1)(b).)

Usetaller3-foot-6-inchsafetyshapeorsingle-slopebridgebarriersonInterstateorfreewayrouteswhereaccidenthistorysuggestsaneedorwhereroadwaygeometricsincreasethepossibilityoflargertruckshittingthebarrieratahighangle(suchason-rampsforfreeway-to-freewayconnectionswithsharpcurvatureinthealignment).

Forbridgeswherehighvolumesofpedestriantrafficareanticipated,seeChapter1020forfurtherguidance.

Approachbarriers,transitions,andconnectionsareusuallyrequiredonallfourcornersofbridgescarryingtwo-waytrafficandonbothcornersoftheapproachendforone-waytraffic.(See710.06(5)forguidanceontransitions.)

Ifthebridgebarriersystemdoesnotmeetthecriteriaforstrengthandgeometrics,modificationstoimproveitsredirectionalcharacteristicsanditsstrengthmayberequired.Themodificationscanbemadeusingoneoftheretrofitmethodsdescribedbelow.

(1) Concrete Safety ShapeRetrofittingwithanewconcretebridgebarrier(seeFigure710-9)iscostlyandrequiresjustificationwhennowideningisproposed.ConsulttheHQBridgeandStructuresOfficefordesigndetailsandtodetermineiftheexistingbridgedeckandothersuperstructureelementsareofsufficientstrengthtoaccommodatethisbridgebarriersystem.

SafetyShapeConcreteBridgeRailRetrofit

Figure 710-9

Traffic Barriers Design Manual M 22-01 Page 710-20 November 2006

(2) Thrie Beam RetrofitRetrofittingwiththriebeamisaneconomicalwaytoimprovethestrengthandredirectionalperformanceofbridgebarriers.Thethriebeamcanbemountedtosteelpostsortheexistingbridgebarrier,dependingonthestructuraladequacyofthebridgedeck,theexistingbridgebarriertype,thewidthofcurb(ifany),andthecurb-to-curbroadwaywidthcarriedacrossthestructure.

TheHQBridgeandStructuresOfficeisresponsibleforthedesignofthriebeambridgebarrier.Figure710-15showstypicalinstallationcriteria.ContacttheHQBridgeandStructuresOfficeforassistancewiththriebeamretrofitdesign.

ConsidertheServiceLevel1(SL-1)systemonbridgeswithwoodendecksandforbridgeswithconcretedecksthatdonothaveadequatestrengthtoaccommodatethethriebeamsystem.ContacttheHQBridgeandStructuresOfficeforinformationrequiredforthedesignoftheSL-1system.

Asidewalkreductionofupto6inchesasaresultofathriebeamretrofitcanbedocumentedasadesignexception.

Manybridgerailretrofitprojectsinvolvebridgesover250feetinlength.TheseprojectswillnormallybefundedfromtheI-2program.Shorterbridgesmaybefundedasaspotsafetyimprovement.ContacttheHQProjectControlandReportingOfficeforclarification.

710.11 OtherBarriers

(1) DragnetTheDragnetVehicleArrestingBarrierconsistsofchainlinkorfibernetthatisattachedtoenergyabsorbingunits.Whenavehiclehitsthesystem,theDragnetbringsthevehicletoacontrolledstopwithaminimumofdamage.Possibleusesforthisdeviceincludethefollowing: Reversiblelaneentrancesandexits Railroadcrossings Truckescaperamps(insteadofarresterbedsseeChapter1010)

T-intersections Workzones Swingspanbridges

Forpermanentinstallations,thissystemcanbeinstalledbetweentowersthatlowertheunitintopositionwhenneededandliftitoutofthewaywhenitisnolongerneeded.Forworkzoneapplications,itiscriticaltoprovidedeflectionspaceforstoppingthevehiclebetweenthesystemandtheworkzone.ForadditionalinformationontheDragnet,contacttheHQDesignOffice.

710.12 DocumentationThelistofdocumentsthataretobepreservedintheDesignDocumentationPackage(DDP)ortheProjectFile(PF)canbefoundonthefollowingwebsite:http://www.wsdot.wa.gov/eesc/design/projectdev/

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-21

ConnectingW-BeamGuardrailto:TransitionsandConnections TransitionType* Connection

Bridge Rail

New 1(1) 4(5) D

Existing Concrete

Concrete Parapet > 20 inches 1

(1) 4(5) Figure 710-6

Concrete Parapet < 20 inches 2 4

(5) Figure 710-6

Existing W-Beam Transition 2

(2)(6) 4(5) (2)

Thrie Beam at face of curb(4)

Approach end 10 naTrailing end (two-way traffic only) 11 12 na

Thrie Beam at bridge rail (curb exposed)(4)

Approach end 13 naTrailing end (two-way traffic only) 14 15 na

Weak Post Intersection Design (see 710.06(4) Cases 12 & 13) 5 Figure 710-6

Concrete BarrierRigid Restrained 1 4(5) Figure 710-6Unrestrained 2 4(5) A

Weak Post Barrier Systems (Type 20 and 21)

6 na

Rigid Structures such as Bridge Piers

New Installation (see Case 11) 16 17 18 naExisting W-Beam Transition (3) na

ConnectingThrieBeamGuardrailto:Bridge Rail or Concrete Barrier

New installation (example: used with thrie beam bull nose) 1B Figure 710-6

* Consult Section C of the Standard Plans for detail on transition types.Notes:(1) A Type 1A transition can be used where there is a problem placing a post within 2-5 from the end of the

bridge, in which case a B or E connection is required. When the E connection is to be used, a special detail for the end of the bridge is required. Contact the HQ Bridge and Structures Office.

