Cross‐section and Roadside Elements  1.3‐1 

SECTION 1, CHAPTER 3

Cross‐section and Roadside Elements 

3.1 Introduction 

ThebasicdesigncontrolsdescribedinChapter1‐2influencethewidth,functionalareasofthecross‐section,andaccommodationfordifferentusers.Thecarefulselectionofroadwaycross‐sectionelements(sidewalks,bicycleaccommodation,motorvehiclelanes,etc.)isneededtoachieveacontext‐sensitivedesignthataccommodatesalluserssafely.Thischapterdescribesthevariouscomponentsofroadwaycross‐section,includingrangesofrecommendeddimensionsfordifferent'areaandroadwaytypes.Thischapteralsodescribesbasicelementsofroadsidedesign.

3.1.1 Multimodal Accommodation and Context Sensitivity 

Thegoalsofselectinganappropriateroadwaycross‐sectionandthedesignofroadsideelementsare: Todevelopatransportationinfrastructurethatprovidesaccessforall,arealchoice

ofmodes,andsafetyinequalmeasureforeachmodeoftravel.

Toensurethattransportationfacilitiesfittheirphysicalsettingandpreservescenic,historic,aesthetic,community,andenvironmentalresourcestotheextentpossible.

Insomecases,thesedesignobjectivescanbeachievedwithintheavailableright‐of‐way.Inothercases,additionalright‐of‐wayneedstobeacquired.Sometimes,tradeoffsinuseraccommodationneedtobemadetopreserveenvironmentalorcommunityresourceslocatedwithinoradjacenttotheright‐of‐way.Inthesesituations,thechallengeistoprovideaccessandsafetyforeachmodeoftravel.Inothersituations,itwillbenecessarytomodifyenvironmentalcharacteristicsinordertoprovidesafeaccommodation.Toassistdesigners,thisPlanprovidesoptionsandrecommendationsforsafeaccommodationofpedestrians,bicycles,vehiculartraffic,andpublictransitoperations.Generalapproachestocross‐sectionformulationarediscussedinSection3.2.

1.3‐2  Cross‐section and Roadside Elements   

Approachestocross‐sectionformulationarepresentedfromright‐of‐wayedgetoedge,ratherthanthemoretraditionalmethodfromcenterlineout.Throughthisapproach,accommodationofpedestriansandbicyclistsispositivelyencouraged,madesafer,andincludedineverytransportationproject.Detaileddescriptionofthefollowingcross‐sectionelementsassociatedwithdifferentroadwayusersaredescribedinSection3.3: Pedestriansincludingpeoplerequiringmobilityaids

Sidewalks Shoulderuse Sharedlanes Sharedusepaths

Bicycles

Bicyclelanes Shoulderuse Sharedlanes Sharedusepaths

MotorVehiclesincludingtransit

Usableshoulders On‐streetparking Travellanes

Oncetheelementsassociatedwithroadwayusergroupsaredescribed,guidanceforassemblingcross‐sectionsisprovided.ThisguidancedescribestheelementstypicallyencounteredfortheroadwayandareatypesdefinedinChapter1‐2.

3.1.2 Additional Topics Covered 

Inadditiontocross‐sectionelementsspecificallyassociatedwiththemovementofpedestrians,bicycles,andmotorvehicles,thereareseveralothercross‐sectionelementsincludedinthischapterasdescribedbelow.

3.1.2.1 Public Transit Elements 

Publictransitoftenoperatesasamotorvehiclewithinthepublicright‐of‐way.Thereareseveraldesignfeatures,bothwithintheroadwayandonthesidewalk,thatshouldbeconsideredincross‐sectiondesign.ThesearediscussedinSection3.4andinclude: Busstops,and Dedicatedlanes.

The challenge is to balance the competing interests of different users in a limited 

amount of right‐of‐way and to provide access for 

all, a real choice of modes, and safety in 

equal measure for each mode of travel. 

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐3 

3.1.2.2 Other Cross‐section Design Features 

Section3.5describestheapplicationofthefollowingfeatures: Mediansandauxiliarylanes, Curbs,berms,andedging,and Cross‐slopes.Therelationshipoftheseaspectsofcross‐sectiondesigntomultimodalaccommodationarealsodescribed.

3.1.2.3 Utilities and Signage 

Utilitiesarefrequentlylocatedwithintheroadwayright‐of‐way.ConsiderationsfortheplacementofutilitiesandroadsidesignageisdiscussedinSection3.6.

3.1.2.4 Right‐of‐Way 

Section3.7describeshowcross‐sectionelementstranslateintoright‐of‐wayrequirements.Thenecessaryright‐of‐wayisthesummationofalldesiredcross‐sectionelements(sidewalks,bufferstrips,curbsandberms,shouldersandon‐streetparking,bicyclelanes,travellanes,andmedians)androadsideelements(clearzones,barriers,drainageditches,utilitypoles,signage,snowstorageareaandmaintenanceareas).

3.2 Multimodal Accommodation  

Oncethepurposeandneedforaprojectisdefined,thedesignershoulddeterminethemostappropriatewaytoprovidesafe,convenient,andcomfortableaccommodationforalluserswithinthecontextoftheproject.ThisprocessisaidedbyinputfromthepublicandtheCityofNorwalkduringprojectplanning.Descriptivecasesforarangeofaccommodationsareprovidedtoassistthedesigner’sunderstandingofuseraccommodationapproachesthatmaybeapplicableinavarietyofcontexts.Thefirstthreecasesdescriberoadwaysectionsboundedbycurbandsidewalk.ThesecasesaremostlikelytobefoundinthemoredenselydevelopedareatypesintroducedinChapter1‐2(Urban,SuburbanVillageandTownCenter,SuburbanHighDensity,andRuralVillage).Theremainingtwocasesareforareaswithoutcurbandsidewalkandaremostlikelytobefoundinthelessdevelopedareatypes(RuralNatural,RuralDeveloped,andSuburbanLowDensity).Thesedescriptivecasesarenotintendedtobe“typicalsections”appliedtoroadwayswithoutregardfortravelspeeds,vehiclemix,adjacentlanduse,trafficvolumes,andotherfactorssinceapplicationof“typicalsections”canleadtoinadequateuseraccommodation(underdesign)orsuperfluouswidth(overdesign).Typicalsectionsalsoleavelittleroomfor

Multimodal Accommodation Performance Goal:  The designer should provide safe, convenient, and comfortable travel for all roadway users. 

1.3‐4  Cross‐section and Roadside Elements   

judgmentreflectingthepurposeandcontextofindividualprojectsandcanoversimplifytherangeofvaluesthatmaybeselectedforeachelementofthecross‐section.Inthefollowingdescriptions,themultimodalaccommodationcasesareconceptualandreflectarangeofpotentialdimensionsforeachelement.Oncethedesignerdeterminesthemultimodalaccommodationdesiredfortheproject,thedesignershouldselectspecificdimensionsforeachcross‐sectionelementwithintherangesprovidedlaterinthischapter.Whenassembled,thespecificelementsinfluencethenecessaryright‐of‐waytoachievetheaccommodationdesiredfortheproject.Thisdesiredcross‐sectioncanthenbecomparedtoenvironmentalconstraintsandavailableright‐of‐way.Ifnecessary,additionalright‐of‐wayrequirementscanbeidentifiedand/orfurtherrefinementstothecross‐sectioncanbemade.

3.2.1 Case 1: Separate Accommodation for All Users 

Case1providesthemaximumseparateaccommodationforallmodesoftravel,asillustratedinExhibit3‐1.Thisisoftenthepreferredoptionintermsofprovidingsafe,convenient,andcomfortabletravelforallusers.Itisusuallyfoundinareasofmoderatetohighdensity(urbanareas,suburbanvillagesandtowncenters,suburbanhighdensityareas,andruralvillages)withcurbedroadways.Case1providesforthemaximumseparationofusers,whichcanprovidethehighestlevelofsafetyandcomfortforallusersinareaswithhighlevelsofactivityorwherelargespeeddifferentialsbetweenthemotorizedandnon‐motorizedmodesarepresent.Case1usuallyrequiresthemostwidth.Inlocationswherethespeeddifferentialbetweendifferentroadwayusersissmall,oroverallactivityislow,Case1maynotbenecessarytosafelyaccommodateallusers.However,insomeinstances,thiscasemightbeachievedbyreallocatingspacewithinanexistingroadway,thuseliminatingpotentialimpactstotheroadsideenvironment.Thiscasemightbeconsideredinawidevarietyofconditionsincluding:areaswithmoderatetohighpedestrianandbicyclevolumes;areaswithmoderatetohighmotorvehiclespeedsandtrafficvolumes;andareaswithoutsubstantialenvironmentalorright‐of‐wayconstraints.InCase1,pedestriansareprovidedwithasidewalkseparatedfromtheroadwaybyaraisedcurbandpreferablyalandscapedbuffer.Theclearwidthofthesidewalkshouldbesufficienttoallowpedestriansorwheelchairuserstopasswithoutinterferingwitheachothers’movement(atleast5feetexcludingthecurbandclearfromitemsalongthesidewalksuchasfirehydrants,signs,treesandutilitypoles).Sidewalksshouldbeprovidedonbothsidesofthestreetunlessthereisaconditionthatsuggeststhatasidewalkisnotneededononesideofthestreet.Thismighthappen,forexample,ifthereisphysicalimpedimentthatwouldprecludedevelopmentononesideofthestreet,suchasarailroadtrackorstream.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐5 

Exhibit 3‐1  Case 1: Separate Accommodation For All Users 

Provisionofastripedbicyclelaneorshouldersuitableforbicycleuse(4feetminimum,5feetpreferred)encouragescycliststousetheroadway.Thebicyclelane/shoulderalsoprovidesforadditionalseparationbetweenmotorvehicletrafficandpedestrians.Ifon‐streetparkingispresent,thebicyclelaneshouldbeatleast5feetwidesothatthecyclistisprovidedwithanadditionalbufferalongtheparkedcars.Motorvehiclesareaccommodatedwithintravellaneswideenoughtoeliminateencroachmentbywidervehiclesoneithertheadjacentbicyclelaneorontheopposingmotorvehicletravellane.Inadditiontoprovidingspaceforbicycles,shouldersalsoaccommodateemergencystopping,maneuvering,andotherfunctions.Whereon‐streetparkingisprovided,shouldersorbicyclelanesshouldbemaintainedbetweenon‐streetparkingandthetravellane.

3.2.2 Case 2: Partial Sharing for Bicycles and Motor Vehicles 

ThereareinstancesinwhichthewidthnecessarytoprovideaccommodationforCase1isnotavailable.Therearealsoinstanceswheresomesharingandoverlapbetweenbicyclistsandmotorvehicletrafficisacceptabletoachieveotherenvironmentalordesignobjectives.Case2describesanapproachtomultimodalaccommodationinthesesituationsandisillustratedinExhibit3‐2.Case2iscommoninareasofmoderatetohighdensity(urbanareas,suburbanvillagesandtowncenters,suburbanhighdensityareas,andruralvillages),wherecurbedroadwaysectionsandseparatesidewalksareprovided.Pedestriansareprovidedwithasidewalkseparatedfromtheroadwaybyaraisedcurbandpreferablyalandscapedbuffer,increasingthesafetyandcomfortofthepedestrian.Theclearwidthofthesidewalkshouldbesufficienttoallowpedestriansorwheelchairuserstopasswithoutinterferingwitheachother’smovement(atleast5feetexcludingthecurbandclearofotherroadsideobstructions).

