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Instructions for Video Taping of Vehicle Traffic

Why do we need to do this?The objective is to measure vehicle activity in terms of vehicle counts and fleet composition. Vehicle counts are the total number of vehicles at different locations and periods (day, and time of day) on a given road. Fleet composition is determined by dividing total vehicle counts into visually identifiable categories of vehicles, obtaining the proportion of vehicle counts for each category.

The permissible categories of vehicle shall include: •Bicycles •Motorized2-wheelers •Motorized3-wheelers •Taxis •Passengercars(otherthantaxis) •Light-dutypassengervehicles •Light-dutycommercial(goods)vehicles •Medium-dutyminibuses •Heavy-dutytrucks •Heavy-dutybuses

I t is also desirable to determine vehicle occupation levels: Number of passengers per vehicle by visually identifiable category of vehicle, at different locations and periods (day, and time of day). In these counts, occupational drivers andotherstaff(taxis,buses,andgoodsvehicles)shallbeexcluded.

HowtomeasurevehicleflowsIn general, there are three ways of getting vehicle counts: •Videorecordings •Manualcounts •Automaticcounts

On-roadvehiclecountsusingdigitalvideocameras

Howtomeasurevehicleflows

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One or two digital video cameras are set up on the roadside or above the road to capture images of the vehicles driving by. This data is later manually reviewed to determine the number,sizeandtypeofvehicle.Itisimportanttosetthecameras at an appropriate height in order to have a good view of traffic on one side of a roadway.

Data is collected on the same roads and at the same times when driving patterns are being collected. This allows driving speeds and patterns determined from the GPSunits(discussedinChapter7)tobecorrelatedwithtrafficcountstakenfromthedigitalvideocameras.Thus,selectionof roadways,asdiscussed inChapter7, shouldconsider the video taping requirements as well.

Where to measureThisshouldbethesameaschapter7...Three representative sections of the city are normally selected for these traffic counts. The areas selected should representthefleetmakeupandthegeneraldrivingtakingplaceinthecity.Itisrecommendedthatoneofthestudyareas represent a generally lower income area of the city, one of the study areas represent a generally upper income area of the city, and one of the study areas represent a commercial area of the city. The sections representing the upper and lower income areas of the city for study should not be the absolute poorest or richest part of the city. It is better to select areas that are representative of the lower half of the income and the upper half of the income. Normallytheurbancenterisselectedasthebestcommercialareatostudy.Duetotheirmuchgreaterknowledgeoftheirowncity,itisanimportanttaskofthelocalpartnerstoplayaprimaryroleintheselectionofthethreeappropriate parts of the urban area to study.

Withineachofthestudyareas,differenttypesofstreetsmustbeanalyzedtogatherdatarepresentativeofallofurbanstreets.Streetsareoftenclassified into threegeneralgroupings.Thefirstgrouprepresents streets thataremajorurbanconnectorsandcanconnectoneurbanareatoanother.Thesestreetsaretypicallycharacterizedbythehighesttravelingspeedinfree-flowtrafficwithminimalstopsfromcross-flowtrafficandarecommonlyreferredtoas highways or freeways in some cases. The second classification of streets represents streets that connect sections of an urban area. They may connect one section of an urban area with another or may provide an important connection within a section of the urban area. These streets are typically referred to as arterials. The third classification of streets

represents the streets that take people to their homesor small commercial sections of an urban area, and are usuallyone-ortwo-laneroadwayswitharelativelyloweraverage speed and frequent intersections. These streets are typically referred to as residential streets.

The following criteria should be used as guidelines for selecting adequate sites:

•Selectionofalowincome,upperincome,andcommercial area with a variety of streets (i.e. residential, freeway, and arterial) in the area.

•Foreachofthestreet-sections,accessibilitytoasafe and legal location for the camera team to be droppedwhere2cameras&tripodscanbesetupwith a clear view of the nearby traffic (tripods are approximately0.5metersindiameter).

