Реферат: The history of railways (История железных дорог)
The history of railways
The railway is аgood example of аsystem evolved in variousplaces to fulfil аneed and then developedempirically. Inessence it consists оfparallel tracks or bars of metal or wood,supported transversely byother bars — stone, wood, steel andconcrete have been used — sothat thе load of the vehicle isspread evenly through the substructure. Such trackswereused inthe Middle Ages for mining tramways in Europe;railways came to England inthe 16th century and went backto Europe in the 19th century as an Englishinvention.
English railways
The first Act of Parliamentfor а railway,giving right of way over other people's property, was passed
in1758, and the first for аpublic railway, to carry the trafficof all comers, dates from1801. The Stockton and DailingtonRailway, opened on 27September 1825, was the first publicsteam railway in the world,although it had only onelocomotive and relied on horse traction for the mostpart,withstationary steam engines for working inclined planes.
The obvious advantages ofrailways as а means of conveyingheavy loads and passengersbrought about а proliferation ofprojects. The Liverpool& Manchester, 30 miles (48 km) longand including formidableengineering problems, became theclassic example of а steamrailway for general carriage. Itopened on 15 September 1830in the presence of the Duke ofWellington, who had been Prime Minister untilearlier in theyear. On opening day, the train stopped for water and thepassengers alighted on tothe opposite track; another locomotive came along and William Huskisson, an МРand а greatadvocate of the railway, was killed. Despite this tragedy therailway was а great success;in its first year of operation,revenue from passenger service was more than tentimes thatanticipated. Over 2500 miles of railway had been authorizedin Britain and nearly 1500completed by 1840.
Britain presented the worldwith а complete system for theconstruction and operation of railways. Solutionswere foundto civil engineering problems, motive power designs and thedetails of rolling stock.The natural result of these achievementswas the calling in ofBritish engineers to provide railwaysin France, where as аconsequence left-hand rujning isstill in force over manylines.
Track gauges
While the majority ofrailways in Britainadopted the 4 ft 8.5 inch (1.43 m) gauge of theStockton &
DarlingtonRailway, the Great Western, on the advice of itsbrilliant but eccentricengineer Isambard Kingdom Brunel,had been laid to а sevenfoot (2.13 m) gauge, as were many ofits associates. Theresultant inconvenience to traders causedthe Gauge of Railways Act in1846, requiring standard gaugeon all railways unless specially authorized. Thelast seven-footgauge on the Great Western was not converted until 1892.
The narrower the gauge theless expensive the constructionand maintenance of the railway; narrow gauges havebeencommonin underdeveloped parts of the world and in mountainous areas.In 1863 steam traction wasapplied to the 1 ft11.5 inch (0.85 m) Festiniog Railway 1n Wales, for whichlocomotives were built tothe designs of Robert Fairlie. Неthen led а campaign for theconstruction of narrow gauges.As а result of the export of English engineering androllingstock, however, most North American and Europeanrailways have been built tothe standard gauge, except inFinland and Russia, where the gauge is five feet(1.5 m).
Transcontinental lines
Thefirst public railway was openedin America in 1830, after which rapid developmenttookplace. А famous 4-2-0 locomotive called the Pioneer firstran from Chicago in 1848, and that city became oneof thelargest rail centres in the world. The Atlantic and the Pacificoceans were first linked on9 Мау 1869, in а famous ceremonyat the meeting point of theUnion Pacific and Central Pacificlines at Promontory Point inthe state of Utah. Canada wascrossed by the Canadian Pacific in 1885; completionof therailway was а condition of British Columbia joining theDominion of Canada, andconsiderable land concessions weregranted in virtuallyuninhabited territory.
The crossing of Asia with the Trans-Siberian Railwaywasbegunby the Russians in 1890 and completed in 1902, exceptfor а ferry crossing LakeBaikal. The difficult passage roundthe south end of the lake,with many tunnels, was completedin 1905. Today more thanhalf the route is electrified. In 1863the Orient Express ran fromParis for the first time andeventually passengers were conveyed all the way toIstanbul(Constantinople).
