MODULE4:TRAFFICSIGNALDESIGNLesson1:TRAFFICSIGNALDESIGN

GRADELEVEL:9–12

ThisSTEMlessonintroducesstudentstoIntelligentTransportationSystem(ITS)conceptswherebythetransportationinfrastructureofroadwaysensors,signalsandcommunicationnetworks,incombinationwithourownvehicles,cancontroltrafficsignalstominimizewaittimesandmaximizetrafficflowefficiency.Tointroduceandreinforcetheseideas,studentswillobserveandcounttrafficatarealintersectionoronavideo,calculatewaittimes,andexploreideasabouthowactivesignalcontrolcanmaximizefloweffectiveness.

CreatedBy:

NanoSonic,Inc.

GilesCountyPublicSchools

Leidos

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Lesson1: TrafficSignalDesignContributedby:NanoSonic,Leidos,GilesCountyPublicSchools

GradeLevel:9-12

LessoninthisModule:1of1

TimeRequired:120minutes

LessonDependency:None

Keywords:transportationengineering;intelligenttransportationsystems;trafficsignals;turningmovements;delay;

RelatedCurriculum

SubjectAreas

Science;technology;engineering;mathematics

CurricularUnits

Intelligenttransportationsystems

Activities

IntersectionDataCollection;TrafficDataAnalysis;TrafficDelayCalculationsandITSIntroduction

EducationalStandards

ThislessonplananditsassociatedactivitiesarecorrelatedtothenationalstandardsintheeachofthecoredisciplineareasofSTEM:NextGenerationScienceStandards,AmericanAssociationfortheAdvancementofScienceStandards,StandardsforTechnologicalLiteracy,InternationalSocietyforTechnologyinEducationStandards,CommonCoreMathematicsStandards,andtheNationalCouncilofTeachersofMathematicsStandards.

Pre-RequisiteKnowledge

None.

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LearningObjectives

• Throughdiscussion,datacollection,andvariousactivities,studentswillrecognizetheneedfortrafficsignals.

• Studentswillusetheengineeringprocesstoeffectivelyevaluateasignalizedintersection.

• StudentswillidentifyspecificITStechnologiesthatcanbeusedtoimprovetrafficflowandreducevehicledelay.

Introduction/Motivation

Allofushavebeenfrustratedwhilesittingatatrafficlightthatneverseemstochange.ThisSTEMlessonintroducesstudentstoIntelligentTransportationSystem(ITS)conceptswherebythetransportationinfrastructureofroadwaysensors,signalsandcommunicationnetworks,incombinationwithourownvehicles,cancontroltrafficsignalstominimizewaittimesandmaximizetrafficflowefficiency.Tointroduceandreinforcetheseideas,studentswillobserveandcounttrafficatarealintersectionoronavideo,calculatewaittimes,andexploreideasabouthowactivesignalcontrolcanmaximizefloweffectiveness.

LessonBackground&ConceptsforTeachers

Trafficsignalsareusedtocontroltrafficthatflowsindifferentdirectionsatintersections.Intersectionsconsistofmultipleapproaches,asseeninthefiguretotheright.Trafficsignalsusered,yellowandgreenindicatorstopermitdifferentapproachestoentertheintersectionatdifferenttimes.Theseindicators,frequentlyreferredtoasredlights,yellowlights,andgreenlights,telltrafficwhetheritistheirturntogothroughtheintersectionormaketheturnthattheywanttomake.

Trafficsignalsworkbyalternatingtheabilityforvehiclestotraveloneachapproachusingdifferentphases,whichcanhavesetorvaryingphaselengths.Phaselengthsaretheamountoftimeassignedtoeachgreen,yellow,orredphase.

• GreenPhase:theamountoftimeallocatedforagreenindicationinaparticulardirection.Greenphasesmaylastbetween20secondsto120secondsormore.

Approach1

Approach4

Approach3

Approach2

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• YellowPhase:theamountoftimeallocatedforayellowindication.Thisphaseallowsvehiclesenoughtimetotravelthroughtheintersectioniftheyareunabletostopfortheredindication.