1.3‐6  Cross‐section and Roadside Elements   

Exhibit 3‐2  Case 2:  Partial Sharing for Bicycles and Motor Vehicles 

InCase2,thereissomeoverlapbetweenthespaceprovidedforbicycleuseandthatprovidedformotorvehicletravel.SignsorpavementmarkingsindicatingthattheroadwayissharedbetweencyclistsandmotorvehiclesareappropriateforCase2roadways.Thistypeofaccommodationisoftenusedinareaswithlowmotorvehiclespeeds,lowtomoderatemotorvehicletrafficvolumes,andareasofenvironmentalorright‐of‐wayconstraintwhereasmallercross‐sectionisnecessary.Thedesignershouldcarefullyconsidertheallocationofwidthtotravellanesandbicyclelanes/shoulderstoprovidethebestbalanceofaccommodationbetweenbicyclesandmotorvehicles.Inmanyinstances,on‐streetparkingwillalsobeprovidedandadditionalwidthmaybeneededtoreduceconflictsbetweenbicyclesandtheadjacentparking.TherearedifferentpossibleconfigurationsoflanesandshoulderspossibleinCase2,butallfeaturesomeoverlapinthespaceneededbybicyclistsandmotorvehicles: Typicaltravellanescombinedwithnarrowshoulders(i.e.11‐to12‐footlaneswith

2‐to3‐footshoulders)providemaneuveringwidthfortruckandbustrafficwithinthetravellane;however,bicyclistsmaybeforcedtoridealongandoverthepavementmarkings.

Narrowtravellanescombinedwithwideshoulders(i.e.9to11‐footlaneswith4to8footshoulders)providegreaterseparationbetweenmotorvehicleandbicycletraffic,butmayresultinmotorvehicletrafficoperatingclosertothecenterlineoroccasionallyencroachingintotheopposingtravellane.

WidecurblaneshavealsobeenusedinCase2;however,studieshaveshownthatmotoristsandbicyclesarelesslikelytoconflictwitheachotherandmotoristsarelesslikelytoswerveintooncomingtrafficastheypassabicyclistwhenshoulderstripingisprovided.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐7 

3.2.3 Case 3:  Shared Bicycle/Motor Vehicle Accommodation 

InCase3,theaccommodationofbicyclesandmotorvehiclesissharedandseparatepedestrianaccommodationismaintainedasillustratedinExhibit3‐3.Case3ismostlikelytobefoundinthemostdenselydevelopedareas(urbanareas,suburbanvillagesandtowncentersandsomeruralvillages)whereright‐of‐wayismostconstrained.Itisalsoapplicabletomostresidentialstreetswherespeedsandtrafficvolumesarelow.

Exhibit 3‐3  Case 3: Shared Bicycle/Motor Vehicle Accommodation 

Pedestriansareprovidedwithasidewalkseparatedfromtheroadwaybyaraisedcurbandpreferablyalandscapedbuffer,increasingthesafetyandcomfortofwalkingalongthisroadway.Theclearwidthofthesidewalkshouldbesufficienttoallowpedestriansorwheelchairuserstopasswithoutinterferingwitheachother’smovement(atleast5feetexcludingthecurbandsidewalkclearofotherroadsideobstructions).InCase3,onelaneisprovidedforjointusebymotorvehiclesandbicycles.Thistypeofaccommodationisusedinthefollowingconditions:areaswithlowtomoderatemotorvehicletrafficvolumes;lowmotorvehiclespeeds;andareasofsevererightofwayconstraintwhereonlyaminimumpavementsectionisfeasible.SignsandpavementmarkingsindicatingthattheroadwayissharedbetweencyclistsandmotorvehiclesshouldbeprovidedforCase3roadways.On‐streetparkingisoftenfoundontheseroadwaysandseparateshouldersorbicyclelanesarenotavailable.

3.2.4 Case 4: Shared Bicycle/Pedestrian Accommodation 

Insparselydevelopedareas(suchasruralnatural,ruraldeveloped,andsuburbanlowdensityareas),curbedroadwaysectionsboundedbysidewalkarelesscommon.ThiscaseisillustratedinExhibit3‐4.

1.3‐8  Cross‐section and Roadside Elements   

Exhibit 3‐4  Case 4: Shared Bicycle/Pedestrian Accommodation 

Intheseareas,pedestriansandcyclistsareoftenaccommodatedontheroadwayshoulder.Thistypeofaccommodationmaybeappropriateforareaswithinfrequentpedestrianactivity.Inareaswithhigherpedestrianvolumes(eithercurrentoranticipated),thepedestrianaccommodationdescribedinCases1,2,and3isdesirable.Pavementstripingandapavedshoulder(atleast4‐feetwide)forsharedpedestrianandbicycleusehelpsdelineatethetravelwayformotorvehicles,thusincreasingsafetyforallusers.Widershouldersshouldbeprovidedasmotorvehiclespeedsandtrafficvolumesincrease.InCase4,motorvehiclesareaccommodatedwithintravellaneswideenoughtoeliminateencroachmentontheshoulderortheopposingmotorvehiclelane.ForCase4,thedesignershouldcarefullyconsidertheallocationofright‐of‐waybetweentravellanesandshoulders.Forexample:

Typicaltravellanescombinedwithwideshoulders(i.e.11or12‐footlaneswith6‐footorwidershoulders)provideforincreasedseparationbetweenpedestrians,bicyclistsmotorvehicles.Widershouldersalsoprovideclearanceforemergencystoppingandmaneuvering.

Typicaltravellanescombinedwithnarrowshoulders(i.e.11or12‐footlaneswith4‐footshoulders)providemaneuveringwidthfortruckandbustrafficwithinthetravellane,reducingencroachmentintoopposinglanesandtheshoulder.However,conflictsbetweenbicyclesandpedestriansaremorelikely.

Narrowtravellanescombinedwithwideshoulders(i.e.,10to11‐footlaneswith6to8footshoulders)providegreaterseparationbetweenbicyclistsandpedestrians,butmayresultinmotorvehicletrafficoperatingclosertothecenterlineorencroachingontheshoulder.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐9 

3.2.5 Case 5: Shared Accommodation for All Users 

Vehicles,bicycles,andpedestriansaresometimesaccommodatedinonesharedtravellane,asillustratedinExhibit3‐5.Thisconditionoccurswhenthereislowuserdemandandspeedsareverylow,orwhensevereconstraintslimitthefeasibilityofprovidingshoulders.Thiscaseprovidesthesmallestpavementwidthwhileaccommodatingalluserseffectivelyonlyinlowvolume,lowspeedconditions.Fences,rockwalls,treelines,andotherroadsideconstraints,canfurtherrestrictemergencymovementbyallusers.Additionalunpavedshouldersorclearzonesshouldbecarefullyconsideredtoprovideadditionalflexibilityandsafety.Additionallyoff‐roadpathsshouldbeconsideredtoimprovetheaccommodationofpedestrians.Thesepathsdonotneedtofollowtheroadalignmentpreciselyandcansometimesavoidobstaclesthatprecludesidewalksandshoulders.

Exhibit 3‐5  Case 5:  Shared Accommodation for All Users 

3.2.6 Summary of Accommodation Option 

Exhibit3‐6providesasummaryofthemultimodalaccommodationoptionsavailabletothedesigner.

1.3‐10  Cross‐section and Roadside Elements   

Exhibit 3‐6  Summary of Multi‐modal Accommodation Options 

Case 1: Separate Accommodation for All Users Often the preferred option to provide safe, convenient, and

comfortable travel for all users. Appropriate for areas with moderate to high levels of

pedestrian and bicycle activity. Appropriate for roadways with moderate to high motor vehicle

speeds. Appropriate in areas without substantial environmental or

right-of-way constraints.

Case 2: Partial Sharing for Bicycles and Motor Vehicles

Used in areas where the width necessary to provide Case 1 accommodation is not available.

Under Case 2, pedestrians are provided with a sidewalk or separate path while space for bicyclists and drivers overlap somewhat.

Appropriate in areas with low motor vehicle speeds and low to moderate motor vehicle volumes.

Case 3: Shared Bicycle/Motor Vehicle Accommodation

Under Case 3, pedestrians remain separate but bicycle and motor vehicle space is shared.

Used in densely developed areas where right-of-way is constrained.

Also applicable to most residential/local streets where speeds and traffic volumes are low.

Case 4: Shared Bicycle/Pedestrian Accommodation

Under Case 4, pedestrians and bicyclists share the shoulder.

Common in rural or sparsely developed areas.

Appropriate for areas with infrequent pedestrian and bicycle use.

Case 5: Shared Accommodation for All Users

Under Case 5, all users share the roadway. Appropriate where user demands and motor vehicle speeds

are very low or when severe constraints limit the feasibility of providing separate accommodation.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐11 

3.3 Design Elements 

Oncetheapproachtomultimodalaccommodationisdetermined,thedesignershoulddeterminethedimensionsofeachelementtobeincludedinthecross‐section.Theseelementsareassembledtodevelopadesiredcross‐section.Thefollowingsectionsdescribethedimensionsofspecificcross‐sectionelementsthatservedifferentroadwayusers.

3.3.1 Pedestrians 

Pedestrianaccommodationshouldbeconsistentwiththeprojectcontext,includingcurrentoranticipateddevelopmentdensity,roadwaycharacteristics,right‐of‐waydimensionsandavailability,andcommunityplans.Optionsforpedestrianaccommodationincludesidewalks,shoulderuse,andsharedlanes,asdescribedbelow,andoff‐roadorsharedusepaths.Inadditiontothetypeofaccommodation,thedesignershouldincludeotherdesignfeaturesthatimprovethepedestrianenvironment.Forexample,thedesignercanconsiderselectingalowermotorvehicledesignspeedthatwillincreasethecomfortandsafetyofthefacilityforpedestrians.Similarly,thedesignershouldconsidergeometricfeaturesthatimprovethepedestrianenvironment,suchascrossingislands,curbextensions,andothertrafficcalmingfeaturesdiscussedinmoredetailinChapter1‐6.Thewalkingpathshouldhaveasmooth,stableandslipresistantsurfacethatdoesnotinducevibrationinwheelchairsandisfreeoftrippinghazards.TheserequirementsarefurtherdiscussedinChapter1‐4.

3.3.1.1 Sidewalks and Buffers 

Sidewalksarepavedareasprovidedalongtheedgesofroadwayssuitableforpedestrianuse.Sidewalksarethemostcommonaccommodationprovidedforpedestrians.Sidewalksaredesirableinallareaswherepedestrianactivityispresent,expected,ordesired.Sidewalksshouldbeprovidedinresidentialareas,nearschools,libraries,parks,andcommercialareas.Sidewalksshouldalsobeprovidedbetweentransitstopsandnearbydestinations.Sidewalksshouldbeprovidedtolinkresidentialareaswithnearbyemployment,shopping,andservicecenters.Inurbanareasorvillage/towncenters,raisedcurbandcurbcutrampsareusuallyprovidedwithsidewalks.Alandscapedbufferbetweenvehiculartrafficandthesidewalkcanprovidegreaterseparationfrommotorvehicles,increasingthecomfortandsafetyofpedestrians.Inruralorsuburbansettingsforminorarterialsorcollectorroadswith5feetormoreofbuffer

All roadways along which pedestrians are not prohibited should include an area where occasional pedestrians can safely walk, whether on unpaved walkways, on shoulders in rural or less developed areas, or on 

sidewalks in more urban areas.

1.3‐12  Cross‐section and Roadside Elements   

space,curbingmaynotbeneeded.On‐streetparking,shoulders,andbicyclelanescanalsoactassidewalkbuffers.

Dimensions and Clear Width 

ThespatialrequirementsofpedestriansaredescribedinChapter1‐2.Theminimumwidthforasidewalkis5feetexcludingthewidthofthecurb,althougha4footclearwidth(plusthewidthofthecurb)issufficienttobypassoccasionalobstructions,asillustratedinExhibit3‐7.Whendevelopingplans,thesidewalkissometimesmeasuredincludingthewidthofthecurb.Ifthismethodofmeasurementisused,theminimumwidthofsidewalkis5½feet.

