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1、FourAspectColorLightThe four aspect color light signaling system allows trains at higher speeds to slow down earr and hence to get closer to the train ahead in a controlled manner. Reading from the top down, the four aspects are yellow, green, yellow andred. Theadvantagewithhavingredatthebottomtitca

2、nbe placedatdriverseyelevelandthere isnolenshoodbelowitmight assist snow to build up and obscure the light. It is a “fail-safe” principle precedence over everything else.ThesequenceoffouraspectsignalingisasGreenContinueatfullt enance of a red light must DoubleFourAspectColorLightThe four aspect colo

3、r light signaling system allows trains at higher speeds to slow down earr and hence to get closer to the train ahead in a controlled manner. Reading from the top down, the four aspects are yellow, green, yellow andred. Theadvantagewithhavingredatthebottomtitcanbe placedatdriverseyelevelandthere isno

4、lenshoodbelowitmight assist snow to build up and obscure the light. It is a “fail-safe” principle precedence over everything else.ThesequenceoffouraspectsignalingisasGreenContinueatfullt enance of a red light must DoubleyellowProceedatcaution,SingleyellowRed eroff,controlledbraking,readytoThussignal

5、scanbe spacedcloser togetherwiththissystemandheadwaytimescanbeshorter,astrainsare subjecttoPresentand future generations of signaling will use computers extensively to enable trains to be controlled in aclosed system. Each trainis constantlyupdatedfrom the trackside computer with um safe speed and t

6、 it go ls the trackside its ition and speed. Some Metro and light rail systems roduced running of trains n ionsand suchATO needs to be compatible with the computer controlled signaling and These combining systems are often known as Automatic Train Operation (ATO), Automatic Train Scheduling (ATS), A

7、utomatic Train Protection (ATP). On such automatic systems the principles of signaling must still be rigidly d safetyistobe erlockingof s,signalsandroutesisstill averyimportantrequirementtot onlyoperatewhenitissafetodoIn operation the trackside computer sends messages to the elling it the value itio

8、n of speed restrictions track gradients ahead and es a zero speed restriction at such a as to protect the train ahead. The train then calculates speedand distance fromthis information, safetymargin o take account of such as characteristics due to weather. The hen monitors itself to t it runs speed e

9、nvelope t it will stop in time whilst running at the performance level required by the automatic ds. The train also transmits back its speed ition t other trains can be kept at a In addition to this, the trackside computer also t the train is operating he safe speed and sends emergencybrakemessage i

10、fitdoes not.Toprotectagainstthe lossof information, shouldthe trainfailtoreceiveastreamofvalidmessage,itwillapplyitsemergencyA Todaythere isaverywide range ofrollingstockusedthroughouttheworldondifferentrailways. Thisrange includesthe following basic types:Freight wagons; Multipleunits(witherin-Metr

11、ocars(usuallymultipleLightrail/Trams(usuallyarticulatedRail mounted machines (cranes, t Inspection and maenancetrolleys.erIt takes energy to move a train and this energy d by motors. The t directly drive the wheels of otive are almostalwayselectric traction motors. In some passenger trains, the elec

12、tric motorsare underneaththe in which passengers ride. For an electric train, the electricity comes from an overhead wire above the track or from a rail which conducts electricity. Third rail is often used for urban rail mass transit. In It takes energy to move a train and this energy d by motors. T

13、he t directly drive the wheels of otive are almostalwayselectric traction motors. In some passenger trains, the electric motorsare underneaththe in which passengers ride. For an electric train, the electricity comes from an overhead wire above the track or from a rail which conducts electricity. Thi

14、rd rail is often used for urban rail mass transit. In a otive, the electricity generated onboard the otive to supplyotive by a diesel engine driving an electric generator. A often has more n erbuttheotiveusuallycontrolstheoperationoftheThereare twobasic typesotivestoday:diesel-electricandAlmost all

15、U.S.otive(orotives are diesels burning liquid diesel fuel. The diesel motor (engine) drives an electric which today is usually an alternator since it generates alternating current (AC). Then diode rectifiers convert the AC to direct current (DC). If AC motors are used to turn the wheels, the DC will

16、 be converted back to AC at frequencies vary with the speed of the motor (and speed of the train). This is done by a which does the inverse of what a rectifier does.er electronic device called an One mayalso think of this as a diesel motor nelectric to get er to the wheels of the train. electric per