• RedPhase:theamountoftimeallocatedforaredindication.Theredindicationwillbeshownforanyapproachortrafficlanethatisnotallowedtoentertheintersectionwhileanotherapproachhasagreenindication.Unliketheotherphases,theredphasemayincludeanall-redtimeinwhichallintersectionapproachesreceivearedindicatioratthesametime.Thisall-redphaselastsapproximately½seccondto1½secondsandprovidesanextralayerofprotectionincaseanyvehicleshavedisobeyedthetrafficsignal.

Thetotaltimeittakesforatrafficsignaltocyclethroughallphasesatanintersectiononceiscalledthecyclelength.Thecyclelengthistheamountoftimeittakesforthetrafficsignaltoalternatefromthemomentoneapproachordirectionreceivesagreenindication,tothetimewhenthesameapproachreceivesagreenindicationagain,afterallapproacheshavebeencycledthroughandservicedwithgreenlightsoftheirown.

Trafficsignalscanoperateinavarietyofdifferenttime-dependentsettings.Forexample,somesignalsareprogrammedtoflashtheyellowindicatoronthemainapproacheslateatnightwhiletheminorapproachesreceiveaflashingredindicator.Inthiscase,thedriverswhoseeaflashingyellowindicatorareallowedtoproceedwithcautionwhilethedriverswhoseetheflashingredindicatorarerequiredtotreatitasastopsign.Anothermeansofprogrammingatrafficsignalistodisplayred,yellow,orgreenarrowstoindicatewhendriversmayturnatahigh-volumeintersection.Theseindicationsaredescribedinthefiguretotheright.

• IntersectionMovementsTherearethreemainmovementsthatdriversmaycompleteatanintersection:leftturn,rightturn,orthroughmovements.Theturningmovementsarefurtherdescribedasbeingeitherprotectedmovementsorpermissivemovements.Aprotectedturningmovementallowsavehicletoturnwithouthavingtoworryaboutoncomingtrafficorpedestriancrossings.Inotherwords,theywillhaveaclearpathwithnoconflicts.Protectedturningmovementsatanintersectioncanbesymbolizedbyeitheragreenleft-orright-turnarrows.Throughmovements(travelingstraightthroughanintersection)arealwayscharacterizedasprotectedmovements.Permittedturningmovementsarethoseinwhichdriversmustyieldtoopposingtrafficorpedestrians.Driversmustwaituntilthereareacceptablegapsin

AsolidredlightmeansSTOP.Driversturningleftmuststopandwait.

Asolidyellowarrowwarnsdriversthattheleft-turnsignalisabouttogotoredandtheyshouldpreparetostop,orpreparetocompletetheirturniftheyarewithintheintersection.

Aflashingyellowarrowmeansturnsarepermitted,butyoumustfirstyieldtooncomingtrafficandpedestriansandthenproceedwithcaution.Oncomingtraffichasagreenlight.

Asolidgreenarrowmeansitissafetoturnleft.Oncomingtrafficmuststop.

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opposingtrafficorpedestriancrossingsinordertosafelyprogressthroughtheintersection.Anexampleofapermittedmovementisturningleftatatrafficsignalwithaflashingyellowarrow.

• TrafficSignalDesignsTrafficsignalsmaybepre-timedtoallocateacertainamountofgreentimeforeachapproach,ortheymayutilizespecializedtechnologytoidentifywhencertainapproachesneedtoreceiveagreenindication.Apre-timedtrafficsignalhasbeenprogrammedtoallowacertainamountofgreentimeperapproachpercyclelength.Asareminder,acyclelengthisthetimeittakesforoneapproachtogofromgreentogreenagain,afterallotherapproacheshavebeencycledthrough.Unlikethenexttwotrafficsignaldesigns,pre-timedsignalsdonotautomaticallychangethecyclelengthorgreentimelengthbasedonthetrafficdemand.Anexampleofapre-timedsystemwouldbegivingeachapproach30secondsofgreentimetomovethroughtheintersection,regardlessofwhetherthereare100carswaitingonacertainapproachorzerocarswaitingtogototheintersection.Trafficsignalscansometimeshavemultiplepre-timedsettingsthatareassignedtodifferenttimesofday.Forexample,ifasidestreetmayhaveahighdemandduringmorningrushhour,butnotashighduringothertimesoftheday,thesignalcouldbepre-timedtoallowlongergreentimesonthesidestreetfrom7am-9am,butshortergreentimesatallothertimes.