Rolling stock
Inthe early days, coaches were constructedentirely of wood, includingthe frames. Ву 1900, steel frameswere commonplace; thencoaches were constructed entirelyof steel and became veryheavy. One American 85-foot(26 m) coach with two six-wheel bogies weighed morethan80tons. New lightweight steel alloys and aluminium began
tobe used; in the 1950s the Budd company in America was
buildingan 85-foot coach which weighed only 27 tons. Thesavings began with thebogies, which were built withoutconventional springs,bolsters and so on; with only two airsprings on each four-wheelbogie, the new design reduced theweight from 8 to 2,5 tonswithout loss оf strength or stability.
In the I880s, 'skyscraper' cars were two-storeywoodenvans with windows used as travelling dormitories for railwayworkers in the USA; they hadto be sawn down when therailways began to build tunnels through themountains.After World War II double-decker cars of а mоrе compactdesign were built, this timewith plastic domes, so that passengers could enjoy the spectacular scenery onthe westernlines, which pass through the Rocky Mountains.
Lighting on coaches was by means of oil lamps atfirst; thengas lights were used, and each coach carried а cylinder оf gas,which was dangerous in theevent of accident or derailment.Finally dynamos on each car,driven by the axle, providedelectricity, storage batteries being used for whenthe car wasstanding.Heating on coaches was provided in the early days
bymetal containers filled with hot water; then steam waspiped from the locomotive,an extra drain on the engine'spower; nowadays heat as well as light is providedelectrically.
Sleeping accommodations were first made on theCumberland Valley Railroad in the United States in 1837. GeorgePullman's first cars ran onthe Chicago & Alton Railroad in1859 and the Pullman PalaceCar Company was formed in1867. The first Pullman cars operated in Britain in1874, аyear after the introduction of sleeping cars by two Britishrailways. In Europe in 1876the International Sleeping CarCompany was formed, but in the meantime GeorgeNagelmackers of Liege and anAmerican, Col WilliamD'Alton Маnn, began operation between Paris andViennain 1873.
Goods vans [freight cars] have developed accordingto theneeds of the various countries. On the North Americancontinent, goods trains aslong as 1,25 miles are run as far as1000 miles unbroken, haulingbulk such as raw materials andfoodstuffs. Freight cars weighing 70 to 80 tons havetwo fourwheel bogies. In Britain, with а denser population andclosely adjacent towns, аlarge percentage of hauling is ofsmall consignments ofmanufactured goods, and the smallestgoods vans of any countryare used, having four wheels and,up to 24,5 tons capacity. Аnumber of bogie wagons are usedfor special purposes, such as carriages fоr steelrails, tank carsfor chemicals and 50 ton brick wagons.
The earliest coupling system was links and buffers,whichallowedjerky stopping and starting. Rounded buffers broughtsnugly together byadjustment of screw links with springswere an improvement. Thebuckeye automatic coupling, longstandard in North America,is now used in Britain. Thecoupling resembles а knuckle made of steel andextendinghorizontally; joining аuоtomаtika11у with the coupling of thenext саr when pushedtogether, it is released by pulling а pin.
The first shipment of refrigerated goods was in 1851whenbutterwas shipped from New York to Boston in а woodenvan packed with ice andinsulated with sawdust. The bulk ofrefrigerated goods werestill carried by rail in the USA in the,1960s, despite mechanicalrefrigeration in motor haulage;because of the greater first cost and maintenancecost ofmechanical refrigeration, rail refrigeration is still mostly
providedby vans with ice packed in end bunkers, four to six inches (10 to 15 cm) ofinsulation and fans to circulate thecool air.
Railways inwartime
The first war in whichrailwaysfigured prominently
wasthe American Civil War (1860-65), in which the Union
(North)was better able to organize andmake use ofits railways than theConfederacy (South). Thewar was marked by а famous incident in which а 4-4-0locomotive
calledthe General was hi-jacked by Southernagents.
The outbreak of World War 1 was caused inpart by the
factthat the mobilization plans of the various countries,including the use оf railwaysand rolling stock, was planned to the last detail, except that there were nоprovisions for stopping the plans once they had been put into action until thearmies were facing each other. In 1917 in the United States, the lessons of theCivil War had been forgotten, and freight vans were sent to their destinationwith nо facilities for unloading, with the result that the railways werebrieflytaken over by the government for the only time in thatnation's history.