Exhibit 3‐7  Clear Accessible Path 

Source: Adapted from the Guide for the Planning, Design, and Operation of Pedestrian Facilities, AASHTO, 2004. Chapter 3

Pedestrian Facility Design

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐13 

Widersidewalksaredesirablewheretherearehighpedestrianvolumesandwherethereisnobufferbetweenhighspeedorhighvolumeroadways.Sidewalkwidthsof6to12feetarepreferredformosttowncenterandurbanlocations.Verywidesidewalks(12to20+feet)arealsoencounteredinthesesettings.Commonwidthsoflandscapebufferarebetween2and6feet,althoughlargerbuffersarepossible.Ifthesidewalkisnotbufferedfrommotorvehicletraffic,thenthedesirabletotalwidthforacurb‐attachedsidewalkis6feetinresidentialareasand8feetincommercialareas.Sidewalkscommonlyaccommodatestreetfurniturewhichincludesitemssuchas,trees,utilities,trafficsignals,trafficsigns,streetlights,parkingmeters,bicycleparking,benches,andrefusebarrels.Additionally,sidewalksoftenabutfences,buildingedges,orvegetationalongtheiroutsideedge.Theseelementsinfluencetherequiredwidthnecessarytoaccommodatepedestrians,aspedestrianstendto“shy”fromtheseobstructions.Thedesignershouldconsiderthedesiredlocationforthesesidewalkfeaturesand,wheretheyexist,thedesignershouldprovideappropriateoffsets(orshydistances)tothepedestrianpath.TypicalshydistancesareillustratedinExhibit3‐8.

Exhibit 3‐8  Typical Shy Distances Between Sidewalk Elements and Effective Pedestrian Path 

Source: Adapted from the Guide for the Planning, Design, and Operation of Pedestrian Facilities, AASHTO, 2004. Chapter 3 Pedestrian Facility Design

Landscape buffers accommodate a variety of functions, including: safety separation, snow storage, 

street furniture, landscaping, utilities and traffic control devices.  As such, it is 

preferable that such buffers be at least 5 feet wide.. 

1.3‐14  Cross‐section and Roadside Elements   

Allnewandreconstructedsidewalksmustbeaccessibletoandusablebypersonswithdisabilities.Aminimumclearpath(WE)of3feetmustbecontinuouslyprovidedalongasidewalk.SidewalkdimensionsandclearwidthsmustconformtotheaccessibilityrequirementsestablishedunderConnecticutGeneralLaws.Toallowfreepassingofpedestrians,includingthosewithdisabilities,awalkwaythatisatleastfive‐feetwide(excludingthecurbwidth)andclearofobstructionsisrequiredatevery200‐feetintervals.Sidewalksarealsocrossedbydrivewaysandintersectedbystreets.ThesecrossingsaredescribedinmoredetailinChapter1‐4.Asageneralapproach,thesidewalkshouldbecontinuousacrossdrivewaysandincludeappropriatetransitionsforthegradechangesassociatedwiththeseinterfaces.Formostdriveways,itisdesirableforthesidewalkelevationtocontrolthedrivewaydesign,ratherthanforthedrivewaytocutthroughthesidewalk.However,highvolumedrivewaysordrivewaysexitinghighspeedroadsmaybemoreappropriatelydesignedasintersections,withlevelconnectionsbetweentheroadwayandthedriveway.Inthesecases,pedestrianrampsandcrosswalksshouldbeincludedtoprovideacontinuouspathoftravel.AllfacilitiesshouldcomplywithADArequirementsincludingthesidewalks,pedestrianrampsandcrosswalks.

Placement 

Indevelopedareas,continuoussidewalksshouldbeprovidedonbothsidesofaroadway,minimizingthenumberofpedestriancrossingsrequired.Ifasidewalkisprovidedononlyonesideofaroadway,thecontextoftheroadwayshouldbethebasisforthisdecision.Forexample,inundevelopedorlow‐densityareas,orwheredevelopmentisheavilyconcentratedononesideoftheroadway,orthereareasignificantnumberofpublicshadetrees,sidewalksononlyonesideoftheroadmaybesufficient.Inthesecases,thesidewalkshouldbeprovidedonthesidethatminimizesthenumberofpedestriancrossings.Crosswalksshouldbeprovidedatreasonableintervals(typicallyevery200to300feetwithmaximumseparationindevelopedareasofapproximately500feet).

3.3.1.2 Shoulder Use 

Inareaswherepedestrianvolumesarelow,orwherebothtrafficvolumesandspeedarelow,apavedusableshoulder,asdescribedinSection3.3.3.1,canprovidepedestrianaccommodation.Thisoccursprimarilyinruralnaturalareas,ruraldeveloped,andsomesuburbanlowdensityareas.Onmostroadwaysthroughsparselydevelopedareas,aminimum4‐footshoulderisusuallyadequateforpedestrianuse.Awidershoulderisdesirablewhenthereissignificanttrucktrafficorhightrafficspeeds.Thewidthofshouldersisusuallydeterminedthroughanassessmentofpedestrian,bicycle,andmotorvehicleneeds.Thedecisiontouseshouldersratherthansidewalksorparallelpathsshouldconsiderexistingandfuturepedestrianvolumes.Evenwithlowpedestrianvolumes,itisdesirabletoprovidesidewalksorpathstoserveschools,libraries,shopsandtransitstops.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐15 

3.3.1.3 Shared Lanes 

Walkingwithintravellanesmaybeappropriateforsomeroadwayswithverylowtrafficvolumesandvehiclespeeds.However,sidewalksorusableshouldersarethepreferredaccommodation.Beforedecidingtoprovidesharedlanesastheonlypedestrianaccommodation,thedesignershouldbecertainthatthetrafficvolumesandvehiclespeedswillbelowenough,nowandinthefuture,sothatallpedestrianscancomfortablyusethestreet.

3.3.1.4 Off Road and Shared Use Paths 

Asharedusepathisadedicatedfacilityforpedestrians,bicyclists,rollerbladers,etc.Althoughsidewalksaregenerallypreferred,off‐roadpathsaresometimessuitableinruralandsuburbanlow‐densityareas.Thepathshouldprovidethesameconnectivityastheroadwaybutcanbesetbackfromtheroadwayanditsroutecandeviatearoundsensitiveenvironmentalareas.ThisisdiscussedindetailinChapter1‐4.TheU.S.AccessBoardguidelinespresentedinitsproposedGuidelinesforOutdoorDevelopedAreasprovideadditionalinformationonthedesignofpathsasdoesAASHTO’s2012GuidefortheDevelopmentofBicycleFacilities.

3.3.2 Bicycles 

Bicycleaccommodationshouldalsobeconsistentwiththeproject’scontext,roadwaycharacteristics,right‐of‐way,communityplans,andthelevelofserviceprovidedforthebicyclist.Thedesignershouldensurethatbicycleaccommodationisbasedonanticipateddevelopment,communityplans,andtheexpectedlevelofskilloftheintendedbicyclist.Bicyclesmaybepresentonallhighwayswheretheyarepermitted(bicyclesaretypicallyexcludedfromfreeways).Inadditiontodeterminingthetypeofaccommodationforbicyclists,thedesignershouldincludeotherdesignfeaturesthatimprovethesafetyandcomfortoftheroadwayforbicyclists.Forexample,ifmotorvehiclespeedsaretoohigh,thedesignershouldconsiderselectingalowermotorvehicledesignspeedtoincreasethecomfortandsafetyofthefacilityforbicycles.Additionally,thedesignercouldconsidernarrowingmotorvehiclelanestoprovidewidershoulders.Inconstrainedcorridors,evenafewfeetofstripedshouldercanmaketravelingalongaroadwaymoreaccommodatingforbicycles.Specificdesignfeaturesthatcanmakeroadwaysmorecompatibletobicycletravelincludeuniformwidths(wherepossible),bicycle‐safedrainagegrates,smoothpavements,adequatesightdistances,andtrafficsignalsthatdetectandrespondtobicycles.Thesedesignfeaturesshouldbeincludedonallroadways.Widecracks,joints,ordrop‐offsattheedgeofthetraveledwayparalleltothedirectionoftravelcantrapabicyclewheelandcauselossofcontrol,ascanholesandbumpsinthepavementsurface.Theseconditionsshouldbeavoidedonallroadways.

1.3‐16  Cross‐section and Roadside Elements   

Drainageinletgratesandutilitycoversarepotentialobstructionstobicyclists.Therefore,bicycle‐safegratesmustbeused,andgratesandcoversshouldbelocatedtominimizesevereand/orfrequentavoidancemaneuveringbycyclists.Inletgratesorutilitycoversinthepathofbicycletravel,mustbeinstalledflushwiththepavementsurface.Gratesshouldbehydraulically‐efficientversionsthatdonotposeahazardtocyclists.ThespatialrequirementsofbicyclesaredescribedinChapter1‐2.Fordesignpurposesawidthof4or5feetiscommonlyusedtoaccommodatebicycletravel.Thisportionoftheroadwayshouldhaveadequatedrainagetopreventponding,washouts,debrisaccumulationandotherpotentiallyhazardoussituationsforbicyclists.Approachestobicycleaccommodationincludebicyclelanes,theuseofshoulders,andsharedroadways.Off‐roadshared‐useorbicyclepathsarealsoanoptionforbicycleaccommodationinsomelimitedcases.Also,insomecases,novicebicyclistsandchildrenalsousesidewalksforcycling.TheFHWA’sBicycleCompatibilityIndexandAASHTO’s2012GuidefortheDevelopmentofBicycleFacilitiesservesasusefultoolsforreviewingthesuitabilityofvariousapproachestobicycleaccommodation.Thetypesofaccommodationtypicallyusedaredescribedinthefollowingsections.

3.3.2.1 Bicycle Lanes 

Bicyclelanesareportionsofthetraveledwaydesignedforbicycleuse.Bicyclelanesshouldbeincorporatedintoaroadwaywhenitisdesirabletodelineateavailableroadspaceforpreferentialusebybicyclistsandmotorists,andtoprovideformorepredictablemovementsbyeach.Bicyclelanemarkingscanincreaseabicyclist’sconfidenceinmotoristsnotstrayingintotheirpathoftravel.Likewise,passingmotoristsarelesslikelytoswervetotheleftoutoftheirlanetoavoidbicyclistsontheirright.Bicyclelanesaregenerallyconsideredthepreferredtreatmentforbicycleaccommodation.Insomecases,theyareneithernecessarynordesirableduetolow‐trafficconditions.Bicyclelanesaremostcommonlyimplementedinurbanandsuburbansettings.Frequently,bicyclelanesarefoundincombinationwithon‐streetparking,raisedcurbs,andsidewalks.Intheseareas,thebicyclelanealsoservestheroadwayshoulderfunctionsassociatedwithmotorvehicles,describedinmoredetaillaterinthischapter.Contraflowbicyclelanesmaybeappropriateonone‐waystreetstoincreasecyclistsconnectivity.ThetreatmentofbicyclelanesatintersectionsandtheirrelationshiptoturninglanesisprovidedinChapter1‐4.BicyclelanesproposedonallroadwaysunderStatejurisdictionwillrequireapprovalfromtheOfficeofStateTrafficAdministration(OSTA).

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐17 

Dimensions and Clear Width 

Theminimumwidthforbicyclelanesis4feetwhenthebicyclelaneisadjacenttotheedgeofpavement;however,5‐footbicyclelanesarepreferredformostconditions,especiallywhenthelaneisadjacenttocurbsideparking,verticalcurb,orguardrail.Onroadwayswithhigherspeeds(50milesperhourormore)orhighervolumesoftrucksandbuses(30ormoreperhour)theminimumbicyclelanewidthis5feetand6‐footbicyclelanesaredesirable.Bicyclelaneswiderthan6feetaregenerallynotusedsincetheymayencourageinappropriateusebymotorvehicles.