Semi-actuatedtrafficsignalshavephasetimingthatchangesbasedontheamountoftrafficonsome,butnotall,approaches.Semi-actuatedtrafficsignalsaretypicallyfoundatintersectionswheretrafficdemandsaremuchhigheronthemainstreetcomparedtothesidestreets.Thetrafficsignalwillmaintainagreenindicationforthemainstreetaslongasnovehiclesaredetectedonthesidestreet.Whenavehicledoespulluptotheintersectionfromthesidestreet,theindicationforthemainstreetwillbrieflyturnyellowthenredandthentheindicationforthesidestreetwillturngreen.Detectorsshouldbeavocab.Specialdetectorshelpsemi-actuatedtrafficsignalstoknowwhethertherearevehiclesorpedestrianswaitingorapproachingtheintersection.Thesedetectorscanbeelectronicunits

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installedinthepavement,camerasmountedattheintersection,orpedestrianpushbuttonsnearthesidewalks.

Fullyactuatedtrafficsignalsusedetectorsonallintersectionapproachesinordertodeterminehowtoallocatethegreentimesforeachapproach.Eachphase’stimingisdependentontheamountorfrequencyoftrafficdetectedoneachapproachapproaches.Thesesignalsaretypicallyfoundwheretwomajorroadwaysintersectandtrafficflowvariesovertime.

• AdvantagesandDisadvantagesofTrafficSignalsTherearemanyadvantagesanddisadvantagesofinstallingtrafficsignals.Whenatrafficsignalisinstalledinanappropriatelocation,asdescribedintheTrafficSignalWarrantssection,itcan:

1. Increasethetrafficcapacityof(ortheabilitytomovelotsofvehiclesthrough)theintersection,2. Reducethenumberofsometypesandseverityof

crashes(specificallyright-anglecrashes,seeimagetotheright),

3. Providecontinuousornearlycontinuousmovementofvehiclesthroughtheintersection,and

4. Allowtrafficfromthelowervolumeroadtosafelycrossorturnontoahighervolumeroad.

Whentrafficsignalsareinstalledtheycouldprovidesomethefollowingdisadvantages,especiallyiftheyareinstalledininappropriatelocationsorifthetrafficsignalsarenotwell-timed:

1. Increaseddelay(ortimetogetwhereyouaregoing),2. Disobedienceofthetrafficsignal(e.g.,runningthrougharedindicationandcausingasevere

crash),3. Increasedtrafficvolumeontypicallylower-volumeroadways(i.e.,trafficusingotherroutesto

avoidlongdelaysataredindication),and4. Increasesincertaintypesofcrashes(especiallyrear-endcrashes).

Trafficengineerscanalleviatesomeofthesedisadvantagesbypayingcloseattentiontothedesignandallocationofthecyclelength,partiallyorfullyactuatingthesignal,orimprovingadriver’sabilitytoseeandrespondtothetrafficsignal.

• TrafficSignalWarrantsTrafficsignalwarrants(or“rules”)describetheminimumconditionsthatmustbepresentonaroadwayinordertodetermineifatrafficsignalcouldimprovesafetyortrafficflowatcertainlocationorintersection.ThetrafficsignalwarrantsaredefinedintheFederalHighwayAdministration’sManualonUniformTrafficControlDevices(MUTCD).Thissectionofthemanualcanbefoundbyvisitinghttp://mutcd.fhwa.dot.gov/htm/2003r1/part4/part4c.htm.Inordertodecidewhetheranintersectionwouldbenefitfromatrafficsignal,thetrafficsignalwarrantsmustbeevaluated,alongwithanengineeringstudythatlooksatthesafetyandmobility(efficienttrafficflow)oftheintersection.