In World War 2, by contrast, the American railwaysperformed magnificently, moving 2,5times the level of freightin 1944 as in 1938, with minimal increase inequipment, andsupplying more than 300,000 employees to the armed forcesin various capacities. Incombat areas, and in later conflictssuch as the Korean war, itproved difficult to disrupt anenemy's rail system effectively; pinpoint bombingwasdifficult,saturation bombing was expensive and in any caserailways were quickly andeasily repaired.
State railways
State intervention began inEngland withpublic demand for safety regulation which resulted inLord
Seymour's Act in 1840; the previously mentionedRailway
Gauges Act followed in 1846. Ever since, the railwayshavebeen recognized as one of the most important of nationalresourcesin each country.
In France, from 1851 onwardsconcessions were granted fora planned regional system forwhich the Government providedways and works and thecompanies provided track androiling stock; there wasprovision for the gradual taking overof the lines by the State,and the Societe Nationale desChemins de Fer Francais(SNCF) was formed in 1937 as аcompany in which the Stateowns 51% of the capital and theompanies 49%.
The Belgian Railways wereplanned by the State from theoutset in 1835. The PrussianState Railways began in 1850;bу the end of the year 54miles (87 km) were open. Italian andNetherlands railways beganin 1839; Italy nationalized herrailways in 1905-07 and the Netherlands in theperiod1920-38. In Britain the main railways were nationalized from1 January 1948; the usualEuropean pattern is that the Stateowns the main lines and minorrailways are privately ownedor operated by local authorities.
In the United States,between the Civil War and WorldWаr 1 the railways, alongwith all the other importantinndustries, experienced phenomenal growth as thecountrydeveloped. There were rate wars and financial piracy duringа period of growth whenindustrialists were more powerfulthan the national government,and finally the InterstateCommerce Act was passed in l887 in order to regulatetherailways,which had а near monopoly of transport. AfterWorld War 2 the railwayswere allowed to deteriorate, asprivate car ownership became almost universal andpublicmoney was spent on an interstate highway system makingmotorway haulage profitable,despite the fact that railwaysare many times as efficient at moving freightandpassengers.In the USA, nationalization of railways would probablyrequire an amendment to theConstitution, but since 1971 аgovernment effort has been made to save the nearlydefunctpassenger service. On 1 May of that year Amtrack was formedby the National RailroadPassenger Corporation to operate аskeleton service of 180passenger trains nationwide, serving29 cities designated by thegovernment as those requiringtrain service. The Amtrack service has been heavilyused, but
notadequately funded by Congress, so that bookings,
especiallyfor sleeper-car service, must be made far in
advance.
The locomotive
Few machines in the machineage have inspired so much affection as railway locomotives intheir 170 years of operation. Railways were constructed inthe sixteenth century, but the wagons were drawn by musclepower until l804. In that year an engine built by RichardTrevithick worked on the Penydarren Tramroad in South Wales. Itbroke some cast iron tramplates, but it demonstrated that steam could beused forhaulage, that steam generation could be stimulated byturning the exhaust steam upthe chimney to draw up the fire, and that smooth wheelson smooth rails could transmit motive power.
Steam locomotives
The steam locomotive is аrobust and
simplemachine. Steam is admitted to а cylinder and by
expandingpushes the piston to the other end; on the return stroke а port opens to clearthe cylinder of the now expanded steam. By means ofmechanical coupling, the travelofthe piston turns the drivewheels of the locomotive.
Trevithick's engine was putto work as а stationary engineat Penydarren. During thefollowing twenty-five years, аlimited number of steamlocomotives enjoyed success oncolliery railways, fostered bythe soaring cost of horse foddertowards the end of theNapoleonic wars. The cast iron plateways,which were L-shaped to guidethe wagon wheels, werenot strong enough towithstand the weight of steam locomotives,and were soon replaced by smoothrails and flangedwheels on the rolling stock.
John Blenkinsop built several locomotivesfor collieries,which ran on smooth rails but transmitted power fromаtoothed wheel to а rack which ran alongside the runningrails. William Hedley wasbuilding smooth-whilled locomotiveswhich ran on plateways,including the first to havethe popular nickname Puffing Billy.
In 1814 George Stephensonbegan building for smooth rails at Killingworth, synthesizing the experience ofthe earlierdesigners. Until this time nearly all machines had thecylinders partly immersed inthe boiler and usually vertical.In 1815 Stephenson and Loshpatented the idea of directdrive from the cylinders by means of cranks on thedrivewheelsinstead of through gear wheels, which imparted аjerky motion, especiallywhen wear occurred on the coarsegears. Direct drive allowedа simplified layout and gavegreater freedom to designers.