17、mits the equivalent of a large number of gear ratios and provides a simple method of er (via electric cables) to each of the many driving wheels of otive. Each axle (which has a pair of attachedtoit)usuallyhasitsownelectricmotortodriveThere are two basic types of railway electrification (and types o

18、f electric (Direct Current). Most urban rail transit uses DC to run trains withoutotives): AC (Alternating Current) and DC otives, each car having its own motors.In order to have an er distribution system, a much higher voltage is desirable in the overhead n required to operate the motors. Thus otiv

19、es contain to reduce the voltage t suitable for motors. Furthermore, as the motorsturn slower, they needless voltage. AC systemsuse a transformer to reduce voltage and then diodes to rectify it to DC.While the otive is quite efficient inconverting o traction force at the wheels, one must this effici

20、ency by the thermal efficiency of generating the electricity at a swires which carry electricity to the train. A major advantage of electric trains islant. Also thereare tlantsmay use awidevarietychas coalto otiveer Not only does otive er to move thetrain, it alsoabsorbsenergyto stopthe train.Anairc

21、ompressor otive providescompressed air to the he train and this air is used to apply their brakes. Thus they use brakes. Also, the traction motors may be connected electrically t e generators. This creates a force at the driving wheels of otive but something must be ith the electricity ay todump o w

22、aste this electric energy is to urrent through large otive and thus convert the Thisisknownasdynamic braking.Itsavesmuchwearonthe brakeshoesofa For an otive the electricity may be put back on the overhead wire provided there are other trains tcanusetheenergy. In somecasesit caneven be transferred ba

23、ckto er systemto supplyhomes,etc.with electricity. otive tothe overhead wire,the voltage Thisis called regenerativebraking. In order er toflow from from otivemustbekeptslightly nthenormal voltageon the overheadwire.NotalltrainshaveregenerativeFreightTherearemanytypesoffreightBoxThereare6popularbox-c

24、ar Unequipped box cars may have sliding doors or plug doors. Plug doors provide a tight seal from weather and a smooth erior. Unequipped box cars are usually of 70-ton capacity. The cars carry typical general merchandise lading: packaged, canned, or bottled foodstuffs; finished lumber; bagged or box

25、ed bulk commodities; or, when equipped temporarydoorfillers,bulkchas lly equipped box cars usually have the same s as unequipped cars but include l equipment restrain lading from impacts and over-the-road vibrations. Equipped cars may have hydraulic-cushion units to d longitudinal shock at the coupl

26、ers.Insulated box cars have plug doors and l insulation. These cars carry foodstuffs such as unpasteurized produce, and dairy products. These cars may be precooled by the shipper and maain a heoss rate equivalent to 0.55C per day.Refrigerated box cars are used where transit times are longer. These c

27、ars are equipped with a diesel- refrigeration unit and are primarily used to carry produce. These are often 100-ton cars.“All door” box cars have doors which open the full length of the car for loading package lumber products such as plywood and gypsum board.ninsidevolumeof10,000ft3(283m3)havebeende

28、signedforlight-density CoveredhopperThey are used to haul bulk commodities ust be protected from the environment. Modern covered hopper cars typically100-toncarswithroofhatchesforloadingandfromtwotosixbottomoutletsfor Theyare usedfor haulingbulk chascoal, ore, or woodchips.A typical100-tonThey are u

29、sed to haul bulk commodities ust be protected from the environment. Modern covered hopper cars typically100-toncarswithroofhatchesforloadingandfromtwotosixbottomoutletsfor Theyare usedfor haulingbulk chascoal, ore, or woodchips.A typical100-toncoal hoppercar will vary volume depending on the lightwe

30、ight of the car and density of the coal to be hauled. Cars may have three or fourmanually operated or 12 to 16 automatically operated bottom hoppers. Theyare open-top cars typically used to haul coal or wood chips. These cars are similar to open-top hopper cars in but require a rotary coupler on one

31、 end for rotary to discharge lading since they do not have bottom Rotary-dump coal gondolas are usually used in dedicated, unit-train service betn a coal mine and an electric BulkheadflatThey are used for hauling such commodities as packaged finished lumber, pipe or with spe pulpwood. Both 70- and 1