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Thereareeightdifferenttrafficsignalwarrantsorrules:

1. Eight-hourvehicularvolume:describestrafficflowthatmustbemetforatleasteighthoursoftheday(notnecessarilycontinuous)

2. Four-hourvehicularvolume:describestrafficflowthatmustbemetforatleastfourhours3. Peakhourvehicularvolume:describestrafficflowthatexistsfortheonecontinuoushourofthe

daywiththehighesttrafficflow4. Pedestrianvolume:describesconditionsforroadwayswithsuchheavytrafficthatitcauses

delaysforpedestrians5. Nearbyschoolcrossing:usedinplaceswherechildrencrossamajorroadwaytogettoschool6. Considerationofcoordinatedsignalsystems:describesthepresenceofandcoordinationwith

othertrafficsignalsonthesameroadwayatnearbyintersections(allowslinesoftraffictomovecontinuouslywithoutbeingbrokenupbyredtrafficsignals)

7. Crashexperience:regardsthetypesandamountofcrashesthathavepreviouslyoccurredattheintersection

8. Roadwaynetwork:describestheconditionsthatneedtobemetforatrafficsignaltobeinstalledtopermittraffictomovesmoothlyandsafelythroughanintersection

• Ruralvs.UrbanWhileintersectionscanbefoundinbothruralandurbanlocations,thefunctionalityorpurposeofatrafficsignalmaydifferfromlocationtolocation.Inruralareas,thereistypicallylesstrafficflow,fewerpedestrians,andhighervehiclespeedsascomparedtourbanareas.Ruralintersectionsmayrelyheavilyonsemi-actuatedorfully-actuatedintersectiondesigns.

Urbanareasaremorelikelytohaveahigheramountofintersectionsduetotheincreasedtrafficvolumeandhighernumberofpedestrians.AnexampleofthisisNewYorkCity,wherethereisatrafficsignalonnearlyeveryblock.Thesesignalsaremorepronetobepre-timedtoallowforsignalcoordinationtohelpmovetrafficthroughacorridorassmoothlyaspossible.

Vocabulary/Definitions

VocabularyWord

Definition

Intersection Alocationwhereseveraltravelpathscross.

IntersectionApproach

Theportionofaroadwayintendedforusebyvehicularorpedestriantrafficapproachinganintersection.Intersectionstypicallyhavethreeorfourapproaches.

Trafficsignal Electricallyoperatedtrafficcontroldevicethatprovidesallowsroadwayuserstoadvancetheirtravelsbygivingeachapproachandmovementtheopportunityto

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move.

Conflict Aneventinvolvingtwoormoremovingvehiclesapproachingeachotherinatrafficflowsituationinsuchawaythatacollisionwouldensueunlessatleastoneofthevehiclesperformsanemergencymaneuver.

CycleLength Thelengthoftimethatittakesasignaltocompleteonecycle(fromthebeginningofapproach1’sgreenindicationtothebeginningofapproach1’snextgreenindication).

Phase Amountoftimeasignalindicatesacertaincolor(red,yellow,orgreen)

Pre-timedsignal Atrafficsignalthathasfixed,pre-determinedphaseandcyclelengthsthatarenotdependentonthenumberofvehiclesorpedestrianspresent.

Semi-actuatedSignal

Atrafficsignalthatusesvehicleorpedestriandetectorsononeortwoapproachestoactivateaparticularphaseonlywhenvehiclesorpedestriansarepresentortoextendgreenphasetimebasedontheamountoftrafficthatistravelingthroughtheintersection.

ActuatedSignal Atrafficsignalthatusesvehicleorpedestriandetectorstoactivateaparticularphaseonlywhenvehiclesorpedestriansarepresentortoextendgreenphasetimebasedontheamountoftrafficthatistravelingthroughtheintersection.

