Chapter 700 Roadside Safety -...

Design Manual Roadside Safety May 2006 Page 700-1

Chapter 700 Roadside Safety

700.01 General700.02 References700.03 Definitions700.04 ClearZone700.05 HazardstoBeConsidered forMitigation700.06 MedianConsiderations700.07 OtherRoadsideSafetyFeatures700.08 Documentation

700.01 GeneralRoadsidesafetyaddressestheareaoutsideoftheroadwayandisanimportantcomponentoftotalhighwaydesign.Therearenumerousreasonswhyavehicleleavestheroadway.Regardlessofthereason,aforgivingroadsidecanreducetheseriousnessoftheconsequencesofaroadsideencroachment.Fromasafetyperspective,theidealhighwayhasroadsidesandmedianareasthatareflatandunobstructedbyhazards.

Elementssuchassideslopes,fixedobjects,andwaterarepotentialhazardsthatavehiclemightencounterwhenitleavestheroadway.Thesehazardspresentvaryingdegreesofdangertothevehicleanditsoccupants.Unfortunately,geographyandeconomicsdonotalwaysallowidealhighwayconditions.Themitigativemeasurestobetakendependontheprobabilityofanaccidentoccurring,thelikelyseverity,andtheavailableresources.

Inorderofpreference,mitigativemeasuresare:removal,relocation,reductionofimpactseverity(usingbreakawayfeaturesormakingittraversable),andshieldingwithatrafficbarrier.Considercost(initialandlifecyclecosts)andmaintenancerequirementsinadditiontoaccidentseveritywhenselectingamitigativemeasure.Usetrafficbarriersonlywhenothermeasurescannotreasonablybeaccomplished.SeeChapter710foradditionalinformationontrafficbarriers.

700.02 ReferencesA Policy on Geometric DesignofHighways and Streets(GreenBook),AASHTO,2001

Revised Code of Washington(RCW)47.24.020(2),“Jurisdiction,control”

RCW47.32.130,“Dangerousobjectsandstructuresasnuisances”

CityandCountyDesignStandards(containedintheLocal Agency Guidelines,M36-63),WSDOT

Roadside Design Guide,AASHTO,2002

Roadside Manual,M25-30,WSDOT

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

700.03 DefinitionsADT Theaveragedailytrafficforthedesignyearunderconsideration.

backslope Asideslopethatgoesupasthedistanceincreasesfromtheroadway(cutslopes).

clear run-out area Theareabeyondthetoeofanonrecoverableslopeavailableforsafeusebyanerrantvehicle.

clear zone Thetotalroadsideborderarea,startingattheedgeofthetraveledway,availableforusebyerrantvehicles.Thisareamayconsistofashoulder,arecoverableslope,anonrecoverableslope,and/oraclearrun-outarea.Theclearzonecannotcontainacriticalfillslope.

critical fill slope Aslopeonwhichavehicleislikelytooverturn.Slopessteeperthan3H:1Vareconsideredcriticalfillslopes.

Design Clear Zone Theminimumtargetvalueusedinhighwaydesign.

foreslope Asideslopethatgoesdownasthedistanceincreasesfromtheroadway(fillslopesandditchinslopes).

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

nonrecoverable slope Aslopeonwhichanerrantvehiclewillcontinueuntilitreachesthebottom,withouthavingtheabilitytorecovercontrol.Fillslopessteeperthan4H:1V,butnosteeperthan3H:1V,areconsiderednonrecoverable.

recoverable slope Aslopeonwhichthedriverofanerrantvehiclecanregaincontrolofthevehicle.Slopesof4H:1Vorflatterareconsideredrecoverable.

recovery area Theminimumtargetvalueusedinhighwaydesignwhenafillslopebetween4H:1Vand3H:1VstartswithintheDesignClearZone.

traffic barrier Alongitudinalbarrier,includingbridgerailoranimpactattenuator,usedtoredirectvehiclesfromhazardslocatedwithinanestablishedDesignClearZone,topreventmediancrossovers,topreventerrantvehiclesfromgoingoverthesideofabridgestructure,or(occasionally),toprotectworkers,pedestrians,orbicyclistsfromvehiculartraffic.

traveled way Theportionoftheroadwayintendedforthemovementofvehicles,exclusiveofshouldersandlanesforparking,turning,andstorageforturning.

700.04  Clear ZoneAclearroadsideborderareaisaprimaryconsiderationwhenanalyzingpotentialroadsideandmedianhazards(asdefinedin700.05).Theintentistoprovideasmuchclear,traversableareaforavehicletorecoveraspractical.TheDesignClearZoneisusedtoevaluatetheadequacyoftheexistingclearareaandproposedmodificationsoftheroadside.Whenconsideringtheplacementofnewobjectsalongtheroadsideormedian,evaluatethepotentialforimpactsandtrytoselectlocationswiththeleastlikelihoodofanimpactbyanerrantvehicle.

(1) Design Clear Zone on All Limited Access State Highways and Other State Highways Outside Incorporated Cities and TownsEvaluatetheDesignClearZonewhentheClearZonecolumnonthedesignmatrices(seeChapter325)indicatesevaluateupgrade(EU)orFullDesignLevel(F)orwhenconsideringtheplacementofanewfixedobjectontheroadsideormedian.UsetheDesignClearZoneInventoryform(Figures700-2a&2b)toidentifypotentialhazardsandproposecorrectiveactions.