Placement 

Bicyclelanesareone‐wayfacilitiesthatcarrybiketrafficinthesamedirectionastheadjacentmotorvehicletraffic.Bicycle‐specificwrong‐waysignagemaybeusedtodiscouragewrong‐waytravel.Onone‐waystreets,bicyclelanesshouldbeprovidedalongtherightsideoftheroadunlessunusualconditionssuggestotherwise.Bicyclelanesshouldbedesignatedbya6‐inchsolidwhitelineontherightedgeofthemotorvehicletravellane.Bicyclelaneswithinroadwaysshouldnotbeplacedbetweenaparkinglaneandthecurb.Thissituationcreatespoorvisibilityatintersectionsanddrivewaysanditisdifficulttopreventdriversfromparkinginthebicyclelane.Bicyclelanesshallbedesignatedbyasolidwhitelineontherightedgeofthemotorvehicletravellane(4‐inchminimum,6‐inchpreferred)andbicyclesymbolorwordmarkings.Thismarkingshouldchangetoabrokenwhitelinebeforeanyintersectionsontherightside,providingsufficientdistanceformotoriststomergetotherightsideoftheroadwaybeforemakingaright‐turn.A4‐inchsolidwhitelineorparkingspacemarkingsontherightedgeofthebicyclelanearerecommendedforaddeddelineationofthebicyclelanewhenadjacenttoparkingareas.Thesemarkingswillencourageparkingclosertothecurb,providinggreaterseparationbetweenbicycles,parkedcars,andmovingmotorvehicles.Thesemarkingscanalsodiscourageuseoftheparkinglaneandbicyclelaneformotorvehicletravelwhenparkingactivityislight.Additionalbicyclelanepavementmarkings,asillustratedinExhibit3‐9,andsignagecanalsobeinstalledtoreinforcetheintendeduseofthebicyclelane.

3.3.2.2 Shoulder Use 

Muchlikebicyclelanes,pavedshouldersprovidespaceforbicyclingoutsideofthetravellanes.Onedifferencebetweenshouldersandbicyclelanesisthatshouldersareusuallyusedforbicycleaccommodationinruralandsuburbanlowdensityareas,whereon‐streetparking,curbs,andsidewalksarerarelyencountered.Intheselocations,shouldersmayprovidesharedaccommodationforpedestriansandbicyclists.Anotherdifferencebetweenshouldersandbicyclelanesisthatthewidthofshouldersisusuallydeterminedthroughanassessmentofcombinedpedestrian,bicycle,andmotorvehicleneeds,discussedlaterinthischapter,inthecontextofprojectgoalsandavailablespace.Additionally,shouldersdonottypicallyincludebicyclelanepavementmarkings.

1.3‐18  Cross‐section and Roadside Elements   

Exhibit 3‐9  Bicycle Lane Pavement Markings 

Source: Manual on Uniform Traffic Control Devices, FHWA, 2009. Chapter 9 Traffic Control for Bicycle Facilities

Toprovidebicycleaccommodation,shouldersshouldbeatleast4feetwide.Themeasurementoftheusableshouldershouldnotincludetheshydistancefromacurborguardrailwherea5‐footminimumwidthisrecommended.Minimum5‐footshouldersarealsorecommendedinareaswithvehicularspeedsover50milesperhour,orwheretruckandbusvolumesexceed30vehiclesperhour,orinareaswithonstreetparking.Rumblestrips,raisedpavementmarkers,orembeddedreflectorsshouldnotbeusedwhereshouldersaretobeusedbybicyclists,unlessthereisaminimumclearpathof1‐footfromtherumblestriptothetraveledwayand4feetfromtherumblestriptotheoutsideedgeofpavedshoulder.Inplacesadjacenttocurb,edging,guardrailorotherverticalobstacles,5feetbetweentherumblestripandtheoutsideedgeofpavementisdesirable.Withrumblestrips,thetotalwidthoftheshouldershouldbebetween7and8feet.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐19 

3.3.2.3 Shared Lanes 

Sharedlanesrefertouseofthenormaltravellanesbybothmotorvehiclesandbicyclists.Bylaw,bicyclistsmayusethetravellane.MostroadwaysinNorwalkhaveneithershouldersnorbicyclelanes.Thuslanessharedbymotoristsandbicyclistsarethemostcommonsituation.Lanesatleast14feetwidearegenerallywideenoughtopermitmotoriststopassbicyclistswithoutchanginglanes.Onlow‐volumeroadways,motoristswillgenerallybeabletopassbicyclistswithoutwaiting.Iftrafficvolumesareaboveacriticalthreshold,itisdesirabletoprovideenoughwidthforlanesharing.Incasesoflowspeed,lowtomoderatetrafficvolumes,andlowoccurrenceoftrucksandbuses,thesharedlanesmaybeadequatetosupportbicycling.Beforedecidingtoprovidesharedlanesasbicycleaccommodation,thedesignershouldbecertainthatthetrafficvolumesandmotorvehiclespeedswillbelowenoughsothatalltypesofbicyclistscancomfortablyusetheroadway.Inlocationswheresharedlanesareused,thedesignershouldconsiderusingsharedlanepavementmarkingssuchasthoseillustratedinExhibit3‐10.“BicyclesMayUseFullLane”signsasdefinedintheManualonUniformTrafficControlDevices(MUTCD)mayalsobeincludedinthedesign.Itisimportanttobearinmindthatsignsareonlyasupplementtoadequatebicycleaccommodationandshouldneverbeconsideredasubstituteforthem.

 

1.3‐20  Cross‐section and Roadside Elements   

Exhibit 3‐10  Shared Lane Pavement Markings 

Source: Manual on Uniform Traffic Control Devices, FHWA, 2009. Chapter 9 Traffic Control for Bicycle Facilities

3.3.2.4 Shared Use Paths 

Sharedusepathsarefacilitiesonexclusiveright‐of‐waywithminimalcrossflowbymotorvehicles.Sharedusepathsshouldbethoughtofasacomplementarysystemofoff‐roadtransportationroutesforbicyclistsandothersthatservesasanecessaryextensiontotheroadwaynetwork.Thepresenceofasharedusepathneararoadwaydoesnoteliminatetheneedtoaccommodatebicyclistswithinaroadway.Provisionofshared‐usepathsisparticularlysuitedtohigh‐speed,high‐volumeroadwayswherethecharacteristicsoftrafficflow,roadwaygeometricsandtrafficcontrolareincompatiblewithbicycleuse,exceptforadvancedcyclists.Similarly,shared‐usepathscanprovideabicyclingrouteparalleltofreeways,wherebicyclingisprohibited.Shared‐usepathsarealsoanoptioninareasoflimitedrightofwayorwhereenvironmentalorculturalresourceslimitthewidthofaroadwayandanearbypathwayisavailable.Finally,sharedusepathscanproviderecreationalamenitiesinwaterfrontareasornearotherattractions.

3.3.3 Motor Vehicles 

Themajorcomponentsoftheroadwaycross‐sectionservingmotorvehicletravelareusableshouldersoron‐streetparking,andtravellanes.Inadditiontothewidthoftheseindividualelements,therightlaneplusshoulderdimensionisimportantfordeterminingtheminimumwidthforatwo‐lanetwo‐wayroadway,asdescribedlaterinthischapter.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐21 

ThewidthrecommendationspresentedinthissectionarebasedonestablishedpracticesandsupplementedbyguidelinesfromAASHTOincludingtheGuideforAchievingFlexibilityinHighwayDesign.Flexibilityispermittedtoencourageindependentdesignstailoredtoparticularsituations.Forexample,designerscanseekexemptionsfromestablisheddesigncriteriaunderspecificconditionstoprovideforthepreservationofrural,suburban,andvillageroads.Thewidthassociatedwiththecross‐sectionelementsdescribedinthissectionisbasedonthespatialdimensionsofdesignvehiclesdiscussedinChapter1‐2.Thelargestvehiclelikelytousethefacilityonaregularbasisisusuallyselectedasthedesignvehicleandimpactstheselectionofshoulderandlanewidth.Usableshoulders,on‐streetparking,travellanes,andtheright‐laneplusshoulderdimensionaredescribedinthefollowingsections.

3.3.3.1 Shoulders 

Theuseofshouldersforpedestrianandbicycleaccommodationisdiscussedintheprevioussections.ShouldersarepavedandgradedareasalongthetravellanestoserveanumberofpurposesasshowninExhibit3‐11.Theyshouldbedelineatedbya4‐inchwidesolidwhitestripetoseparatethetravellaneandtheedgeofpavement.Shouldersdonotincludeon‐streetparkingsincetheshoulderscannotservethepurposeslistedinExhibit3‐11iftheyareoccupiedbyparkedcars.On‐streetparkinganditsrelationshiptopedestrianandbicycleaccommodationarediscussedlaterinthischapter.Duringtheplanningprocess,thedesignershouldselectanappropriateshoulderwidthgiventheroadway’scontext,purposeandneed,bicycleandpedestrianaccommodation,speed,andtransportationdemandcharacteristics.

Exhibit 3‐11  Minimum Shoulder Width (in feet) to Provide Various Functions  

Roadway Type Shoulder Function Arterials Collectors

Drainage of Traveled Way 1.0 1.0 Lateral Support of Pavement 1.5 1.0 Encroachment of Wide Vehicles 2.0 2.0 Off-tracking of Wide Vehicles 2.0 2.0 Errant Vehicles 3.0 2.0 Bicycle and Pedestrian Use 4.0 4.0 Emergency Stopping 6.0 6.0 Emergency Travel 6.0 6.0 Mail Delivery and Garbage Pickup 6.0 6.0 Law Enforcement Operations 8.0 6.0 Large Vehicle Emergency Stopping 10.0 10.0 Occasional Travel/Detours 10.0 9.0 Highway Maintenance 8.0 8.0 Source: Flexibility in Highway Design, AASHTO 2004. Chapter 6 Cross Section Elements

1.3‐22  Cross‐section and Roadside Elements   

Exhibit3‐12providesrangesofshoulderwidthfordifferentareaandroadwaytypes.Asshownabove,shouldersprovidemanyimportantsafetyandoperationaladvantagesandthedesignershouldstrivetoprovide6‐to8‐footshouldersformostarterials.Asdescribedintheprevioussections,ifshouldersareprovidedforpedestrianorbicycleaccommodationtheirminimumwidthshouldbe4feet.

Exhibit 3‐12  Widths of Usable Shoulders (In Feet) 

Roadway Type Area Type Arterials1 Collectors1 Local Roads

Rural Natural 4 to 12 4 to 10 2 to 8 Rural Developed 4 to 12 4 to 10 2 to 8 Rural Village 4 to 12 4 to 10 2 to 8 Suburban Low Density 4 to 12 4 to 10 2 to 8 Suburban High Density 4 to 12 4 to 10 2 to 8 Suburban Village/Town Center 4 to 12 4 to 10 2 to 8 Urban 4 to 12 4 to 10 2 to 8

Source: Flexibility in Highway Design, AASHTO 2004. Chapter 6 Cross Section Elements 1 Shoulder widths less than the values shown above may be used if approval from the City of Norwalk is obtained.

Situations where narrower shoulders may be considered are described below. Note: An additional 2-foot offset from the edge of the shoulder is required to vertical elements over 6-inches in height

(such as guardrail).

Minimum4‐footshouldersarerecommendedforallarterialsandcollectorsbecauseofthevaluetheyprovideforbicycleandpedestrian(particularlyinruralareas)accommodation,andmotorvehiclesafety.IfapprovalfromtheCityofNorwalkisobtained,shouldersnarrowerthan4feetmaybeusedinconstrainedareaswhereseparatepedestrianaccommodationisprovidedandsharedbicycle/motorvehicleaccommodationissuitable.Examplesoftheseconditionsarewheredesignspeedsarelessthan45milesperhourandtrafficvolumesarerelativelylow(lessthan4,000vehiclesperday),orwherethedesignspeedis30milesperhourorless.Theusableshoulderiscomposedofbothagradedshoulder,and,insomecases,roundingofgradetransitionsattheedgeoftheroadway,asshowninExhibit3‐13.Usableshouldershavethefollowingcharacteristics: Theareamusthaveasideslopeof1footverticalto6feethorizontal(1v:6h)or

flatter,includingroundedareasforgradetransitions.

Theareaisusuallyflushwiththeadjacentroadwayandmustbefreeofverticalobstructionshigherthan0.5feet(guardrail,walls,trees,utilitypoles).

Shouldersareusuallypaved.Ifunpaved,shouldersshouldbeflushwiththeroadwaysurfaceandsufficientlystabletosupportvehicularuseinallkindsofweatherwithoutrutting.Additionally,sufficientpavedwidthtoaccommodatebicyclesshouldbeprovided.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐23 

Anadditional2feetofclearanceshouldbeaddedtotheusableshoulderdimensiontoallowforanoffsettoverticalroadwayelementsover0.5feetinheight,suchasguardrail,bridgerail,concretebarrier,walls,trees,utilitypoles,etc.