IntelligentTransportationSystems

Advancedtechnologiesthattransportationengineersusetoimprovetransportationsafetyandtrafficflow.Inthismodule,actuatedorsemi-actuatedtrafficsignalsrepresentoneformofintelligenttransportationsystems.

TrafficSignalController

Aroadsidedevicethatalternatesservicebetweenconflictingtrafficmovements.Thisdeviceisfrequentlyhousedinsideabigmetalboxrightnexttoanintersection.Itallowstrafficengineerstomanuallyreprogramasignalizedintersection.

CoordinatedSignalSystems

Aseriesofsignalizedintersectionsthatworktogethertomaximizetheflowoftrafficalongthemainroad.Coordinatedsignalsystemsfrequentlyallocategreenindicationsinamannerthatminimizesthenumberofstopsandtheamountoftimethatvehiclesonthemainroadhavetowaitforasignaltodisplayagreenindication.

Urban Ahighlypopulatedareathatisfrequentlyusedtodescribecitieswithlotsofman-madebuildingsandinfrastructure.Thisistheoppositeofarurallocation(seedefinitionbelow).

Rural Asparselypopulatedareathatmaybedescribedasfarmlandorforests.Thisistheoppositeofanurbanlocation(seedefinitionabove).

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TrafficDelay Trafficdelayistheadditionaltimetrafficcongestionaddstoanormaltrip.

PeakversusOff-PeakTimes

Apeaktimeisatimeperiodinwhichtrafficistheheaviestandthemostcongestionoccurs(example,duringrushhours,7-9amand5-7pm).

Off-peaktimesareallhoursthatarenotconsideredpeakhours(example,lateatnight,12-4am.

TrafficVolumes Trafficvolumesaretheamountsofcarsthattravelonaroadwayduringaspecificperiodoftime.

TurningMovementCounts

Turningmovementcountsareusedtomeasurethemovementofvehiclesthroughanintersectionbycountingthenumberofvehiclesthatturnleft,turnright,orcontinuestraight.

MajorRoadway Describesthemainroadwaythattravelsthroughanintersection.Itisaroadwaythatisfrequentlytraveled,servicingmanyvehiclesatatime.

MinorRoadway Describesthelower-volumeroadwaythattravelsthroughanintersection.Itisaroadwaythatisfrequentlytraveled,servicingfewervehiclesatatime.Aminorroadwayoftenreferstoasidestreetinsteadofamainroad.

AssociatedActivities

• Activity1–DiscussiononTrafficSignalPurposeandDesign

o Whydosomeintersectionshavetrafficsignalsandotherintersectionsdonot?Thedecisiontoplaceatrafficsignalisdependentontheamountoftrafficatanintersection.Intersectiontrafficmayincludethenumberofvehiclesthatusetheintersectionandalsothenumberofpedestriansorbicycliststhatuseanintersectionoverthecourseofasettime.

o Whattypeofintersectionsdoweobservearoundourcity/town?Studentanswerswillvarybasedonlocaltransportationinfrastructure.Answersmayincludesignalizedintersections,stop-controlledintersections,andintersectionswithyieldsigns.OthercharacteristicsthatstudentsmayidentifymayincludeT-intersections(three-wayintersections),four-wayintersections,interchanges,roundabouts,andotheralternativedesigns.Somesignalizedintersectionsmayoperatedifferentlybasedonthetimeofday.Forexample,asignalizedintersectionnearaschoolmayonlydisplaythetraditionalred/yellow/greenindicationsduringschooldrop-offordismissal–itmaydisplayflashingyellow(onthemainroad)andflashingred(ontheaccessroad)allothertimes.

o Howmighttrafficsignalsoperatedifferentlyinaruralversusurbanarea?Trafficsignalsinruralareaslikelyhavemuchloweramountsoftrafficthatutilizeeach