GuidanceforestablishingtheDesignClearZoneforhighwaysoutsideofincorporatedcitiesisprovidedinFigure700-1.Thisguidancealsoappliestolimitedaccessstatehighwayswithinthecitylimits.Providingaclearrecoveryareathatisconsistentwiththisguidancedoesnotrequireanyadditionaldocumentation.However,theremightbesituationswhereitisnotpracticaltoprovidetheserecommendeddistances.Inthesesituations,documentthedecisionasanevaluateupgradeordeviationasdiscussedinChapter330.

ForadditionalDesignClearZoneguidancerelatingtoroundabouts,seeChapter915.

Whilenotrequired,thedesignerisencouragedtoevaluatepotentialhazardsevenwhentheyarebeyondtheDesignClearZonedistances.

Forstatehighwaysthatareinanurbanenvironmentbutoutsideofanincorporatedcity,evaluatebothmedianandroadsideclearzonesasdiscussedaboveusingFigure700-1.However,theremightbesomeflexibilityinestablishingtheDesignClearZoneinurbanizedareasadjacenttoincorporatedcitiesandtowns.Toachievethisflexibility,anevaluationoftheimpactsincludingsafety,aesthetics,theenvironment,economics,modalneeds,andaccesscontrolcanbeusedtoestablishtheDesignClearZone.Thisdiscussion,analysis,andagreementmusttakeplaceearlyintheconsiderationofthemedianandroadsidedesigns.Anagreementontheresponsibilityforthesemedianandroadsidesectionsmustbeformalizedwiththecityand/orcounty.ThejustificationforthedesigndecisionfortheselectedDesignClearZonemustbedocumentedaspartofaprojectorcorridoranalysis.(SeeChapter330.)

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(2) Design Clear Zone Inside Incorporated Cities and TownsFormanagedaccessstatehighwayswithinanurbanarea,itisrecognizedthatinmanycasesitwillnotbepracticaltoprovidetheDesignClearZonedistancesshowninFigure700-1.Roadwayswithinanurbanareagenerallyhavecurbsandsidewalksandmighthaveobjectssuchastrees,poles,benches,trashcans,landscaping,andtransitsheltersalongtheroadside.

(a) Roadside. Formanagedaccessstatehighways,itisthecity’sresponsibilitytoestablishanappropriateDesignClearZoneinaccordancewithguidancecontainedintheCityandCountyDesignStandards.DocumenttheDesignClearZoneestablishedbythecityintheDesignDocumentationPackage.

(b) Median. Formanagedaccessstatehighwayswithraisedmedians,themedian’sDesignClearZoneisevaluatedusingFigure700-1.Insomeinstances,amediananalysiswillshowthatcertainmediandesignsprovidesignificantbenefitstooverallcorridororprojectoperations.Inthesecases,flexibilityinestablishingtheDesignClearZoneisappropriate.Toachievethisflexibility,anevaluationoftheimpacts(includingsafety,aesthetics,theenvironment,economics,modalneeds,andaccesscontrol)canbeusedtoestablishthemedianclearzone.Thisdiscussion,analysis,andagreementmusttakeplaceearlyintheconsiderationoftheflexiblemediandesign.Anagreementontheresponsibilityforthesemediansectionsmustbeformalizedwiththecity.ThejustificationforthedesigndecisionfortheselectedDesignClearZonemustbedocumentedaspartofaprojectorcorridoranalysis.(SeeChapter330.)

(3) Design Clear Zone and CalculationsTheDesignClearZoneguidanceprovidedinFigure700-1isafunctionofthepostedspeed,sideslope,andtrafficvolume.Therearenodistancesinthetablefor3H:1Vfillslopes.Althoughfillslopesbetween4H:1Vand3H:1Vareconsideredtraversableiffreeoffixedobjects,theseslopesaredefinedasnonrecoverableslopes.Avehiclemightbeabletobeginrecoveryon

theshoulder,butwillbeunabletofurtherthisrecoveryuntilreachingaflatterarea(4H:1Vorflatter)atthetoeoftheslope.Undertheseconditions,theDesignClearZonedistanceiscalledarecoveryarea.ThemethodusedtocalculatetherecoveryareaandanexampleareshowninFigure700-3.

Forditchsections,thefollowingcriteriadeterminetheDesignClearZone:

(a) Forditchsectionswithforeslopes4H:1Vorflatter(seeFigure700-4,Case1,foranexample)theDesignClearZonedistanceisthegreaterofthefollowing:• TheDesignClearZonedistancefora10H:1V

cutsectionbasedonspeedandtheaveragedailytraffic(ADT).

• Ahorizontaldistanceof5feetbeyondthebeginningofthebackslope.

Whenabackslopesteeperthan3H:1Vcontinuesforahorizontaldistanceof5feetbeyondthebeginningofthebackslope,itisnotnecessarytousethe10H:1Vcutslopecriteria.

(b) Forditchsectionswithforeslopessteeperthan4H:1V,andbackslopessteeperthan3H:1VtheDesignClearZonedistanceis10feethorizontalbeyondthebeginningofthebackslope.(SeeFigure700-4,Case2,foranexample.)

(c) Forditchsectionswithforeslopessteeperthan4H:1Vandbackslopes3H:1Vorflatter,theDesignClearZonedistanceisthedistanceestablishedusingtherecoveryareaformula(Figure700-3).(SeealsoFigure700-4,Case3,foranexample.)

700.05  Hazards to Be Considered for MitigationTherearethreegeneralcategoriesofhazards:sideslopes,fixedobjects,andwater.Thefollowingsectionsprovideguidancefordeterminingwhentheseobstaclespresentasignificanthazardtoanerrantmotorist.Inaddition,severalconditionsrequirespecialconsideration:• Locationswithhighaccidentratehistories.• Locationswithpedestrianandbicycleusage.

