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(gè)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(gè)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(gè)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(gè)有用的技術(shù)是集合了一個(gè)或多個(gè)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(gè)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(gè)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(shí)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(gè)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(huì)完成的計(jì)劃和一個(gè)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(gè)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(gè)整體的交通流微觀參數(shù)的交通流特征與相互尊重的個(gè)別車輛的行為。阿交通流可能是從宏觀上描述了三個(gè)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(shí)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(shí)間。1。日均交易量與使用一個(gè)共同的時(shí)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(gè)參數(shù)，廣泛應(yīng)用于（一）年平均每日流量（AADT）是平均24小時(shí)，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(shí)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(huì)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(gè)平均24小時(shí)為一段時(shí)間不到一年的時(shí)間特定地點(diǎn)的交通流量。雖然一AADT為全年就是一個(gè)ADT可能為6個(gè)月來衡量，一個(gè)賽季，一個(gè)月，一周，還是很少，兩天。一個(gè)ADT是一個(gè)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(shí)交通量為平日一段時(shí)間發(fā)生不到一年，如一個(gè)月或一個(gè)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(gè)設(shè)施總數(shù)。2。每小時(shí)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(gè)24小時(shí)工作制的過程通常與最大音量的時(shí)期，在早上和晚上下班發(fā)生“火拼”一小時(shí)。這一天具有最高每小時(shí)單量每小時(shí)稱為“繁忙時(shí)間”。它是在這一小時(shí)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(shí)間量通常是一個(gè)方向性的量即在其中流動(dòng)的方向是分開的音量。高峰每小時(shí)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(dòng)高峰高峰小時(shí)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(shí)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(shí)段交通量。高峰每小時(shí)產(chǎn)量是有益的這一目的，因?yàn)橐谙乱还?jié)討論SUBHOURLY流動(dòng)。在設(shè)計(jì)，高峰每小時(shí)量有時(shí)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(shí)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(shí)，作為一個(gè)十進(jìn)制表示在繁忙時(shí)間在交通高峰方向行駛的比例，表示為一個(gè)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(shí)間發(fā)生。在繁忙時(shí)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(shí)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(shí)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(gè)較長時(shí)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(gè)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