32、00-ton bulkhead flats are used.l inward canted They are used for liquids, compressed gases, and other ladings, such as sulfur, which can be loaded and unloaded in molten e. Nonhazardous ch as corn syrup, crude oil, and mineral spring water are carried in re Cars used to haul such as liquefied petrol

33、eum gas (LPG),vinyl chloride, and anhydrous ammonia regulatedbytheU.S.Departmentofermodalermodal flat cars are equipped to haul trailers with or without nose-mounted refrigeration units combinationsofMillThey are 70-ton or 100-ton open-up cars principally used to haul pipe, structural steel, scrap m

34、etal, and when spe equipped, coils of aluminum or tinplate and other steel materials.eormachineryflatThey are 70-ton or 100-ton used to haul machinery such as farm equipment and highway tractors. These cars usually wooddecksfornailinglading- Theyareusedforhaulingtransformersandotherheavy,largemateri

35、alswhichrequireSchnabellclearanceTheyare lcarsfortransformersandnuclearcomponents.WiththesecarstheloaditselfprovidesthecentersectionthecarstructureduringPassengerDuring the past two decades most main-line or long-haul passenger service in merica e a function ernmentagencies, i.e., he United esand Vi

36、a Rail in Canada. Equipment raurbanservice is o 3 major categories: commuter rail, full-scale transit, and light rail transit, depending upon the characteristics the service. Commuter rail equipment operates on a conventional railroad, ermixed with other long-passenger and freight traffic. Full-scal

37、e ratransit operates on a dedicatedright-of-waywhich iscommonly insubwaysor onelevated sections. Light-railtransit (LRT) utilizing light railvehicles (LRV) is derivedfrom the older trolley orconcepts and may operate in any combination of ubway or elevated dedicated right-of-way, right-of-waywithgrad

38、ecrossing,ermixedwithother traffic on treets. In a fewcases LRT shares the withfreightoperationswhichareusuallyconductedatnightonaerferenceThe gage of railway track is the distance n the inner sides of the rail heads measured 5/8in (15.9mm) the top of rail. merican railways are laid nominal gage of

39、4ft 81/2 in (1,435mm), which is known standard gage. Rail wear causes an increase in gage. On sharp curves, is been the practice to widen the gage to reduce rail wear.The basic track structure is com ed of six major elements: rail, tie plates, fasteners, cross ties, ballast, The tion of American Rai

40、lroads has defined standards for the cross section of rails of various weights yard.TheAmericanRailwayEngineeringtion（AREA）standardsprovideforrailweightsvaryingfromto 140lb/yd. A few railroads use l sections of their own design. The standard length in use is 39 ft althoughsomemillsarenowrolling78ft(

41、23.8m)orlongerThe prevailing weight of rails ain-line track is 112 to 140 lb/yd. secondary andyard.TheAmericanRailwayEngineeringtion（AREA）standardsprovideforrailweightsvaryingfromto 140lb/yd. A few railroads use l sections of their own design. The standard length in use is 39 ft althoughsomemillsare

42、nowrolling78ft(23.8m)orlongerThe prevailing weight of rails ain-line track is 112 to 140 lb/yd. secondary and branch lines are laid with 75 to 100 lb/yd rail which has been previously used and partly ain-he past, wereconnectedusingboltedbars.Currentpracticeistheuseofcontinuousweldedrail(CWR).Ingener

43、al,o lengths up to 20 rails or more, then laid, and later field welded to eliminate conventional sn rail strings and other track . Electric-flash, gas-, and Thermit welding ses are CWR requires the use of more rail n bolted rail to the base of the rail ition it against sides of cross ties in order t

44、o prevent rail movement. This is sary to restrain longitudinal which fromthermalandcontractionduetoambienttemperaturechanges.Failuretoyhecan rackbucklingeither longitudinally, laterally,or both, inextremely hotweather orinrail“pullin extremely cold weather. Care must be exercised to install the rail

45、 at temperatures which do not approachhigh lowAvarietyofheat-treatingand alloyingseshavebeen dtoproducet ismoreresistant towear less susceptible to fatigue damage. Comprehensive studies indicate reduce the wear rate of rail in curves. This results in rail fatigue some longer life.Tiet gage face lubr