SeeChapters1020,“BicycleFacilities,”and1025,“PedestrianDesignConsiderations.”

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• Playgrounds,monuments,andotherlocationswithhighsocialoreconomicvalue.

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

UseofatrafficbarrierforhazardsotherthanthosedescribedbelowrequiresjustificationintheDesignDocumentationPackage.

(1) Side Slopes(a) Fill Slopes. Fillslopescanpresentahazardtoanerrantvehiclewiththedegreeofseveritydependentupontheslopeandheightofthefill.Providingfillslopesthatare4H:1Vorflattercanmitigatethishazard.Ifflatteningtheslopeisnotfeasibleorcosteffective,theinstallationofabarriermightbeappropriate.Figure700-5representsaselectionprocedureusedtodeterminewhetherafillsideslopeconstitutesahazardforwhichabarrierisacost-effectivemitigation.Thecurvesarebasedontheseverityindexesandrepresentthepointswheretotalcostsassociatedwithatrafficbarrierareequaltothepredictedaccidentcostassociatedwithselectedslopeheightswithouttrafficbarrier.IftheADTandheightoffillintersectonthe“BarrierRecommended”sideoftheembankmentslopecurve,thenprovideabarrierifflatteningtheslopeisnotfeasibleorcosteffective.DonotuseFigure700-5forslopedesign.DesignguidanceforslopesisinChapters430and640.Also,ifthefigureindicatesthatbarrierisnotrecommendedatanexistingslope,thatresultisnotjustificationforadeviation.

Forexample,iftheADTis4,000andtheembankmentheightis10feet,barrierwillbecosteffectivefora2H:1Vslope,butnotfora2.5H:1Vslope.

Thisprocessonlyaddressesthepotentialhazardoftheslope.Obstaclesontheslopecancompoundthehazard.Wherebarrierisnotcosteffective,usetherecoveryareaformulatoevaluatefixedobjectsoncriticalfillslopeslessthan10feethigh.

(b) Cut Slopes. Acutslopeisusuallylessofahazardthanatrafficbarrier.Theexceptionisarockcutwitharoughfacethatmightcausevehiclesnaggingratherthanprovidingrelativelysmoothredirection.

AnalyzethepotentialmotoristriskandthebenefitsoftreatmentofroughrockcutslocatedwithintheDesignClearZone.Acost-effectivenessanalysisthatconsiderstheconsequencesofdoingnothing,removal,orsmoothingofthecutslope,andallotherviableoptionstoreducetheseverityofthehazard,canbeusedtodeterminetheappropriatetreatment.Alsoconsideroptionstoreducethepotentialforroadwaydepartures.Somepotentialoptionsare:• Gradedlandformalongthebaseofarockcut.• Flexiblebarrier.• Morerigidbarrier.• Rumblestrips.

Conductanindividualinvestigationforeachrockcutorgroupofrockcuts.Selectthemostcost-effectivetreatment.

(2) Fixed ObjectsConsiderthefollowingobjectsformitigation:• Woodenpolesorpostswithcrosssectional

areagreaterthan16squareinchesthatdonothavebreakawayfeatures.

• Nonbreakawaysteelsignposts.• Nonbreakawaylightstandards.• Treeshavingadiameterof4inchesormore

measuredat6inchesabovethegroundsurface.

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• Fixedobjectsextendingabovethegroundsurfacebymorethan4inches;forexample,boulders,concretebridgerails,signalandelectricalcabinets,piers,andretainingwalls.

• Existingguardrailthatdoesnotconformtocurrentdesignguidance.(SeeChapter710.)

• Drainageitems,suchasculvertandpipeends.

MitigatehazardsthatexistwithintheDesignClearZonewhenfeasible.Althoughlimitedinapplication,theremaybesituationswhereremovalofahazardoutsideoftheR.O.W.isappropriate.Thepossiblemitigativemeasuresarelistedbelowinorderofpreference.• Remove.• Relocate.• Reduceimpactseverity(usingabreakaway

feature).• Shieldtheobjectbyusinglongitudinalbarrier

orimpactattenuator.

(a) Trees. Whenevaluatingnewplantingsorexistingtrees,considerthemaximumallowablediameterof4inchesmeasuredat6inchesabovethegroundwhenthetreehasmatured.WhenremovingtreeswithintheDesignClearZone,completeremovalofstumpsispreferred.However,toavoidsignificantdisturbanceoftheroadsidevegetation,largerstumpsmaybemitigatedbygrindingorcuttingthemflushtothegroundandgradingaroundthem.SeetheRoadside Manualforfurtherguidanceonthetreatmentofthedisturbedroadside.

(b) Mailboxes. EnsurethatallmailboxeslocatedwithintheDesignClearZonehavesupportsandconnectionsasshownintheStandardPlans.Theheightfromthegroundtothebottomofthemailboxis3feet3inches.Thisheightmayvaryfrom3feet3inchesto4feetifrequestedbythemailcarrier.Ifthedesiredheightistobedifferentfrom3feet3inchesprovidethedesiredheightinthecontractplans.SeeFigure700-6forinstallationguidelines.