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intersection.Studentsmayindicatethattrafficlightsinruralareaseitherhavelongwaittimeswhileyouwaitforthesignaltoturngreen(pre-timedsignal)ortheymayautomaticallyturngreenwhenthereisverylittletrafficontheroad(semi-orfully-actuatedsignals).Trafficsignalsinurbanareasoftenseemuchmoretrafficduringtheday.Thesignalsmaybedesignedtoallowcertaintrafficmovementstogobeforeothertrafficmovements.Forexample,vehiclesturningleftmaygettoturnleftbeforethestraightvehiclesreceivetherightofway.Sometrafficsignalsinurbanareasmayprohibitrightturnsonredduetohighamountsofoncomingtraffic,orduetotheinabilitytohaveaclearlineofsight.

o Whatsignsorotherobjectsdoyouobserveneartheintersection?(i.e.,signs,cameras,signalcontrolboxes,etc.)Trafficsignalsmayhavespecialcameraspointedatthetrafficorelectricalcomponentsembeddedintothepavementtodeterminewhenvehiclesarewaitingforasignaltoturngreen.Somesignalsmayalsohaveadvancedwarningsignstowarndriversthatthereisasignalizedintersectionupahead–thisismorecommonlyusedinruralareasthathaveveryfewtrafficsignalsalongagivenroad.Trafficsignalsalsohaveatrafficcontrolboxwhereengineerscanre-programthelightson-site.Thismaybenecessaryincaseofanemergencyoraspecialeventthatrequiresspecialsignalprogrammingtomaximizetheflowoftraffic.

• Activity2–IntersectionDataCollection

o Asaclass,chooseanintersectioninyourcity/townthatyouthinkmaybenefitfromaddingorremovingatrafficsignal.Studentswillvisuallyobservetrafficatthisintersectionbyvisitingtheintersection.Ifstudentswillbecollectingtrafficdataon-siteattheintersection,theteachershouldcoordinatewiththelocalorstateDOTtoobtainrecommendationsforpositionsthatprovideasafeplaceforstudentstomonitortheintersection.Ifdesired,theteachermaypre-recordtrafficatthisintersectionusingavideocamera.

o Studentswillcollectdataonthenumberofvehicles,waittimeofeachvehicle,andtheirturningmovementforeachintersectionapproach.Thisdatacanbecollectedusingamobiledeviceortabletapplication(forexample,https://play.google.com/store/apps/details?id=com.portablestudies.classroom.tmc&hl=en)orbyusingpenandpaperwiththeattachedworksheet.Thedownloadableappisavailablefreeofcostforeducationalpurposes,butitwillrequirealicensenumberobtainedthroughtheappdeveloper.

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• Activity3–TrafficDataAnalysis

o Createabargraphofthenumberofvehiclesandpedestriansthatarrivedateachapproachin5-minuteintervals.

o TheIntersectionVolumegraph(above)canbemadeinExcelbycreatingthreecolumnstitledTime,VehicleMovements,andPedestrian,respectively,andthenfillinginthecolumnswiththerelevantdata.

Time VehicleMovements Pedestrians8:00 3 18:05 5 08:10 3 08:15 4 28:20 6 08:25 2 18:30 3 2

8:00 8:05 8:10 8:15 8:20 8:25 8:30VehicleMovements 3 5 3 4 6 2 3

Pedestrians 1 0 0 2 0 1 2

0

1

2

3

4

5

6

7

Num

bero

fVeh

icles

andPe

destria

ns

IntersectionVolume

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o ToturnthisintoanExcelgraph,selectallthreecolumnsofthedata,gototheInserttabnearthetopoftheExcelwindow,andselectCharts.Selectacolumngraph.Aftermakingtheselection,thegraphwillappear.

o AftermakingthegraphinExcel,thespecificnumberofvehiclemovementsandpedestrianscanbeshownbelowthegraphusingadatatable.Todothis,clickonthechart(makingsuretheentirechartisselected),andatabatthetopcalledChartToolsshouldappear.ThecomputerwilldefaulttotheDesignTab.

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o Underthechartlayoutoption,selectthefollowingicon.

o Editthecharttoaddacharttitleandaxistitle.

o Usesimilarmethodstographthenumberofvehicleturningright,drivingthrough,orturningleft.

