2 ResDev Final

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PENNSYLVANIA STANDARDS FOR RESIDENTIAL SITE DEVELOPMENT: APRIL 2007

CHAPTER 2:

STREET STANDARDS


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Chapter 2: Street Standards

2 - 2 PENNSYLVANIA STANDARDS FOR RESIDENTIAL SITE DEVELOPMENT: APRIL 2007

Sections Page #

2.0 OVERVIEW 4

2.1 PURPOSE AND STRATEGY 5

2.1.1 Purpose 52.1.2 Strategy 5

2.2 FUNCTIONAL CLASSIFICATION SYSTEM 52.2.1 Residential Access Streets 6

2.2.1.1 TrafcVolume-ResidentialAccess

Streets 72.2.2 Residential Collectors 8

2.2.2.1 TrafcVolume-ResidentialCollectors 10

2.2.3 Residential Mixed-Use Collectors 10 2.2.3.1 TrafcVolume-ResidentialMixed- 11

Use Collectors2.2.4 Special Use Streets 11

2.2.4.1 Alleys 112.2.4.2 Divided Streets 122.2.4.3 Stub Streets 13

2.2.5 Non-Residential Streets 14 2.2.5.1 Commercial/IndustrialAccessStreets 14

2.2.5.2 Municipal Collector 142.2.6 Existing Streets 14

2.3 GENERAL DESIGN STANDARDS 14 2.3.1 TrafcPatterns 14

2.3.2 On-Street Parking 152.3.3 Intersections 17

2.3.3.1 IntersectionHorizontalAlignment 17

2.3.3.2 Intersection Spacing 182.3.3.3 Intersection Corner Radius 202.3.3.4 Intersection Sight Distance 232.3.3.5 Intersection Approach Grade for Stop

Streets 252.3.3.6 Turn Bays and Deceleration Lanes 25

2.3.4 Driveways 25 2.3.4.1 DrivewaystoSingle-familyDwellings,

DuplexHouses,orApartments 26

Sections (cont.) Page #

2.3.4.2 EntranceDrivesforMulti-family

DevelopmentsandOff-StreetParking

Lots 29

2.3.5 Easements 292.3.6 Rights-of-way 292.3.7 Cart-way Cross Section 292.3.8 TrafcCalming 30

2.3.8.1 Intersection - Bulb-Outs 312.3.8.2 Intersection - Raised 32

2.3.8.3 Intersection-TrafcCircle 33

2.3.8.4 Intersection - Diagonal Diverter 342.3.8.5 Chicanes 342.3.8.6 Raised Median Islands 35

2.3.8.7 SpeedTable/Hump 36

2.3.8.8 Raised Crosswalk 372.3.9 Street Landscaping 372.3.10 Street Lighting 392.3.11 Signage and Signalization 402.3.12 Streets and Special Hazard or EnvironmentalConservationAreas 41

2.3.13 Trip Generation Rates 412.3.14 TrafcImpactStudies 42

2.4 DESIGN STANDARDS FOR RESIDENTIALACCESS STREETS (RA) 422.4.1 Design Speed 42

2.4.2 Street Width 422.4.3 Bicycle Access 452.4.4 Pedestrian Access 452.4.5 On-street Parking 452.4.6 Right-of-way Width 452.4.7 Street Slope 462.4.8 Horizontal Curvature 462.4.9 Cul-de-sacs 46

2.4.10.1 Cul-de-sac Turnarounds 462.4.10.2 Cul-de-sac Right-of-way 49

2.5 DESIGN STANDARDS FOR RESIDENTIAL 49COLLECTOR STREETS (RC)

Contents


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2 - 3PENNSYLVANIA STANDARDS FOR RESIDENTIAL SITE DEVELOPMENT: APRIL 2007


2.5.1 Design Speed 492.5.2 Lot Access Restrictions 492.5.3 Street Width 50

2.5.4 On-street Parking 512.5.5 Bicycle Access 512.5.6 Pedestrian Access 512.5.7 Right-of-way Width 522.5.8 Street Slope 522.5.9 Horizontal Curvature 52

2.6 DESIGN STANDARDS FOR RESIDENTIAL 53MIXED-USE COLLECTORS (RMC)2.6.1 Design Speed 532.6.2 Street Width 532.6.3 On-Street Parking 552.6.4 Bicycle Access 552.6.5 Pedestrian Access 552.6.6 Right-of-way Width 552.6.7 Street Slope 562.6.8 Horizontal Curvature 56

2.7 DESIGN STANDARDS OF ALLEYS 572.7.1 GeometricStandards 57

2.7.2 Parking 582.7.3 Drainage 58

2.8 DIVIDED STREETS 592.8.1 Street Width 592.8.2 On-Street Parking 602.8.3 Right-of-way Width 60

2.9 STUB STREETS 60

2.10 CONSTRUCTION STANDARDS 612.10.1 Street Cross Section 61

2.10.2 PavementStructure 61

2.10.3 Curb Detail 622.10.4 Shoulder Structure 682.10.5 Driveway Curb-Cut Details 70

Contents


REFERENCES 70

APPENDICES

Appendix A - Curbed Streets 72Appendix B - Uncurbed Streets 74Appendix C - Parkways 76Appendix D - Boulevards 78


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2 - 4 PENNSYLVANIA STANDARDS FOR RESIDENTIAL SITE DEVELOPMENT: APRIL 2007

Figures Page #

Figure 2.1. Residential Access 7Figure 2.2. Through Streets 8Figure 2.3. Single Access Streets 8

Figure 2.4. Residential Collector 9Figure 2.5. Two Sided Parking 11Figure 2.6. Alley Widths 12Figure 2.7. Boulevard with Parking 13Figure2.8. TypesofTrafcFlow 15

Figure 2.9. Parking Adjacent to Street 16Figure2.10. RealignmentofanAngledStreet 18

Figure 2.11. Intersection Spacing 19Figure 2.12. Intersection Curb Transition 22Figure2.13. MinimumIntersectionSiteDistance 23

Figure 2.14. Concrete Sidewalk Continues Across Driveway 26Figure 2.15. Typical curb Return Entrance 27Figure 2.16. Typical Flared Driveway Entrance 27Figure 2.17. Typical Non-Curbed Driveway Entrance 28Figure2.18. CrownedPavementSection 30

Figure 2.19. Intersection Bulb-Outs 31Figure 2.20. Raised Intersection 32Figure2.21. TrafcCircles 33

Figure 2.22. Diagonal Diverter 34Figure 2.23. Chicanes 34Figure 2.24. Raised Median Islands 35Figure2.25. SpeedTable/Hump 36

Figure 2.26. Raised Crosswalk 37

Figure2.27. SmallerStreetTreesAlternative 38Figure2.28. Cross-SectionProle-CurbedResidential

Access Street 43Figure2.29. Cross-SectionProle-ResidentialAccessStreet

with Reinforced Shoulder 44Figure 2.30. Circular Turnarounds Without Center Islands 47Figure 2.31. Circular Turnarounds with Center Islands 48Figure 2.32. T Turnarounds 40Figure2.33. Cross-SectionProle-CurbedResidential

Collector Street 50Figure2.34. Cross-SectionProle-ResidentialCollector

with Reinforced Shoulder 51

List of Graphics

Figures (cont.) Page #

Figure2.35. Cross-SectionProle-CurbedResidential

Mixed-Use Collector Street 54Figure2.36. Cross-SectionProle-ResidentialMixed-Use

Collector with Reinforced Shoulder 54Figure 2.37. Alley Layout 57Figure 2.38. Alley Cross Section 58Figure 2.39. Alley Right-of-way 58Figure2.40. Cross-SectionProle-DividedStreets,

Boulevard with Curb 59Figure2.41. Cross-SectionProle-DividedStreets,Parkway

with Reinforced shoulder 60Figure2.42. RoadwayPavementStructureDetail 62

Figure 2.43. Vertical Face Extruded Curb Detail 63Figure 2.44. Mountable Extruded Curb Detail 64Figure 2.45. Mountable Extruded Curb Detail 65Figure 2.46. Granite Block Vertical Curb Detail 66Figure 2.47. Granite Block Mountable Curb Detail 67Figure 2.48. Concrete Rolled Curb and Gutter Detail 68Figure 2.49. PA DOT Type 3 Shoulder Detail 69Figure 2.50. Shoulder Detail with Reinforced Grass Parking

Strip 70Figure 2.51. Driveway Curb-Cut Detail for Extruded Curbs 71Figure 2.52. Driveway Curb-Cut Detail for Full Depth Vertical

Face Curb 72Figure 2.53. Driveway Curb-Cut Detail for Rolled Curb 73Figure 2.54. Cross-Section - Curbed Streets 74


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2 - 5PENNSYLVANIA STANDARDS FOR RESIDENTIAL SITE DEVELOPMENT: APRIL 2007

Illustrations Page #

Illustration 2-a. Street Function 4Illustration2-b.EagleViewSubdivision,ChesterCounty

&GreyhamptonSubdivision,CentreCounty 7

Illustration 2-c. Street Access Points 8Illustration2-d.CollectorConnectsDevelopments 9Illustration 2-e. Collector in Grid Setting 9Illustration2-f.Firstoorretailwithofcesand/or

residences above. 11Illustration 2-g. Mixture of different housing types. 11Illustration2-h.AlleyinaHistoricVillage(Boalsburg,PA) 12

Illustration2-i.AlleyinNewerDevelopment(Kentlands,MD) 12

Illustration 2-j. Typical Parkway 12Illustration 2-k. Typical Boulevard 12Illustration 2-l. Back-in Only Angled Parking 16I llustration2-m.StripedSpacesforParal lel Parking 17

Illustration 2-n. Acute-angled Intersection 18Illustration2-o.a.Jogmaneuver; 19

b.Separateturningmovement 20

Illustration 2-p. Effective Turning Radius at ResidentialIntersections 22

Illustration 2-q. Illustration of bulb-out 22Illustration 2-r. Obstructions to Corner Sight Distance 24Illustration 2-s. Methods of Preserving Intersection

Sight Distance 24I llustration2-t. DrivewayOff-setfromIntersection. 26

Illustration 2-u. Shared Driveway 27Illustration 2-v. Bulb-Out 31Illustration 2-w. Raised Intersection 32Illustration2-x. TrafcCircle 33

Illustration 2-y. Diagonal Diverter 34Illustration 2-z. Chicanes 35Illustration 2-aa. Raised Median Islands 35Illustration2-bb.SpeedTable/Hump 36

Illustration 2-cc. Raised Crosswalk 37Illustration 2-dd. Tree Canopy 38Illustration 2-ee. Light Fixture Shielding 40Illustration 2-ff. Cul-de-sac Center Island 48Illustration 2-gg. Rectangular Center Island 48

Illustration 2-hh. Curb with Breaks for Drainage 59

List of Graphics


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Recommended StandardsCommentary


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2.0 OVERVIEW

Federal and state transportation agencies categorize streets by function into three classes:locals,collectors,andarterials.AsillustratedinIllustration2-a,thisclassicationscheme

ischaracterizedbyacontinuuminfunctionbetweenlandaccessandmobility.Most,ifnotall,subdivisionstreetsinPennsylvaniacanbeclassiedaslocalorlower-endcollector

streets.Assuch,thesestreetsareasubsetofthetraditionalDepartmentofTransportation

classicationsystem.