(2) If work requires reconstruction or resetting of the transition, upgrade as shown above. Raising the guardrail is not considered reconstruction. If the transition is not being reconstructed, the existing connection may remain in place. (See Section 710.06(4)(d) for guidance when Type 3 anchors are encountered.)

(3) For new/reconstruction, use Case 11 (thrie beam). For existing Case 11 with W-beam, add a second W-beam rail element.

(4) For Service Level 1 bridge rail, see Section 710.06(6), Case 14.(5) Use on highways with speeds 45 miles per hour or less.(6) If existing transition has adequate guardrail heightthree 10x10 (nominal) posts and three 6 x 8 (nominal)

posts spaced 3-1.5 apartit is acceptable to nest existing single W-beam element transitions.

TransitionsandConnectionsFigure 710-10

Traffic Barriers Design Manual M 22-01 Page 710-22 November 2006

BarrierLengthofNeedonTangentSectionsFigure 710-11a

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-23

DesignParameters

PostedSpeed(mph)

ADT BarrierTypeOver

10,0005,000 to 10,000

1,000 to 4,999

Under 1,000

Rigid Barrier

Unrestrained Barrier

Semirigid Barrier

LR (ft) LR (ft) LR (ft) LR (ft) F F F70 460 395 345 295 20 18 1560 360 295 260 230 18 16 1455 310 260 230 195 16 14 1250 260 215 180 165 14 12 1145 245 195 165 150 12 11 1040 215 180 150 130 11 10 935 185 155 130 115 11 10 930 165 135 115 105 11 10 925 150 125 105 95 11 10 9

L1 = Length of barrier parallel to roadway from adjacent-side hazard to beginning of barrier flare. This is used if a portion of the barrier cannot be flared (such as a bridge rail and the transition).

L2 = Distance from adjacent edge of traveled way to portion of barrier parallel to roadway.L4 = Length of barrier parallel to roadway from opposite-side hazard to beginning of barrier flare.L5 = Distance from centerline of roadway to portion of barrier parallel to roadway. Note: If the hazard is outside the

Design Clear Zone when measured from the centerline, it may only be necessary to provide a crashworthy end treatment for the barrier.

LH1 = Distance from outside edge of traveled way to back side of adjacent-side hazard. Note: If a hazard extends past the Design Clear Zone, the Design Clear Zone can be used as LH1.

LH2 = Distance from centerline of roadway to back side of opposite-side hazard. Note: If a hazard extends past the Design Clear Zone, the Design Clear Zone can be used as LH2.

LR = Runout length (measured parallel to roadway).X1 = Length of need for barrier to shield an adjacent-side hazard.X2 = Length of need for barrier to shield an opposite-side hazard.F = Flare rate value.Y = Offset distance required at the beginning of the length of need.Differentendtreatmentsrequiredifferentoffsets.For the SRT 350 and FLEAT 350, use Y = 1.8 feet.For evaluating existing BCTs, use Y = 1.8 feet.For the FLEAT TL-2, use Y = 0.8 feet.No offset is required for the nonflared terminals or impact attenuator systems. Use Y = 0.Buried terminal end treatments are used with barrier flares and have no offset. Use Y = 0.

BarrierLengthofNeedFigure 710-11b

Traffic Barriers Design Manual M 22-01 Page 710-24 November 2006

Notes: This is a graphical method for determining the length of need for barrier on the outside of a curve. On a scale drawing, draw a tangent from the curve to the back of the hazard. Compare T to LR from Figure

710-11b and use the shorter value. If using LR, follow Figures 710-11a and 11b. If using T, draw the intersecting barrier run to scale and measure the length of need.

BarrierLengthofNeedonCurvesFigure 710-11c

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-25

W-BeamGuardrailTrailingEndPlacementforDividedHighwaysFigure 710-11d

Traffic Barriers Design Manual M 22-01 Page 710-26 November 2006

Notes: Use Cases 1, 2, and 3 when there is a 2-foot or greater shoulder widening from face of guardrail to the

breakpoint. Use Cases 4, 5, and 6 when there is less than a 2-foot shoulder widening from face of guardrail to the

breakpoint.

BeamGuardrailPostInstallationFigure 710-12

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-27

BeamGuardrailTerminalsFigure 710-13

Traffic Barriers Design Manual M 22-01 Page 710-28 November 2006

Notes:(1) Cable barrier may be installed in the center of the ditch. The cable barrier may be offset from the ditch

centerline a maximum of 1 foot in either direction.(2) Avoid installing cable barrier within a 1 foot to 8 foot offset from the ditch centerline.(3) Cable barrier may be installed a distance of 8 feet or greater from the ditch centerline.(4) Depending on the system used and post spacing, this distance varies from 6 feet 8 inches to 12 feet.(5) Applies to slopes between 6H:1V to 10H:1V.

CableBarrierLocationsonSlopesFigure 710-14

Design Manual M 22-01 Traffic Barriers November 2006 Page 710-29

ThrieBeamRailRetrofitCriteriaFigure 710-15

ConcreteBridgeDeck

WoodBridgeDeckor

Low-StrengthConcreteDeck

CurbWidth BridgeWidth ConcreteBridgeRail(existing)SteelorWoodPostBridgeRail(existing)

18inches >28feet(curbtocurb)Thrie beam mounted to steel posts(2) at the face of curb.(1) Height = 32 inches Height = 32 inches

>18inches