Usableshouldersmustbeclearedofsnowandiceduringthewintermonthsinordertofunctionproperly.Therefore,itisoftenpracticalforusableshoulderstobepaved.

Theedgeoftheusableshouldershouldnotbelocatedattheedgeofright‐of‐way.Anoffsetisrequiredforroadmaintenance,snowremoval,andplacementofsigns.

Incertaininstances,usuallytocontroldrainage,theuseofamountablebermoredgingispermissiblewithinashoulderarea,asdiscussedlaterinthischapter.

Atintersections,usableshouldersmaybeeliminatedinordertobetterprovideforturningmovementsorshortenpedestriancrossingdistances.Howeverprovisionsforbicyclistsmustbeconsideredwhentheshoulderiseliminatedatintersections.

1.3‐24  Cross‐section and Roadside Elements   

Exhibit 3‐13  Usable Shoulders 

Source: Adapted from A Policy on Geometric Design of Highways and Streets, AASHTO 2011, Chapter 4 Cross-Section Elements.

3.3.3.2 On‐street Parking 

On‐streetparkingisprovidedinplaceofusableshouldersinmanydifferentsettingstosupportadjacentlanduses.Ifshouldersareusedtoaccommodatebicyclesoutsideoftheon‐streetparkingzone,thedesignershouldmaintainthecontinuityofbicycleroutesthroughtheparkingzonethroughtheuseofbicyclelanesor,ataminimumsharedlanemarkings.Curbextensionsareaneffectivedesigntreatmentatintersectionsandpedestriancrossingsthathelpprohibitillegalparking,reducethecrossingdistanceforpedestrians,andimprovevisibility.Curbextensionscanbecarefullydesignedsothatbicycletravelisnotcompromisedandshouldonlybeusedinconjunctionwithactivecurb‐sideuses(suchasparkingortransitstops).Curbextensionsshouldextendnofurtherthan6feetfromthecurb.Sidewalksarealmostalwaysprovidedadjacenttoon‐streetparking.Parkingprovidesabufferbetweenmotorvehicletrafficandpedestriansonthesidewalk.On‐streetparkingcanalsoinfluencethetrafficflowalongroadways,sometimesresultinginreducedspeeds,reducedcapacity,andincreasedconflictsforbothbicycleandmotorvehicletraffic.AlthoughnotcommononNorwalkroadwaysnotunderstatejurisdiction,on‐streetparkingshouldnotbeprovidedwithhighdesignspeeds(over45milesperhour)duetoitsimpactsontrafficflowandthesafetyimplicationsofparkingmaneuversathighspeeds.Parallelon‐streetparkingrequiresaminimumof7feetofpavedcross‐sectioninadditiontotherequiredtravellanewidthandshouldnotbepermittedwherethiswidthisnotavailable.Forareaswithhighturnover,areaswithtruckloading,

Parking often replaces usable shoulders in village, town center, and urban settings.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐25 

andareaswithbusstops,8feetofwidthisrecommended.Parkinglanewidthsof10feetaredesirableinareaswithsubstantialamountsoftruckparkingorbusstops.Widerparkinglanes,upto12feet,areestablishedtopreserveroadwaycapacityforpossibleconversiontotravellanes,orforuseastravellanesduringpeakperiods.However,parkingregulationsandenforcementarerequiredtopreservethedesiredoperationalcharacteristicsoftheroadwayintheseinstances.Requirementsforthestripingandsignageofparallelon‐streetparkingisprovidedintheManualonUniformTrafficControlDevices(MUTCD).Parkingcanbemarkedandregulatedbytime‐of‐dayorotherrestrictionsinhighdemand/highturnoverareas.Inotherlocations,parkingmaybepermitted,butisnotformallymarkedorregulated.AccessibleparkingspacesshouldbeprovidedinnumbersagreedtobytheCityofNorwalkortheState,andshouldbelocatedattheendofablocksothattheyarenearacurbcutramp.EachaccessibleparkingspaceshouldbedesignatedwithanInternationalSymbolofAccessandbeconsistentwiththerequirementssetforthintheConnDOTHighwayDesignManualatleastonroadwaysunderStatejurisdiction,butpreferablyonallroads.ParkingshouldalsomeetcurrentAmericanswithDisabilitiesAct(ADA)designguidelines.On‐streetangleparkingiscurrentlypermittedinsomeruralvillages,suburbantowncenters,andurbanareas.Whereangleparkingiscreatedorretained,thedesignershouldconsiderback‐inangleparkingasanalternativetotraditionalhead‐inangleparking.Accessibleparkingshouldbeprovidedwithanadjacent5‐footto8‐footaccessaisle.Eightfootacceptableaislescanaccommodatevanswithlifts.AllparkinglocatedonStateroadways,includingNoParking,durationalparking,handicapparking,andloadingzonesrequireapprovalfromtheOfficeofStateTrafficAdministration(OSTA).TheCTGeneralStatutesprohibitson‐streetparkingwithin10feetofafirehydrantandwithin25feetofanintersection,markedcrosswalkorstopsign.

3.3.3.3 Travel Lanes 

Travellanesarethecomponentoftheroadwaycrosssectionthatservemotorvehicletravel,orinsomecases,jointuse.Inmostcases,thetravellanesarethewidestcomponentoftheroadwaycross‐section.Thenumberoflanesineachdirectionshouldbedeterminedbasedonthedesignyeartransportationdemandestimatesandtheselecteddesignlevelofservicedeterminedintheprojectplanningprocess(seeChapter1‐2).Insomeinstancesitmaybepossibletoreducethenumberoftravellanestoprovidesidewalks,landscapebuffers,bicyclelanes,andcrossingislands.Thewidthoftravellanesisselectedthroughconsiderationoftheroadwaycontext,approachtomultimodalaccommodation,thephysicaldimensionsofvehicles,speeds,andothertrafficflowcharacteristics.Thenormalrangeofdesignlanewidthisbetween

1.3‐26  Cross‐section and Roadside Elements   

10and12feet.Travellanesbetween11and12feetinwidthareusuallyselectedfordesigncross‐sectionsandareparticularlydesirableforroadwayswithhigherdesignspeeds(45milesperhourormore),highertrafficvolumes(2,000ormorevehiclesperday),orhighertruckandbusactivity(greaterthan30perhour).Exhibit3‐14summarizestravellanewidthsforvariousareaandroadwaytypes.OnStateroadways,lanewidthsshouldbeconsistentwiththeDepartment’sHighwayDesignManual.

Exhibit 3‐14  Range of Travel Lane Widths (In Feet) 

Roadway Type Area Type Arterials1 Collectors2 Local Roads

Rural Natural 11 to 12 10 to 12 9 to 12

Rural Developed 11 to 12 10 to 12 9 to 12

Rural Village 11 to 12 10 to 12 9 to 12

Suburban Low Density 11 to 12 10 to 12 9 to 12

Suburban High Density 11 to 12 10 to 12 9 to 12

Suburban Village/Town Center 11 to 12 10 to 12 9 to 12

Urban 11 to 12 10 to 12 9 to 12 1 Lane widths less than the values shown above may be used if approval from the City of Norwalk is obtained.

Situations where narrower lanes may be considered are described below. 2 Minimum 11-foot lanes are required for design speeds of 45 miles per hour or greater. N/A Not Applicable Source: Adapted from A Policy on Geometric Design of Highways and Streets, AASHTO 2011, Chapter 4 Cross-Section Elements.

Inadditiontothroughlanes,auxiliarylanessuchasadditionalturninglanes,climbinglanes,orotherlanesmaybeprovidedonsteepgrades,atintersections,orinotherspecialcircumstances.TurninglanesatintersectionsarediscussedindetailinChapter1‐4.Otherauxiliarylanesarediscussedlaterinthischapter.Formultilaneroadways,theadditionallanes(ifprovided)maybedifferentwidthsthanthecurblanes.

Lanes Wider than 12 Feet 

Laneswiderthan12feetaresometimesusedwhereshouldersarenotprovided,suchasinruralvillages,suburbanhigh‐densityareas,suburbanvillagesandtowncenters,orurbanareas.Anotherapplicationofwidelanesisinareaswithhighdrivewaydensity.Thisapplicationprovidesmoremaneuveringroomfordriversenteringorexitingdriveways,orinareasoflimitedsightdistance.Inthesecaseswidelanesaretypically12to14feetwide.However,ifmorethan12feetisavailable,itisoftenpreferabletostripeashoulder.Ifnecessary,thedesignershouldincludeadditionalwidthoncurvestominimizeencroachmentintoopposingtraffic,adjacenttravellanes,bicyclelanes,orsidewalkssincevehiclesoff‐track,whichmeansthattheirtravelpathexceedsthewidthofthevehicle.Ifhighvolumesofbusandtrucktrafficareanticipatedonaroadway,suchasinanindustrialpark,oronadedicatedbusway,thedesignermayconsiderwhetherlaneswiderthan12feetareappropriate.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐27 

Lanes Narrower than 11‐Feet 

Narrowerlanesreducetheamountofright‐of‐waydedicatedtomotorvehicletravel,leavingroomforwidersidewalks,bicyclelanes,shouldersandon‐streetparking.Narrowerlanesalsoreducethecrossingdistanceforpedestriansandcanencourageloweroperatingspeeds.Insomesettings,narrowerlaneshelptoreducetheimpacttoroadsideenvironmentalorculturalresources.Forlowerspeed,lowervolumeroadsthatprimarilyprovideaccesstoadjoiningproperty,(suchasminorcollectorsandlocalroads)narrowerlanesmaybeappropriatetominimizeright‐of‐wayrequirementsandpotentialimpactstothebuiltandnaturalenvironment.Inareasoflimitedright‐of‐way,10‐footlanescanbeprovidedsothatthewidthoftheshouldercanbeincreasedtoprovidegreaterseparationbetweenpedestriansandbicyclesandmotorvehicles.Thefollowingsectiondiscussestherelationshipbetweenlanewidthandshoulderwidth.Travellanesnarrowerthan10feetareonlyappropriateforlocalroadwaysandsomeminorcollectorswithverylowtrafficvolumesandspeeds.Lanesnarrowerthan9feetaregenerallynotrecommended.However,onsomelow‐volumelocalroadsinresidentialareas,sharedstreetsthatdonotallowtwocarstopasssimultaneouslymaybeprovided.

3.3.3.4 Curb Lane Plus Shoulder Width 

Independentoftheallocationbetweenshouldersandtravellanes,thetotalwidthofthecurblaneplusshoulderavailableforbicycleandmotorvehicletravelisanimportantdesignelement.Fortwo‐laneroadways,thecurblaneplusshoulderwidthiskeyfordeterminingtheminimumcross‐section.Forexample,a14‐footcurblaneplusshoulderdimensionwillallowamotorvehicletopassabicyclistwithoutneedingtochangelanes(onamultilanesection)orswerveintotheoncominglane(onatwolanesection)andistheminimumvalueforcollectorsdeterminedusingExhibit3‐11and3‐14.Thisexampleresultsinawidthof28feetforatwo‐lanecollector.UsingtheminimumvaluesinExhibits3‐11and3‐14,theminimumwidthforatwo‐lanearterialis30feet.Althoughtheseminimumexamplesareprovided,theallocationofthepavementwidthbetweenthecurblaneandshouldershouldbedeterminedonaproject‐specificbasis,asdescribedinSection3.2.