Thischapterprovidesstandardsforresidentialstreets.Inthecontextofthisdocument,res-identialstreetclassicationandstandardsencompassbothpureresidentiallanduses,and

amixofresidentialandcommunity-servingcommerciallanduses.Saferesidentialstreets

areattainedbyspecifyingstreetgeometriesthatdiscourageexcessivespeeds,emphasize

access,andminimizeconictsbetweenpedestrianandvehicularmovements.

Therecommendedstandardspresentedinthischapterassistwithmeetingthegoalof

providingsaferesidentialstreets.Recognizingthemanysub-classicationspossiblefor

residentialstreets,theAmericanAssociationofStateHighwayandTransportationOfcials

(AASHTO)recommends(asarststepinthedesignprocess)thateachstreetbedened

intermsofitsspecicfunctionwithinthecommunity(Ref.1,Page13).Section2.2ofthis

chapterpresentsastreetclassicationsystemwhichmeetsthefunctionalrequirementsof

municipalstreetsinPennsylvania.Section2.3providesgeneralstreetandparkingdesign

guidance,andsections2.4through2.9providespecicgeometricandotherdesignstan-dards for each class of residential street. Section 2.10 and the Appendix contain a series oftypical construction details for street design and construction.

Theoverridinggoalofthischapteristoprovidestandardsthatnotonlymeettheneedfor

safeandefcientmovementofvehiclesandpedestrians,butalsominimizeenvironmentalimpacts,andconstructionandmaintenancecosts.

Illustration 2-a. Street Function

Source: AASHTO (Ref. 1)

Land access refers to entering and exiting individualproperties.Whilethisdiagramreferstotheimportance

ofvehicularaccessovervehicularmobility,inalocal

streetsetting,individualpropertiesarealsoaccessed

bythoseonfoot;therefore,thepedestrianmodeofac-cessisalsoofimportancewhendesigninglocalstreets.


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Commentary


Recommended Standards

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Residentialstreetsarecommonlyusedforpur-

posesotherthanefcienttrafcmovement.Thedesignofresidentialandmixed-usestreetsmust

considerandbalancecommunityneeds,including

lotaccess,visualaesthetics,parking,drainage,

utilityaccess,pedestrianandbicyclecirculation,

emergencyaccess,andmaintenance.Aboveall,

sincethesearestreetswhereepoplelive,creat-

ingasafeenvironmentforpedestrians,aswellas

vehiclecirculation,iscritical.

Pursuingstrategybmaymeandepartingfrom

strictcompliancewiththestreetgradestandardsin

sections2.4.7,2.5.8,2.6.7,and2.7.1.Theintentof

anysuchvariancewillbetominimizesiteimpacts

andpreservenaturalsitefeatureswhilemaintaining

a safe street.

Strategydwillminimizestormwaterrun-offim-

pactsandreduceconstructionandmaintenance

costs.

Theintentofstrategyeistopromoteappropriate

streetwidths(travel-wayandparkinglane)tomeet,butnotexceed,communityneeds.

Different types of residential streets have different

characteristics with regard to density of residences

andlanduse.Consequently,asingledesignfora

typical residential street is not practical. A func-

tionalclassicationsystemdifferentiatesbetween

the various types of residential streets in order to

provideadesignthatbestmeetstheneedsofthe

community.

2.1 PURPOSE AND STRATEGY

2.1.1 Purpose

Theprimarypurposeofresidentialandmixed-usestreetsistoprovidelocalaccesstoindi-

vidualproperties.Thesestreetsmayalsofunctionascollectorstodistributetrafchavinganoriginordestinationataresidentialorcommunity-commercial/businesspropertytoa

higher-levelcollectororarterial.Residentialstreetsshallpromote:

a. safeandefcientmovementofvehicular,pedestrianandbicycletrafc;

b. costefciencythattakesintoconsiderationlanduse,construction,andfuture

maintenance;and

c. environmentalstewardshipandsustainabilitybyminimizingadverseimpacts

onthenaturalenvironment.

2.1.2 Strategy

Thedesignandplanningofresidentialandmixed-usestreetsshall:

a. usethefunctionalclassicationsystempresentedinSection2.2;

b. follow the natural contours of the land and preserve natural features whenever practi-cal;

c. minimizetrafcspeedandvolume,noise,congestion,andhazardstopedestrians;

d. minimizetheamountofpavedarea;and

e. provideanaffordableandmaintainablestreetsystemthatservestheresidentsin

thecommunity.

2.2 FUNCTIONAL CLASSIFICATION SYSTEM

Residential streets provide a variety of functions within residential neighborhoods. Eachstreetwithinaresidentialneighborhoodshallbedesignedtoreecttheoverallpurposeitis

intendedtoserve.Proposedorexistingstreetsshallbeclassiedaccordingtotheirfunc-tion. The function of the street shall provide the basis for residential street design.

Thefollowingclassicationsystemsshallbeusedtoidentifystreetfunction.

Theresidentialstreetclassicationsinclude:


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2 - 6

Residential access streets Residential Collectors

Residentialmixed-usecollectors

Specialusestreets(alleys,dividedstreets,andstubstreets)

Non-residentialstreetclassicationsinclude:

Commercial/industrialaccessstreets

Municipal Collectors Municipal Arterials

Therecommendedstandardsprovidedinthischapterareprovidedforresidentialstreetclas-sications.

Streetsclassicationsarebasedonaveragedailytrafc(ADT)volume.EstimatedADTis

tobebasedontripgenerationratesintripsperday(TPD)asdenedinSection2.3.13.A

tripdistributionanalysiswillberequiredtodetermineeachstreetsusagewithinaresidentialdevelopmenttoassurethatappropriatedesignstandardsaremet.

2.2.1 Residential Access Streets

Residential access streets provide direct access to individual residential properties abuttingthatstreet.Theycarrytrafcthathasitsdestinationororiginonthatstreetorfromwithinthe

local neighborhood.

TheAmericanAssociationofStateTransportation

Ofcials(AASTO)presentsstreetclassicationas

ahierarchyofmovementsbeginningwiththemain

movementdenedbythehighestvolumestreets.

Thefunctionalclassicationsystempresentedhereispresentedfromaresidentialaccessperspec-

tive,movingfromthelowestclassicationofstreet

whichprovidesindividuallotaccess,tohigherclas-

sicationswithgreateremphasisonmobilityand

efciencyoftrafcmovement.

Thetrafcvolumelimitsusedthroughoutthisdocu-

mentarebasedonameasureofaveragedaily

trafc(ADT).AverageDailyTrafc(ADT)isdened

byAASHTO(Ref.1)asthetotalvolumeoftrafc

onastreetduringagiventimeperiod(inwhole

numbersofdays),greaterthanonedayandless

thanoneyear,dividedbythenumberofdaysinthe

timeperiod.ADTisacountofalltrafconastreet

(inbothdirections)forthegiventimeperiod.This

unitofmeasureisconsistentwiththeInstituteof

Transportation Engineers trip generation rates. Trip

generationismeasuredasthetotalnumberoftrip

ends(originordestination)measuredataparticular

driveway.Forresidentialstreetdesignpurposes,

ADTisassumedtobebasedontripgeneration

rates (trip ends per day or trips per day [TPD])

asdenedinthemostcurrentversionofThe TripGeneration Handbook,InstituteofTransportation

Engineers (Ref. 10).

ResidentialAccessStreetsnormallyserveonlythose residences located on that street or within theimmediateneighborhood.Trafcvolumesarelow;

therefore,astreetcanbedesignedthatisnotex-cessiveandthatmeetstheneedsofthecommunitywithin a reasonable footprint. Typical residentialaccess streets are illustrated below:


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Commentary



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Figure 2.1. Residential Access

ModiedfromSource:TheHamerCenterforCommunity

Design Assistance (Ref. 2)

Residentialaccessstreetsplayasignicantroleindeningthecharacterofneighborhoods.

Residencesalongthesestreetsalsoserveastheoriginanddestinationfornon-motorized

circulation (walking or cycling). These streets should therefore be designed to bepedestrian- and bicycle-friendly (Figure 2.1).

Residentialaccessstreetsofferlevelsofservicecommensuratewithlowdesignspeeds

andshortvehiculartriproutes.Throughtrafcisdiscouragedonthesestreets.Reecting

neighborhoodcharacterandcreatingapedestrian-friendlyenvironmentisofhigherimpor-tancethanvehicularmobility.

2.2.1.1 TrafcVolume--ResidentialAccessStreet

LimitingtrafcvolumesforeachresidentialaccessstreetclassaretabulatedinTable2-1.

TrafcvolumesshallbecomputedusingtripgenerationratesprovidedinTable2-8.

Table2-1.ResidentialAccessStreetLimitingTrafcVolumes

Street Class LimitingTrafcVolume(ADT)

RA-ASingle AccessMultiple Access

RA-B

300800

1600

Illustration 2-b.

Eagle View

Subdivision,Chester County

Source:TheHamerCenterforCommunity

Design Assistance(Ref. 2)

GreyhamptonSubdivision,

Centre County

Thetrafcvolumelimitsforresidentialaccess

streets are based on the standards in Residential

Streets(Ref.5).Thisdocumentwasdeveloped

throughapartnershipamongtheNationalAs-

sociationofHomeBuilders,theAmericanSociety

ofCivilEngineers,theInstituteofTransportation

Engineers,andtheUrbanLandInstitute.These

standardsarenotbasedonspecicresearch;

rather,theyrepresentaconsensusthatreectsthe

experienceandjudgmentoftheseorganizations.


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2 - 8

Streets connected at both ends are through streets (Figure 2.2).

Straight Loop

Figure 2.2. Through Streets

ModiedfromSource:BucksCountyPlanningCommission(Ref.4)

Singleaccessstreets(self-loopingstreetsandcul-de-sacs)areasub-classicationofresi-dential access streets that have only one access point. Self-looping streets and cul-de-sacsarelimitedtoanaveragedailytrafcvolume(ADT)of300tripsperday.SeeFigure2.3.

Self-Looping Cul-de-sac

Figure 2.3.Single Access StreetsModiedfromSource:BucksCountyPlanningCommission(Ref.4)

Design standards for residential access streets are provided in Section 2.4.