In 1825 only 18 steamlocomotives were doing useful work.One of the first commercial railways,the Liverpool & Manchester, was being built, and the directors had stillnotdecidedbetween locomotives and саblе haulage, with railsidesteam engines pulling thecables. They organized а competitionwhich was won by Stephensonin 1829, with hisfamous engine, the Rocket,now in London's Science Museum.
Locomotive boilers hadalready evolved from а simple
flueto а return-flue type, and then to а tubular design, inwhich а nest of fire tubes,giving more heating surface, ranfrom the firebox tube-plateto а similar tube-plate at thesmokebox end. In the smokebox the exhaust steam fromthecylinderscreated а blast on its way to the chimney whichkept the fire up when theengine was moving. When thelocomotive was stationary а blower was used, creatingаblastfrom а ring оf perforated pipe into which steam wasdirected. А furtherdevelopment, the multitubular boiler,was patented by Henry Booth,treasurer of the Liverpool &Manchester, in 1827. It wasincorporated by Stephenson inthe Rocket,after much trial and error in making the ferrulesof the copper tubes to givewater-tight joints in the tube
plates.
After 1830 the steamlocomotive assumed its familiar form,with the cylinders level orslightly inclined at the smokeboxend and the fireman's standat the firebox end.
As soon as the cylinders andaxles were nо longer fixed inor under the boiler itself,it became necessary to provide аframe to hold the variouscomponents together. The barframe was used on the early British locomotives andexported to America;theAmericans kept со the bar-frame design,which evolved from wroughtiron to cast steel construction,with the cylinders mountedoutside the frame. The bar framewas superseded in Britain bythe plate frame, with cylindersinside the frame, spring suspension (coil orlaminated) forthe frames and axleboxes (lubricated bearings) to hold the
axles.
As British railways nearlyall produced their own designs,а great many characteristic types developed. Somedesignswith cylinders inside the frame transmitted the motion tocrank-shaped axles ratherthan to eccentric pivots on theoutside of the drive wheels; there were alsocompoundlocomotives, with the steam passing from а first cylinder orcylinders to another set oflarger ones.
When steel came into use forbuilding boilers after 1860,higher operating pressures became possible. By theend ofthe nineteenth century 175 psi (12 bar) was common, with200 psi (13.8 bar) forcompound locomotives. This rose to250 psi (17.2 bar) later inthe steam era. (By contrast,Stephenson's Rocketonly developed 50 psi, 3.4 bar.) In thel890s express engines hadcylinders up to 20 inches (51 cm)in diameter with а 26 inch(66 cm) stroke. Later diametersincreased to 32 inches (81 cm) in places like theUSA, wherethere was more room, and locomotives and rolling stockin general were built larger.
Supplies of fuel and waterwere carried on а separatetender, pulled behind the locomotive. The first tankenginecarrying its own supplies, appeared tn the I830s; on thecontinent of Europe theywere. confusingly called tenderengines. Separate tenders continued to be commonbecausethey made possible much longer runs. While the firemanstoked the firebox, theboiler had to be replenished withwater by some means underhis control; early engines hadpumps running off the axle, but there was always the difficultythat the engine had to be running. The injector was invented in 1859. Steam fromthe boiler (or latterly, exhaus steam) went through а cone-shaped jet and lifted thewaterinto the boiler against the greater pressure there throughenergyimparted in condensation. А clack (non-return valve)
retainedthe steam in the boiler.
Early locomotives burned wood in America,but coal in Britain. As British railway Acts began to includepenalties for emission of dirty black smoke, many engines werebuilt after 1829 to burn coke. Under Matthetty Kirtley on theMidlandRailway the brick arch in the firebox and deflector plateswere developed to direct thehot gases from the coal to passover the flames, so that а relatively clean blastcame out of
thechimney and the cheaper fuel could be burnt. After 1860this simple expedient wasuniversа11у adopted. Fireboxeswere protected by being surrounded with а waterjacket;stays about four inches (10 cm) apart supported the innerfirebox from the outer.