8:00 8:05 8:10 8:15 8:20 8:25 8:30Left 1 1 0 1 2 0 1

Through 2 3 2 3 3 2 1

Right 0 1 0 0 1 0 1

00.51

1.52

2.53

3.5

Num

bero

fVeh

icles

TurningMovementCounts

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o Calculatetheaveragenumberofvehiclesper5-minuteintervalsandper15-minuteintervals.

§ Averageleft:0.86vehiclesper5-minuteinterval§ Averagethrough:2.29vehiclesper5-minuteinterval§ Averageright:0.43vehiclesper5-minuteinterval§ Averageleft:2.5vehiclesper15-minuteinterval§ Averagethrough:7.5vehiclesper15-minuteinterval§ Averageright:1vehicleper15-minuteinterval

o Discussion:Howmightthesetrafficcountsdifferifthedatawascollectedatadifferentperiodoftime?Trafficcountscouldbehigherorlowerdependingonwhattimeofdaydatawascollected,theratioofvehiclestopedestrianscouldvarythroughouttheday,etc.

• Activity4-TrafficDelayCalculationsandITSIntroduction

o Nowthatyou’vewitnessedtrafficflowatanintersection,considerhowlongpeopleneedtowaitbeforetheirindicationchanges.

o Trafficengineersdesigntrafficsignalstoreduceintersectiondelaytimesand,therefore,reducedriverfrustration.Askthestudentsiftheythinktheycanmanagetheflowoftrafficandwhilekeepingdriverfrustrationtoaminimum.Linktogame:http://www.its.umn.edu/GridlockBuster/game/

o Thiswordproblemdemonstratesasimplemethodforcalculatingdelay.Anorthboundtrafficindicationturnsred.15secondslater,abluevanstopsattheredindication.8secondsafterthat,agreencararrivesandstopsbehindthebluevan.12secondslater,twovehiclesarrivesimultaneously.Ifthetotalredindicationtimeis90seconds,calculatethedelaytimepervehicleandtheaveragedelayforthisintersectionapproach.Showthesearrivalsonanumberline.Delayistheamountoftimeavehiclehastowaituntilthelightturnsgreen.Forexample,thebluevan’sdelayis90secondsminus15seconds(75seconds).Thegreencar’sdelayis90secondsminus15+8seconds(67seconds).

o Discussion:UsingITStoreducedelayhttps://www.youtube.com/watch?v=OtukPI-9IeQ

§ Whyisitgoodtocoordinatetrafficsignals?Itisgoodtocoordinatetrafficsignalstoensurevehicularflowisconsistentonaroadwaywithlotsofintersectionsandtrafficsignals.Uncoordinatedtrafficsignalscanleadtocongestionandvehicularbackuponroadwaysthatmightnotbeabletoaccommodatealargenumberofvehicleswaitingonatrafficlight.Additionally,bycoordinatingtrafficsignals,driversreceivemoreconsecutive

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greenlightsthusdecreasingdriverfrustration(reduceddelay)anddecreasingvehiclepollutionandgasusage(causedbyidlingandacceleratingvehicles).Coordinatedtrafficsignalsalsoreducethenumberofrearendcrashesandred-lightrunning.Overall,coordinatingtrafficsignalsimprovestheoperationoftheroadway.

§ Whathappenswhenthesystemdoesnotworkwell?Ifthesystemdoesnotworkwell,trafficcongestionandvehicularbackupatintersectionapproachescanoccur.Vehiclesmaybestuckwaitingataredindicationwhenthereisnoonecrossingintheopposingdirection,creatingunnecessarydelay.Also,abadsystemcancausedriverstodisobeytrafficsignals,leadingtohigherriskofrunningredindicationsandcausingcrashes.

LessonClosure

• Basedonyourdatacollection,evaluatetheintersection.Istheintersectiongoodthewayitis,orshoulditbeimprovedsomehow?Agoodintersectioneffectivelymanagestheflowoftrafficfromeachdirection,orapproach.Ifatrafficsignalallowsforcontinuousmovementofvehiclesandpedestriansthroughanintersectionwithoutcreatingbackuporexcessivedelayonanyapproach,thetrafficsignalcanbeconsideredeffective.