3.3.4 Complete Cross‐Section Guidance 

Theprevioussectionsprovideguidanceanddimensionsforaccommodationofindividualroadwayuserswithinthecross‐section.Thefollowingsectionsprovidemorespecificguidancefortheassemblyofcross‐sectionsbasedontheareaandroadwaytypesintroducedinChapter1‐2includingadiscussionofthespecificelementsand

Curb lane plus shoulder

Shoulder Curb Lane

1.3‐28  Cross‐section and Roadside Elements   

dimensionscommonlyusedindifferentareatypes.AdiscussionoffreewayshasbeenintentionallyomittedfromthisPlan.AlthoughtherearefreewaysinNorwalk,theyareunderthejurisdictionoftheStateofConnecticutandaresubjecttodesignstandardsforInterstateHighwaysestablishedbytheFederalHighwayAdministration(FHWA)sincetheyarecomponentsoftheNationalHighwaySystem(NHS).

3.3.4.1 Arterials and Major Collectors 

Arterialsandmajorcollectorsvarywidelyincharacterdependingupontheareasthroughwhichtheypass.Arterialsandmajorcollectorsalmostalwaysaccommodatepedestrianandbicycletravel.Inmostinstances,arterialsandmajorcollectorsaredesignedtoaccommodatepedestriansandbicyclesusingthefirstfourcasesdescribedinSection3.2.Sidewalksareusuallyprovidedindevelopedareas(suburbanhighdensityareas,suburbanvillagesandtowncentersandurbanareas).Sidewalksmayalsobedesirableinareaswithlowerdevelopmentdensitysuchassuburbanlowdensityareas,ruraldevelopedareasandruralvillages.Inruralnaturalareasandothersparselydevelopedareas,pedestriantravelisoftenaccommodatedintheshoulderorbysidepaths.Usableshouldersareusuallyprovidedonarterialsandmajorcollectorsoutsideofdenselydevelopedareas.Inmostcases,theseshouldersareatleast4feetwidetoaccommodatebicycletravel.Shouldersbetween6and8feetwidearedesirableforemergencystoppingandotherfunctions,especiallyinhighvolumeandhightruckandbusareas.AlthoughnotcommoninNorwalk,inthecaseofhighdesignspeeds(greaterthan45milesperhour)10‐footshouldersshouldbeconsidered.Inthecaseofwideshoulders,itispossibletoprovideacombinationofpavedandunpavedsurfacesifthecircumstancesdictatesuchatreatment.Inruralvillages,suburbantowncenters,andurbanareas,usableshouldersareoftenreplacedwithon‐streetparking.Intheseareasitisdesirabletoprovidebicyclelanestomaintainseparateaccommodationforbicycles.Ifthereisinsufficientright‐of‐waytosupportbicyclelanesandparking,thenthedesignershoulddeterminewhichelementtoprovidewithintheavailableright‐of‐wayorshouldconsidertrafficcalmingandsharedlanepavementmarkingstoimprovetheperformanceofsharedbicycle/motorvehicleaccommodation.Travellanesof11and12feetareusuallyprovidedonarterialsandmajorcollectors.Inhighvolume,hightruckandbuspercentage,andhighdesignspeedareas,12footlanesareparticularlydesirable.10‐footlanesaresometimesusedifspeedsandtruckandbusvolumesarelow(lessthan250perdayor30inonehour),inmultilanesections,ortoprovidewidershouldersinareasoflimitedright‐of‐way.Majorcollectorsaresometimesconstructedwith10footlanesinruralvillages,suburbanvillagesandtowncenters,andurbanareaswhererightofwayisparticularlylimitedandcompetingdemandsareespeciallyhigh.Lanesnarrowerthan10feetaregenerallynotusedonarterialsormajorcollectors.

Minor arterial in a town center

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐29 

Inmostcases,thedesignershouldprovideacombinedshoulderpluscurblanedimensionofatleast14feetsothatmotorvehiclescanpassbicycleswithoutchanginglanesorswerving.OnStateroadways,however,themaximumshoulderwidthshallbe8‐feet.

3.3.4.2 Minor Collectors 

Thedesignofminorcollectorsissimilartothatdescribedabove,especiallyforareaswithhighertrafficvolumesandspeeds.However,minorcollectorsareoftendesignedforlowspeed,lowvolumeoperations.Inthesecases,minorcollectorsaresometimesdesignedtoprovidesharedaccommodationforallusers,asdescribedinSection3.2,Case5,withacurb‐laneplusshoulderwidthofatleast12feet.Thedesignermayneedtoconsidertrafficcalmingmeasurestoensurethatmotorvehiclespeedsareappropriateforshareduseoftheroadway.

3.3.4.3 Local Roads 

Theguidanceprovidedforarterialsandmajorcollectorsissuitableforlocalroadswithhighvolumesandhighspeeds.Muchlikeminorcollectors,localroadsaresometimesdesignedtoprovidesharedaccommodationforallusers.Onsomelow‐volumelocalroadsinresidentialareas,sharedstreetsthatdonotallowmotorvehiclestopasssimultaneouslyareacceptable.Thedesignermayneedtoconsidertrafficcalmingmeasurestoensurethatmotorvehiclespeedsareappropriateforshareduseoftheroadway.

3.4 Public Transit Operations 

Publictransitoftenoperatesonroadways.Insomecases,busesoperatewithinmixedtrafficandstopalongthecurbside.Also,aroadwaydesigncanincorporatelanesdedicatedto,orwithpriorityfor,transitoperations.Thefollowingsectionsdiscussthesepublictransitconsiderationsassociatedwithroadwaycross‐section.AmoredetaileddiscussionofdesignfortransitstopsatintersectionsisprovidedinChapter1‐4.

3.4.1 Bus Stops 

Thespacingofbusstopsisacriticaldeterminantoftransitvehicleandsystemperformance.Theconsiderationofwheretolocatebusstopsisabalancebetweenprovidingshortwalkingdistancestobusstopsandtheincreasedtraveltimewhenthebusstopsfrequently.Thus,thedecisionofbusstoplocationshouldbemadebythetransitagenciesandtheCity.OnStateroadways,busstopdeterminationsrequireapprovalfromtheOfficeofStateTrafficAdministration(OSTA)andshouldbemadeinconjunctionwithitsstaff.Busstoplocationsalsoneedtocarefullyconsidertheavailabilityofsidewalks,crosswalks,andwaitingareas.Theroleofthedesigneristoevaluateproposedlocationstoensurethattheyareappropriatewithregardstosafetyandoperations.

Project designers must consult with regional transit authorities to 

determine proper locations for bus stops.. 

1.3‐30  Cross‐section and Roadside Elements   

Thischapterfocusesonmid‐blockbusstopssincebusstopslocatedatintersectionsarediscussedinChapter1‐4.Mid‐blockstopsaregenerallylocatedadjacenttomajorgeneratorsoftransitridershipandofferthefollowingadvantages: Mid‐blockstopsminimizethesightdistanceimpactsofbusesonpedestrians

crossings(i.e.limitedabilitytoseearoundthebus).

Mid‐blockstopsmayresultinlesscongestedpassengerwaitingareas.Therearedifficultiesassociatedwithmid‐blockstops;forexample,mid‐blockstopscreatecrossingdifficultiesforpedestriansunlessamid‐blockcrosswalkisalsoprovided.Busstopsandpedestrianroutesshouldbeconsideredtogethertomakesurethatthestopsaresafeandconvenientforusers(peopletendtowalkupto¼miletoaccessbusroutes).Mid‐blockstopsalsorequiretheremovalofon‐streetparkingforasubstantialdistancetoaccommodatethepull‐in,stop,andpull‐outmaneuvers.

3.4.1.1 Bus Stop Dimensions 

Thetwoprimarycategoriesofbusstopsare(1)curb‐sidebusstopsand(2)busbays.Themostcommonarecurb‐sidebusstopswherethebussimplystopsatthecurbinthetravellane,shoulderorparkinglane.Avariationofthisisastopatacurbextension.Busbaysallowthethroughtraffictoflowfreelypastthestoppedbus.Mostbusbaysoccuratmid‐blocklocations,althoughitissometimesdesirabletocreatebusbaysforfar‐sidestops,withorwithoutaqueuejumperlane.

Curbside Bus Stop Zones 

Theminimumlengthofbusstopsis80feetformid‐blockbusstopsand60feetforbusstopsatintersections.Thesedimensionsareforatypical40‐foottransitbus.Ifarticulatedbusesareused,anadditional20feetisrequired.Shorterdistancesmaybeacceptabletoaccommodatetransitvansormid‐sizebuses.Anadditional50feetoflengthisneededforeveryadditionalbusthatistypicallyatthestopatthesametime.Unlessthestopisusedforthelayoverofbuses,asinglestoppositionwillbeadequateifpeakhourbusflowislessthan30perhour.Oftenthecurbsidestopmakesuseofaparkinglane.Parkinglanesaretypically7to8feetwide.Busesrequireaminimumwidthof10feet.Therefore,ifthereissignificantbusactivityalongacorridoranditisdesirabletoallowthroughtraffictopassunimpeded,awiderparkinglaneshouldbeprovided.Inareaswithouton‐streetparking,awideshouldershouldbeprovidedifbusstopsarefrequentanddwelltimesarelong.Somevariationtotheseguidelinesmaybenecessaryinconstrainedareaswithsensitiveroadsideresources.

Bus Bays 

Thedesignermustdeterminewhenbusbaysaremoreappropriatethancurb‐sidebusstopzones.Amongthefactorsare:

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐31 

Trafficinthecurblaneexceeds250vehiclesduringthepeakhour, Trafficspeedisgreaterthan40mph, Busvolumesare10ormoreperpeakhourontheroadway, Passengervolumesexceed20to40boardingsanhour, Averagepeak‐perioddwelltimesexceed30secondsperbus,and Busesareexpectedtolayoveratthelocation.Itshouldbenoted,however,thatwhentrafficvolumesapproach1,000vehiclesperhourperlane,busdriverstendnottousebusbaysduetodifficultiesencounteredinre‐enteringtrafficlanes.Considerationshouldbegiventotheseoperationalissueswhencontemplatingthedesignofabayonahigh‐volumeroad.Accelerationlanes,signalpriority,orfar‐sideplacementsarepotentialsolutions.Ideallythedesignofbusturnoutsshouldincludetapersandlanesfordecelerationandmerging,butitisusuallynotpracticaltoprovidedecelerationandmerginglanes.Somekeydesignelementsare: Ataperof5feetinlengthforevery1footofdepth(5:1)istheminimumfor

deceleration.Whenthebusstopisonthefarsideoftheintersection,theintersectionmaybeusedastheentryareatothestop.

Ataperof3feetoflengthforevery1footofdepth(3:1)istheminimumforreentry.Wherethestopisonthenearsideoftheintersection,thewidthofthecrossstreetisusuallysufficienttoprovidetheneededmergingspace.

Busbaywidthsshouldbe12feet,although10feetissufficientwhentrafficspeedsare30mphorless.

3.4.1.2 Bus Stop Waiting Areas 

Thedesignforthecurb‐sideelementsofthebusstop(shelters,boardingplatforms,walkways)mustconformtoADArequirements.TheADAregulations,aswellastheTCRPreportGuidelinesfortheLocationandDesignofBusStops,providedetailedinformation.Amongthekeydesignelementsare: Anaccessiblepedestrianroutetothebusstop.

Toaccommodateuseofawheelchairlift,theremustbealevel(2percent)landingareaatleast60incheswide.Thedepthofthelandingareamustbe8feet.Thebusstoppadmustbefreeofobstructions.

Bus waiting area

60-foot transit

1.3‐32  Cross‐section and Roadside Elements   

Bussheltersaretypically5to6feetwideand10feetlong.Interiorclearanceof4feetisrequired.Ideally,thesheltersareashouldbesizedfortheanticipatedvolumeofwaitingpassengersduringpeakboardingperiods.Theymustbeat‐gradeorrampedtoaccommodateapersonusingawheelchair.Bussheltersshouldnotbeplacedwheretheywillrestrictvehicularsightdistance.

InadditiontoADArequirements,thedesignershouldconsiderurbandesignissuesassociatedwiththelocationofbusstopsincluding: Thecharacterandadequacyofaccessroutesforpedestrians,cyclists,andother

potentialtransitusers,

Connectivitytonearbydemandcenters,

Streetscapetreatmentstoimprovethevisualcharacterofthebusstop,and

Architecturalelementsofshelterdesignorselection.