2.2.2 Residential Collectors

Residentialcollectorsprovidemobilityoutofresidentialneighborhoodsandservetolink

residentialaccessstreetsand/orentrancestomulti-familyresidentialcomplexes.Theirpri-maryfunctionistocollectanddistributeresidentialtrafctocollectorsandotherhigher-level

streets.Theymayincludesomelimitedindividuallotanddrivewayaccessalthoughsuch

access,isdiscouraged.

llustration2-ccomparesaresidentialstreetwithtwoaccess points with a loop street. The loop streetonly has one point of connection with a higher-orderstreet.Thenumberofsingle-familydwellingsindicated is based on a trip generation rate of 10tripsperday,astabulatedinTable2-8.

Illustration 2-c. Street Access Points

ModiedfromSource:BucksCountyPlanning

Commission(Ref.4)

Thelimitingtrafcvolumeforsingleaccessstreetsis based on Appendix D of the International Fire

Code (Reference 19).

Limitingtrafcvolumesforsingle-accessstreetsare

basedonadesiretominimizetheriskofanyone

residencebeingcut-offfromemergencyservicesin

theeventthestreetisblocked,whileatthesame

timerecognizingthesestreettypesasvaluableand

viabledevelopmentandplanningoptions.Thetraf-

climitforself-loopingstreetsis50%greaterthanthat for cul-de-sacs because the residents in the

loop can exit the loop in either direction.

Residentialcollectorsmaytakeanumberofforms.

Illustration 2-d shows a residential collector con-

nectingdevelopment,andIllustration2-eshowsa

residentialcollectorinamoreinterconnectedgrid

pattern.


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Commentary



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Figure 2.4. Residential Collector

ModiedfromSource:TheHamerCenterforCommunityDesign Assistance (Ref. 2)

Neighborhoodcharactershallbeofequalimportancetovehicularmobilityinthedesignof

residentialcollectors.Withinthesecorridorsbicycleandpedestrianmovementsaresec-ondarytovehicularmovements.However,itisrecommendedthatbicycleandpedestrian

facilitiesbeincludedwithinthesecorridors,andthatappropriateseparationandbufferingbe

providedtoavoidconicts.Seechapter3formoredetails.

Illustration 2-d. Collector Connects

Developments

Illustration 2-e. Collector in Grid Setting

Inmanycases,streetsfunctioningascollectorsin

developmentsbuiltbeforetheadoptionofthisstan-

dard were designed with continuous lot f rontage

andon-streetparking.Forthisreason,lotfrontage


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2 - 10

2.2.2.1 TrafcVolume-ResidentialCollectors

Residentialcollectorsshallbelimitedtoanaveragedailytrafcvolume(ADT)of3,000.If

theanticipatedtrafcvolumeexceedsthisvalue,thestreetshallbeclassiedasastreetof

higher order and PennDOT standards shall be used.

Design standards for residential collectors are provided in section 2.5.

2.2.3 Residential Mixed-Use Collectors

Residentialmixed-usecollectorsprovideaccesstoamixofresidentialandneighborhood

commercialuses.Theyalsoserveasresidentialcollectors,andconnectorsbetweenresi-dentialneighborhoodsandhigher-orderstreets.Inthedesignofresidentialmixed-usecol-lectors,reectingneighborhoodcharacterisofequalimportancetomobility.

andparkingarenotrestrictedwhendeningstreets

existingatthetimeoftheadoptionofthisstandard.

Parking is restricted on residential collectors to

promotemobilityandminimizepedestrianconicts.

Thisrequirementmaybewaivedalongportionsofthecorridortomeetspecialneedssuchascom-

munityfacilities,ballelds,etc.Otherthanthese

exceptions,parkingalongthesestreetsshouldbe

discouraged.

The authors are unaware of any other street clas-

sicationschemethatincludesapurelyresidential

collector. Collectors are typically considered to

carrytrafcfrommultiplesourceswithnoupper

limitontrafcloading.Asdenedhere,aresiden-

tial collector is intended to be part of a residential

neighborhood.Theupperlimitprovidedisbased

ontheneedtolimitthesizeofstreetswithinstrictly

residential neighborhoods for health and safety

reasons.Highertrafcloadsshouldbelimitedto

Municipal collectors or higher-level streets.

ThemaximumAverageDailyTrips(ADT) of3,000

vehicletripsisestablishedtominimizeconictsduetothenumberofturningmovementsontoandoffresidential collector streets.

Residentialmixed-usecollectorscantakeon

distinctly different characteristics depending on the

neighborhoodtypeanddevelopmentstyle.


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Commentary



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Figure 2.5. Two Sided Parking



Residentialdwellingsalongmixed-usecollectorstypicallyincludequadhouses,townhouses,

ormulti-familyunitsthatareaccessedthroughoff-streetparkinglots,alleys,orsharedentry-

ways.Accesstodrivewaysofindividualdwellingunitsshouldbediscouragedonmixed-usecollectors.

On-streetparkingmaybeusedforaccesstoneighborhoodcommercialproperties,andto

accommodatespill-overparkingforresidentialproperties.

Mixed-usecollectorsmayalsoserveasoriginanddestinationnodesforpedestriansand

cyclists.Pedestrianandbicycleaccessneedsshallbeaccommodatedalongthesestreet

corridors.

2.2.3.1 TrafcVolume--ResidentialMixed-UseCollector

Residentialmixed-usecollectorsarelimitedtoanaveragetrafcvolumeof2,000ADT.Iftheanticipatedtrafcvolumeexceedsthisvalue,thestreetshallbeclassiedasastreetof

higher-order,andthedesignshallbebasedonPennDOTstandards.

Designstandardsforthisstreetclassicationareprovidedinsection2.6.

2.2.4 Special Use Streets

Special use streets include alleys and divided streets and stub streets.

2.2.4.1 Alley: Alleysproviderear-lotaccesstoabuttingproperties.Todiscouragethroughtrafc

andparking,theyareintentionallynarrow.Theycanprovidetheprimaryvehicularaccessto

apropertyorserveassecondaryaccess.Whereappropriate,ancillaryunitssuchasgarage

Illustration 2-f. Illustration 2-g.

Firstoorretailwith

ofcesand/orresidences above.

Mixture of different housingtypes.

Source:TheHamerCenterforCommunity

Design Assistance(Ref. 2)

Usesalongresidential/mixed-usecollectorsserve

asoriginsanddestinationsnotonlyforvehicles,butalsoforpedestriansandbicycles.Themaximumaveragedailytrafcvolumeof2,000vehicletripsrecognizes the collector characteristics of thesestreets,andalsotheneedtominimizeconicts

amongpedestrians,bicycles,andvehicles.

Asaprimaryvehicularaccess,alleysenableprop-

ertiestohaveanunencumberedpublicfrontfacing


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2 - 12

convertions and in-law units face directly onto an alley.

Figure 2.6. Alley Widths



2.2.4.2 Divided Streets:Dividedstreetsareresidentialcollectorsorresidentialmixed-use

collectorswithaplantedornaturalmedianthatseparatesopposingtrafclanes.

Thereisnolimitingtrafcvolumefordividedstreets.However,iftheaveragetrafcvolume

exceeds3,000ADT,thestreethorizontalandverticalgeometryshallbedesignedbasedon

PennDOT standards for collector streets.

thestreetbyeliminatingtheneedfordriveways.

Alleys were used frequently in older villages in

Pennsylvania,asshownhereattheleftbelow.

Illustration 2-h. Illustration 2-i.

Alley in a historic village

(Boalsburg,PA)Source:TheHamer

CenterforCommunityDesign Assistance

(Ref. 2)

Alley in newerdevelopment

(Kentlands,MD)Source:TheHamer

CenterforCommunityDesign Assistance

(Ref. 2)

Theuseofalleyscancreateanordered,

pedestrian-scaledfronttoapropertybypermitting

serviceandmaintenancefunctionsinlessvisible

locations.Modernuseofalleysisillustratedabove,

right.

Dividedstreetsareusedtocreatecommunitychar-

acter and provide esthetic value. They can also be

usedtosplittrafcaroundandpreserveexisting

signicantnaturalfeatures.

Illustration 2-j. Illustration 2-k.

Typical Parkway Typical Boulevard

Source:TheHamerCenterforCommunityDesign Assistance (Ref. 2)


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Commentary



2 - 13

Figure 2.7. Boulevard with Parking

Source:TheHamerCenterforCommunityDesignAssistance(Ref.2)

a. ParkwayAdividedstreetwithnoparking,oftenuncurbed,withlimitedornodirectlotaccess.Parkwaysaretypicallymoreruralinnature,andmedianwidthmayvary

alongitslengthtoaccommodatenaturalfeatures.

b. Boulevard-Adividedstreet,oftencurbed,whereparkingispermittedalongitslengthatdesignatedlocations,orsecondaryaccessstreetsthatrunparalleltobou-levardcartway.Somedirectlotaccessispermitted.Boulevardsaretypicallymore

urban in nature.

2.2.4.3 Stub Streets:Astubstreetisaportionofastreetconstructedasapartofadevelopmentordevelopmentphasethatistobeextendedwhentheadjacentpropertyisdeveloped.Stub

streetsarepermittedinthefollowingcases:

a. Residential access, collector, and residential mixed-use collector streetsmaybe constructedasstubstreetswithinsubsectionsofaphaseddevelopmentfor

whichtheproposedstreetextensionhasbeenapprovedaspartofthedevelopment

masterplan.

b. Residential collector and mixed-use collector streetsmayalsobeconstructedas stubstreetstoadjoiningpropertiesnotincludedinthedevelopmentplanifthefuture

extension of the street is anticipated or planned.

The creation of stub streets provides an opportunityfor interconnection of neighborhoods which has

manyadvantages.Itprovidesmoredirectroutes

betweenlocaldestinationsandeliminatestheneed

tofunneltrafcoflocaloriginanddestinationonto

higher-volumestreets;encouragespedestrianand

bicycletraveltolocaldestinations;andprovides

efciencyinschoolbusrouting,transitservices,

emergencyaccess,andmunicipalservicesofall

kinds.Inaddition,interconnectivityofneighbor-

hoodsencouragesdevelopmentofcommunitycom-

mercialuseswithinneighborhoodsandpromotes


16/80




2 - 14

2.2.5 Non-Residential Streets

Streetsthatdonotprovideaccesstoresidentialorcommunity-servingcommercial

properties.

2.2.5.1 Commercial / Industrial Access Streets: Commercial/industrialaccessstreetsprovide

directaccesstocommercial/industrialpropertiesabuttingthatstreet.Theycarrytrafcthat

iscommercialinnature,andhasitsdestinationororiginonthatstreetorfromwithinthelo-calindustrial/commercialarea.

2.2.5.2 Municipal Collector: Municipalcollectorstreetsfunctionprimarilytoprovidemobility

betweencommunitiesandbusinesscenters;theylinkimportanttrafcgeneratorswithinthe

municipality.Theyalsoprovidelandaccessforstripbusinessandcommercialcentersand

providedirectlinkstohigher-order,state-ownedstreets.

Municipal collector streets should be designed in accordance with standards for PennDOTcollector and arterial streets.