Inurbanareaswheresidewalksareprevalent,contactthepostalservicetodeterminethemostappropriatemailboxlocation.LocatemailboxesonlimitedaccesshighwaysinaccordancewithChapter1430“LimitedAccess”.Aturnout,asshownonFigure700-6,isnotrequiredonlimitedaccesshighwayswithshouldersof6feetormorewhereonlyonemailboxistobeinstalled.Onmanagedaccesshighways,mailboxesmustbeontheright-handsideoftheroadinthedirectionoftravelofthepostalcarrier.Avoidplacingmailboxesalonghigh-speed,high-volumehighways.LocateNeighborhoodDeliveryandCollectionBoxUnits(NDCBUs)outsidetheDesignClearZone.

(c) Culvert Ends. ProvideatraversableendtreatmentwhentheculvertendsectionoropeningisontheroadwaysideslopeandwithintheDesignClearZone.Thiscanbeaccomplishedforsmallculvertsbybevelingtheendtomatchthesideslope,withamaximumof4inchesextendingoutofthesideslope.

Barsmightbenecessarytoprovideatraversableopeningforlargerculverts.PlacebarsintheplaneoftheculvertopeninginaccordancewiththeStandardPlanswhen:

1. Singlecrossculvertopeningexceeds40inchesmeasuredparalleltothedirectionoftravel.

2. Multiplecrossculvertopeningsthatexceed30incheseach,measuredparalleltothedirectionoftravel.

3. Culvertapproximatelyparalleltotheroadwaythathasanopeningexceeding24inchesmeasuredperpendiculartothedirectionoftravel.

Barsarepermittedwheretheywillnotsignificantlyaffectthestreamhydraulicsandwheredebrisdriftisminor.ConsulttheregionalMaintenanceOfficetoverifytheseconditions.Ifdebrisdriftisaconcern,consideroptionstoreducetheamountofdebristhatcanenterthepipe.(SeetheHydraulics Manual).OthertreatmentsareextendingtheculverttomovetheendoutsidetheDesignClearZoneorinstallingatrafficbarrier.

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(d) Sign Posts. Wheneverpossible,locatesignsbehindexistingorplannedtrafficbarrierinstallationstoeliminatetheneedforbreakawayposts.Placethematleast25feetfromtheendofthebarrierterminalandwiththesignfacebehindthebarrier.Whenbarrierisnotpresent,useterrainfeaturestoreducethelikelihoodofanerrantvehiclestrikingthesignposts.Wheneverpossible,dependingonthetypeofsignandthesignmessage,adjustthesignlocationtotakeadvantageofbarrierorterrainfeatures.Thiswillreduceaccidentpotentialand,possibly,futuremaintenancecosts.SeeChapter820foradditionalinformationregardingtheplacementofsigns.

Signpostswithcrosssectionalareasgreaterthan16squareinchesthatarewithintheDesignClearZoneandnotlocatedbehindabarriermusthavebreakawayfeaturesasshownintheStandardPlans.

(e) Traffic Signal Standards/Posts/Supports. Breakawaysignalpostsgenerallyarenotpracticalordesirable.Sincethesesupportsaregenerallylocatedatintersectingroadways,thereisahigherpotentialforafallingsupporttoimpactvehiclesand/orpedestrians.Inaddition,signalsupportsthathaveoverheadmastsmaybetooheavyforabreakawaydesigntoworkproperly.Othermitigationsuchasinstallingatrafficbarrierisalsoverydifficult.Withvehiclesapproachingthesupportfrommanydifferentangles,abarrierwouldhavetosurroundthesupportandwouldbesubjecttoimpactsathighangles.Additionally,barriercaninhibitpedestrianmovements.Therefore,barrierisgenerallynotanoption.However,sincespeedsnearsignalsaregenerallylower,thepotentialforasevereimpactisreduced.Forthesereasons,theonlymitigationistolocatethesupportasfarfromthetraveledwayaspossible.

Inlocationswheresignalsareusedforrampmeters,thesupportscanbemadebreakawayasshownontheStandardPlan.

(f) Fire Hydrants. FireHydrantsareallowedonWSDOTrightofwaybyfranchiseorpermit.Firehydrantsthataremadeofcastironcanbeexpectedtofractureonimpactandcanthereforebeconsideredabreakawaydevice.Anyportionofthehydrantsthatwillnotbebreakawaymustnotextendmorethen4inchesabovetheground.Inaddition,thehydrantmusthaveastemthatwillshutoffwaterflowintheeventofanimpact.Mitigateallotherhydrants.

(g) Utility Poles. Sinceutilitiesoftensharetherightofway,utilityobjectssuchaspoleswilloftenbelocatedalongtheroadside.Itisundesirable/impracticaltoinstallbarrierforalloftheseobjectssomitigationisusuallyintheformofrelocation(undergroundortotheedgeoftherightofway)ordelineation.Insomeinstanceswherethereisahistoryofimpactswithpolesandrelocationisnotpossible,abreakawaydesignmightbeappropriate.

ContactHeadquartersDesignforinformationonbreakawayfeatures.CoordinatewiththeUtilitiesOfficewhereappropriate.

(h) Light Standards. Providebreakawaylightstandardsunlessfixedlightstandardscanbejustified.Fixedlightstandardsmaybeappropriateinareasofextensivepedestrianconcentrations,suchasadjacenttobusshelters.DocumentthedecisiontousefixedbasesintheDesignDocumentationPackage.

(3) WaterWaterwithadepthof2feetormoreandlocatedwithalikelihoodofencroachmentbyanerrantvehiclemustbeconsideredformitigationonaproject-by-projectbasis.Considerthelengthoftimetrafficisexposedtothishazardanditslocationinrelationshiptootherhighwayfeaturessuchascurves.