Steam was distributed to the pistons bymeans of valves.The valve gear provided for the valves to uncover the portsat different parts of thestroke, so varying the cut-off toprovide for expansion ofsteam already admitted to thecylinders and to give lead or cushioning by lettingthe steamin about 0.8 inch (3 mm) from the end of the stroke to beginthe reciprocating motionagain. The valve gear also providedfor reversing by admittingsteam to the opposite side of thepiston.
Long-lap or long-travelvalves gave wide-openports for theexhaust even when early cut-оff was used, whereas with shorttravel at early cut-off,exhaust and emission openings becamesmaller so that at speeds ofover 60 mph (96 kph) one-third ofthe ehergy of the steam wasexpanded just getting in and outof the cylinder. Thiselementary fact was not universal1y
accepteduntil about 1925 because it was felt that too muchextra wear would occur withlong-travel valve layouts.
Valvе operation on mostearly British locomotives was byStephenson link motion,dependent on two eccentrics on thedriving ах1е connected byrods to the top and bottom of anexpansion link. А block inthe link, connected to the reversing lever under the control of the driver,imparted thereciprocating motion tо the valve spindle. With the block atthe top of the link, theengine would be in full forward gearand steam would be admittedto the cylinder for perhaps75% of the stoke. As the engine was notched up bymovingthe lever back over its serrations (like the handbrake leverof а саr), the cut-off wasshortened; in mid-gear there was nosteam admission to thecylinder and with the block at thebottom of the link theengine was in full reverse.
Walschaert's valvegear,invented in 1844and in general useafter 1890, allowed more precise adjustment andeasier operation for the driver. An eccentricrod worked from а returncrank by the driving axle operated the expansionlink; theblock imparted the movement to the valve spindle, but themovement was modified by аcombination lever from аcrosshead on the piston rod.
Steam was collected as dryas possible along the top of theboiler in а perforated pipe,or from а point above the boilerin а dome, and passed to аregulator which controlled itsdistribution. The most spectacular development ofsteamlocomotivesfor heavy haulage and high speed runs was theintroduction ofsuperheating. А return tube, taking thesteam back towards thefirebox and forward again to а headerat the front end of theboiler through an enlarged flue-tube, was invented by WilhelmSchmidt of Cassel, and modified byother designers. The firstuse of such equipment in Britain was in 1906 and immediately thesavings in fuel and especiallywater were remarkable. Steam at 175 psi, forexample, was generated 'saturated' at 371'F (188'С); by adding200'F (93'C) of superheat, the steam expanded much more readily in thecylinders, so that twentieth-century locomotives were able to work at high speedsat cut-offsas short as 15%. Steel tyres, glass fibre boilerlagging, long-lap piston valves, direct steam passage andsuperheating all contributed to the last
phaseof steam locomotive performance.
Steam from the boiler wasalso for other purposes.
Steamsanding was introduced for traction in 1887 on th
MidlandRailway, to improve adhesion better than gravity
sanding,which often blew away. Continuous brakes were
operatedby а vacuum created on the engine or by соmpressed air supplied by аsteam pump. Steam heat was piped to the carriages, arid steamdynamos [generators] providedelectric light.
Steam locomotives areclassified according to the numberof wheels. Except for smallengines used in marshalling уаrds,all modern steam locomotiveshad leading wheels on apivoted bogie or truck to help guide them aroundсurves.The trailing wheels helped carry the weight of the firebox.For many years the 'Americanstandard' locomotive was a4-4-0, having four leading wheels, four drivingwheels and notrailing wheels. The famous Civil War locomotive, theGeneral, was а 4-4-0, as was the New York Central EngineNo999,which set а speed record о1 112.5 mph (181 kph) in1893. Later, а commonfreight locomotive configuration wasthe Mikado type, а 2-8-2.
А Continental classificationcounts axles instead оf wheels,and another modification gives drive wheels а letterof thealphabet, so the 2-8-2 would be 1-4-1 in France and IDI inGermany.
The largest steamlocomotives were articulated, with twosets of drive wheels andcylinders using а common boiler.The sets оf drive wheelswere separated by а pivot; otherwise such а large engine couldnot have negotiated curves. The largest ever built was theUnion Pacific Big Вoу, а 4-8-8-4,used to haul freight in themountains of the western United States. Even though it wasarticulated it could not run onsharp curves. It weighed nearly 600 tons, comparedto less than five tons for Stephenson's Rocket.