2.2.6 Existing Streets

Eachexistingstreetabuttingoraffectingthedesignofasubdivisionorlanddevelopment

shallbeclassiedaccordingtoitsfunction,design,andusebythemunicipalityatthe

requestoftheapplicant,orduringplanreview.Theclassicationofexistingstreetsshalltakeintoaccountthehierarchyoutlinedinthissection,andmayalsoincludehigherorders

asdeterminedbythemunicipality.

2.3 GENERAL DESIGN STANDARDS

2.3.1 TrafcPatterns

Thestreetstandardspresentedhereareshowninthetrafcowpatternsillustratedin

Figure2.8,anddescribedbelow:

moreofacommunityorsmall-townatmosphere.

Manymunicipalitiesownandmaintainnon-resi-

dentialstreets.Non-residentialstreetdenitions

areprovidedhereforthesakeofclarity.However,design standards for these street types are not

providedinthisdocument.

These streets typically serve the lots in industrial orbusiness parks.

Existingstreetsshouldbeclassiedbasedonfunc-tionandtrafcvolume.Existingstreetsdonotneedtomeetdesignstandardsfortheparticularclassi-cation of streets outlined here.

Trafcpatternsareusedtocontroltrafcmovement

andspeed.Slowandyield-owpatternsareusedalongresidentialaccessstreetstominimizetrafc

speedandpedestrian-vehicleconicts.


17/80


Commentary



2 - 15

Free-ow: Free-owtrafcrequiresauniquelanefortrafcmovingineachdirection.

Free-owstreetsshallhaveamarkedcenterline.

Slow-ow: Slow-owtrafcoccurswhenparkedvehiclesand/orconstrictedlane widthsrestrictthepassingspaceavailabletovehiclesmovingin

oppositedirections.Slow-owstreetsshallnothaveamarkedcenterlineexcept in the vicinity of intersections.

Yield-ow: Yield-owoccurswhentwo-waytrafcisimpossiblewhenparkedvehicles

arepresent. Yield-owstreetsshouldnothaveamarkedcenterlineexcept

in the vicinity of intersections.

Free Slow Yield

Figure2.8.TypesofTrafcFlow.

ModiedfromSource:NationalAssociationofHomebuildersetal.,

Residential Streets (Ref. 5)

2.3.2 On-Street Parking

Angledorparallelon-streetparkingmaybeusedtomeetallorapartoftheparkingrequire-mentdenedinchapter4.On-streetparkingcanservetoslowtheadjacenttravelway-lane

trafcaswellastoprovideabufferbetweenstreettrafcandpedestrians.

Angledon-streetparkingshallbedesignedinaccordancewiththedimensionsinTable2-2.

Inafree-owtrafcpattern,eachlaneisonlyused

tofacilitatetrafcmovement.

Inaslow-owpattern,lanesarewideenoughtoac-commodatetwo-waytrafcbutarenarrowenoughthat if there is a parked car along the side of the

street,somedriverswillchoosetostopandyieldtheright-of-waytotheoncomingdriver.

Inayield-owpattern,somemotoristsmuststopandyieldtheright-of-waytooncomingvehicles.

Fordecadespriortothe1960s,yieldowwasthewidelyacceptednormforlocalstreets.Yieldoperation continues to be explicitly endorsed intheAASHTOGreenbook(Ref.1),whichacknowl-edgestheconditionofoneunobstructedmovinglanewhereopposingconictingtrafcwillyieldand

pauseontheparkinglaneuntilthereissufcientwidthtopass.However,yieldtrafcpatternsraise

safetyconcerns(pedestrianandvehicular),andmaydelayemergencyresponses.Specialconsid-eration should be given to adequate site distance.Forthesereasons,yieldtrafcowpatternsshould

onlybeconsideredforlow-volumeResidentialAc-cessStreetsasspeciedinSection2.4.2.

Inhigh-densityresidentialandmixed-useresiden-tialareas,on-streetparkingcanbeusedtocreatean effective barrier between streets and sidewalks.

Also,inmanyinstanceson-streetparkingcreateslessimperviousareathanoff-streetparkingwhich

mustincludeadditionaltravelandaccessisles.


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2 - 16

Table 2-2. On-Street Angled Parking Dimensions

StallAngle

(degrees)

S*

StallWidth

(ft)

C*

StallLength

(ft)

D*

StallDepth

(ft)

O*

FrontOver-hang

(ft)

A*Minimum

Lane Width

(ft)

45 10 14.1 20 2.1 12/14**

*SeeFigure2-9fordenition.

**12-footwidthappliestotwo-waytrafc;14-footwidthappliestoone-waytrafc

(Boulevard,forexample).

ModiedfromSource:Stover,V.G.,andF.J.Koepke(Ref.6,1988Edition)

Figure 2.9. Parking Adjacent to Street

Wherecurboverhangisallowed,thestalldepth(D)maybereducedbythefrontoverhang

(O).Ifasidewalkexistsatthecurb,thecombinedwidthofthecurbandsidewalkshallbe

sufcienttopermita3-footunobscuredwalkwaywidth(i.e.,theminimumwidthofsidewalk

pluscurbshallbe3feetplusthedimensionO).

Parallel on-street parking spaces shall be 23 feet long. The parking lane width shall be asspeciedinTables2-9,2-10,2-14,and2-16.

Althoughangledon-streetparkingispermitted,its

useisonlyrecommendedwheretrafcvolumeandspeedaresufcientlylowtonotposesignicantriskof an accident when vehicles back into the travellane.

Manycommunitiesarerequiringback-inonlyan-gled parking to enhance safety. All parking requiresabackingmovement,eitherasthevehicleisparkedor when the vehicle leaves the space. Backing intoadened,emptyparkingspaceissaferthanedgingout into a travel lane where the view is obstructedby adjacent parked vehicles. Doing the backingmovementasthevehiclepullsin,ratherthanasitpullsouthasseveraladvantages:1)whenexiting,

thedrivercanmoreeasilyseethetrafcowwith-outpullingintothetravellane,2)loading/unload-ing at the rear (trunk) happens at the safety of thesidewalk,ratherthanoutinthetravellane,and3)the open door directs people (children) easily to thesidewalk,ratherthantheneedtostepbacknearorin the travel lane to close the door and then walk tothesidewalk.SeeIllustration2-1.a,below.

Angledon-streetparkingdimensionsarebasedon the values reported in angled off-street parkingwith additional parking space width and length forpedestrian safety.

Illustration 2-l. Back-in Only Angled Parkinga. b.

HighStreet,Pottstown, PASource:TomHylton


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Commentary



2 - 17

2.3.3 Intersections

Design standards for the intersection of residential streets follow:

2.3.3.1 Intersection Horizontal Alignment: Streets should intersect each other at 90-degreeangles.Wherethisisnotpossible,a50-footsectionofthelower-orderstreet(orstreetwith

lowertrafcvolume)shouldbeangledtomeetthehighervolumestreetata90-degreeangle

(Figure 2.6).

The length of on-street parking is based on thelengthnecessarytoparallel-parkastandardormid-sizedautomobile.Manycommunitiesareadding

painted-stripingtoguidedriversintoaspecicspotalong the parking lane. The stripes between thespaceshelptodecreasethetimeneededtopull

intoandoutofaparallelspacebecausemaneuver-ingroomhasbeensetaside.

Illustration 2-m. Striped Spaces forParallel Parking

CollegeAve.,StateCollege,PA

Intersectionsarepointsofconictandpotentialhazard.Thereadilyobviousassignmentofright-

of-waythatisinherenttothree-wayintersections,togetherwithsubstantiallyfewerconictpoints,

makesthethree-wayintersectionmuchsaferthanafour-way intersection.

Right-angleintersectionsarethemostcomfortable

fordrivers,andprovidethemostdirectviewofap-proachingtrafc.

If local site conditions require an acute-angledintersection,andprecludebendingtheangledstreet,themunicipalauthoritycanconsiderwaiving

thisrequirement.Suggestedmaximumintersec-tion angles are provided in Table 2-2. Note thatadequatesightdistancemustbeprovidedforall


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2 - 18

Figure 2.10. Realignment of an Angled Street

ModiedfromSource:NationalAssociationof

Homebuildersetal.,Residential Streets (Ref. 5)

2.3.3.2 Intersection Spacing: The spacing of streets or other driveway access locations along aparticularstreetshallbeasindicatedinTable2-5.Residentialdrivewaysasdenedinsec-tion2.3.4.1areexemptfromthisstandardexceptforcornerlotsonoradjacenttoaresi-dentialcollectororresidential/mixedusecollectorstreet.Theseresidentialdrivewaysmust

meettheintersectionspacingstandardsinTable2-5.

intersections.

Table 2-3. Intersect ion Alignment Angle

Intersection TypeMinimum

Intersection

Angle *Arterial - Residential CollectorCollector - CollectorCollector - Residential

Access

> 80 0> 70 0> 70 0

*SeeFigure2.10foranglealignmentSource:Stover,V.G.,andF.J.Koepke(Ref.6)

Anothermethodofcompensatingforabadlyangledintersection is to install an island that separates traf-candchannelstheleft-turntrafc(seeIllustration2-k).Theseislandsmustbedesignedtoaccom-

modatetheoccasionaltruckorlargeemergencyve-hicle.Appropriateradiimustbeprovided.Incases

whereappropriateradiicannotbemet,theislandsshouldbedesignedtobemountable.

Illustration 2-n. Acute-angled Intersection

ModiedfromSource:NationalAssociationofHomebuildersetal.,Residential Streets (Ref. 5)

Intersections should be spaced far enough apartto not interfere with each other and restrict egresscapacity. Reference 6 (chapter 6) provides adetailed analysis of the factors affecting intersectionand access drive spacing. Since the spacingrequiredtominimizeegressconictsisdependent


21/80


Commentary



2 - 19

Table 2-4. Intersection Spacing

Through-StreetClassication

Intersection Spacing S

(Edge of pavement or curb corner to

corner spacing; see Figure 2-5)

Residential Access

Residential Collector

Residential/Mixed-UseCollector

Higher-Order Non-Residential Street

125 feet

175 feet

250 feet

>325feet*

*TobedeterminedbymunicipalityorPennDOTbasedontrafccharacteristicsof

the higher-order street. PennDOT standards for signalized intersections require a500-foot separation between adjacent intersections.

ModiedfromSource:Stover,V.G.,andF.J.Koepke(Ref.6)

Figure 2.11. Intersection Spacing


Homebuildersetal.,Residential Streets (Ref. 5)

ontrafcvolumes,tripdirections,andturning

movements,itisdifculttodeveloprecommendedstandards for intersection spacing. The intersectionspacingguidelinesidentiedinTable2-3arebased on considerations presented in Reference6andsimpliedrecommendationssuggestedin

Reference5.Theserecommendationsarealsointendedtominimizetrafcconictsresultingfromjoggingorcorner-cutting.Driversmakeajog

movementwhenintersectionsonoppositesidesofthe street are too closely spaced (Figure 2-o a).

