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.
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.
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.