Steam engines could take аlot of hard use, but they arenow obsolete, replaced by electric and especiallydiesel-electric locomotives. Because of heat losses and incompletecombustion of fuel, theirthermal efficiеncу was rarely morethan 6%.
Diesel locomotives
Diesel locomotives are mostcommonly diesel-electric.А diesel engine drives а dynamo [generator]whichprovides power for electricmotors which turn the
drivewheels, usually through а pinion gear driving а ringgear on the axle. The firstdiesel-electric propelled rail car was built in 1913, and afterWorld War 2 they replacedsteam engines completely, except whereelectrificationof railways is economical.
Diesel locomotives haveseveral advantages over steam engines. They are instantlyready for service, and can be shut down completely for shortрeriods, whereas it takes sometime to heat the water in the steam engine,especially in coldweather, and the fire must be kept up while the steam engineis on standby. The dieselcan go further without servicing,as it consumes nо water; itsthermal efficiency is four timesas high, which means furthersavings of fuel. Acceleration and
high-speedrunning are smoother with а diesel, which means less wear on rails androadbed. The economic reasons for turning to diesels wereoverwhelming after the war, especially in North America, where the railwayswere in directcompetition with road haulage over very long distances.
Electric traction
The first electric-poweredrail car wasbuilt in 1834, but early electric cars were battery powered,and the batteries were heavyand required frequent recharging. Тоdау е1есtriс trains are not self-contained,whichmeansthat they get their power from overhead wires orfrom а third rail. The powerfor the traction motors iscollected from the third rail
bymeans of а shoe or from theoverhead wires by а pantograph.
Electric trains are the mostесоnomical to operate,
providedthat traffic is heavy enough to repay electrificationof the railway. Where trainsrun less frecuentlу over longdistances the cost of electrification isprohibitive. DCsystems have been used as opposed to АС because lightertraction motors can be used,but this requires powersubstations with rectifiers to convert the power toDС fromthe АС of the commercial mains. (High voltage DC power isdifficult to transmit overlong distances.) The latest development
ofelectric trains has been the installation of rectifiersin the cars themselves andthe use of the same АС frequencyas the commercial mains (50Hz in Europe, 60 Hz in NorthAmerica),which means that fewer substations arenecessary.
Railway systems
The foundation of а modernrailway system is track whichdoes not deteriorate under stress of traffic.Standard track inBritain comprises a flat-bottom section of rail weighing 110lbper yard (54 kg per metre)carried on 2112 cross-sleepers permile (1312 per km).Originally creosote-impregnated woodsleepers [cross-ties] wereused, but they are now made ofpost-stressed concrete. This enables the rail totransmit the
pressure,perhaps as much as 20 tons/in2(3150 kg/cm2) fromthe small area of contact withthe wheel, to theground belowthe track formation where itis reduced through the soleplate and the sleeper to about 400 psi (28 kg/cm2).In softground, thick polyethylene sheets are generally placed underthe ballast to preventpumping of slurry under the weight oftrains.
The rails are tilted towardsone another on а 1 in 20 slоре.Steel rails tnay last 15 or 20 years in traffic, butto prolong theundisturbed life of track still longer, experiments have beencarried out with pavedconcrete track (PACТ) laid by а slippaver similar to concretehighway construction in reinforcedconcrete. The foundations,if new, are similar to those for а
motorway.If on the other'hand, existing railway formation isto be used, the old ballastis sеа1еd with а bitumen emulsionbefore applying the concretewhich carries the track fastenings glued in with cement grout or epoxy resin. The trackismaderesilient by use of rubber-bonded cork packings0.4 inch (10 mm) thick.British Railways purchases rails in60 ft (18.3 m) lengths whichare shop-welded into 600 ft(183 m) lengths and then welded on site intocontinuouswelded track with pressure-relief points at intervals ofseveral miles. The contfnuotlswelded rails make for а
steadierand less noisy ride for the passenger and reduce thetractive effort.
Signalling
The second important factorcontributing to safe rail travel is the system ofsignalling. Originally railways relied on the time intervalto ensure the safety of a succession of trains, but the defectsrapidly manifested themselves,anda space interval, or the blocksystem, was adopted, although itwas not enforced legally onBritish passenger lines until the
Regulationof Railways Act of 1889. Semaphore signals
becameuniversally adopted on running lines and the interlocking оf points [switches] and signals (usually accomplished mechanicallyby tappets) to prevent conflicting movementsbeing signalled was also аrequirement of the 1889 Асt. Lock-and-block signalling,which ensured а safe sequenceof movements by electric checks,was introduced on the London, Chatham and Dover Railway in1875.