Table2-4speciesintersectionspacingS,where

Sistheedgeofpavementorcurb-linecornertocorner distance between intersecting streets asillustrated in Figure 2-11. These standards apply tocross intersections as well as off-set intersections.

Illustration 2-o. a. Jog Maneuver


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2 - 20

2.3.3.3 Intersection Curb/ Edge Pavement Radii: Minimumrequiredintersectioncurb/edge-of-

pavementcornerradiiaregiveninTable2-5.

Table 2-5. Minimum Required Curb/ Edge Pavement Radii -- Without Bulbouts

Intersection Type Connecting Street Paved WidthsMinimum

Curb Radii

(ft)

Residential Access to Residential Ac-cess

Curbed (see note 1)

Uncurbed

18/20-ftconnectingto18/20-ft

18/20ftconnectingto26/28ft



18/20ftconnectingto18/20ftwithinter-section curbing (see note 2)

201515

40

20

Illustration 2-o. b. Separate Turning Movement


Homebuilders,etal.,Residential Streets (Ref. 5)

Intersectionspacingrequirementsaredependent

ontrafcvolumes,tripdirections,andfrequencyofturningmovements.Itisrecommendedthatintersections be aligned wherever possible.

Curb/edge-of-pavementradiiistheradiusofthecircle joining the intersecting street edges. As thisradiusincreases,thepavingcostandpedestrian

crossingdistancesfortheintersectionincrease,dangerousincompletestopsbecomemore

frequent,anddriversmaketurnsathigherspeeds.However,ifthisradiusisinadequate,trafcconicts

canarise,andvehiclesmightdriveovercurbsorrutshoulders and the adjacent landscape (Ref. 5).

ThecurbradiiinTable2-5weredeterminedthrough

adetailedanalysisofvehicle-turningmovements.This analysis was based on the followingassumptionsandconditions:

Asingle-unittruck(SU),asdenedinReference1,wasusedatallintersections

todenecurbradii.Typicaltrashcollection


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Commentary



2 - 21

Residential Access to Residential Col-lector

Curbed

Uncurbed

18/20ft(RA)connectingto26ft(RC)



18/20ft(RA)connectingto24ft(RC)with

intersection curbing (see note 2)

2520

40

25

Residential Collector to ResidentialCollector

Curbed (see note 3)

Uncurbed

26 ft connecting to 26 ft

24 ft connecting to 24 ft24 ft connecting to 24 ft withintersection curbing (see note 2)

20

40

25

Residential Access to ResidentialMixed-Use Collector (Curbed)

18/20ft(RA)connectingto38ft(RMC)

26/28ft(RA)connectingto38ft(RMC)

18/20ft(RA)connectingto22/30ft(RMC)

26/28ft(RA)connectingto22/30ft(RMC)

1510

25

15

Residential Collector to ResidentialMixed-Use Collector -- Curbed 26 ft (RC) connecting to 38 ft (RMC)

26ft(RC)connectingto22/30ft(RMC)

(see note 4)

20

40

Residential Mixed-Use Collector toResidential Mixed-Use Collector --Curbed

(see note 5)

38 ft (RMC) connecting to 38 ft (RMC)38 ft (RMC) connecting to 30 ft (RMC)22/30(RMC)connectingto22/30ft(RMC)

102020

Notes:1. TopermitaccesstothefullpavementwidthbytheWB-50designvehicle,parkingshall

berestrictedwithin50feetoftheintersectionmeasuredalongthecurb-line.

2. The use of curbing at the intersection of uncurbed streets is intended to keep the wheelpathofturningvehiclesonthepavementsurface.Figure2-12illustratesintersection

curbplacementalongotherwiseuncurbedstreets.

3. Requiresdesignvehicletooccupyapproximately10%ofopposinglane.Thiscanbe

avoided by using a 25-foot curb radius.4. Thecurbradiusmaybereducedto25feetifitisacceptabletoallowtheSUdesign

vehicletooccupyupto50%oftheopposinglaneoftrafctomaketheturning

vehicles,servicevehicles,emergencyservice

vehicles,andschoolbusses(conventionalandlarge)haveturningradiisimilarto,but

slightlyshorterthan,theSUdesignvehicle.ItwasassumedthattheSUvehiclecoulduseboth lanes of a residential access roadway

tonegotiateturns,butonotherstreettypesitwouldberestrictedtothelanedeningitsdirectionalmovement.

The SU design vehicle coupled with its statedturningpathlanerestrictionsdenedthelimitingturningradiusatallintersections.An

IntermediateSemitrailer(WB-50),asdenedinReference1,wasusedtofurtherdene

curbradiiatallintersectionswherecommercialdeliverieswouldneedaccess.Itwasassumedthat the WB-50 design vehicle would usethe full width of the street on both legs oftheintersectiontonegotiateaturn.Somecommunitiesrestrictdeliverytimestoearly

morning,whentrafcislighter,toreducethepossibilitiesoftrafcconictswiththeWB-50vehicles.

Whenstreetwidthsaccommodateon-streetparking,thebeginningandendoftheturnis

off-setfromthecurbbyadistanceequaltotheparkinglanewidth(seeIllustration2-p),makingthe

availableeffectiveturningradiusmuchlargerthanthe curb radius.


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2 - 22

movement.IfvehiclessimilarinsizetotheSUdesignvehiclewillusetheintersection

infrequently,itmaybedesirabletoreducethecurbradiitoreduceimperviousareaand

pedestrian crossing distance at the intersection. It is noted that the pedestrian crossingdistancewouldbereducedby24feetifthecornerradiiarereducedfrom40-to25feet

(Ref. 21).

5. TopermitaccesstothefullpavementwidthbytheWB-50designvehicle,parkingshallberestrictedwithin40feetoftheintersectionasmeasuredalongthecurb-line.

Theminimumintersectioncurb/edge-of-pavementradiiidentiedinTable2-5arebased

onthestreetwidthsindicated.Ifwiderstreetsarespecied,smallerintersectioncurb/

edge-of-pavementradiimaybeappropriate.Anyreductioninthespeciedradiimustbe

supportedbydocumentationspecifyinganappropriatedesignvehicleanddemonstrating

thatthevehiclescorrespondingturningmovementscanbeadequatelyaccommodatedby

theproposedcurb/edge-of-pavementradii.

Figure 2.12. Intersection Curb Transition

(a)Uncurbedstreettouncurbedstreet,(b)curbedstreettouncurbedstreet,(c)Endcurbtransition


Illustration 2-p. Effective Turning Radius at

Residential Intersections

ModiedfromSource:Stover,V.G.,

andF.J.Koepke(Ref.6)

Bulb-outsmaybeusedinconjunctionwithon-streetparking to provide a shorter crossing distance forpedestrians,andproduceachokerthathelpsreduce vehicle speed (see section 2.3.8.1). Whenusedinresidentialareas(seeIllustration2-n),theymayalsoreduceimperviousarea.

Illustration 2-q. Illustration of Bulb-out

Source:Stover,V.G.,andF.J.Koepke(Ref.6)


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Commentary



2 - 23

WhenamunicipalstreetintersectsStateright-of-way,PennDOTstandardsforcurband

edgeofpavementradiiapply.

Whenacurbedstreetintersectswithanuncurbedstreet,provideacurbtransitionas

illustrated in Figure 2.12.

Whenbulb-outs(Section2.3.8.1)areusedatintersections,theresultingeffectivestreet

widthatthebulb-outshallbeusedtodetermineanappropriatecurbradii.Ifbulb-outsare

designedtobemountable,thefullstreetwidthmaybeused.

WhenamunicipalstreetintersectsaStateright-of-way,PennDOTstandardsforcurb/edge-

of-pavementradiishallapply.

2.3.3.4 Intersection Sight Distance: Whenever a proposed street intersects an existing orproposedstreetofhigher-orderortrafcvolume,thestreetoflower-orderortrafcvolume

shallbemadeastopstreet.Thestreetoflowerorderortrafcvolumeshallalsobe

designedtoprovideaminimumclearline-of-sightasdenedinFigure2.13andTable2-6.

Theclearsighttriangleisdenedbyalineofsightfromthepositionoftheeyeofthedriver

(3.5feetabovethestreetsurface)inthestoppedvehicle,tothepositionofanoncoming

vehicle in either lane approaching the intersection. The elevation of the sight-line at theapproaching vehicle is taken as 3.5 feet above the street surface to represent the approachvehicledriverseye.Thebaseofthetriangleisdenedasthecornersightdistance(Yin

Figure 2.13). Points A and B of the clear sight triangle are located along the centerline of theapproachingtravellanes.PointCislocatedatthecenterofthestoppedvehicleslaneand

15feetbehindtheintersectingstreetedge-of-pavement.

*a10-footoff-setdistancemaybeusedwhenresidentialaccess

streets intersect other residential access streets.

Figure 2.13. Minimum Intersection Sight Distance


Keyareasalonganintersectionapproachandacross the corners of the intersection should beclearofobstructionsthatmightblockadriversview

ofoncomingtrafc.Theseareasareknownasclear sight triangles.

The elevation of the sight-line at the approachingvehicles is taken as 3.5 feet to ensure the enteringdriversabilitytojudgetherateofclosureof,and

gapsizebetween,approachingvehicles.

The corner sight distance is dependent on theapproachingtrafcspeed,reactiontimeand

decisiontimeoftheenteringdriver,streetgrades,andotherfactors.Theminimumintersectionsightdistances in Table 2-6 and Figure 2.13 are basedonPennDOTstandardsatthetimeofthiswriting

(Chapter2,Reference18).

The reduced site triangle off-set of 10 feet forresidential access streets intersecting otherresidentialaccessstreetsreectsthereducedriskofanincidentattheseintersections,andpermitsreduced yard setbacks.

The intersection line-of-sight could be obstructedbyverticalalignment,orhorizontalobstructionsin

thesitetriangle,oracombinationofboth.Thisisillustrated in Illustration 2-r.


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2 - 24

Table 2-6. Minimum Intersection Sight Distance (passenger cars)

Design Speed

(mph)

Sight Distance (Y)

(ft.)

2025303540455055

225280335390445500555610

ThesitedistancevaluesinTable2-6applytoavehiclestartingfromastoponastreetgrade

notexceeding3%,andenteringorcrossingatwo-lane,two-waystreet.Ifthereartiresof

thestoppedvehiclearerestingonagradesteeperthan3%,thesightdistancesinTable2-6

shouldbeincreasedby10%.Ifthethroughstreetcontainsamedianorincludesmorethan

onethroughlaneineitherdirection,anadjustmentshouldbemadetothesightdistanceasfollows:

Y = 1.47 V (7.5 + 0.5 X AL)

Where:Y = site distance (ft)

V=throughstreetdesignspeed(mph)

AL=numberofadditionaltravellanes(countlanesinbothdirections)

Note:Anymedianwidthshouldbeconvertedtoequivalentlanesbydividingthemedian

width by 12 feet.