AnalyzethepotentialmotoristriskandthebenefitsoftreatmentofbodiesofwaterlocatedwithintheDesignClearZone.Acost-effectivenessanalysisthatconsiderstheconsequencesofdoingnothingversusinstallingalongitudinalbarriercanbeusedtodeterminetheappropriatetreatment.

Forfencingconsiderationsalongwaterfeatures,seeChapter1460.

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700.06  Median ConsiderationsMediansmustbeanalyzedforthepotentialofanerrantvehicletocrossthemedianandencounteroncomingtraffic.Medianbarriersarenormallyusedonlimitedaccess,multilane,high-speed,hightrafficvolumehighways.Thesehighwaysgenerallyhavepostedspeedsof45mphorgreater.Medianbarrierisnotnormallyplacedoncollectorsorotherstatehighwaysthatdonothavelimitedaccesscontrol.Providingaccessthroughmedianbarrierrequiresopeningsand,therefore,end-treatments.

Providemedianbarrieronfullaccesscontrol,multilanehighwayswithmedianwidthsof50feetorlessandpostedspeedsof45mphormore.Considermedianbarrieronhighwayswithwidermediansorlowerpostedspeedswhenthereisahistoryofcrossmedianaccidents.

Wheninstallingamedianbarrier,provideleft-sideshoulderwidthsasshowninChapters430and440andshydistanceasshowninChapter710.Considerawidershoulderareawherethebarrierwillcastashadowontheroadwayandhinderthemeltingofice.SeeChapter640foradditionalcriteriaforplacementofmedianbarrier.SeeChapter710forinformationonthetypesofbarriersthatcanbeused.SeeChapter650forlateralclearanceontheinsideofacurvetoprovidetherequiredstoppingsightdistance.

Whenmedianbarrierisbeingplacedinanexistingmedian,identifytheexistingcrossoversandenforcementobservationpoints.ProvidethenecessarymediancrossoversinaccordancewithChapter960,consideringenforcementneeds.Chapter1050providesguidanceonHOVenforcement.

700.07 Other Roadside Safety  Features

(1) Rumble StripsRumblestripsaregroovesorrowsofraisedpavementmarkersplacedperpendiculartothedirectionoftraveltoalertinattentivedrivers.

Therearethreekindsofrumblestrips:

(a) Roadway rumble stripsareplacedacrossthetraveledwaytoalertdriversapproachingachangeofroadwayconditionorahazardthatrequiressubstantialspeedreductionorothermaneuvering.Examplesoflocationswhereroadwayrumblestripsmaybeusedareinadvanceof:• Stopcontrolledintersections.• Portofentry/customsstations.• Lanereductionswhereaccidenthistoryshows

apatternofdriverinattention.

Theymayalsobeplacedatlocationswherethecharacteroftheroadwaychanges,suchasattheendofafreeway.

ContacttheHeadquartersDesignOfficeforadditionalguidanceonthedesignandplacementofroadwayrumblestrips.

Documentjustificationforusingroadwayrumblestrips.

(b) Shoulder rumble stripsareplacedontheshouldersjustbeyondthetraveledwaytowarndriverswhentheyareenteringapartoftheroadwaynotintendedforroutinetrafficuse.Shoulderrumblestripsmaybeusedwhenananalysisindicatesaproblemwithrun-off-the-roadaccidentsduetoinattentiveorfatigueddrivers.Acomparisonofrolled-inandmilled-inShoulderRumbleStrips(SRS)hasdeterminedthatmilled-inrumblestrips,althoughmoreexpensive,aremorecosteffective.Milled-inrumblestripsarerecommended.

WhenSRSareused,discontinuethemwherenoedgestripeispresentsuchasatintersectionsandwherecurbandgutterarepresent.Wherebicycletravelisallowed,discontinueSRSatlocationswhereshoulderwidthreductionscancausebicycliststomoveintooracrosstheareawhererumblestripswouldnormallybeplaced,suchasshouldersadjacenttobridgeswithreducedshoulderwidths.

SRSpatternsvarydependingonthelikelihoodofbicyclistsbeingpresentalongthehighwayshoulder,andwhethertheyareplacedondividedorundividedhighways.Rumblestrippatternsforundividedhighwaysareshallowerandmaybe

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narrowerthanpatternsusedondividedhighways.Theyalsoprovidegapsinthepattern,providingopportunitiesforbicyclestomoveacrossthepatternwithouthavingtorideacrossthegrooves.Therearefourshoulderrumblestrippatterns.ConsulttheStandardPlansforthepatternsandconstructiondetails.

1. Divided Highways

SRSarerequiredonboththerightandleftshouldersofruralInterstatehighways.Considerthemonbothshouldersofruraldividedhighways.UsetheShoulderRumbleStripType1patternondividedhighways.

OmittingSRSonruralhighwaysisadesignexception(DE)underanyoneofthefollowingconditions:

• Whenanotherprojectscheduledwithintwoyearsoftheproposedprojectwilloverlayorreconstructtheshouldersorwillusetheshouldersfordetours.

• WhenapavementanalysisdeterminesthatinstallingSRSwillresultininadequateshoulderstrength.

• Whenoverallshoulderwidthwillbelessthan4feetwideontheleftand6feetwideontheright.

2. Undivided Highways

SRSarenotrequiredonundividedhighways,butmaybeusedwhererun-off-the-roadaccidentexperienceishigh.SRSusageontheshouldersofundividedhighwaysdemandsstrategicapplicationbecausebicycleusageismoreprevalentalongtheshouldersoftheundividedhighwaysystem.Rumblestripsaffectthecomfortandcontrolofbicycleriders;consequently,theiruseistobelimitedtohighwaycorridorsthatexperiencehighlevelsofrun-off-the-roadaccidents.Applythefollowingcriteriainevaluatingtheappropriatenessofrumblestripsontheshouldersofundividedhighways.