Track circuiting, by whichthe presence of а train isdetected by an electric current passing from onerail to another through the wheels and axles, dates from 1870 whenWilliam Robinson applied itin the United States. In Englandthe Great Eastern Railwayintroduced power operationof points and signals atSpitaifields goods yard in 1899, and threeyears later track-circuitoperation of powered signals was inoperation on 30 miles (48 km)of the London and SoutWestern Railway main line.
Day colour light signals,controlled automatically by the trains through trackcircuits, were installed on the LiverpoolOverhead Railway in 1920 andfour-aspect day colour lights(red, yellow, double yellow and green) were providedonSouthernRailway routes from 1926 onwards. These enabledrivers of high-speed trainsto have а warning two blocksections ahead of а possible need to stop. Withtrackcircuitingit became usual to show the presence оf vehicles onа track diagram in thesignal cabin which allowed routes to becontrolled remotely by meansof electric relays. Today, panel
operationof considerable stretches of railway is common-рlасе; at Rugby, for instance, аsignalman can control thepoints at а station 44 miles (71 km) away, and thesignalboxat London Bridge controls movements on the busiest 150track-miles of British Rail.By the end of the I980s, the 1500miles (241О km) of theSouthern Region of British Rail are tobe controlled from 13signalboxes. In modern panel installationsthe trains are not onlyshown on the track diagram as they move from one section to another, but thetrainidentificationnumber appears electronically in each section.Соmputer-assisted traindescription, automatic train rеporting and, at stations such as London Bridge,operation ofplatform indicators, is now usual.
Whether points are operatedmanually or by an electricpoint motor, they have to be prevented from movingwhilea trainis passing over them and facing points have to belocked, аnd рroved tо Ьеlосkеd (оr 'detected' ) before thеrelevant signal can permit аtrain movement. The blades ofthe points have to be closed accurately (О.16 inchor 0.4 cmis the maximum tolerance) so as to avert any possibility of аwheel flange splitting thepoint and leading to а derailment.
Other signallingdevelopments of recent years include completely automatic operation of simplepoint layouts, such asthe double crossover at the Bank terminus of theBritishRails's Waterloo and City underground railway. On LondonТransport's undergroundsystem а plastic roll operatesjunctions according to the timetable by means ofcodedpunchedholes, and on the Victoria Line trains are operatedautomatically once thedriver has pressed two buttons toindicate his readiness tostart. Не also acts as the guard,controlling the opening оfthе doors, closed circuit televisiongiving him а view along thetrain. The trains are controlled(for acceleration andbraking) by coded impulses transmittedthrough the running rails toinduction coils mounted on thefront of the train. The absence of code impulsescuts off thecurrent and applies the brakes; driving and speed control iscovered by command spots inwhich а frequency of 100 Hzcorresponds to one mile per hour (1.6 km/h), and l5kHz
shutsoff the current. Brake applications are so controlledthat trains stop smoothlyand with great accuracy at the desired place on platforms. Occupation of thetrack circuit ahead by а train automatically stops the following train, whichcannot receive а code.
On Вritish main linesanautomaticwarningsystemisbeing installed by which thedriver receives in his саb а visual and audible warning of passing а distantsignal at caution; if he does not acknowledge the warning the brakes areapplied automatically. This is accomplished by magnetic induction between аmagnetic unit placed in the track and actuated according to the signal aspect,and а unit on the train.
Train control
In England train controlbegan in l909 on the Midland Railway, particularly to expedite themovement оf coal trains and to see that guards and enginemen were
relievedat the end of their shift and were not called upon to work excessive overtime.Comprehensive train control systems, depending on completediagramsof thetrack layout and records ofthe position of engines, crews and rolling stock, were developed for the wholeof Britain, the Southern Railway being the last to adopt it during World War 2,having hitherto given а great deal of responsibility to signalmen for theregulation of trains. Refinements оf control includeadvancetrafficinformation(ATI) inwhich information is passedfrom yard to yard by telex giving types of wagon, wagon number, route code,particulars оf the load, destination
stationand consignee. In l972 British Rail decided to
adoptа computerized freight information and traffic control system known as TOPS(total operations processing system) which was developed over eight years bythe Southern Pacific company in the USA.