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InstructionsforVideoTapingofVehicleTrafficIt must be decided at the beginning of the study if one or two cameras are to be used at each site in the study. The primary camera is intended to capture the overall traffic flow in one direction of traffic flow on the selected road(s). If a second camera is used, this second camera will be used to either collect data concerning the number of passengers in the vehicle, the licenses plate of the vehicle, or detailed information concerning the technology of the vehicle. The camera operator should clearly establish with the study director the purpose of the second camera. In almost all cases the second camera, if used, will be focused more tightly on vehicles and can only collect data on one lane of traffic.

PrimaryCameraLocationThePrimaryCameraisusedtocountthenumberofvehiclesgoinginonedirectionontheroadandtodeterminewhatfractionofthevehiclesarepassengercars,trucks,buses,motorcycles,andthelike.Thus,itshouldbesetuptoallowatapereviewpersontomakesuchcountsatalaterdate.Thisisconsideredtobethe“Counter”camera.Video recordings from this camera are used by the reviewer to establish counts of vehicles by type (passenger car, smallbus,taxi,truck,etc.).

ItisbestifthePrimaryCameracanbeelevatedsothatvehiclesinthelaneclosesttothecameradonotobscurethevehiclesintheotherlanesofthestreet.Thisbecomesthemostdifficultonstreetswithmorethan2lanes,butcanbeaproblemevenon2laneroads.ThebestplacetolocatethePrimaryCameraisonanoverpassorinsomeotherelevatedpositionthathasaclearviewoftheroad.Thecameraisthenzoomedintotheappropriateframesizethatwill capture the entire roadway in one direction. If it is not possible to find an elevated camera location then the camerastandshouldbeadjustedtogetthebestviewpossible.ThecamerastandsuppliedforthePrimaryCamerawasselectedtobetall.ThecameraoperatorshouldmakesureandselectthetallestreachingcamerastandforthePrimaryCamera.

Useful data can be captured with the cameras located at the roadside, but on busy roads it is best to have the cameras elevated1to3metersabovethestreetlevelwhenpossible.FigurebelowshowsvideotapingfromanoverpassofafreewayinLosAngeles,California.Inthiscaseduetothehightrafficvolumeandthemultiplelaneroadway,datais best collected from directly above the street.

CamerasCollectingDataonaResidentialRoadwayinSantiago,Chile

SecondaryCameraLocation

TheSecondaryCameraisnormallylocatedalongsidethePrimaryCamera.Itis,however,zoomedintolookatwhatever feature of the traffic (generally vehicle occupancy) that the program director specifies. Otherwise, the samestepsaretakenasusedforthePrimaryCamera.CareshouldbetakentomakesurethatthetapesfromtheSecondaryCameraareclearlymarkedtoindicatethatthetapeis fromtheSecondaryCamera.This isgenerallyconsideredtobethe“Occupancy”cameraandisusedbythereviewerstoestablishtheaveragenumberofoccupantsperpassengervehicle.FigurebelowshowsvideotapingwithtwocamerasinSantiago,Chileonaresidentialstreet.Inthiscaseduetothelowtrafficvolumeandsmallstreetsize,videotapingcouldbecarriedoutatstreetlevel.

Personnelneededandtimerequired

Anappropriateteamshouldbeconformedby6members.Thereisaleadpersonwhoselectscameralocations,explainsthebasicrequirementstotherestoftheteamandgetspermissiontocarryouttheworkwhenneeded.Twopeoplearerequiredtooperatethevideocamerasonthefield,onenominatedVideoCameraOperatorandanotheroneVideoCameraSupportPerson.Theoperatormustbeapersonwhocanbetaughttouseavideocameraandalsoapersonfrom the city being studied. It is recommendable to include a guard or police for protecting the team while they are on the field with the cameras. Finally, reviewingthedailycollecteddatarequirestwoadditionaltrainedvideotapereaders,theyshouldbeabletorecognizevarioustypesofvehiclesandoperatevideotapereadersorcomputersoftware.Thislastworkisnotverycomplexbuttiresome.