• Useonruralroadsonly.

• Ensureshoulderpavementisstructurallyadequatetosupportmilledrumblestrips.

• Postedspeedis45mphorgreater.

• Ensurethatatleast4feetofusableshoulderremainsbetweentherumblestripandtheoutsideedgeofshoulder.Ifguardrailorbarrierispresent,increasethedimensionto5feetofusableshoulder.

• Preliminaryevaluationindicatesarun-off-the-roadaccidentexperienceofapproximately0.6crashespermileperyear,orapproximately34crashesper100millionmilesoftravel.(Thesevaluesareintendedtoproviderelativecomparisonofcrashexperienceandarenottobeusedasabsoluteguidanceonwhetherrumblestripsareappropriate.)

• Donotplaceshoulderrumblestripsondownhillgradesexceeding4%formorethan500feetinlengthalongrouteswherebicyclistsarefrequentlypresent.

• Anengineeringanalysisindicatesarun-off-the-roadaccidentexperienceconsideredcorrectablebyshoulderrumblestrips.

• ConsulttheregionalmembersoftheWashingtonBicycleandPedestrianAdvisoryCommitteetodeterminebicycleusagealongaroute,andinvolvetheminthedecision-makingprocesswhenconsideringrumblestripsalongbiketouringroutesorotherrouteswherebicycleeventsareregularlyheld.

TheShoulderRumbleStripType2orType3patternisusedonhighwayswithminimalbicycletraffic.Whenbicycletrafficontheshoulderishigh,theShoulderRumbleStripType4patternisused.

ShoulderrumblestripinstallationconsideredatanyotherlocationsmustinvolvetheWSDOTBicycleandPedestrianAdvisoryCommitteeasapartnerinthedecision-makingprocess.

Consultthefollowingwebsiteforguidanceonconductinganengineeringanalysis:http://www.wsdot.wa.gov/EESC/Design/Policy/RoadsideSafety/Chapter700/Chapter700B.htm

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(c) Centerline rumble stripsareplacedonthecenterlineofundividedhighwaystoalertdriversthattheyareenteringtheopposinglane.Theyareappliedasacountermeasureforcrossoveraccidents.Centerlinerumblestripsareinstalledwithnodifferentiationbetweenpassingpermittedandnopassingareas.Pavementmarkingshouldberefreshedwhenremovedbycenterlinerumblestrips.

Driverstendtomovetotherighttoavoiddrivingoncenterlinerumblestrips.Narrowlaneandshoulderwidthsmayleadtodroppingatireoffthepavementwhendrivershaveshiftedtheirtravelpath.Centerlinerumblestripsareinappropriatewhenthecombinedlaneandshoulderwidthsineachdirectionislessthantwelvefeet.SeeChapters430and440forguidanceonlaneandshoulderwidth.Considershortsectionsofroadwaythatarebelowthiswidthonlywhenaddedforroutecontinuity.

Applythefollowingcriteriainevaluatingtheappropriatenessofcenterlinerumblestrips:• Anengineeringanalysisindicatesacrossover

accidenthistorywithcollisionsconsideredcorrectablebycenterlinerumblestrips.Reviewtheaccidenthistorytodeterminethefrequencyofcollisionswithcontributingcircumstancessuchasinattention,apparentlyfatigued,apparentlyasleep,overcenterline,oronwrongsideofroad.

• Centerlinerumblestripsaremostappropriateonruralroads,butwithspecialconsiderationmayalsobeappropriateforurbanroads.Someconcernsspecifictourbanareasarenoiseindenselypopulatedareas,thefrequentneedtointerrupttherumblestrippatterntoaccommodateleftturningvehicles,andareducedeffectivenessatlowerspeeds(35MPHandbelow).

• Ensuretheroadwaypavementisstructurallyadequatetosupportmilledrumblestrips.Consulttheregion’sMaterialsEngineertoverifypavementadequacies.

• Centerlinerumblestripsarenotappropriatewheretwo-wayleft-turnlanesexist.

(2) Headlight Glare ConsiderationsHeadlightglarefromopposingtrafficcancausesafetyproblems.Glarecanbereducedbytheuseofwidemedians,separatealignments,earthmounds,plants,concretebarrier,andbyglarescreens.Considerlongtermmaintenancewhenselectingthetreatmentforglare.Whenconsideringearthmoundandplantingtoreduceglare,seetheRoadside Manualforadditionalguidance.Whenconsideringglarescreens,seeChapter650forlateralclearanceontheinsideofacurvetoprovidetherequiredstoppingsightdistance.Inadditiontoreducingglare,tallerconcretebarriersalsoprovideimprovedcrashperformanceforlargervehiclessuchastrucks.

Glarescreenisrelativelyexpensiveanditsusemustbejustifiedanddocumented.Itisdifficulttojustifytheuseofglarescreenwherethemedianwidthexceeds20feet,theADTislessthan20,000vehiclesperday,ortheroadwayhascontinuouslighting.Considerthefollowingfactorswhenassessingtheneedforglarescreen:• Higherrateofnightaccidentscomparedto

similarlocationsorstatewideexperience.• Higherthannormalratioofnighttoday

accidents.• Unusualdistributionorconcentrationof

nighttimeaccidents.• Overrepresentationofolderdriversinnight

accidents.• Combinationofhorizontalandvertical

alignment,particularlywheretheroadwayontheinsideofacurveishigherthantheroadwayontheoutsideofthecurve.