• Howcouldconnectedvehicletechnologyimprovetrafficflowatsignalizedintersections?Connectedvehicletechnologyallowsforwirelesscommunicationbetweenvehiclesandtransportationinfrastructure(i.e.,trafficsignals).Whenavehicleapproachesthetrafficsignal,itsendsoutabeaconwithup-to-dateinformationonavehicle’sspeed,trajectory,andaccelerationordecelerationdata.Thetrafficsignalcanthencalculatethetimeatwhichthevehiclewillentertheintersectionandcanadjustthetrafficsignaltodisplayagreenindicationforthatvehicle.Iftherearemultiplevehiclescomingfromalldirections,thetrafficsignalcanprioritizewhichapproachesreceivethegreenindicationandforhowlonginordertoreducetheintersection’soveralldelay.Withtheabilitytodynamicallycontrolwhichvehicleshavetherightofway,therewouldbefewerintersection-relatedcrashessuchasright-anglecrashesandrear-endcrashes.

Connectedvehicletechnologycouldprovidedriverswithacountdownforwhenthesignalwillchangefromonecolortoanother.Thiswillallowvehiclesstoppedatanintersectiontostartmovingsimultaneouslyassoonasthetrafficindicationturnsgreen.Thiswouldreducethedelaycausedbythefluctuationsbetweenvehiclesstartingtomoveagainwhenaredindicationturnsgreen.Ontheotherhand,bywarningdriversthatalightwillturnyellow/redwithinafewseconds,driverscanpreparetoslowdowntoavoidrunningaredlightorcrashingintothevehicleinfrontofthem.

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Attachments

• TurningMovementDataCollectionWorksheetandLabReport• TurningMovementDataCollectionApplication:

https://play.google.com/store/apps/details?id=com.portablestudies.classroom.tmc&hl=en• Onlinegame:http://www.its.umn.edu/GridlockBuster/game/• VideodemonstratingintersectionITS:https://www.youtube.com/watch?v=OtukPI-9IeQ

Extensions/Multimedia

• Interviewyourparents.Whatdoyourparentsthinkofaparticularlocalsignalizedintersection?Theteachermayassignaspecificintersection,orstudentsmayasktheirparentstoidentifyagoodorbadintersectionandexplainwhyitisgood/bad.

• Ifthestudentsdeterminedthatatrafficsignaliswarranted,considerschedulingameetingwithalocaltransportationengineer.Ifresultsareconfirmed,considermeetingwiththecity/towncounciltodiscussaddingasignal.

• UtilizeEdmodo(www.edmodo.com)toprovidefurtherquestioninganddiscussionbetweenstudentsandteacher.Edmodoissafesociallearningwebsitemadespecificallyforteachersandstudents.Itisawaytocollaborateonassignments,homework,projects,andafter-schoolSTEMprogramsandisusedasacommunicationtooltoprovideadditionalquestioningandfeedbackfromteachersandstudents.

References

• "FHWA-MUTCD-2003EditionRevision1Chapter4C."FHWA-MUTCD-2003EditionRevision1Chapter4C.FederalHighwayAdminstration,n.d.Web.01Oct.2014.

• "IntersectionSafety."-FHWASafetyProgram.N.p.,n.d.Web.30Sept.2014.• "IntersectionSafetyIssueBriefs-IssueBrief5:TrafficSignals."-FHWASafetyProgram.

FederalHighwayAdminstration,Nov.2009.Web.30Sept.2014.• John,PatriciaL.,andReynnells,Louise."WhatIsRural?"NationalAgriculturalLibrary,n.d.

Web.30Sept.2014.• "TrafficControlSystemsHandbook:Chapter7.LocalControllers."FederalHighway

Adminstration,n.d.Web.30Sept.2014.• Wing,JP."Glossary-TheUpstateN.Y.RoadsSite."Glossary-TheUpstateN.Y.RoadsSite.

N.p.,n.d.Web.01Oct.2014.