LESSON1GENERALKNOWLEDGEOFROADSTEXTADEVELOPMENTOFROADSWHENWESPEEDALONGAMODERNHIGHWAY,WERARELYSTOPTOTHINKWHATITISWEARERIDINGONTOUNDERSTANDWHATAROADIS,WEMUSTSTUDYTHEWAYSINWHICHPEOPLEHAVETRAVELEDINTHEPASTTHEVERYFIRSTROADSWEREREALLYTRACKSBEATENINTHEGROUNDBYWILDANIMALSINPREHISTORICTIMESPEOPLEFOLLOWEDTHESEWINDINGTRAILSBECAUSETHEYPROVIDEDANEASYANDQUICKWAYTOGETTHROUGHTHICKFORESTSINTIME,PEOPLEBEGANTOIMPROVETHEPATHSBYFILLINGHOLESWITHEARTHANDLAYINGLOGSACROSSSOFT,BOGGYSPOTSTHESEATTEMPTSWERECRUDE,BUTTHEYWERETHEBEGINNINGOFROADCONSTRUCTIONASPEOPLEBEGANTOTRANSPORTGOODSOVERLONGERDISTANCES,THEYDEVELOPEDNEWWAYSOFTRAVELINGFIRSTTHEYPACKEDTHEIRWARESONANIMALSTHENTHEYINVENTEDVARIOUSKINDSOFSLEDSFINALLY,AFTERTHEINVENTIONOFTHEWHEEL,THEYBUILTWAGONSEACHADVANCEMENTBROUGHTANEEDFORBETTERTRAVELINGROUTESLATERINHISTORY,WHENWELLTRAVELEDROUTESWEREMADESTURDIERWITHROCKSANDSTONES,THEPATHWASRAISEDABOVETHESURROUNDINGLAND,ITBECAMEA“HIGHWAY”THEGREATCIVILIZATIONSTHROUGHOUTHISTORYWEREALSOTHEGREATROADSBUILDERSROADSWERENECESSARYTOCONTROLANDEXTENDEMPIRES,TOPERMITTRADEANDTRAVEL,ANDTOMOVEARMIESMOSTOFTHESEEARLYROADSWERESIMPLYHARDPACKEDDIRT,BUTSOMEWEREPAVEDWITHSTONEBLOCKSORBURNTBRICKSTHEROMANSBOUNDTHEIREMPIRETOGETHERWITHANEXTENSIVESYSTEMOFROADSRADIATINGINMANYDIRECTIONSFROMROMESOMEOFTHESEEARLYROADSWEREOFELABORATECONSTRUCTIONFOREXAMPLE,THEAPPIANWAY,BUILTSOUTHWARDABOUT312BC,ILLUSTRATESONEOFTHEPROCEDURESUSEDCYTHEROMESFIRSTATRENCHWASEXCAVATEDTOSUCHADEPTHTHATTHEFINISHEDSURFACEWOULDBEATGROUNDLEVELTHEPAVEMENTWASPLACEDINTHREECOURSEALAYEROFSMALLBROKENSTONES,ALAYEROFSMALLSTONESMIXEDWITHMORTARANDFIRMLYTAMPEDINTOPLACE,ANDAWEARINGCOURSEOFMASSIVESTONEBLOCKS,SETANDBEDDEDINMORTARSOMEOFTHEROMANROADSARESTILLINEXISTENCETODAYANDMANYMODERNHIGHWAYSFOLLOWTHEANCIENTROMANROUTESFEWROADSWEREBUILTDURINGTHEEARLYHISTORYOFTHEUNITEDSTATESSINCEMOSTOFTHEEARLYSETTLEMENTSWERECONNECTEDWITHTHENEARESTWHARF,BUTTHECONNECTINGROADUSUALLYWASJUSTACLEARINGTHROUGHTHEFORESTBEFORETHEREVOLUTIONARYWAR,TRAVELWASMAINLYONFOOTORHORSEBACK,ANDROADSWEREMERELYTRAILSCLEAREDTOGREATERWIDTHDEVELOPMENTWASEXTREMELYSLOWFORATIMEAFTERTHEWARSENDIN1783BETWEEN1795AND1830NUMEROUSTURNPIKES,PARTICULARLYINTHENORTHEASTERNSTATES,WEREBUILTBYCOMPANIESORGANIZEDTOGAINPROFITSTHROUGHTOLLCOLLECTIONSFEWOFTHEMWEREFINANCIALLYSUCCESSFULDURINGTHISPERIODMANYSTAGECOACHLINESANDFREIGHTHAULINGCOMPANIESWEREORGANIZEDTHEEXTENSIONOFTURNPIKESINTHEUNITEDSTATESWASABRUPTLYBYTHEDEVELOPMENTOFTHERAILROADSIN1830PETERCOOPERCONSTRUCTEDAMERICASFIRSTSTEAMLOCOMOTIVE,THETOMTHUMB,WHICHATONCEDEMONSTRATEDITSSUPERIORITYOVERHORSEDRAWNVEHICLESRAPIDGROWTHOFTHERAILROADFORTRANSPORTATIONOVERLONGDISTANCESFOLLOWEDCROSSCOUNTRYTURNPIKECONSTRUCTIONPRACTICALLYCEASED,ANDMANYALREADYCOMPLETEDFELLINTODISUSERURALROADSSERVEDMAINLYASFEEDERSFORTHERAILROADSIMPROVEMENTSPRIMARILYLEDTOTHENEARESTRAILROADSTATIONANDWEREMADELARGELYBYLOCALAUTHORITIESANDWERETOLOWSTANDARDSWHENITRAINED,THEROADSWERESLIPPERY,ANDINDRYWEATHERTHEYWEREDUSTYPEOPLEUSINGHORSESANDWAGONSACCEPTEDTHISBUTWITHTHEBEGINNINGOFTHE20THCENTURYANEWINVENTION,THEAUTOMOBILE,BEGANTOTAKEOVERTHEROADTHEFIRSTTWODECADESOFTHETWENTIETHCENTURYSAWTHEIMPROVEMENTOFTHEMOTORVEHICLEFROMA“RICHMANSTOY”TOAFAIRLYDEPENDABLEMETHODFORTRANSPORTINGPERSONSANDGOODSTHEREWERESTRONGDEMANDSNOTONLYFROMFARMERSBUTFROMBICYCLISTSTHROUGHTHELEAGUEOFAMERICANWHEELMENFORRURALROADIMPROVEMENT,LARGELYFORROADSAFEWMILESINLENGTHCONNECTINGOUTLYINGFARMSWITHTOWNSANDRAILROADSTATIONSTHISDEVELOPMENTHASBEENAPTLYDESCRIBEDAS“GETTINGTHEFARMEROUTOFTHEMUD”FROM1920TO1935,HIGHWAYDEVELOPMENTWASFOCUSEDPRIMARILYONTHECOMPLETIONOFANETWORKOFALLWEATHERRURALROADSCOMPARABLETOTHESTREETSYSTEMSUNDERTAKENBYLOCALGOVERNMENTSBY1935HIGHWAYACTIVITIESINRURALAREASHAVEBEENDEVOTEDMAINLYTOANATTEMPTTOPROVIDEFACILITIESOFHIGHERSTANDARDSANDWITHGREATERCAPACITYANDLOADCARRYINGABILITYDURINGTHESAMEPERIOD,INCREASINGATTENTIONHASBEENFOCUSEDONURBANAREAS,WHICHHAVEBEENSTRUCKSIMULTANEOUSLYBYRAPIDLYINCREASINGPOPULATION,LOWERPOPULATIONDENSITIESRESULTINGFROMA“FLIGHTTOTHESUBURBS”,ANDASHIFTFROMMASSTRANSPORTATIONTOTHEPRIVATEAUTOMOBILEINDICATIONSARETHATONLYMINORADDITIONSTOROADMILEAGEWILLBEMADEINTHEFUTURECOMPREHENSIVEEXERCISESPUTTHEFOLLOWINGCHINESEEXPRESSIONSINTOENGLISH,ORVICEVERSA運(yùn)載能力LOADCARRYINGABILITY全天候道路ALLWEATHERROADS夯實(shí)土HARDPACKEDDIRT貨運(yùn)公司FREIGHTHAULING要求道路的改善DEMANDFORROADIMPROVEMENTATGROUNDLEVEL地面HORSEDRAWNVEHICLES馬車APAVEMENTPLACEDINTHREECOURSES分三層建造道路INTHEFIRSTDECADEOFTHISCENTURY在這個世紀(jì)的頭十年P(guān)OPULATIONDENSITIES人口密度LESSON2SURVEYINGTEXTAAERIALSURVEYSAERIALPHOTOGRAPHS航空拍攝HAVEBECOMEMOSTVALUABLETOOLSINTHEHANDSOF在掌握之中THEHIGHWAYENGINEERTHEYAREVERYUSEFULVISUALAIDSINTECHNICALCONFERENCESANDATPUBLICHEARINGS,ANDTHEYAREALSOVERYVALUABLEINSEEKINGTHEMOSTSUITABLETOPOGRAPHICLOCATIONFORTHEHIGHWAYADDITIONALQUALIFYINGFACTORSWHICHCANBEDETERMINEDBYASKILLEDINTERPRETERAREASFOLLOW1LOCATESANDANDGRAVELDEPOSITS,BORROWPITS,ANDROCKAREASSUITABLEFORQUARRYING2RATESOILBEARINGCAPACITIESASGOOD,FAIRORPOOR3OUTLINESOILSASTOTHEIRTEXTURE,ANDESTIMATETHEDEPTHSOFORGANICDEPOSITS4CLASSIFYBEDROCKASTOPHYSICALTYPESANDTHEIRRELATIVEDEPTHSBELOWTHESURFACE5ESTIMATEDEPTHSOFGLACIALDRIFTANDWINDBLOWNMATERIAL6ESTIMATEHYDROLOGICALFACTORS7DELINEATEACTIVEANDPOTENTIALAREASINVOLVINGPROBLEMSSUCHASSINKHOLES,SLIDES,ROCKFALLSANDFROSTHEAVE8LOCATEUNDERGROUNDUTILITIESPLACEDBYCUTANDCOVERMETHODSNEWAERIALPHOTOGRAPHSPROVIDETHEMOSTUPTODATEINFORMATIONREGARDINGCURRENTLANDUSE,ANDTHISISOFPARTICULARIMPORTANCEATTHERECONNAISSANCEPHASEOFAHIGHWAYLOCATIONSTUDY,PARTICULARLYIFITISBEINGCARRIEDOUTINANURBANAREASIMILARLYTHESEPHOTOGRAPHSCANBEEASILYUSEDTOLOCATEIMPORTANTINTERMEDIATECONTROLPOINTS,SOTHATPOSSIBLEBANDROUTESCANBESELECTEDATTHISSTAGEOFTHERECONNAISSANCEASMALLSCALEMOSAICWILLPROVIDESUFFICIENTDETAILTOENABLEELIMINATIONOFALLBUTACOUPLEOFPOSSIBLEBANDSTOENABLETHECHOICETOBENARROWED,ANENLARGEDMOSAICCANBEVIEWEDINCONJUNCTIONWITHATOPOGRAPHICALMAPAUSEFULTECHNIQUEISTOASSEMBLEONEORMOREMOSAICBANDSANDTOOVERLAYTHEMWITHTOPOGRAPHICMAPSTHATAREENLARGEDTOTHESAMESCALEANDDRAWNONTRANSPARENTMATERIALTRIALLINESFOREACHROUTECANTHENBESKETCHEDONTHEMOSAICSANDPROFILESPLOTTED,DIRECTLYFROMTHECONTOURSOFTHEOVERLAYWHENROUTEPROFILESAREFOUNDWHICHINDICATEALIGNMENTSTHATMIGHTSATISFYTHEHIGHWAYSDESIGNSTANDARDS,THEYCANBECOMPAREDONABENEFITCOSTBASISTOAIDINTHEFINALSELECTIONLARGESCALEPHOTOGRAPHYISNECESSARYATBOTHTHEPRELIMINARYANDFINALLOCATIONPHASEOFALOCATIONSURVEYAIRPHOTOINTERPRETATIVEMETHODSCANBEUSEDTOCUTDOWNTHEAMOUNTOFSOILSURVEYFIELDWORKWHICHISNORMALLYCARRIEDOUTDURINGTHEFINALLOCATIONSURVEYASPARTOFTHEROUTINEFIELDSTUDIES,ITISCUSTOMARYTOCARRYOUTAUGERINVESTIGATIONSATFIXEDINTERVALSALONGTHELOCATIONLINE,ANDTHENTOCARRYOUTOTHERDETAILEDSTUDIESASINDICATEDBYTHERESULTSOBTAINEDMUCHOFTHISROUTINEAUGERINGANDSUBSEQUENTLABORATORYANALYSISMAYBEELIMINATEDIFTHEAIRPHOTOSAREUSEDTODELINEATEGROUNDAREASWITHSIMILARPHYSICALCHARACTERISTICSTHENITISONLYNECESSARYTOGOTOTHEFIELDANDTESTALIMITEDNUMBEROFPOINTSWITHINEACHDELINEATEDAREASIMILARLY,SOURCESOFSUITABLEAGGREGATESAREMOREEASIESDETERMINEDFROMTHEPHOTOGRAPHSANDTHEAMOUNTOFFIELDINVESTIGATIONANDLABORATORYTESTINGMINIMIZEDWHENLARGESCALEAERIALPHOTOGRAPHYISUSEDTOPREPARETHENECESSARYMAPS,ITMAYBEPOSSIBLETOCOMPLETETHEPLANSANDSPECIFICATIONSFORAHIGHWAYANDTOLETTHECONSTRUCTIONCONTRACTWITHOUTACTUALLYPLACINGACENTERLINEPEGINTHEGROUNDWHENTHISOCCURS,THEFINALLOCATIONLINENEEDNOTBEPEGGEDUNTILTHECONTRACTORISABOUTTOBEGINCONSTRUCTION,INWHICHCASETHEFINALLOCATIONSURVEYBECOMESACOMBINEDLOCATIONANDCONSTRUCTIONSURVEY新的空中拍攝的照片提供最先進(jìn)的最新信息關(guān)于土地利用現(xiàn)狀，這是特別重要的一條公路在偵察階段的定位研究，特別是如果它是一個正在進(jìn)行的市區(qū)了。