• Directobservationofglare.• Publiccomplaintsconcerningglare.

Themostcommonglareproblemisbetweenopposingmainlinetraffic.Otherconditionsforwhichglarescreenmightbeappropriateare:• Betweenahighwayandanadjacentfrontage

roadorparallelhighway,especiallywhereopposingheadlightsmightseemtobeonthewrongsideofthedriver.

Roadside Safety Design Manual Page 700-10 May 2006

• Ataninterchangewhereanon-rampmergeswithacollectordistributorandtheramptrafficmightbeunabletodistinguishbetweencollectorandmainlinetraffic.Inthisinstance,considerothersolutions,suchasillumination.

• Whereheadlightglareisadistractiontoadjacentpropertyowners.Playgrounds,ballfields,andparkswithfrequentnighttimeactivitiesmightbenefitfromscreeningifheadlightglareinterfereswiththeseactivities.

Therearecurrentlythreebasictypesofglarescreenavailable:chainlink(seeStandardPlans),verticalblades,andconcretebarrier.(SeeFigure700-7.)

Whentheglareistemporary(duetoconstructionactivity),considertrafficvolumes,alignment,duration,presenceofillumination,andtypeofconstructionactivity.Glarescreenmaybeusedtoreducerubberneckingassociatedwithconstructionactivity,butlessexpensivemethods,suchasplywoodthatsealsofftheviewoftheconstructionarea,mightbemoreappropriate.

700.08  DocumentationAlistofdocumentsthatarerequiredtobepreservedintheDesignDocumentationPackage(DDP)ortheProjectFile(PF)isonthefollowingwebsite:http://www.wsdot.wa.gov/eesc/design/projectdev/

Design Manual Roadside Safety May 2006 Page 700-11

Design Clear Zone Distances for State Highways Outside Incorporated Cities**(In feet from edge of traveled way***)

Posted Speed mph

AverageDaily

Traffic

Cut Section (Backslope) Fill Section(H:V) (H:V)

3:1 4:1 5:1 6:1 8:1 10:1 3:1 4:1 5:1 6:1 8:1 10:135 or Less The Design Clear Zone distance is 10 feet

Under 250 10 10 10 10 10 10 * 13 12 11 11 10251-800 11 11 11 11 11 11 * 14 14 13 12 11

40 801-2000 12 12 12 12 12 12 * 16 15 14 13 122001-6000 14 14 14 14 14 14 * 17 17 16 15 14Over 6000 15 15 15 15 15 15 * 19 18 17 16 15Under 250 11 11 11 11 11 11 * 16 14 13 12 11251-800 12 12 13 13 13 13 * 18 16 14 14 13

45 801-2000 13 13 14 14 14 14 * 20 17 16 15 142001-6000 15 15 16 16 16 16 * 22 19 17 17 16Over 6000 16 16 17 17 17 17 * 24 21 19 18 17Under 250 11 12 13 13 13 13 * 19 16 15 13 13251-800 13 14 14 15 15 15 * 22 18 17 15 15

50 801-2000 14 15 16 17 17 17 * 24 20 18 17 172001-6000 16 17 17 18 18 18 * 27 22 20 18 18Over 6000 17 18 19 20 20 20 * 29 24 22 20 20Under 250 12 14 15 16 16 17 * 25 21 19 17 17251-800 14 16 17 18 18 19 * 28 23 21 20 19

55 801-2000 15 17 19 20 20 21 * 31 26 23 22 212001-6000 17 19 21 22 22 23 * 34 29 26 24 23Over 6000 18 21 23 24 24 25 * 37 31 28 26 25Under 250 13 16 17 18 19 19 * 30 25 23 21 20251-800 15 18 20 20 21 22 * 34 28 26 23 23

60 801-2000 17 20 22 22 23 24 * 37 31 28 26 252001-6000 18 22 24 25 26 27 * 41 34 31 29 28Over 6000 20 24 26 27 28 29 * 45 37 34 31 30Under 250 15 18 19 20 21 21 * 33 27 25 23 22251-800 17 20 22 22 24 24 * 38 31 29 26 25

65 801-2000 19 22 24 25 26 27 * 41 34 31 29 282001-6000 20 25 27 27 29 30 * 46 37 35 32 31Over 6000 22 27 29 30 31 32 * 50 41 38 34 33Under 250 16 19 21 21 23 23 * 36 29 27 25 24251-800 18 22 23 24 26 26 * 41 33 31 28 27

70 801-2000 20 24 26 27 28 29 * 45 37 34 31 302001-6000 22 27 29 29 31 32 * 50 40 38 34 33Over 6000 24 29 31 32 34 35 * 54 44 41 37 36

* When the fill section slope is steeper than 4H:1V but net steeper than 3H:1V, the Design Clear Zone distance is modified by the recovery area formula (Figure 700-3) and is referred to as the recovery area. The basic philosophy behind the recovery area formula is that the vehicle can traverse these slopes but cannot recover (control steering) and, therefore, the horizontal distance of these slopes is added to the Design Clear Zone distance to form the recovery area.

** This figure also applies to limited access state highways in cities and median areas on managed access state highways in cities. See 700.04 for guidance on managed access state highways within incorporated cities.

