axles, dates from 1870 when William Robinson applied it in the United

States. In England the Great Eastern Railway introduced power operation of

points and signals at Spitaifields goods yard in 1899, and three years

later track-circuit operation of powered signals was in operation on 30

miles (48 km) of the London and Sout Western Railway main line.

Day colour light signals, controlled automatically by the trains

through track circuits, were installed on the Liverpool Overhead Railway in

1920 and four-aspect day colour lights (red, yellow, double yellow and

green) were provided on Southern Railway routes from 1926 onwards. These

enable drivers of high-speed trains to have а warning two block sections

ahead of а possible need to stop. With track circuiting it became usual to

show the presence оf vehicles on а track diagram in the signal cabin which

allowed routes to be controlled remotely by means of electric relays.

Today, panel

operation of considerable stretches of railway is common-рlасе; at Rugby,

for instance, а signalman can control the points at а station 44 miles (71

km) away, and the signalbox at London Bridge controls movements on the

busiest 150 track-miles of British Rail. By the end of the I980s, the 1500

miles (241О km) of the Southern Region of British Rail are to be controlled

from 13 signalboxes. In modern panel installations the trains are not only

shown on the track diagram as they move from one section to another, but

the train identification number appears electronically in each section.

Соmputer-assisted train description, automatic train rеporting and, at

stations such as London Bridge, operation of platform indicators, is now

usual.

Whether points are operated manually or by an electric point motor,

they have to be prevented from moving while a train is passing over them

and facing points have to be locked, аnd рroved tо Ье lосkеd (оr 'detected'

) before thе relevant signal can permit а train movement. The blades of the

points have to be closed accurately (О.16 inch or 0.4 cm is the maximum

tolerance) so as to avert any possibility of а wheel flange splitting the

point and leading to а derailment.

Other signalling developments of recent years include completely

automatic operation of simple point layouts, such as the double crossover

at the Bank terminus of the British Rails's Waterloo and City underground

railway. On London Тransport's underground system а plastic roll operates

junctions according to the timetable by means of coded punched holes, and

on the Victoria Line trains are operated automatically once the driver has

pressed two buttons to indicate his readiness to start. Не also acts as the

guard, controlling the opening оf thе doors, closed circuit television

giving him а view along the train. The trains are controlled (for

acceleration and braking) by coded impulses transmitted through the running

rails to induction coils mounted on the front of the train. The absence of

code impulses cuts off the current and applies the brakes; driving and

speed control is covered by command spots in which а frequency of 100 Hz

corresponds to one mile per hour (1.6 km/h), and l5 kHz

shuts off the current. Brake applications are so controlled that trains

stop smoothly and with great accuracy at the desired place on platforms.

Occupation of the track circuit ahead by а train automatically stops the

following train, which cannot receive а code.

On Вritish main lines an automatic warning system is being installed by

which the driver receives in his саb а visual and audible warning of

passing а distant signal at caution; if he does not acknowledge the warning

the brakes are applied automatically. This is accomplished by magnetic

induction between а magnetic unit placed in the track and actuated

according to the signal aspect, and а unit on the train.

Train control

In England train control began in l909 on the Midland Railway,

particularly to expedite the movement оf coal trains and to see that guards

and enginemen were

relieved at the end of their shift and were not called upon to work

excessive overtime. Comprehensive train control systems, depending on

complete diagrams of the track layout and records of the position of

engines, crews and rolling stock, were developed for the whole of 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 the

regulation of trains. Refinements оf control include advance traffic

information(ATI) in which information is passed from yard to yard by telex

giving types of wagon, wagon number, route code, particulars оf the load,

destination

station and consignee. In l972 British Rail decided to

adopt а computerized freight information and traffic control system known

as TOPS (total operations processing system) which was developed over eight

years by the Southern Pacific company in the USA.