The digital video cameras and the two operators usually travel with one of the instrumented vehicles to their desired location. Videotapes for analysis are collectedforatleast10minutesoutofeachhourandpreferablyfor20minutesofeachhour.

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Localcitizenspassingthecamerasoftenhavequestionsanduponoccasion,thepolicebecomeconcernedabouttheoperationofthecameras.Itisimportanttoprovidealocalpersontoexplainthepurposeofthedatacollectionefforttoavoidraisinglocalconcerns.Itshouldalsobenotedthatworkingalongsidethestreetforupto7hoursadaycouldexposethevideotapingcrewtoconsiderabledustandotherpollutantsorevenrain.Itisrecommendedthatthecameraoperatorshavegoodqualitydustmasksforcaseswherethedustlevelsarehighandplasticprotectionsor umbrellas.

Eachdayabout3.5hoursofvideotapesarecollected.Forestablishingon-roadfleetfractionsthesevideotapesareanalyzedthefollowingdaybystudentorstafftodeveloptheneededdata.Itisnecessarytoprovidetwovideotapereaders and/or laptop computers to support analysis of the data during the data collection process.

CameraOperation

The cameras used are standard consumer digital cameras. They usestandardmini-DVtapesorbuilt-indatastoringdisks.Thedirector of the study or his designee will demonstrate how to use the cameras supplied for this study including putting in DV tapes, starting the camera, and zooming to theproper frame.The cameras have an automatic focus and this does not normally have to be touched. The camera operator should, however, be-come familiar with how to turn the automatic camera focus on in case it accidentally gets turned off. During camera operation theoperatorshouldchecktheviewofthecameraeverythreeorfourminutestoinsurethatthefocusisokayandthatthecamerais recording data and pointed in the proper direction.

Acamera stand is supplied foreachcameraused in the study.The study director will demonstrate how to attach the camera to the camera stand. In cases where the camera must be operated at street level, the camera stand is normally elevated to as high a position as possible to capture the needed data.

Thecamerabatteries,iffullycharged,willoperatefor4-5hoursofrecording.Thus,thebatteriesdonotneedtobechangedduringtheday.Asparebatteryisprovidedincaseaproblemdevelopswithoneofthecamerabatteries.Itis critical that all of the camera batteries be charged each night.

Therehavebeencaseswherepassersbyhitortrytostealthecamerasandcamerastands.Caremustbetakentowatchthe cameras at all times. It is also important to find a safe location to store the cameras when they are not in use.

Bestpractices

Inanormaldayoftesting,7hoursoftrafficwillbestudied.Inordertosimplifydataanalysisandreducethenum-berofDVtapesused,only20minutesofvideoarerecordedoutofeachhour.Thisalsoallowstimeforthecameraequipmenttobemovedandsetupatthesiteforthenexthour’staping.Thus,asingletapewillworktorecordtrafficflowforeachhourofthestudyforthreehourlysegments.Aseven-hourstudydaywillrequire3DVTapesper camera. The camera operator should carry at least four tapes per camera in case a tape fails during use.

Beforefilmingofthetrafficateachlocationisstarted,thecameraoperatorshouldclearlyprintoutthefollowinginformation on a white piece of paper: name of location, route designation, date, hourly period, and camera de-signation.Thisinformationshouldthenbefilmedfor10seconds.Thishelpstoavoidthefilmeddatafrombeing

FieldLocationRecordingSheettoBeFilledOutandVideotapedatEachHourandLocation

NOTE:Adequatecopiesshouldbetakenintothefieldeachdaysothatthereisonesquareforeachhourtobevideotaped.

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International Sustainable Systems Research Center21573 Ambushers Street / Diamond Bar, CA 91765