Embankments,buildings,fences,landscaping,crops,parking,treeoverhangs,signs,etc.,

shall be designed so that they do not interfere with the sight distance anywhere within thesighttrianglefromanelevationof2feetabovethegroundto8feetabovetheground.

Areas within the clear sight triangle shall be dedicated as additional right-of-way or shall bemaintainedinasighteasement.

Illustration 2-r. Obstructions to

Corner Sight Distance

ModiedfromSource:Stover,V.G.,

andF.J.Koepke(Ref.6)

The standards for clear site distance used hereare based on data presented in References 1and6.Thesestandardswerederivedfromeldobservations of driver gap-acceptance behavior(Ref. 9).

Methodsofensuringmaintenanceoftheline-of-

sight sight triangles are illustrated in Illustration 2-s.

Illustration 2-s. Methods of Preserving

Intersection Sight Distance

a. Sight triangle incorporated as right-of-way


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Commentary



2 - 25

2.3.3.5 Intersection Approach Grade for Stop Streets:Intersectionapproaches,wherevehicles

stopwhilewaitingtoproceed,shallbedesignedwithanapproachpavementgradelessthan

+3%.Thelimitingapproachgradescanbeincreasedto5%ifitcanbeshownthaticeand

snowconditionswillnotcreateasignicantproblem.

Onresidentialaccessstreets,theapproachgradeshallbemaintainedforaminimum

distanceof25feetfromtheintersectionalongtheminorstreetfromtheedgeofcartwayon

thethroughstreet.Forallotherstreetclassications,aminimumdistanceof50feetshallbemaintained.

2.3.3.6 Turn Bays and Deceleration lanes: Turn bays and deceleration lanes shall be constructedwhenwarrantedbyatrafcimpactstudy(seesection2.3.14).Whenwarranted,turnbay

anddecelerationlanegeometryshallbedesignedinaccordancewithPennDOTstandards

(Ref. 18).

2.3.4 Driveways

a. General:Drivewaysshallbelocated,designed,constructedandmaintainedinsuchamannerasnottointerfereorbeinconsistentwiththedesign,maintenance,and

drainage of the street.

b. Approach:Alldrivewayentrancesshallbedesignedtomaintainproperdrainagefromthestreet.Wherethestreetiscurbed,drivewayapproachesshallbeinstalledto

maintaincontinuationofowalongthegutter-line.Alternatively,agutter-linemaybe

formedinthepavementacrossthedrivewayentrancetoensureproperdrainage.

b. Sight triangle protected by acquisition of use(easement)

ModiedfromSource:Stover,V.G.,andF.J.Koepke

(Ref. 6)

Thelimitingstreetgrades(lessthan3%)arebased

onminimizinghazardsfromsnowandice,andallowingforunimpededvehicleaccelerationfroma stop. In areas where snow and ice are not ofparticularconcern,streetgradescouldbeincreased

to5%(Ref.1and5)aslongasanappropriateadjustmentismadetothestoppingsightdistanceinsection 2.3.3.4.

Thelengthoftheminimumapproachgradeisreduced to 25 feet for residential access streets tominimizesitegradingimpacts.Thisisjustiedbythe low design speed of these streets.

Turn bays and deceleration lanes provide for safetyandefciencyonstreets.Limitedtrafcvolumes

onresidentialaccessstreetstypicallydontwarrantthesefeatures.However,thesefeaturesshouldbeprovided whenever they are warranted based on atrafcimpactstudy.

Inthiscontext,properdrainagemeansthatdrainagefromandalongthestreetwithintheright-

of-wayismaintained.Wherethestreetiscurbed,anadequateow-linemustbemaintainedalongthe gutter so runoff is not directed into the drivewayentrance.Thiscanbeaccomplishedbyensuringthat the driveway elevation rises at least to the curbheightalongtheentranceprolepriortodroppingto

thedesiredgrade.Wherethestreetisnotcurbed,entrance grading shall direct runoff to a street swale


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2 - 26

c Minimum distance from Intersections:Thedistancefromtheedgeofpavementoftheintersectingstreettothepointofcurvatureofthedrivewayedgeofpavementorcurb

radiusshallbeaminimumof20feetoncurbedstreetsand30feetonuncurbedstreets.

Forareddriveways,measurementshallbetothebeginningoftheair.Innocase

shallthetangentdistancebetweentheintersectionradiusanddrivewayradiusorair

point be less than 10 feet.

d. Corner lots:Whenboundedbystreetsoftwodifferentstreetclassications,drivewaysforcornerlotsshallgainaccessfromthestreetoflowerclassication.However,access

shallbepermittedfromthestreetofhigherclassicationinthefollowingcases:

1. ifnootherreasonableaccessisavailable;and

2. whengradinglimitationsorotherrestrictionsdictatethataccessbefromthehigher-

order street.

e. Property line clearance:Exceptforjoint-usedriveways,noportionofanyaccessshallbe located outside the property frontage boundary line.

f. Sidewalk Crossing: Ifasidewalkispresent,thesidewalkpavementmaterialshallbecontinued across the driveway width. See Figure 2.14.

Figure 2.14. Concrete Sidewalk Continues Across Driveway

2.3.4.1 Driveways to Single-family Dwellings, Duplex Houses, or Apartments with Five Units

or Fewer:

a. Joint driveways: Jointorcommondrivewaysservingnomorethanthree(3)single-familydwellingsarepermittedandshallbedesignedinaccordancewiththestandards


andawayfromthedrivewayentrance.

Theminimumdistancefromintersectionstandards

areasspeciedinPACodeTitle67,Chapter441.8.Tominimizevehicleconicts,alargerseparationdistance should be used when possible. This

requirementmaybewaivedonlyiftheintersectingstreet radius extends along the property frontage totheextentthatcomplianceisphysicallyimpossible.See Illustration 2-t for a graphic description ofspecieddistances.

Illustration 2-t. Driveway Off-set

from Intersection

ComparabletoaPennDOTminimumusedriveway(PACODETitle67,Chapter441.8).Illustration2-ushows a typical shared driveway.


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Commentary



2 - 27

of this section.

b. Curb Cut:Theminimumcurbcutordrivewaywidthatthecartwayedgeshallbe10ft.Themaximumcurbcutordrivewaywidthatthecartwayedgeshallbe20ft.

c. Curb return entrance: A curb return entrance is illustrated in Figure 2.15. When curbreturnentrancesareused,thecurbshallhaveaminimum3-footradius.However,any

driveway entering into a PennDOT right-of-way shall be designed in accordance with PA

CodeTitle67,Chapter441.

Figure 2.15. Typical Curb Return Entrance

Note:fordrivewaysenteringintoPennDOTROW,designshallbeinaccordancewithstandardsinPACodeTitle67,Chapter441.

ModiedfromSource:AASHTO(Ref.1)

d. Flaredentrances:Whenareddrivewayentrancesareused,aminimum2-footair

shallbeprovided.AtypicalaredentranceisillustratedinFigure2.16.

Illustration 2-u. Shared Driveway

ModiedfromSource:NationalAssociationofHomebuild-

ers,etal.Residential Streets (Ref. 5)

ThedrivewayreturnradiusstandardisfromReference1,p.402.A5-footradiusiscommonpractice.

The2-footarewidthprovidesaneffectivedrivewaywidthsimilartothatofa3-footcurbradius.


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2 - 28

Figure 2.16. Typical Flared Driveway Entrance


e. Non-curbedentrance:Non-curbeddrivewayentrancesshallhaveaminimumedge-of-

pavementradiusof5feetasillustratedinFigure2.17.

Figure 2.17. Typical Non-curbed Driveway Entrance


f. DrivewayProle:Drivewayprolesshallprovideefcientaccesstotheabutting

residentialstreet,allowforlow-speed90-degreeturnsintothedriveway,andprovide

safe access to the residential garage or parking area. The following standards shallapply:

1. The algebraic change in grade between the street cross slope and the drivewayapproachapronshallbelessthanorequalto8%.

2. Whenthealgebraicchangeingradeatanypointalongthedrivewayexceeds10%,

averticalcurvehavingalengthspeciedinTable2-7shallbeused.

An entrance radius slightly larger than the curbreturnentranceradiusisspeciedfornon-curbed

drivewayentrancestominimizeshoulderrun-off.

Excessive changes in driveway grade at theentranceoralongtheprolewillcausethefrontor

rearbumpertodragonthesurfacesofthestreetordriveway.The8%changeingradeatdrivewayentrances is based on PennDOT standards inReference 18.

When the change in grade at a point along thedrivewayislessthan10%,eldroundingwillprovideanadequatetransition.However,whenthe

changeingradeequalsorexceeds10%,averticalcurve should be provided.

Thestandardsherehavebeenadaptedfrom

chapter7ofReference6andmodiedtoreect


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2 - 29

Table 2-7. Length of Vertical Curves for Extreme Changes in Driveway Grade

Algebraic Change

in Grade (%)

Length of Vertical Curve

Sag Crest

10

152025

25

354555

10

203040

3. Drivewaygradesshallnotexceed10%fortherst18feetfromthestreetedgeof

pavement.Inaddition,thedrivewaygradeshallnotexceed10%inanyareaused

fordesignatedparkingalongthedriveway,orwithin20feetofgarageentrances.

4. Drivewaysservingresidentialdwellingsshouldtheygenerallybelessthan15%,but

innocaseshouldexceed20%.

2.3.4.2 Entrance Drives for Multi-family Developments and Off-street Parking Lots:

1. Exceptasoutlinedinsection2.3.4,alldrivewayentrancesontopublicrights-of-wayshall

bedesignedinaccordancewithPennDOTentrancestandardsasdenedinPACode,

Title67,Chapter441.

2. Withtheexceptionofdrivewaysoutlinedinsection2.3.4.1,allprivatedrivewaysand

streets shall be designed in accordance with the standards for public streets in Sections2.5 through 2.8.

2.3.5 Easements

Toeconomizeonthelossofsitearea,easementsmaybeusedinlieuofrights-of-wayfor

utilities,sidewalks,snowstorage,sighttriangles,slopemaintenanceareas,etc.,whenever

possible.Streets,curbs,streetgutters,andcrossdrainagepipesandculvertsmustbe

placed in the street right-of-way.

PennDOT standards (Reference 18).

An 18-foot area at the driveway entrance providesvehicles with a transition and landing area at theentrancefromwhichtosafelyenterthestreet.On

steepdriveways,thisareaalsoprovidesasafeparkingareawheninclementweatherprevents

thevehiclefromdrivingtheremaininglengthofthedriveway.

Easementsgrantrightsofpassagethroughand/

oruseofprivatelyownedproperty.Easementsprovidethesameaccesstoutilitiesasrights-of-way(Ref.13,p.62).Theuseofeasementsmayallow

theplacementofutilitylinesalongtheshortestpath,thereby decreasing both the overall length of theline and the associated costs.