同樣這些照片可以很容易地用于定位的重要中間控制點(diǎn)，使可能帶路線可以選擇。在今年的偵察階段的小型馬賽克將提供足夠的細(xì)節(jié)，讓所有可能的消除，而是一個帶夫婦。為了使選擇收窄，擴(kuò)大馬賽克可以用地形圖聯(lián)系起來看。一個有用的技術(shù)是集合了一個或多個馬賽克樂隊(duì)，并與所覆蓋的同等規(guī)模的擴(kuò)大和透明材料繪制地形圖他們。各條路線的試驗(yàn)線便可以勾勒的馬賽克和繪制剖面，直接從覆蓋的輪廓。當(dāng)路線剖面發(fā)現(xiàn)這表明路線可能滿足高速公路的設(shè)計(jì)標(biāo)準(zhǔn)，它們可以在一個比較效益費(fèi)用的基礎(chǔ)上，以幫助在最后的選擇。大型攝影是需要在雙方的初步和最后一個位置測量位置的階段。空氣照片解釋性方法可以用來降低土壤的調(diào)查領(lǐng)域的工作通常是在最后的位置進(jìn)行調(diào)查的數(shù)額。作為常規(guī)領(lǐng)域研究的一部分，這是習(xí)慣進(jìn)行沿固定的時間間隔螺旋線的位置進(jìn)行調(diào)查，然后進(jìn)行結(jié)果表明所獲得的其他詳細(xì)研究。本例行AUGERING和實(shí)驗(yàn)室分析后，可消除大部分的航空照片，如果是用來劃定具有類似的物理特性地面的地方。然后，它是唯一有必要到外地和測試每個劃定區(qū)域內(nèi)的點(diǎn)數(shù)量有限。同樣，合適的骨料來源是從照片更EASIES決定和實(shí)地調(diào)查和實(shí)驗(yàn)室檢測量減少。當(dāng)大規(guī)模的空中攝影是用來準(zhǔn)備必要的地圖，它可能會完成的計(jì)劃和一個高速公路的規(guī)格和讓沒有實(shí)際放置在地上一中心線掛施工合同。當(dāng)發(fā)生這種情況，最終位置無須掛線，直至承包即將開始建設(shè)的，在這種情況下，最終成為一個聯(lián)合調(diào)查地點(diǎn)的位置和施工測量。LESSON8TRAFFICSTREAMCHARACTERISTICSTEXTABASICPARAMETERSOFTRAFFICSTREAMVOLUMETRAFFICSTREAMPARAMETERSFALLINTOTWOBROADCATEGORIESMACROSCOPICPARAMETERSCHARACTERIZETHETRAFFICSTREAMASAWHOLEMICROSCOPICPARAMETERSCHARACTERIZETHEBEHAVIOROFINDIVIDUALVEHICLESINTHETRAFFICSTREAMWITHRESPECTTOEACHOTHERATRAFFICSTREAMMAYBEDESCRIBEDMACROSCOPICALLYBYTHREEPARAMETERS1VOLUMEORRATEOFFLOW2SPEED3DENSITYVOLUMETRAFFICVOLUMEISDEFINEDASTHENUMBEROFVEHICLESTHATPASSAPOINTONAHIGHWAY,ORAGIVENLANEORDIRECTIONOFAHIGHWAY,DURINGASPECIFIEDTIMEINTERVALTHEUNITFORVOLUMEISSIMPLY“VEHICLES”,ALTHOUGHITISOFTENEXPRESSEDASVEHICLESPERUNITOFTIME1DAILYVOLUMEANDTHEIRUSEACOMMONTIMEINTERVALFORVOLUMESISADAYDAILYVOLUMESAREFREQUENTLYUSEDASTHEBASISFORHIGHWAYPLANNINGANDGENERALOBSERVATIONSOFTRENDSTRAFFICVOLUMEPROJECTIONSAREOFTENBASEDUPONMEASUREDDAILYVOLUMESFOURDAILYPARAMETERSAREWIDELYUSED1AVERAGEANNUALDAILYTRAFFICAADTISTHEAVERAGE24HOURTRAFFICVOLUMEATAGIVENLOCATIONOVERAFULL365DAYSYEARSTHATIS,THETOTALNUMBEROFVEHICLESPASSINGTHESITEINAYEARDIVIDEDBY3652AVERAGEANNUALWEEKDAYTRAFFICAAWTISTHEAVERAGE24HOURTRAFFICVOLUMEOCCURRINGONWEEKDAYSOVERAFULLYEARTHISVOLUMEISOFCONSIDERABLEINTERESTWHEREWEEKENDTRAFFICISLIGHT,SOTHATAVERAGINGHIGHERWEEKDAYVOLUMESOVER365DAYSWOULDMASKTHEIMPACTOFWEEKDAYTRAFFICAAWTISCOMPUTEDBYDIVIDINGTHETOTALWEEKDAYTRAFFICVOLUMEFORTHEYEARBY2603AVERAGEDAILYTRAFFICADTISANAVERAGE24HOURTRAFFICVOLUMEATAGIVENLOCATIONFORSOMEPERIODOFTIMELESSTHANAYEARWHILEANAADTISFORAFULLYEAR,ANADTMAYBEMEASUREDFORSIXMONTH,ASEASON,AMONTH,AWEEK,ORASLITTLEASTWODAYSANADTISAVALIDNUMBERONLYFORTHEPERIODOVERWHICHITWASMEASURED4AVERAGEWEEKDAYTRAFFICAWTISANAVERAGE24HOURTRAFFICVOLUMEOCCURRINGONWEEKDAYSFORSOMEPERIODOFTIMELESSTHANONEYEAR,SUCHASAMONTHORASEASONTHERELATIONSHIPBETWEENAAWTANDAWTISANALOGOUSTOTHATBETWEENAADTANDADTTHEUNITBYWHICHALLOFTHESEVOLUMESAREDESCRIBEDISVEHICLESPERDAYVPDDAILYVOLUMESGENERALLYARENOTDIFFERENTIATEDBYDIRECTIONORLANEBUTARETOTALSFORANENTIREFACILITYATTHESPECIFIEDLOCATION2HOURLYVOLUMESANDTHEIRUSEWHILEDAILYVOLUMESAREUSEFULINHIGHWAYPLANNING,THEYCANNOTBEUSEDALONEFORDESIGNOROPERATIONALANALYSISPURPOSESVOLUMEVARIESCONSIDERABLYDURINGTHECOURSEOFA24HOURDAY,USUALLYWITHPERIODSOFMAXIMUMVOLUMEOCCURRINGDURINGTHEMORNINGANDEVENINGCOMMUTER“RUSH”HOURTHESINGLEHOUROFTHEDAYTHATHASTHEHIGHESTHOURLYVOLUMEISREFERREDTOASTHE“PEAKHOUR”ITISTHETRAFFICVOLUMEWITHINTHISHOURTHATISOFGREATESTINTERESTTOASTRAFFICENGINEERSINDESIGNOROPERATIONALANALYSISTHEPEAKHOURVOLUMEISGENERALLYADIRECTIONALVOLUMETHATIS,AVOLUMEINWHICHTHEDIRECTIONSOFFLOWARESEPARATEDPEAKHOURLYVOLUMESAREUSEDASTHEBASISFORHIGHWAYDESIGNANDFORMANYTYPESOFOPERATIONALANALYSISHIGHWAYSMUSTBEDESIGNEDTOADEQUATELYSERVETHEPEAKHOURTRAFFICVOLUMEINTHEPEAKDIRECTIONOFFLOWSINCETHISTRAFFICGENERALLYTRAVELSONEWAYINTHEMORNINGANDTHEOTHERATNIGHT,BOTHDIRECTIONSOFTHEFACILITYARENORMALLYDESIGNEDTOACCOMMODATETHEDIRECTIONALPEAKHOURVOLUMEMOSTOPERATIONALANALYSES,WHETHERCONCERNINGIMPOSITIONOFCONTROLMEASURES,SAFETY,ORCAPACITY,MUSTADDRESSCONDITIONSEXISTINGDURINGPERIODSOFPEAKTRAFFICVOLUMEPEAKHOURLYVOLUMESAREUSEFULFORTHISPURPOSE,ASARESUBHOURLYFLOWSTOBEDISCUSSEDINTHENEXTSECTIONINDESIGN,PEAKHOURLYVOLUMESARESOMETIMESESTIMATEDFROMDAILYVOLUMEPROJECTIONS,USINGTHEFOLLOWINGRELATIONSHIPDDHVAADTKDWHEREDDHVDIRECTIONALDESIGNHOURVOLUMEVPHAADTAVERAGEANNUALDAILYTRAFFICVPDKTHEPROPORTIONOFDAILYTRAFFICOCCURRINGDURINGTHEPEAKHOUR,EXPRESSEDASADECIMALDTHEPROPORTIONOFPEAKHOURTRAFFICTRAVELINGINTHEPEAKDIRECTION,EXPRESSEDASADECIMALFORDESIGNPURPOSES,KOFTENREPRESENTSTHEPROPORTIONOFAADTOCCURRINGDURINGTHETHIRTIETHHIGHESTPEAKHOUROFTHEYEARTHEPEAKHOURSVARYFOREACHDAYANDMAYBERANKEDINORDEROFDECREASINGVOLUMETHETHIRTIETHHIGHESTPEAKHOURVOLUMEINSUCHALISTINGISACRITERIONOFTENUSEDFORRURALDESIGNANDANALYSISOTHERS,SUCHASTHEFIFTIETH,ARESOMETIMESUSEDINURBANSITUATIONSTHEKANDDFACTORSUSUALLYARECOMPUTEDBASEDUPONLOCALORREGIONALCHARACTERISTICSATEXISTINGLOCATIONSINGENERAL,THEKFACTORDECREASESASTHEDENSITYOFDEVELOPMENTSURROUNDINGTHEHIGHWAYINCREASESINDENSERAREAS,THEREISMOREOFFPEAKTRAFFIC,ANDCAPACITYDEFICIENCIESTENDTOSPREADDEMANDACROSSALONGERPERIODTHANINMORESPARSELYDEVELOPEDAREASTHEDFACTORISMOREVARIABLEITDEPENDUPONDEVELOPMENTDENSITYANDUPONTHESPECIFICRELATIONSHIPOFTHEFACILITYINQUESTIONTOMAJORTRAFFICGENERATORSINTHEAREATABLE81GIVESGENERALRANGESFORTHESEFACTORSASANILLUSTRATION交通流參數(shù)可分為兩大類宏觀參數(shù)描述作為一個整體的交通流微觀參數(shù)的交通流特征與相互尊重的個別車輛的行為。阿交通流可能是從宏觀上描述了三個參數(shù)1體積或流速2SPEED3DENSITYVOLUME交通量被定義為通過的車輛在高速公路上，或某一線或公路的方向點(diǎn)在指定的時間間隔，數(shù)量。對于體積單位是簡單的“車輛”，盡管它經(jīng)常被車輛表示每單位時間。1。日均交易量與使用一個共同的時間間隔是量一天。每日量經(jīng)常作為公路的規(guī)劃和趨勢一般性意見的基礎(chǔ)。交通量的預(yù)測往往是基于每日量測。每天4個參數(shù)，廣泛應(yīng)用于（一）年平均每日流量（AADT）是平均24小時，比1365天，年滿某一地點(diǎn)的交通量即在通過在除以365年地盤車輛總數(shù)。（2）平均每年平日交通（AAWT）是平均24小時交通量較平日全年發(fā)生。本卷是相當(dāng)感興趣的地方是周末交通燈，使平均高出365天工作日量會掩蓋平日交通的影響。AAWT是除以260計(jì)算的總工作日全年交通量。（3）平均每日交通（ADT）的是一個平均24小時為一段時間不到一年的時間特定地點(diǎn)的交通流量。雖然一AADT為全年就是一個ADT可能為6個月來衡量，一個賽季，一個月，一周，還是很少，兩天。一個ADT是一個只有在它的有效期是衡量數(shù)量。（4）平均平日交通（AWT的）是平均24小時交通量為平日一段時間發(fā)生不到一年，如一個月或一個賽季。之間AAWT和AWT之間的關(guān)系類似于AADT和ADT了這一點(diǎn)。利用這些都說明這些量的單位是每天的車輛（VPD的）。每日量一般都沒有方向或行車區(qū)別，但在指定的位置對整個設(shè)施總數(shù)。2。每小時卷及其使用雖然每天都在公路的規(guī)劃量有用，但不能單獨(dú)使用，設(shè)計(jì)或運(yùn)作分析的目的。音量相差很大，在一個24小時工作制的過程通常與最大音量的時期，在早上和晚上下班發(fā)生“火拼”一小時。這一天具有最高每小時單量每小時稱為“繁忙時間”。它是在這一小時是最感興趣的是交通量在設(shè)計(jì)或操作分析交通工程師。在繁忙時間量通常是一個方向性的量即在其中流動的方向是分開的音量。高峰每小時卷是用作公路設(shè)計(jì)的基礎(chǔ)和多種類型的業(yè)務(wù)分析。公路設(shè)計(jì)必須充分服務(wù)的方向流動高峰高峰小時交通量。由于該旅游交通一般在早上一晚上的方法和其他有關(guān)設(shè)施的設(shè)計(jì)通常都是以適應(yīng)定向高峰小時容量的方向。大部分業(yè)務(wù)分析，就是否實(shí)施控制措施，安全，或能力，必須在現(xiàn)有條件下解決高峰時段交通量。高峰每小時產(chǎn)量是有益的這一目的，因?yàn)橐谙乱还?jié)討論SUBHOURLY流動。在設(shè)計(jì)，高峰每小時量有時從日交易量估計(jì)預(yù)測，使用下面的關(guān)系DDHVAADT深K表其中DDHV定向設(shè)計(jì)小時量（VPH）AADT年平均每日交通（VPD的）K二，每日交通高峰期間發(fā)生的比例時，作為一個十進(jìn)制表示在繁忙時間在交通高峰方向行駛的比例，表示為一個小數(shù)為設(shè)計(jì)目的，鉀往往代表了AADT比例在第三十屆最高的一年繁忙時間發(fā)生。在繁忙時間不盡相同，每一天，可能是為了排名的下降量。第三十屆最高峰小時的這種上市量往往是農(nóng)村的設(shè)計(jì)和分析用的標(biāo)準(zhǔn)。其他如五十，有時在市區(qū)情況下使用。