Although а great deal ofrail 1rаffiс in Britain is handled by block trains from point of origin todestination, about onefifth ofthe originating tonnage is less than a train-load.Thismeans that wagons must be sorted on their journey. InBritain there are about 600 terminal points on a 12,000 mile network whitch isserved by over 2500 freight trains made up of varying assortments of 249,000wagonsand 3972 locomotives, of witch 333 are electric. This requires thespeed of calculation and the information storage and classification capacity ofthe modern computer, whitch has to be linked to points dealing with orgenerating traffic troughout the system.The computer input, witch is by punchedcards, covers details of loading or unloading of wagons and their movements intrains, the composition of trains and their departures from and arrivals atyards ,and the whereabouts of locomotives. The computer output includesinformation on the balanse of locomotives at depots and yards, withparticulars of when maintenanseexaminations are due, the numbers ofempty and loaded wagons, with aggregate weight and brake forse, and whedertheir movement is on time, the location of empty wagons and a forecast of thosethat will become available, and the numbers of trains at any location, withcollective train weigts and individual details of the component wagons.
Acloser check on what is happening troughoud the
system is thus provided, with the position ofconsignments in transit, delays in movement, delays in unloading wagons bycustomers, and the capasity of the system to handle future traffic among theinformation readily available. The computer has a built-in self-check on wronginput information.
Freight handling
Themerry-go-round system enables coal for power
stations to be loaded into hopper wagons at acolliery
without the train being stopped, and at thepower station the train is hauled round a loop at less than 2mph (3.2 km/h), atrigger devise automatically unloading the wagons without the train being stopped. Thearrangementsalso provide for automatic weighing of the loads. Other bulkloads can be dealt with inthe same way.
Bulk powders, includingcement, can be loaded and discharged pneumatically, using either rаi1 wagons orcontainers.Iron ore is carried in 100 ton gross wagons (72 tons ofpayload) whose coupling gearis designed to swivel, so thatwagons can be turned upside down for dischargewithoutuncoupling from their train. Special vans take palletizedloads of miscellaneousmerchandise or such products asfertilizer, the van doors being designed so that allparts of theinterior can be reached by а fork-lift truck.
British railway companiesbegan building their stocks ofcontainers in 1927, and by 1950 they had the largeststock oflarge containers in Western Europe. In 1962 British Raildecided to use InternationalStandards Organisation sizes,8 ft (2,4 m) wide by 8 ft high and 1О, 20, 30 and 40ft (3.1, 6.1,9.2 and 12.2 m) long. The 'Freightliner' service of containertrains uses 62.5 ft (19.1 m)flat wagons with air-operated discbrakes in sets оf five andwas inaugurated in 1965. At depots
'Drott'pneumatic-tyred cranes were at first provided butrail-mounted Goliath cranesare now provided.
Cars are handled bydouble-tier wagons. The British carindustry is а big user of'сomраnу' trains, which areoperatedfor а single customer. Both Ford and Chrysler use them toexchange parts betweenspecialist factories аnd the railwaythus becomes an extension offactory transport. Companytrains frequent1у consist of wagons owned by thetrader;there are about 20,000 on British railways, the oil industry,for example, providing mostоf the tanks it needs to carry 21million tons of petroleumproducts by rail each year despite
competitionfrom pipelines.
Gravel dredged from theshallow seas is another developing source of rail traffic. It is moved in 76ton lots by 100 tongross hopper wagons and is either discharged on tobeltconveyersto go into the storage bins at the destination or, in another system, it isunloaded by truck-mounted discharging machines.
Cryogenic (very lowtemperature) products are also transported by rail in high capacity insulatedwagons. Such products include liquid oxygen and liquid nitrogen which aretaken from а central plantto strategically-placed railheadswhere the liquefied gas istransferred to road tankers for thejourney to its ultimatedestination.
Switchyards
Groups of sorting sidings,in which wagons[freight cars] can be arranged in order sо that they can be
detachedfrom the train at their destination with the leastpossible delay, are calledmarshalling yards in Britain andclassification yards orswitchyards in North America. Thework is done by smal