Legalrightstoeasementlandareasaretypicallyassignedtothemunicipality,utilitycompany,and/or

homeowners.Easementareasacrosslotsaremaintainedbytheowners,savingthemunicipality

upkeepfunds.(AdoptedfromReference14,p.25.)


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2 - 30

2.3.6 Rights-of-way

Rights-of-way shall be set aside to provide adequate space for the construction andmaintenanceofstreets,shoulders,curbs,streetgutters,andcrossdrainagepipesand

culverts.Theymayalsoaccommodatesidewalks,snowstorage,sighttriangles,slopemaintenanceareas,andutilitiessuchaswater,sewer,stormdrainage,electricalservice,

cableTV,andgaslineswhereappropriate.

2.3.7 Travelway Cross Section

Withtheexceptionofalleysanddividedstreets,residentialstreetsshallbeconstructedwith

a center-crowned street cross-section as illustrated in Figure 2.18. Cross slopes between2%and4%areappropriateforresidentialstreets.

Figure 2.18. Crowned Pavement Section

Forstreetshavingmorethanonetravellaneineachdirection,PennDOTstandardsfor

street cross slope should be followed.

2.3.8 TrafcCalming

Trafccalmingmeasuresaretechniquesdesignedtoslowtrafcandreducecut-through

trafcvolumesinresidentialneighborhoods.Theminimumroadwidthstandardscontained

inthischapterwereestablishedtoenhancetrafccalming.Themeasuresincludedinthe

followingsub-sectionsmaybeusedtofurtherenhancetrafccalming.

TrafccalmingmeasuresshallbedesignedinaccordancewiththestandardsinReference

12,Pennsylvanias Trafc Calming Handbook.

Rights-of-wayusedforutilities,sidewalks,snowstorage,sighttriangles,slopemaintenanceareas,

orotherdesignelementsshallbesubjecttoreview

toensurethattheminimumrequiredright-of-waywidth does not unfairly contribute to an increase inhousing cost through an associated reduction indensity.(AdaptedfromReference14,p.25)

A center-crowned street cross-section facilitatespavementdrainageatthestreetedge.Pavementcross-slopesbetween2%and6%are

recommendedinReference1.A3%crossslopeisrecommendedforresidentialstreets.Crossslopes

lessthan2%willnotprovideadequatepavementcross drainage. Steeper cross slopes produce

enhancedpavementdrainageandnarrowergutterowwidths(lessspread)forthesamegutterow

rate.Crossslopesgreaterthan4%mayresultinsomedriverdiscomfort.

Crossslopesgreaterthan4%aresometimesused

onmulti-lanestreetstoprovideadequatepavementcrossdrainage.Formulti-lanestreets,PennDOT

cross-slopestandardsbasedonpavementdrainagerequirementsshouldbefollowed.

Trafc-calmingmeasuresaremainlyusedto

addressspeedingandtoreducethevolumeofcut-throughtrafconneighborhoodstreets.These

issuescancreateanatmosphereinwhichnon-motoristsareintimidated,orevenendangered,by

motorizedtrafc.Byaddressinghighspeedsandcut-throughvolumes,trafccalmingcanincreaseboth the real and perceived safety of pedestrians


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2.3.8.1 Intersection -- Bulb-Outs

Figure 2.19.

Intersection Bulb-OutsSource: PennDOT (Ref. 12)

Bulb-outs are curb extensions used to narrow the pavedstreetwidth,typicallyatplaceswherepedestrianscross.They

usuallyextendthewidthofaparkinglane,about6-to8-feet

fromtheconventionalcurbline.Theyareappropriateforuse

onallresidentialstreetclassications.Typicalreasonsfor

their use include: Reduce pedestrian crossing distance

Improvetheline-of-sightforpedestrians Makepedestriansmorevisibletooncomingtrafc

Slowtrafcbyfunnelingitthroughanarrowerstreet

opening Slowvehiclesmakingarightturnbyreducingthe

effective curb radius

Bulb-outdesignshouldconsiderthefollowingelements:

Adequatedrainagemustbeprovided.Pondingmayoccuralongthecurb-lineoron

thesidewalkifadequateprovisionisnotmadefordrainage.

Considerationshouldbegiventotheneedforsnowandiceremoval.

Verticalcurbsarerecommendedtocreateapositivebarrier.Howevermountablecurbscanbeusedifnecessarytoaccommodateturningtrucksandbusses.

Mid-blockbulb-outsshouldbecombinedwithcrosswalkswheneverpossible.

Foradditionalguidanceandforfutureupdates,seeReference12,ch.5,pp.24-25.

andbicyclists,andimprovethequalityoflifewithinneighborhoods (Ref. 12).

Severaltrafc-calmingmeasuresareincludedasapartofotherstandards.Forexample,narrow

streetwidthsarepromotedasapartofthestreet

standardsforeachstreetclassication,andbulb-outs are included as an option under intersectioncartwayradiusdenitionsinsection2.3.3.

Bulb-outsareperhapsthemostcommontrafc-calmingtechnique.Theygreatlyreducethetimeneeded for pedestrians to cross an intersection andhelptoclearlydenetheparkinglane.Bulb-out

congurationsalsoimprovepedestrianvisibilityat intersections. Bulb-outs have been observedtoreducetravelspeedsbyupto5mph(Ref.12).However,whenthebulb-outwidthislessthanthe

widthoftheparkinglane,littlereductionintravelspeed is realized.

Illustration 2 - v. Bulb-Out

Bulb-outs are typically used at intersections.However,theycanbeusedatmid-blocklocations

wherethereissignicantpedestrianactivity(nearschools,forexample),whereablockislongand

amid-blockcrossingisdesired,ortoaddressspeeding.Bulb-outsarealsosometimesreferredto

ascurbextensions,knockdownsorchokers.


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2 - 32

2.3.8.2 Intersection -- Raised

Figure 2.20.

Raised intersectionSource: PennDOT (Ref. 12)

Raisedintersectionscomprisetheentireintersection,

including the associated crosswalks. The intersectionsare raised 3-inches to 6-inches above street level. Raisedintersections function to lower travel speeds and decreaseconictsbetweenvehiclesandpedestriansbybetter

demarcatingcrossingareasandelevatingpedestrians

abovethestreetlevel.Theyaremostappropriatelyused

wherethereishighpedestrianactivityinresidential/mixed-

use areas.

Design considerations include: Therampgradeof4%to8%shouldbemaintainedontheapproachtotheraised

intersection. Useoftactilemeasurestowarnvisuallyimpairedpeopleofthelocationofthecross

walk and raised intersection. Useofappropriatedrainageelements.

AllADArequirementsmustbemet.

Considerationmustbegiventosnowandiceremoval.



Raised intersections have been observed to haveonlyaminoraffectonvehiclespeed(Ref.12).The effectiveness of raised intersections can be

enhanced through the use of textured surfacematerials.

Illustration 2 - w. Raised Intersection

Source: PedestrianandBicycleInformationCenter

(Ref. 26)


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2.3.8.3 Intersection--TrafcCircle

Figure2.21.TrafcCircles

Source: PennDOT (Ref. 12)

Trafccirclesareraisedislandslocatedinthecenterof

anunsignalizedintersection.Alltrafcmustnegotiatethe

circle and circulate in a counterclockwise direction. Theirprimaryfunctionistoimprovetheefciencyandsafetyof

stop-sign controlled (2-way or 4-way) intersections.

Trafccirclescanbeusedonanystreetwheretrafc

volumesarelessthan3,500tripsperday,butshouldnotbe

usedwheretheremaybeasignicantpedestriancrossing

volumeorhighleft-turnmovements.

Other design considerations include: Turninganalysisshouldbecompletedtoensurethatthedesignvehiclecannegotiate the circle.

Careful consideration needs to be given to intersection paving and drainage. canbeusedifnecessarytoaccommodateturningtrucksandbusses.

Forsafety,streetlightingshouldbeconsideredinthevicinityoftrafccircles.

Provisionsshouldbemadeforsnowandiceremoval.

Foradditionalguidance,includingrecommendedgeometricstandards,andforfuture

updates,seeReference12,ch.5,pp.34-36.

Thecurveofatrafccircleforcesthedrivertoslowdownandpayattentiontoothervehicles.Trafccircles have been observed to reduce accidents

at intersections and reduce the speed of vehiclestraveling along an uncontrolled street at two-waystopintersections.Trafccirclesaremosteffectiveat reducing speeds when several are used in aseries.Onaverage,speedsarereducedby4to6

mphinthevicinityofcircles.

Illustration2-x.TrafcCircle

Source: PedestrianandBicycleInformationCenter,Ref.26.

However,trafccirclesmaymakeitdifcultfor

emergencyvehicles,busses,andtruckstoturn

left.Inaddition,emergencyvehiclesexperiencedelays (5 to 8 seconds per circle) when travelingstraightthroughtrafccircles(Ref.12);therefore,

theyshouldnotbeusedalongemergencyresponseroutes.

Ch 2 S S d d


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2 - 34

2.3.8.4 Intersection - Diagonal Diverter

Figure 2.22.

Diagonal DiverterSource: PennDOT (Ref. 12)

A diagonal diverter is a physical barrier placed diagonallyacross a four-way intersection. Their purpose is toeliminatethroughtrafc.Theyaremostappropriatelyused

onresidentialaccessorresidential/mixed-usestreetsto

controltrafcowthroughaneighborhood.Avarietyof

diverter designs are possible.

Design considerations should include: The diverter radius should be appropriate for the

street design speed or a reduction in speed shouldbe posted.

The design and location of diverters shall becoordinatedwithemergencyresponseagencies.

Include curb cuts and breaks in diverters toaccommodatepedestrianandbicyclemovements.

Divertersshouldbeclearlyvisibleatalltimes.Usepaintedcurbs,delineation,streetlights,and

advance warning directional arrow signs.


updates,seeReference12:Ch.5,p.48-49

2.3.8.5 Chicanes

Figure 2.23. ChicanesSource: PennDOT (Ref. 12)

Chicanes are a series of three curb extensions staggeredonalternatingsidesofthestreetatmid-blocklocations.

Theprimaryfunctionofchicanesistoslowvehiclesby

makingmotoristsweavethroughtheextensions.

Chicanesareappropriateforuseontwo-lane,two-way

streetsaswellasone-lane,one-waystreets.Chicanes

canbeusedonanystreetclassicationwithtrafc

volumeslessthan3,500vehiclesperday.However,they

arenotrecommendedinareaswheretheymayinterfere

withdrivewayaccess,orwheretrafcvolumesarelowor

unbalanced(movementspredominantlyinonedirection).

Forthesereasons,theiruseisnotrecommendedon

residential access streets.