Although а great deal of rail 1rаffiс in Britain is handled by block

trains from point of origin to destination, about onefifth of the

originating tonnage is less than a train-load. This means that wagons must

be sorted on their journey. In Britain there are about 600 terminal points

on a 12,000 mile network whitch is served by over 2500 freight trains made

up of varying assortments of 249,000 wagons and 3972 locomotives, of witch

333 are electric. This requires the speed of calculation and the

information storage and classification capacity of the modern computer,

whitch has to be linked to points dealing with or generating traffic

troughout the system.The computer input, witch is by punched cards, covers

details of loading or unloading of wagons and their movements in trains,

the composition of trains and their departures from and arrivals at yards

,and the whereabouts of locomotives. The computer output includes

information on the balanse of locomotives at depots and yards, with

particulars of when maintenanse examinations are due, the numbers of

empty and loaded wagons, with aggregate weight and brake forse, and wheder

their movement is on time, the location of empty wagons and a forecast of

those that will become available, and the numbers of trains at any

location, with collective train weigts and individual details of the

component wagons.

A closer check on what is happening troughoud the

system is thus provided, with the position of consignments in transit,

delays in movement, delays in unloading wagons by customers, and the

capasity of the system to handle future traffic among the information

readily available. The computer has a built-in self-check on wrong input

information.

Freight handling

The merry-go-round system enables coal for power

stations to be loaded into hopper wagons at a colliery

without the train being stopped, and at the power station the train is

hauled round a loop at less than 2mph (3.2 km/h), a trigger devise

automatically unloading the wagons without the train being stopped. The

arrangements also provide for automatic weighing of the loads. Other bulk

loads can be dealt with in the same way.

Bulk powders, including cement, can be loaded and discharged

pneumatically, using either rаi1 wagons or containers. Iron ore is carried

in 100 ton gross wagons (72 tons of payload) whose coupling gear is

designed to swivel, so that wagons can be turned upside down for discharge

without uncoupling from their train. Special vans take palletized loads of

miscellaneous merchandise or such products as fertilizer, the van doors

being designed so that all parts of the interior can be reached by а fork-

lift truck.

British railway companies began building their stocks of containers in

1927, and by 1950 they had the largest stock of large containers in Western

Europe. In 1962 British Rail decided to use International Standards

Organisation sizes, 8 ft (2,4 m) wide by 8 ft high and 1О, 20, 30 and 40 ft

(3.1, 6.1, 9.2 and 12.2 m) long. The 'Freightliner' service of container

trains uses 62.5 ft (19.1 m) flat wagons with air-operated disc brakes in

sets оf five and was inaugurated in 1965. At depots

'Drott' pneumatic-tyred cranes were at first provided but rail-mounted

Goliath cranes are now provided.

Cars are handled by double-tier wagons. The British car industry is а

big user of 'сomраnу' trains, which are operated for а single customer.

Both Ford and Chrysler use them to exchange parts between specialist

factories аnd the railway thus becomes an extension of factory transport.

Company trains frequent1у consist of wagons owned by the trader; there are

about 20,000 on British railways, the oil industry, for example, providing

most оf the tanks it needs to carry 21 million tons of petroleum products

by rail each year despite

competition from pipelines.

Gravel dredged from the shallow seas is another developing source of

rail traffic. It is moved in 76 ton lots by 100 ton gross hopper wagons and

is either discharged on to belt conveyers to go into the storage bins at

the destination or, in another system, it is unloaded by truck-mounted

discharging machines.

Cryogenic (very low temperature) products are also transported by rail

in high capacity insulated wagons. Such products include liquid oxygen and

liquid nitrogen which are taken from а central plant to strategically-

placed railheads where the liquefied gas is transferred to road tankers for

the journey to its ultimate destination.

Switchyards

Groups of sorting sidings, in which wagons [freight cars] can be

arranged in order sо that they can be

detached from the train at their destination with the least possible delay,

are called marshalling yards in Britain and classification yards or

switchyards in North America. The work is done by small locomotives called

switchers or shunters, which move 'cuts' of trains from one siding to

another until the desired order is achieved.