3.4.2 Dedicated Lanes 

Insomelocations,lanesareprovidedfortheexclusiveorpreferentialusebytransitvehicles.Onmostarterialsandcollectors,thecurblaneismostcommonlydesignatedasadedicatedorprioritytransitlane.Thischoiceallowsthetransitvehicletostopatcurbsidebusstops.Often,theselanesaresharedwithbicycles,right‐turningvehicles,taxicabs,bicyclists,orhighoccupancyvehicles.Anotheralternativeistoprovidededicatedtransitlaneswithinacentermedian.Inthiscase,passengersmustcrosstheotherroadwaylanestoreachthetransitfacility.Thisalternativeoperatesinamannersimilartorailtransit,describedearlierinthissection.Foralldedicatedorprioritylanes,thedesignershouldstrivetoprovideadequatelaneandshoulderwidthsothattransitvehiclesoperatewithminimalinterferencefromgeneraltraffic.

3.5 Other Cross‐section Elements 

Thefollowingsectionsdescribethreeimportantelementsofcrosssectiondesign,mediansandauxiliarylanes,cross‐slopesrequiredforpositivedrainage,andcurbing.

3.5.1 Medians and Auxiliary Lanes 

Amedianistheportionofaroadwayseparatingopposingdirectionsofthetraveledway.Medianscaninfluencethequalityofserviceandsafetyprovidedforallroadwayusers.Forexample,medianscanbreakupthewidthofaroadwayandproviderefugeforpedestrianscrossingthestreetandvehicles(includingbicycles)makingturningorcrossingmovements.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐33 

Continuousmedianscanincreasethespeedsalongaroadway,improvingitsefficiencyformotorvehicles;however,thisincreasedspeedcanhaveanegativeimpactonneighborhoodsandonthesafetyofpedestriansandbicyclists.PotentialtrafficcalmingapplicationsofmediansarediscussedfurtherinChapter1‐6.Medianscanalsobeusedtomanagepropertyaccess,channelizetrafficmovements,andaccommodateaesthetictreatments.Medianwidthisexpressedasthedimensionbetweentheedgesoftraveledwayandincludesleftshouldersiftheyareprovided.Auniformmedianwidthisdesirable.However,variablewidthmediansmaybeadvantageouswhererightofwayisrestricted,at‐gradeintersectionsarewidelyspaced,oranindependentalignmentisdesirabletominimizecutandfill,tominimizeenvironmentalimpacts,orforaestheticpurposes.Thetypeofmedianselectedanditsdimensionswilldependuponmanyfactors,including: Areatype, Roadwaytype, Availabilityofrightofway, Transportationdemands, Pedestrianandbicyclecrossings, Presenceandtypeoftransitoperations, Designspeed, Clearzoneandrecoveryareaguidelines, Landscapingandaestheticconsiderations, Drainageneeds, Snowandiceimpacts, Maintenanceconsiderations,and Superelevationimpacts.Mediansaremostfrequentlyusedonmultilaneroads.Mediansmayalsobeincludedontwo‐laneroadways;howeveradditionaltravelwaywidthisoftenrequiredforemergencyvehicleaccess.Insomecases,mediansincludeauxiliary(turning)lanesthatprovideaccesstodrivewaysorincreasecapacityandsafetyatintersections.TheseauxiliarylanesarediscussedinmoredetailinChapter1‐4.Severaldifferenttypesofmediansarepossibleasdescribedinthefollowingsections.

3.5.1.1 Raised Medians 

Raisedmediansarecentralareasatanelevationhigherthanthesurfaceoftheroad.Araisedcurbusuallyprovidesthiselevationdifference.Raisedmediansareusuallyfoundonarterials,collectorsandlocalroadsinmoredenselydevelopedareaswithdesignspeedsof45milesperhourorless.

1.3‐34  Cross‐section and Roadside Elements   

Raisedmediansareoftenthepreferredmediantypeinareaswithhighpedestriancrossings,whereaccesscontrolisdesired,orwheredecorativelandscapingisdesired.Raisedmediansoffersomeadvantagesoverothermediantreatmentsincluding: Mid‐blockleftturnsareeliminated,

Spaceisavailableforaesthetictreatments,

Aprotectedlocationisavailablefortrafficsigns,signals,pedestrian,bicycle,andturningtrafficrefuge;,

Left‐turnscanbemoreeffectivelychannelized,

Alocationisprovidedforsnowstorage,

Themedianedgesarediscernible,and

Drainagemaybeimproved.Somedisadvantagesofraisedmedianswhencomparedtoothermediantreatmentsinclude: Theyaremoreexpensivetoconstruct,

Theymayrequiregreaterwidthsthanothermediantoservethesamefunction(e.g.,left‐turnlanesatintersections),

Curbsmaycauseadrivertolosecontrolifstruck,and

Prohibitingmid‐blockleftturnsmayoverloadstreetintersectionsandmayincreasethenumberofU‐turns

Theminimumtotalwidthoftheraisedmedianshouldbe4feetincludingcurbs,andonStateroadwaysitshouldbeconsistentwiththeDepartment’sHighwayDesignManual.Inareaswithlowpedestrianandbicycleactivity,raisedareasmayuseslopededging.Thisconfigurationprovidestheminimalwidthmedianandminimumoffsetsbetweenthetravellaneandverticalcurb.Inmostcases,itisdesirabletoprovidean8‐to10‐footmedianwitha6‐footraisedrefugeareaand1‐to2‐footoffsetsbetweentheverticalcurbandthetravellane.Whererefugeisrequiredforpedestriansandbicyclesverticalcurbshouldbeused.Additionally,crossingsshouldbecarefullylocatedtoservedesiredcrossinglocationsandaccessibilitymustbeprovidedforwheelchairusers.

Typical raised median on an urban arterial

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐35 

Widermedians,between10and18feet,moreeffectivelysupportlandscaping,providehigherqualityrefuge,provideincreasedlateralclearancetosignage,streetlights,andlandscapefeatures,andsupportleft‐turnlanes.Whenleftturnsareprovidedatintersections,an18‐footwidthisdesirabletosupporta12‐footturnlaneandmaintaina6‐footmedian,althoughnarrowerconfigurationsarepossible.Thedesignermustconsidersightdistancelimitationsandpotentialobstacleswhenselectingmedianplantings.

3.5.1.2 Flush Medians 

Flushmedianscontainacentralareaatapproximatelythesameelevationastheroadwaysurface.Flushmediansareusuallyfoundonarterials,collectorsandlocalroadsinareaswithlimitedright‐of‐way.Flushmediansmaybefoundonfreewaysifcombinedwithamedianbarrier.Aflushmedianisgenerallypavedandmayormaynothaveabarrierdependingontrafficconditions.Itisnormallycrownedtoprovidepositivedrainageanddiscourageparking.Themedianisoftendesignatedusingscoredconcreteorpavementmarkings.AllflushmediansshouldbemarkedaccordingtothecriteriaintheManualonUniformTrafficControlDevices(MUTCD).Whenincludedonarterials,collectorsandlocalroadstoprovideleft‐turnlanes,themedianisusuallybetween12feetand16feetwide.The16‐footmedianprovidesfora4‐footseparationfromtheopposingtraffic.Inareaswithlowtruckandbusvolumes,aleft‐turnlaneasnarrowas10feetcanbeprovided,reducingthedesirablemedianwidthto14feet.Whereleftshouldersareprovided,thedimensionrequiredforusableshouldershouldbeaddedtotheabovemedianwidths.

Two‐Way Continuous Left‐Turn (TWLT) Lanes 

Thetwo‐wayleft‐turnlaneisaspecialapplicationofflushmedianswhichallowsturningmovementsalongitsentirelength.TWLTsmaybeappropriateinareaswithfrequentdrivewayspacinginhighlydeveloped,orcommercializedareas.Two‐wayleft‐turnlanesareappropriateonroadwayswithnomorethantwothroughlanesineachdirectionandwhereoperatingspeedsareintherangeof30milesperhour.TWLTlanesmaybeusedwheredailytrafficthroughvolumesarebetween10,000and20,000vehicleperdayfor4‐laneroadwaysandbetween5,000and12,000vehiclesperdayfor

Center two-way left turn lane striping

8 to 16 ft.

1.3‐36  Cross‐section and Roadside Elements   

2‐laneroadways.Left‐turnmovementsshouldconsistofatleast70turnsperquartermileduringthepeakhoursand/or20percentofthetotalvolume.CarefulevaluationofindividualsitesisrequiredforimplementationofTWLTlanes.ThesignageandstripingpatternsforTWLTlanesshouldbedesignedinaccordancewiththeMUTCD.Lanewidthsbetween12and16feetaresuitableforTWLTlanes.Onroadwayswithhighvolumes,ormoderatetohighspeeds(30to45milesperhour)a14‐footTWLTlaneshouldbeprovided.TWLTlanesarenotappropriateonroadwayswithdesignspeedsgreaterthan45milesperhour.Inmostcases,itispreferabletoprovidearaisedmedianwithperiodicturnlanesservingmajordrivewaysandintersectingstreetsinsteadofaTWLTlane.Thispreferredtreatmentprovidesimproveddelineationofturningmovementsandimprovedpedestrianrefuge.However,ifdrivewayspacingisfrequentandturningvolumesareheavy,thenthetwo‐wayleft‐turnlanemaybesuitable.AccessmanagementtechniquessuchasdrivewayconsolidationtofacilitatethepreferredtreatmentarediscussedinChapter1‐7.

3.5.1.3 Context Influence on Median Design 

Designofmediansvariesconsiderablybasedontheareathroughwhichtheroadwaypasses.Inruralnatural,ruraldeveloped,andsuburbanlowdensityareas,widermediansareoftenselected.Insuburbanhighdensity,andurbanareas,narrowmediansaremorefrequentlyencountered.Theadditionofmediansinruralvillages,suburbanvillagesandtowncenters,andsomeurbanareasmayconflictwiththecharacteroftheseareasandshouldbeconsideredcarefullyfromanurbandesignperspective.Similarly,theadditionalright‐of‐wayrequiredformediansmayresultinincreasedcosts,environmentalimpacts,andcommunityimpacts.Thebenefitsandimpactsofprovidingamediananditswidthshouldalsobecarefullyconsidered.Inmanycasesmedianscanoccupyright‐of‐waythatcouldbeusedforotherpurposessuchasbicyclelanes,on‐streetparking,andwidersidewalks.Incaseswheremediansareproposedforaestheticpurposes,thedesignershouldconsiderwhetheritismoreadvantageoustolocatethelandscapedspacealongthesidesoftheroadway.Inallareas,ifamedianisdesired,anarrowmedianorbarrier,suchasdouble‐facedguardrailorconcrete“jersey”barriers,maybeappropriatetolimittheneededrightofwayandimpactstothenaturalorbuiltenvironment.However,forfreewaysandmajorarterials,widermediansmayprovidegreatersafetyandoperationalbenefitsandmayallowseparatealignmentsforeachdirectionoftravel,reducingtheimpactoftheroadwayonthesurroundingcontext.Whiledouble‐facedguardrailorconcrete“jersey”barriersmayconflictwiththecharacterofaparticulararea,therearetimeswhenaconstrainedwidththatrequiresseparationcallsforthesetypesofbarrierstominimizelanduseimpacts.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐37 

3.5.1.4 Roadway Type Influence on Median Design 

Thefunctionsthatamedianprovidesvarydependingonthetypeofroadwayonwhichtheyarefound.Mediansareprovidedonallfreewaysandsomearterials,primarilytoachievesafetyandoperationalbenefitsthroughaccessmanagement.Oncollectorsandlocalroads,mediansareprovidedprimarilyforaccessmanagement,aestheticreasons,toprovidealocationfortrafficsignalsandsignage,andtoproviderefugeforpedestriansorbicyclistscrossingtheroad.TypicalmedianfunctionsfordifferentroadwaytypesareshowninExhibit3‐15anddiscussedinthefollowingsections.