*** See 700.03 for the definition of traveled way.Design Clear Zone Distance Table

Figure 700-1

Roadside Safety Design ManualPage 700-12 May 2006

Design Clear Zone Inventory Form Figure 700-2a

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Design Manual Roadside SafetyMay 2006 Page 700-13

Design Clear Zone Inventory Form Figure 700-2b

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Roadside Safety Design Manual Page 700-14 May 2006

Recovery AreaFigure 700-3

* Recovery area normally applies to slopes steeper than 4H:1V, but no steeper than 3H:1V. For steeper slopes, the recovery area formula may be used as a guide if the embankment height is 10 feet or less.

Formula: Recovery area = (shoulder width) + (horizontal distance) + (Design Clear Zone distance - shoulder width)

Example: Fill section (slope 3H:1V or steeper)

Conditions: Speed – 45 mph Traffic – 3000 ADT Slope – 3H:1V

Criteria: Slope 3H:1V – use Recovery area formula

Recovery area = (shoulder width) + (horizontal distance) + (Design Clear Zone distance - shoulder width) = 8 + 12 + (17-8) = 29 feet

Design Manual Roadside Safety May 2006 Page 700-15

Cut section with ditch (fore slope 4H:1V or flatter)

Conditions: Speed - 55 mph Traffic - 4200 ADT Slope - 4H:1V

Criteria: Greater of (1) Design Clear Zone for 10H:1V

Cut Section, 23 feet (2) 5 feet horizontal beyond beginning

of back slope, 22 feet

Design Clear Zone = 23 feet

Case 1

Cut section with ditch (fore slope 3H:1V or steeper and back slope steeper than 3H:1V)

Conditions: NA

Criteria: 10 feet horizontal beyond beginning of back slope

Design Clear Zone = 19 feet

Case 2

Cut section with ditch (fore slope 3H:1V or steeper and back slope not steeper than 3H:1V)

Conditions: Speed - 45 mph Traffic - 3000 ADT Foreslope - 2H:1V Back slope 4H:1V

Criteria: Use recovery area formula

Recovery Area = (shoulder width) + (horizontal distance) + (Design Clear Zone distance - shoulder width)

= 6 + 6 + (15 - 6) = 21 feet

Case 3

Design Clear Zone for Ditch SectionsFigure 700-4

Cut section with ditch (fore slope 4H:1V or flatter)

(1) Design Clear Zone for 10H:1V Cut Section, 23 ft

(2) 5 ft horizontal beyond beginning of back slope, 22 ft

Case 1 Cut section with ditch (fore slope 3H:1V or steeper and back slope steeper than 3H:1V)

Case 2 Cut section with ditch (fore slope 3H:1V or steeper and back slope not steeper than 3H:1V)

Criteria: Use recovery area formula

Recovery Area = (shoulder width) + (horizontal distance) + (Design Clear Zone distance -

Design Clear Zone = 23 ft

Edge oftraveled way

4H:1V 3H:1V

8 ft6 ftshld 3 ft

Design Clear Zone = 19 ft

Edge oftraveled w ay

3H:1V 2H:1V

10 ft6 ft3 ftshld

Recovery Area = 21 ft

Edge oftraveled way

2H:1V 4H:1V

6 ft6 ftshld

Cut section with ditch (fore slope 4H:1V or flatter)

(1) Design Clear Zone for 10H:1V Cut Section, 23 ft

(2) 5 ft horizontal beyond beginning of back slope, 22 ft

Case 1 Cut section with ditch (fore slope 3H:1V or steeper and back slope steeper than 3H:1V)

Case 2 Cut section with ditch (fore slope 3H:1V or steeper and back slope not steeper than 3H:1V)

Criteria: Use recovery area formula

Recovery Area = (shoulder width) + (horizontal distance) + (Design Clear Zone distance -

Design Clear Zone = 23 ft

Edge oftraveled way

4H:1V 3H:1V

8 ft6 ftshld 3 ft

Design Clear Zone = 19 ft

Edge oftraveled w ay

3H:1V 2H:1V

10 ft6 ft3 ftshld

Recovery Area = 21 ft

Edge oftraveled way

2H:1V 4H:1V

6 ft6 ftshld

Cut section with ditch (fore slope 4H:1V or flatter)

(1) Design Clear Zone for 10H:1V Cut Section, 23 ft

(2) 5 ft horizontal beyond beginning of back slope, 22 ft

Case 1 Cut section with ditch (fore slope 3H:1V or steeper and back slope steeper than 3H:1V)

Case 2 Cut section with ditch (fore slope 3H:1V or steeper and back slope not steeper than 3H:1V)

Criteria: Use recovery area formula

Recovery Area = (shoulder width) + (horizontal distance) + (Design Clear Zone distance -

Design Clear Zone = 23 ft

Edge oftraveled way

4H:1V 3H:1V

8 ft6 ftshld 3 ft

Design Clear Zone = 19 ft

Edge oftraveled w ay

3H:1V 2H:1V

10 ft6 ft3 ftshld

Recovery Area = 21 ft

Edge oftraveled way

2H:1V 4H:1V

6 ft6 ftshld

Roadside Safety Design Manual Page 700-16 May 2006

Guidelines for Embankment BarrierFigure 700-5

Design Manual Roadside Safety May 2006 Page 700-17

Mailbox Location and Turnout DesignFigure 700-6

Roadside Safety Design Manual Page 700-18 May 2006

Glare ScreensFigure 700-8

Roadside Safety Design ManualPage 700-16 English Version August 1997

Glare ScreensFigure 700-7

Chain Link

Glare ScreensFigure 700-8

Roadside Safety Design ManualPage 700-16 English Version August 1997

Vertical Blades

Glare ScreensFigure 700-8

Roadside Safety Design ManualPage 700-16 English Version August 1997

Concerete Barrier