Diagonaldivertersmaybeexpectedtoreducetrafcvolumesby20to70%(mostreductions

around35%)(Ref.12).Unlesstheneighborhood

isconnedtoalimitedarea,installingasingledivertermaymerelyshiftthroughtrafctootherlocal streets. Diagonal diverters generally need tobe installed in a group or cluster to effectively routetrafctocollectorandarterialroadways.

Illustration 2 - y. Diagonal Diverter

Chicanesworkbydeectingthevehiclepathandtherebyshorteningthedriverssightdistance.Chicanes have been observed to reduce travel

speedsinsidethechicanesby5to13mph,andinthevicinityofthechicanesby1to6mph(Ref.12).

Ch t 2 St t St d d


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2 - 35


2.3.8.6 Raised Median Islands

Figure 2.24.

Raised Median IslandsSource: PennDOT (Ref. 12)

Median islands are narrow islands between travel lanesthatcanbedesignedtoaccommodatepedestrians

through breaks in the curbing and landscaping. Theycanbeusedatintersectionsormid-block.Theprimary

functionofraisedmedianislandsistoreducethe

crossingdistanceforpedestriansbyallowingthemtocrosshalfthestreetatatime.Althoughthetravellanes

donotchangewidth,themedianislandcreatesthe

perception that the width is narrower.

Design considerations include:

Drivewayandintersectionlocationmustbeconsideredwhendeterminingmedian

island location and length.

Width:6-to8feettocomfortablyaccommodatepedestrians.

Illustration 2 - z. Chicanes

Source: PedestrianandBicycleInformationCenter,Ref.26.

Chicanes have been observed to lose theireffectivenesswhenmotoristshavetheopportunity

tocrossthecenter-lineandmaintainnearlyastraightlineoftravel(Ref.12).Thismayhappenon

low-volumeroadwaysorwhentrafcmovementsareprimarilyone-directional.

Raisedmedianislandscanalsobeusedtovisuallyenhance the street if landscaped appropriately.They are also effective in preventing passingmovements,andcanbeusedincombinationwithchicanestokeepvehiclesfromcrossingthemiddleline.

Ch t 2 St t St d d


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Length:12-to20feetminimumneededtoresultinsomereductionintravelspeed.

Provisionsshouldbemadeforsnowandiceremoval.

Foradditionalguidanceandforfutureupdates,seeReference12:Ch.5,p.30,32.

2.3.8.7 Speed Table / Hump

Figure 2.25.

Speed Table / HumpSource: PennDOT (Ref. 12)

Aspeedtable/humpisaraisedsurfaceontheroadway

thatistypically3-to4-inchesinheight,and12-to20-feet

inlength.Theyareprimarilyusedatmid-blocklocationsfor

speedreduction.Theuseofspeedhumpsshouldbelimited

to application on residential access streets.

Avarietyofspeedhumpdesignshavebeendeveloped

(Watts,SeminoleCounty,GwinnettCounty,etc.)andtested.

Specicdesigndetailsandapplicationrecommendations

foreachareoutlinedinReference12.Speedhumpshave

beenfoundtobeaveryeffectivemeansofvehiclespeedreduction.

Design considerations include: Humpheight,length,andprole

Spacing/locationalongthestreet

Drainage Appropriatesignageandpavementmarkings

Should not be installed on curves Cannot be used on streets without curbs unless restrictive signing or fencing is used

adjacenttothehump

Illustration 2 - aa. Raised Median Island

Raisedmedianislandshavealsobeenfoundtoresultinasmallreductionintravelspeed(2to3

mph)iftheycreatealocalreductionintravel-waywidth (Ref. 12).

Eachspeedtable/humpdesignhasunique

speed-reducingcharacteristicsbasedonprole,height,length,andspacing.Reference12provides

detailedinformationontheeffectivenessofeachdesign.

Illustration 2 - bb. Speed Table/Hump

Source: PedestrianandBicycleInformationCenter,Ref.

26.



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Commentary



2 - 37

Shouldnotbeusedonemergencyresponseroutes

Considerationshouldbegiventosnowandiceremoval

Foradditionalguidanceandforfutureupdates,seeReference12:Ch.5,p.38-45.

2.3.8.8 Raised Crosswalk

Figure 2.26.

Raised CrosswalkSource: PennDOT (Ref. 12)

Raisedcrosswalksaresimilartospeedtables/humps,

thoughthesearemarkedandelevatedforpedestrian

crossing purposes. Raised crosswalks serve as anextensionofthesidewalkatmid-blocklocationsor

intersections. Their purpose is to reduce vehicle speedsandimprovethevisibilityofpedestriansbyclearlydening

crossinglocations.Theyaremostappropriatelyused

inareasofsignicantpedestriancrossingactivityalong

residentialaccessandresidential/mixed-usestreets.Theiruseisnotrecommendedalongresidentialcollector

roadwaysorprimaryemergencyresponseroutes.

Design considerations include:

Useoftactilemeasurestowarnvisuallyimpairedpeopleofthelocationofthecross

walk Appropriateplacementofsignagetoalertdriversofcrosswalk

Therampgradeof4%to8%shouldbemaintainedontheapproachtotheraised

crosswalk

Appropriatedrainageelementsmustbeconsideredinthedesign AllADArequirementsmustbemet

Considerationmustbegiventosnowandiceremoval


updates,seeReference12,ch.5,pp.46-47.

2.3.9 Street Landscaping

Street trees are usually planted within a buffer area between the street edge and thesidewalk(seechapter3,Section3.1.2,Buffering).Streetlandscapingshallbedesigned

totthescaleandcharacterofthedevelopment.Thefollowingstandardsshallbeapplied

Speedtable/humpsshouldbedistinguished

fromspeedbumps,whichmaybeencounteredinparkinglots.Speedbumpsare3to6incheshigh

and1to3feetinlength.Speedbumpsresultinsignicantverticaldisplacementatlowspeeds,but

arenotappropriateastrafc-calmingmeasureson

through streets.

Duetotheirwidth,markingsormaterialchange,

andtheirelevationchange,raisedcrosswalksprovide both a visual and physical device forslowingtrafc.Raisedcrosswalkshavebeenobservedtoreducespeedsanaverageof6mph(Ref. 12). The effectiveness of raised crosswalkscan be enhanced through the use of texturedsurfacematerials.

Illustration 2 - cc. Raised Crosswalk

Inadditiontoefcientcirculationforvehiclesandpedestrians,residentialstreetsshouldalso



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2 - 38

(Ref. 22).

a. Plant trees on both sides of the street with spacing as follows:

1. Under30-footspreadatmaturity: 15-35feetoncenter

2. 31to50-footspreadatmaturity: 25-55feetoncenter3. Over50-footspreadatmaturity: 40-80feetoncenter

b. Plant trees on only one side of the street as an option when the street is adjacent to asignicantfeaturethatprecludesplantingonbothsidesofthestreet,suchas:

1. Preserved hedgerows or woods

2 Open space or conservation areas

3. Commongreenorcentralopenspace

c. Whenalessformalarrangementisdesired,orwheremorescreenedviewsormore

lteredviewsaredeemedappropriate,groupingsofsmallertreesmaybeusedtoreplacethetreesspeciedinaabove.

Figure 2.27. Smaller Street Trees Alternative

Less-formalstreettreelayoutisappropriateduetoadjacentfarmviews

ModiedfromSource:Judith Larkin (Ref. 22)

d. Whenpossible,retainexistingtreeslocatedwithintheproposedright-of-way.Thesewill

becountedtowardfulllmentofthestreettreerequirementsspeciedabove.

e. Street trees should be planted at least 3 feet behind the back-of-curb. If the street is not

create positive aesthetic qualities for residentsandvisitors.Streettreesgrowtobecomeoneofthelargerelementsofthestreetenvironment,yet

theyareinstrumentalincreatingacomfortable,human-scaledspace(seeIllustration2-dd).Along

withhelpingtonaturalizeastreet,streettreesalso

minimizeairpollutionandcreateshade,whichreducessummertemperaturesinthatarea(Ref.2).

Illustration 2-dd. Tree Canopy

Tree canopy assists in creating a pleasant pedestrianspace along the street

Source:TheHamerCenterforCommunityDesign

Assistance (Ref. 2)

Much of the character of older neighborhoods isderivedfromthematurestreettreesthatformacanopy over the entire street (Ref. 5).

Whenplantmaterialsforastreetscapeareselected,theimageandscaleoftheneighborhood,

locationofutilities,trafccontroldevices,street-lightinghardware,trafcclearances,aswellas intersection clear sight triangles should beconsidered (Ref. 5).

The choice of tree species should take intoconsiderationtheirmatureheightandspread,therootsystemspotentialfordamagingsidewalksand

streetpavements,maintenancerequirements,and



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Commentary



2 - 39

curbed,streettreesshallnotbeplantedwithintheclearzone.

2.3.10 Street Lighting

Residential street lighting shall be required only where there is concern for public safety.Wheninstalled,streetlightingshallmeetthestandardsofthissection.Standardsforthe

lightingfornon-vehicularpedestrianandbicyclepathsandwalkwaysshallbeasspeciedin

chapter 3.

Pole Height:Allpole-mountedluminairesusedtoilluminateresidentialstreetswithinthe

municipalityshallhaveapoleheightsuchthatthemaximumelevationofthebottomofthe

luminairedoesnotexceed25feetabovethestreetsurface.Municipalstreetlightsmounted

onsignalpoles,existingutilitypoles,orwhereutilityeasementswillconictwiththe

streetlightsmountedaccordingtotherequirementsofthissectionshallbeexemptedfrom

theheightrequirementsassetforthunderthissection.

Shielding: Allmunicipalstreetsshallbeshieldedinaccordancewiththefollowingstandard:

Initialluminaireoutput2,000lumens Fullyshielded

Afullyshieldedluminaireisoneinwhichalllightemittedbythexture,eitherdirectlyfrom

thelamporadiffusingelement,orindirectlybyreectionorrefractionfromanypanofthe

luminaire,isprojectedbelowthehorizontalasdeterminedbyphotometrictestorcertied

bythemanufacturer.Anystructuralpartofthelightxtureprovidingthisshieldingmustbe

permanentlyattached.

adaptabilitytothespecicstreetenvironment(Ref.5).

Shrubs selected for right-of-way planting should belowgrowingor,inthecaseoflargeshrubs,tolerant

ofunder-trimming.Lowshrubsandgroundcovers

withvigorousrootsystemscanbeeffectiveforerosion control on slopes within the right-of-way(Ref. 5).

Beforeplantingtreesorshrubsnearstreetlights,check their photosensitivity. Continuous exposuretostreetlightscancauseabnormalgrowthincertaintrees and shrubs. In northern states where salt isusedonthestreetsforsnowandiceremoval,salt-tolerant species should be selected (Ref. 5).

Residentialstreetlighting,whereused,doesnot

servethesamepurposeashighwaylighting.Vehicles traveling at slow speeds can easilytraverse residential streets at night without externallighting.Forpedestriansafety,streetlightsshouldbe considered at inte

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