As railways became more complicated in their system

layouts in the nineteenth century, the scope and volume of necessary

sorting became greater, and means of reducing the time and labour involved

were sought. (Ву 1930, for every 100 miles that freight trains were run in

Britain there were 75 miles of shunting.) The sorting of coal wagons for

return to the collieries had been assisted by gravity as early as 1859, in

the sidings at Tyne dock on the North Eastern Railway; in 1873 the London &

North Western Railway sorted traffic to and from Liverpool on the Edge Hill

'grid irons': groups of

sidings laid out on the slope of а hill where gravity provided the motive

power, the steepest gradient being 1 in 60 (one foot of elevation in sixty

feet of siding). Chain drags were used for braking he wagons. А shunter

uncoupled the wagons in 'cuts' for the various destinations and each cut

was turned into the appropriate siding. Some gravity yards relied on а code

of whistles to advise the signalman what 'road' (siding) was required.

In the late nineteenth century the hump yard was introduced to provide

gravity where there was nо natural slope of the land. In this the trains

were pushed up an artificial mound with а gradient of perhaps 1 in 80 and

the cuts were 'humped' down а somewhat steeper gradient on the other side.

The separate cuts would roll down the selected siding in the fan or

'balloon' of sidings, which would еnd in а slight upward slope to assist in

the stopping of the wagons. The main means of stopping the wagons, however,

were railwaymen called shunters who had to run alongside the wagons and

apply the brakes at the right time. This was dangerous and required

excessive manpower.

Such yards арреаrеd all over North America and north-east England and

began to be adopted elsewhere in England. Much ingenuity was devoted to

means of stopping the wagons; а German firm, Frohlich, came up with а

hydraulically operated retarder which clasped the wheel of the wagon as it

went past, to slow it down to the amount the operator throught nесеssarу.

An entirely new concept came with Whitemoor yard at

March, near Cambridge, opened by the London & North

Eastern Railway in l929 to concentrate traffic to and from East Anglian

destinations. When trains arrived in one of ten reception sidings а shunter

examined the wagon labels and prepared а 'cut card' showing how the train

should be sorted into sidings. This was sent to the control tower by

pneumatic tube; there the points [switches] for the forty sorted sidings

were preset in accordance with the cut card; information for several trains

could be stored in а simple pin and drum device.

The hump was approached by а grade of 1 in 80. On the far side was а

short stretch of 1 in 18 to accelerate the wagons, followed by 70 yards {64

m) at 1 in 60 where the tracks divided into four, each equipped with а

Frohlich retarder. Then the four tracks spread out to four balloons of ten

tracks each, comprising 95 yards (87 m) of level track followed by 233

yards (213 m) falling at 1 in 200, with the remaining 380 yards

(348 m) level. The points were moved in the predetermined sequence by

track circuits actuated by the wagons, but the operators had to estimate

the effects on wagon speed of the retarders, depending to а degree on

whether the retarders were grease or oil lubricated.

Pushed by an 0-8-0 small-wheeled shunting engine at 1.5 to 2 mph (2.5

to 3 km/h), а train of 70 wagons could be sorted in seven minutes. The yard

had а throughput of about 4000 wagons а day. The sorting sidings were

allocated: number one for Bury St Edmunds, two for Ipswich, and sо forth.

Number 31 was for wagons with tyre fastenings which might be ripped off by

retarders, which were not used on that siding. Sidings 32 tо 40 were for

traffic to be dropped at wayside stations; for these sidings there was an

additional hump for sorting these wagons in station order. Apart from the

sorting

sidings, there were an engine road, а brake van road, а

'cripple' road for wagons needing repair, and transfer road to three

sidings serving а tranship shed, where small shipments not filling entire

wagons could be sorted.

British Rail built а series of yards at strategic points; the yards

usually had two stages of retarders, latterly electropneumatically

operated, to control wagon speed. In lateryards electronic equipment was

used to measure the weight of each wagon and estimate its

rolling resistance. By feeding this information into а computer, а suitable

speed for the wagon could be determined and the retarder

operatedautomatically to give the desired amount of braking. These

predictions did not always prove reliable.

At Tinsley, opened in l965, with eleven reception roads and 53 sorting

sidings in eight balloons, the Dowty wagon speed control system was

installed. The Dowty system uses many small units (20,000 at Tinsley)

comprising hydraulic rams on the inside of the rail, less than а wagon

length apart. The flange of the wheel depresses the ram, which returns

after the wheel has passed. А speed-sensing device determines whether the

wagon is moving too fast from thehump; if the speed is too fast the ram

automatically has а retarding action.

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