Exhibit 3‐15  Typical Median Functions by Roadway Type 

Median Function

Arterials

Collectors and Local Roads

Separation from opposing traffic X

Access management X X

Refuge area for pedestrians and bicyclists X X

Refuge for emergency stops X

Area for control of errant vehicles X

Reduction in headlight glare X

Area for deceleration and storage of left-turning and U-turning vehicles X X

Enforcement and traffic management areas X X

Area for storage of vehicles crossing at intersections X X

Space for snow storage X

Landscaping (Medians greater than 10 feet wide) X X

Increased drainage collection area X

Area for placement of luminary supports, traffic signs, traffic signals, guardrail, and bridge piers X X

Area for future additional lanes (Medians greater than 30 feet wide) X X

Source: Flexibility in Highway Design, AASHTO 2004. Chapter 6 Cross Section Elements

Arterials 

Mediansaredesirableonarterialscarryingfourormorelanes.However,thedesignershouldusuallyprovidethemostdesirableaccommodationforroadwayusersbeforededicatingspacetoamedian.Themedianwidthisoftenselectedbasedontheneedforleft‐turnstoragelanes.Additionally,forunsignalizedorruralroadways,amedianmustbeatleast25feetwidetoallowacrossingpassengervehicletostopsafelybetweenthetworoadways;however,atsignalizedintersections,widemedianscanleadtoinefficienttrafficoperations.Mediansintherangeof12to25feetarecommonlyselectedforthesetypesofroadways.

1.3‐38  Cross‐section and Roadside Elements   

Collectors and Local Roads 

Mediansmayalsobeincludedinthedesignofcollectorsandlocalstreets,althoughtheseapplicationsarelessfrequentgiventhelowerspeedsandvolumesassociatedwiththeseroadwaytypes.Inthesecases,mediansareoftenincludedtoenhancethevisualappearanceofaroadwaythroughdecorativelandscapingratherthantorealizesubstantialsafetyoroperationalbenefits.Mediansinthesecircumstancesareusuallyatleast10feetwidetoimprovethehealthofthelandscapingandtofacilitateitsmaintenance.

3.5.2 Cross Slopes 

Surfacecrossslopesarenecessaryonallcomponentsofthecross‐sectiontofacilitatedrainage.Thisreducesthehazardofwetpavementsandstandingwater.Onhot‐mixasphaltpavementtravellanesshouldbedesignedforacrossslopeof2percent.Concretepavementscrossslopesshouldbedesignedto1.6percentforlanesadjacenttothecrown,and2percentforallotherlanes.Forlowerclassesofpavement,highercrossslopesmaybedesirabletoachievethedesigndrainage.Cross‐slopesshouldalsobeprovidedonsidewalks,shoulders,parkinglanes,intersections,drivewaycrossings,andbicyclelanes.

3.5.3 Curbs, Berms and Edging 

Curbs,berms,andedgingareroadsideelements,usuallyconstructedofgraniteorextrudedbituminousconcreteusedtodefinethepavementedgeandtocontroldrainage.Typicaltypesofcurbs,berms,andedgingandtheirheightsareprovidedinExhibit3‐16.

Exhibit 3‐16  Typical Curb Heights 

Curb Type Vertical Height

(inches)

Bridge curb 8

Barrier curb 6

Sloped edging 4

Type A berm 2 Adapted from A Policy on Geometric Design of Highways and Streets, AASHTO, 2011. Chapter 4 Cross Section Elements

Barriercurbsareverticalandareusuallygranite.Barriercurbsrangeinheightfrom6to8incheswithabatterof15:1orsteeper.Six‐inchcurbsaretypicallyusedalongroadways.Bridgecurbsarebarriercurbs,usuallywith8‐inchrevealusedonbridgestoprovideadditionalprotectionforpedestriansorotherbridgeelementsalongtheroadside.However,eventhesecurbsarenotadequatetopreventavehiclefromleavingtheroadway.Wherepositiveprotectionisrequired,asuitabletrafficbarriershouldbeprovided.

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐39 

Curbsareusedextensivelyonurbanandsuburbanstreetsandhighways.Curbsarenotcommonlyusedinruralareasunlesstheyareprotectinganadjacentsidewalk.Curbshelprestrictvehiclestothepavementarea,anddefinepointsofaccesstoabuttingproperties.Verticalcurbingisappropriateonlowerspeed,urbanstreetswherelandscaping,signalequipment,streetlights,orotherfeaturesarelocatedwithinthemedianoralongtheroadside.Verticalcurbingshouldalsobeusedoncrossingislandsandotherlocationswhereprotectionofpedestriansisneeded.Slopededgingisusuallygraniteandshouldbeusedforedgedelineationandontrafficislandswhendesignspeedsaregreaterthan45milesperhoursinceverticalcurbsarenotsuitableforthehighspeedenvironment.TypeABermisusuallyextrudedbituminousconcreteandcanbeusedwhendrainagecontrolisneededonroadwaysthatdonothavecontinuouscurb.Itdirectswatertocloseddrainagesystems,preventssloughingofthepavementedgeandprovidesadditionallateralsupport.TheTypeAbermshouldbeusedonly: wherethelongitudinalgradeexceeds5%foranextendedlength,or wherecontrolandcollectionofdrainageisotherwiserequired.Pavementmillingmulch,orothersuitablematerial,shouldbeusedinlieuofbermunderguardrailsandinotherareaswherecontroloferosionfromroadwayrunoffisaconcern.Ifthepavedshouldersonhighspeedfacilitiesarenotwideenoughforavehicletomoveoutofthetraveledway,slopededgingorbermsshouldbeeasilymountabletoencouragemotoriststoparkclearofthetraveledway.Bermsorslopededgingusedinthesesituationsis4inchesorlessinheightandhaveroundedorplaneslopingfaces.

3.6 Roadside Elements 

Roadsidefeaturessignificantlyaffectsafety,constructionandmaintenancecosts,rightofwayrequirements,drainage,environmentalimpacts,andaesthetics.Thedesignershouldconsultthe2011AASHTORoadsideDesignGuide(ormostrecentversion)whichprovidesstandardsandrecommendationsonthedesignofroadsideelementsincludingclearzones,roadsidebarriers,medianbarriers,impactattenuators,sideslopes/cuts,andditchsections.

3.7 Utilities and Signage 

Thelocationofutilitiesandtheplacementofsignageareoftensignificantissuesinthedesignofroadwayimprovementsasdescribedbelow.

1.3‐40  Cross‐section and Roadside Elements   

3.7.1 Utility Placement or Relocation 

Sincetheyprovideapublicservice,utilitiesareallowedtooccupythepublicright‐of‐way.Coordinationwithutilitycompaniesisessentialduringthedesignandconstructionprocesstoidentifytheappropriatelocationforutilitiesandthenecessarystepsforrelocationofexistingutilities(ifrequired).Ideally,utilityplacementorrelocationwilloccurissequencewiththeconstructionoftheroadwayprojectsothatdisruptiontothepublicminimized.Ingeneral,overheadutilitypolesshouldbelocatedoutsidetheshoulders,sidewalk,androadsiderecoveryareas(ifprovided).Ifutilitypolescannotbelocatedoutsideofthesidewalkarea,itisimportantthattheminimumclearpathoftravelforpedestriansdescribedpreviouslyisprovided.Additionally,utilitypolesshouldbeoffsetatleasttwofeetfromthefaceofcurbwhenlocatedwithinthesidewalkareaorbufferstrip.Itisusuallyadvisabletoassesstheconditionandneedforreplacementofbelow‐gradeutilitiesduringtheplannedroadwayconstruction.Theproponentshouldcoordinatewithmunicipaldepartmentsandotherutilitiestoidentifyanyutilityworktobecoordinatedwiththeroadwayproject.

3.7.2 Signage Placement 

Thetypesandmountingsofsignsvariessignificantlydependingontheroadwaytypeandsetting.DetailedguidancefortheplacementofsignsiscontainedintheMUTCD.Similartoutilities,signagecannotprotrudeintotheshouldersortraveledway.Inlocationswherethesidewalkisimmediatelyadjacenttothestreet,itisoftendesirabletoplacesignageatthebackofsidewalk.Ifsignageisplacedalongthecurbedge,signpostsshouldbelocatednocloserthan½thewidthofthesignfaceplusoneadditionalfootfromthefaceofcurb.

3.8 Right‐of‐Way 

Thenecessaryright‐of‐way(ROW)widthisthesummationofallcross‐sectionelements:utilityaccommodations,clearzones,drainageditches,sidewalks,bufferstrips,curbsorberms,shouldersandbicyclelanes,motorvehicletravellanes,andmedians.Considerationshouldalsobegiventothepossibilityofaddingtravellanesinthefuture.However,landusepatterns,availabilityandcostofright‐of‐waymaydictatethetypeandwidthofcross‐sectionelementsthatareprovided.TheROWwidthwillvarygreatlyandthedesignermustalwaysresearchthecurrentROWwidthasaninitialstep.Typically,anundivided,two‐laneruralmajorcollectororarterialhasaROWwidthof66feet.LowerclassesofroadwayorlowvolumefacilitiesmighthavenarrowerROWswhilemajorhighwaysrequiremoreROW.Inmostcases,urbanstreetsandhighwayshavelessavailableROWthanruralhighways.Ideally,ROWwidthshouldbeuniformalongaroadwaysegment.Inurbanareas,variablewidthsmaybenecessaryduetoexistingdevelopment.Varyingsideslopesandembankmentheights

Section 1 – Chapter 3

  Cross‐section and Roadside Elements  1.3‐41 

maymakeitdesirabletovaryROWwidthandROWlimitswilllikelyhavetobeadjustedatintersectionsandfreewayinterchanges.OtherspecialROWcontrolsshouldalsobeconsidered: AthorizontalcurvesandintersectionsadditionalROWacquisitionmaybewarranted

toensurethatthenecessarysightdistanceisalwaysavailableinthefuture.

InareaswherethedesiredROWwidthscannotbereasonablyobtained,thedesignerwillhavetoconsidertheadvisabilityofusingsteeperslopes,revisinggrades,orusingsloperetainingtreatments.

Rightofwayshouldbeacquiredandreservedforfutureimprovementssuchasroadwaywideningandinterchangecompletion.

Onsectionsofhighwayadjacenttorailroads,anyencroachmentonrailroadROWshouldbeavoided,wheneverpossible.

Permanentslopeeasementswithmaintenancerightsshouldbeconsideredtominimizepublicownershipofland.

Becausearoadisaninherentpartofacommunity,theengineerneedstopayspecialattentiontoright‐of‐wayimpactonculturalandcommercialfeatures.

Additionalrightofwayisoftenrequiredforwetlandmitigation.

3.9 For Further Information 

HighwaySafetyManual,1stEdition,AASHTO2010.

AGuidetoAchievingFlexibilityinHighwayDesign,AASHTO2004.

FlexibilityinHighwayDesign,FHWA,1997.

APolicyonGeometricDesignofHighwaysandStreets,AASHTO,2011.

HighwayCapacityManual,SpecialReportNo.209,TransportationResearchBoard1995.

RoadsideDesignGuide,4thEdition,AASHTO,2011.

AGuideforTransportationLandscapeandEnvironmentalDesign,AASHTO,1991.

GuideforHighOccupancyVehicleFacilities,AASHTO,2004.

CompendiumoftheSafetyEffectivenessofHighwayDesignFeatures,PublicationFHWA‐RD‐91‐044through049(6volumes),1991.

AmericanswithDisabilitiesActHandbook,December1991.

AASHTOGuidefortheDevelopmentofBicycleFacilities,2012.

UrbanBikewayDesignGuide,NACTO,2011.

FHWABicycleCompatibilityIndex,ALevelofServiceConcept,ImplementationManual,PublicationFHWA‐RD‐98‐095,1998.

1.3‐42  Cross‐section and Roadside Elements   

AASHTOGuideforthePlanningDesignandOperationofPedestrianFacilities,July2004.

ManualforAssessingSafetyHardware,1stEdition,AASHTO,2009.

ManualonUniformTrafficControlDevices,FederalHighwayAdministration,2009.

TCRPReport19–GuidelinesfortheLocationandDesignofBusStops,1996.