46、ication can ing the dominant cause for Rail pported on tie plates which he rail laterally, distribute the vehicle loads onto the cross tie, ition the rail for optimum vehicle performance. Tie plates cant the rail toward the gage side. Cants vary from 1:14 to 1:40, depending on service conditions and

47、 operating speeds.Railandtieplatesarefixedtothecrosstiesbyfasteners.Conventionalconstructionwithwoodcrosstiesutilizes es othe tie through he tie plate. In somecases, screw type fasteners are used to provide to vertical . Elastic, clip-type fasteners are used on concrete and, at times, on wooden cros

48、s ties provideauniform,CrossentandlongitudinaluofTo retain gage and provide a further distribution of vehicle loads to the ballast, lateral cross ties are used. majority of cross ties used in merica are wood. However, concrete cross ties are being used more and frequently in areas where track surfac

49、e and lateral stability are difficult to maain and in high-speed passenger Ballast serves to further distribute vehicle loads to the subgrade, restrain vertical and lateral displacement of the track structure, and provide for drainage. Typical main-line ballast materials are limestone, trap rock, gr

50、anite, or slag. Lightly-built secondary lines use gravel, ciders or sand.The subgrade serves as erface n the ballast and the native soil. Subgrade material is compacted or stabilized soil. Instability of the subgrade due to ermeation is a concern in some In some difficult locations, a semipermeable

51、geotextile fabric is used to separate the ballast and subgrade and prevent subgrade material from fouling the ballast.Railroad enance , e standards, AREA standards, and, more recently, FRA (Federal Administration) safety standards specify characteristicsconsideredions on geometric deviations for tra

52、ck structure. Among Gage;Alignment(the itionoftherails);Curvature;Easement(therate ofchangefromtangenttoSuperelevation;Runoff(therateofchangeinsuperelevation);Crosslevel(therelativeheightof(thechangeinitionoftherailsaboutalongitudinaliterails);FRA standards specify Class 6 (excellent).The curvature

53、of track um operating speeds by class of track ranging from Class I (poorest acceptable) designated in terms of “degrees of curvature”. Superelevation;Runoff(therateofchangeinsuperelevation);Crosslevel(therelativeheightof(thechangeinitionoftherailsaboutalongitudinaliterails);FRA standards specify Cl

54、ass 6 (excellent).The curvature of track um operating speeds by class of track ranging from Class I (poorest acceptable) designated in terms of “degrees of curvature”. The degree of curve is the number degreesofcentralanglesubtendedbyachordof100-ftlength(measuredonthetrackOn important main lines whe

55、re trains are operated at relatively high speed, the curves are ordinarily not n 6 to ountainous territory, in rare , main-line curves as sharp as 18 occur. Most diesel otives are designed to traverse curves up to 21. Most uncoupled cars will pass considerably curves, the limiting his case being the

56、 clearance of the truck components to car body structural orequipmentortheflexibilityofthebrakeconnectionstothetrucks. The AREA standard clearance diagrams provide for a clear height of 22 ft (6.7m) above the tops of the rail and for a width of16 ft (4.9m) on bridges and 15ft (4.6m) elsewhere. Where

57、 conditions require the clearance, unnels, these s are much reduced. For tracks entering buildings, an opening 12ft wideand17ft(5.2m)highwillordinarilysufficetopasstheotivesandThe distance n centers of main-line track varies n 12 and 14 ft (3.6 and 4.3m). Twelve-foot exists, however, only on old con

58、struction. The prevailing spacing, 14ft (4.3m), has the impd endorsement of the AREA and is required by some sRailway turnouts (switches) are described by frog number. The frog number is the cotangent of the frog Typical turnouts in yard and industry trackage range from number 7 to number 10. For ma

59、in-rvice, turnouts range from number 10 to number 20. Generally, the higher the turnout number, the higher the speed for a raversing the diverging track. As a general rule, the allowable speed l/h) is twice the senger ion may be o three sections: the building which is to he booking and sary for the

60、comfort of the passengers and the business of the railway staffs, the platform by which passengers enter or leave the trainand the trackthe platformshe yardoutside the ion.Fromthe of view the lastis the most important, for upon it hinges thecapacity of the ionto dealwith um oftrainsllyatthehoursofgr