的K和D的因素通常是計(jì)算依據(jù)當(dāng)?shù)鼗蛟诂F(xiàn)有地點(diǎn)的區(qū)域性特征。一般來說，與周圍的公路增加開發(fā)密度K因子減少。在密集的地區(qū)，有更多的非高峰期的交通和能力不足往往分散在一個較長時期的需求比發(fā)達(dá)地區(qū)更稀少。D的因素是多變量，它在發(fā)展密度，并呼吁對有關(guān)設(shè)施的具體關(guān)系在該地區(qū)的主要交通發(fā)電機(jī)依賴。表81給出了一個例子，這些因素的綜合范圍。TABLE81GENERALRANGESFORKANDDFACTORSFACILITYTYPENORMALRANGEOFFACTORSKFACTORDFACTORRURAL015025065080SUBURBAN012015055065URBANRADIALROUTE007012055060CIRCUMFERENTIALROUTE0070120500553SUBHOURLYVOLUMESANDRATESOFFLOWTHEQUALITYOFTRAFFICFLOWISOFTENRELATEDTOSHORTTERMFLUCTUATIONSINTHETRAFFICDEMANDAFACILITYMAYHAVECAPACITYADEQUATETOSERVETHEPEAKHOURDEMAND,BUTSHORTTERMPEAKSOFFLOWWITHINTHEPEAKHOURMAYEXCEEDCAPACITY,THEREBYCREATINGABREAKDOWNVOLUMESOBSERVEDFORPERIODSOFTIMELESSTHANONEHOURAREGENERALLYEXPRESSEDASEQUIVALENTHOURLYRATESOFFLOWFOREXAMPLE,1000VEHICLESOBSERVEDINA15MINUTEPERIODWOULDBEEXPRESSEDASVPHHRE40251THERELATIONSHIPBETWEENHOURLYVOLUMEANDMAXIMUMRATEOFFLOWWITHINTHEHOURISDEFINEDTHEPEAKHOURFACTORPHF,ASFOLLOWSFLOWRATEIMUVHOLYPHFX15MINUTEPERIODSOFFLOW,THEEQUATIONBECOMES154VHPFWHEREHVHOURLYVOLUMEVPHMAXIMUM15MINUTEVOLUMEWITHINTHE15VHOURVEHLESSON9HIGHWAYCAPACITYANDSAFETYTEXTACONCEPTSOFCAPACITYANDLEVELOFSERVICECAPACITYTHE1985HIGHWAYCAPACITYMANUALDEFINEDTHECAPACITYOFAFACILITYAS“THEMAXIMUMHOURLYRATEATWHICHPERSONSORVEHICLESCANREASONABLYBEEXPECTEDTOTRAVERSEAPOINTORUNIFORMSEGMENTOFALANEORROADWAYDURINGAGIVENTIMEPERIODUNDERPREVAILINGTRAFFIC,ROADWAY,ANDCONTROLCONDITIONS”SEVERALKEYPOINTSINTHISDEFINITIONREQUIREEMPHASIS1THECAPACITYOFAFACILITYISDEPENDENTUPONPREVAILINGCONDITIONSTRAFFICCONDITIONSREFERPRIMARILYTOTHECOMPOSITIONOFTRAFFICUSINGTHEFACILITIES,GENERALLYEXPRESSEDASTHEPROPORTIONOFPASSENGERCARS,TRUCKS,BUSES,ANDRECREATIONALVEHICLESINTHETRAFFICSTREAMROADCONDITIONSREFERTOTHEGEOMETRICCHARACTERISTICSOFTHEROADWAY,SUCHASDESIGNSPEED,HORIZONTALANDVERTICALALIGNMENT,NUMBERANDWIDTHOFLANES,LATERALCLEARANCES,ANDLANECONFIGURATIONCONTROLCONDITIONSREFERTOTHEPRESENCEOFCONTROLSTHATIMPACTROADWAYUTILIZATION,SUCHASSIGNALS,STOPANDYIELDSIGNS,LANEUSECONTROLS,ONEWAYSTREETSANDOTHERSACHANGEINPREVAILINGCONDITIONSWILLRESULTINACHANGEINCAPACITY2CAPACITYREFERSTOA“POINTORUNIFORMSEGMENT”O(jiān)FTHEFACILITYCAPACITYANALYSISISCONDUCTEDFORSEGMENTSOFAFACILITYHAVINGUNIFORMTRAFFIC,ROADWAY,ANDCONTROLCONDITIONSBECAUSECAPACITYDEPENDSONTHESEFACTORS,SEGMENTSHAVINGDIFFERENTPREVAILINGCONDITIONSWILLHAVEDIFFERENTCAPACITIES3CAPACITYISTHEMAXIMUMRATEOFFLOW,WHICHTHEFACILITYCANACCOMMODATETHEPERIODOFANALYSISFORMOSTCAPACITYANALYSESISAPEAK15MINUTEPERIODWITHINTHEHOUROFINTERESTCAPACITYREFERSTOTHEMAXIMUMRATEOFFLOWTHATCANBEACCOMMODATEDWITHINSUCHA15MINUTEPERIOD,NOTTOTHEMAXIMUMHOURLYVOLUMETHATCANBEACCOMMODATEDWITHINAFULLHOUR4CAPACITYISDEFINEDONTHEBASISOF“REASONABLEEXPECTANCY”THATIS,ASTATEDCAPACITYFORAGIVENFACILITYISARATEOFFLOWTHATCANBEREPEATEDLYACHIEVEDDURINGEVERYPEAKPERIODFORWHICHSUFFICIENTDEMANDEXITSANDTHATCANBEACHIEVEDONANYFACILITYWITHSIMILARCHARACTERISTICSANYWHEREWITHINNORTHAMERICAITISNOTTHEABSOLUTEMAXIMUMRATEOFFLOWEVEROBSERVEDONSUCHAFACILITYDRIVERCHARACTERISTICSVARYFROMPLACETOPLACE,ANDINDEEDCAPACITYOFAFACILITYISTHATMAXIMUMRATEOFFLOWWHICHTHETRAFFICENGINEERMAYBEREASONABLYASSUREDOFBEINGABLETOACHIEVEDAYINANDDAYOUTANYWHEREINNORTHAMERICAITMEANS,HOWEVER,THATOCCASIONALLYMEASUREDRATESOFFLOWATCRITICALLOCATIONSWILLEXCEEDTHETEXTBOOKORDEFINED“CAPACITY”O(jiān)FTHEFACILITYSUCHRATES,HOWEVER,AREOFTENNOTSUSTAINABLEORCANNOTBEACHIEVEDREPEATEDLYORATSIMILARLOCATIONSINOTHERPARTSOFNORTHAMERICA5CAPACITYMAYBEDEFINEDINTERMSOFPERSONS/HOURORVEHICLES/HOUR,DEPENDINGUPONTHETYPEOFFACILITYINVOLVEDTHE1985HIGHWAYCAPACITYMANUALINCLUDESPROCEDURESADDRESSINGPEDESTRIANANDTRANSITFACILITIES,FORWHICHCAPACITIESAREDEFINEDINTERMSOFPERSONS/HOURFOROTHERTYPESOFFACILITIES,CAPACITYISGENERALLYDEFINEDINTERMSOFVEHICLES/HOURFORTHEPREVAILINGMIXOFVEHICLESTHECAPACITYOFAHIGHWAYFACILITYISANIMPORTANTCHARACTERISTICOPERATINGCONDITIONSATCAPACITYARE,HOWEVER,GENERALLYPOORFEWFACILITIESAREDESIGNEDTOOPERATEATORNEARCAPACITYBECAUSEOFPOOROPERATINGCHARACTERISTICSANDTHEDIFFICULTYINMAINTAININGCAPACITYOPERATIONSWITHOUTBREAKDOWNTHUS,THEABILITYTOANALYZETHETRAFFICCARRYINGABILITYOFFACILITIESUNDERBETTEROPERATINGCONDITIONSISAMAJORASPECTOFCAPACITYANALYSISTHELEVELOFSERVICEALEVELOFSERVICEISALETTERDESIGNATIONTHATDESCRIBESARANGEOFOPERATINGCONDITIONSONAPARTICULARTYPEOFFACILITYTHE1985HIGHWAYCAPACITYMANUALDEFINESTHELEVELOFSERVICECONCEPTAS“AQUALITATIVEMEASUREDESCRIBINGOPERATIONALCONDITIONSWITHINATRAFFICSTREAMANDTHEIRPERCEPTIONBYMOTORISTSAND/ORPASSENGERS”THECRITICALPOINTINTHISDEFINITIONISTHENEEDTODEFINESERVICEQUALITYINTERMSTHATAREPERCEIVEDBYDRIVERSANDPASSENGERSSEVERALKEYMEASURESAREUSEDINTHE1985HIGHWAYCAPACITYMANUALTODESCRIBESERVICEQUALITYINTHESETERMS1SPEEDANDTRAVELTIMEONEOFTHEMOSTEASILYPERCEIVEDMEASURESOFSERVICEQUALITYISSPEED,ORITSINVERSE,TRAVELTIMEDRIVERSAND