How Things Work on Railroads:

Railroad, mode of land transportation in which flange-wheeled vehicles move over two parallel steel rails, or tracks, either by self-propulsion or by the propulsion of a locomotive.


After the first crude beginnings, railroad-car design took divergent courses in North America and Europe, because of differing economic conditions and technological developments. Early cars on both continents were largely of two-axle design, but passenger-car builders soon began constructing cars with three and then four axles, the latter arranged in two four-wheel swivel trucks, or bogies. The trucks resulted in smoother riding qualities and also spread the weight of heavy vehicles over more axles.

Freight cars

Throughout the world the great majority of freight cars for all rail gauges are built with four axles, divided between two trucks. Because of the layout constraints of some freight terminals, several European railroads still purchase a proportion of two-axle vehicles, but these have a much longer wheelbase and hence a considerably larger load capacity than similar cars in the past. Some bulk mineral cars in Germany and the United States have been built with two three-axle trucks, and Russia and various other former Soviet states still have a number of freight cars carried on four two-axle trucks; these are the world’s largest. Concern to maximize payload capacity in relation to tare vehicle weight has led to U.S. and European adoption of articulation for cars in certain uses, notably intermodal transport. In this system a car comprises several frames or bodies (usually not more than five), which, where they adjoin, are permanently coupled and mounted on a single truck. One type of vehicle that is virtually extinct is the caboose, or brake-van. With modern air-braking systems, the security of a very long train can be assured by fixing to its end car’s brake pipe a telemetry device that continually monitors pressure and automatically transmits its findings to the locomotive cab.

Before World War II, freight cars consisted almost entirely of four basic types: the semiwalled open car, the fully covered boxcar, the flatcar, and the tank car. Since then, railroads and car builders have developed a wide range of car types designed specifically for the ideal handling and competitive transport of individual goods or commodities. At the same time, the payload weight of bulk commodities that can be conveyed in a single car without undue track wear has been significantly increased by advances in truck design and, in North America, by growing use of aluminum instead of steel for bodywork, to reduce the car’s own tare weight. In Europe and North America, where highway competition demands faster rail movement of time-sensitive freight, cars for such traffic as perishable goods, high-value merchandise, and containers are designed to run at 120 km (75 miles) per hour. The French and German railways both operate some selected merchandise and intermodal trains at up to 160 km (100 miles) per hour to achieve overnight delivery between centres up to about 1,000 km (600 miles) apart. In the United States, container trains traveling at 120 km/hr where route characteristics allow are scheduled to cover about 3,500 km (2,200 miles) in 52 hours.

In terminals two-way radio greatly speeds yard-switching work. Through its use, widely separated elements of mechanized track-maintenance gangs can maintain contact with each other and with oncoming trains. Supervisory personnel often use radio in automobiles to maintain contact with the operations under their control.

As the demand for more railroad communication lines has grown, the traditional lineside telegraph wire system has been superseded. As early as 1959, the Pacific Great Eastern Railway in western Canada began to use microwave radio for all communications, doing away almost entirely with line wires. Other railroads all over the world turned to microwave in the 1970s and ’80s. More recently many railroads have adopted optical-fibre transmission systems. The high-capacity optical-fibre cable, lightweight and immune to electromagnetic interference, can integrate voice, data, and video channels in one system.


A major reason for the growing use of microwave and optical-fibre systems was the tremendously increased demand for circuits that developed from the railroads’ widespread use of electronic computers.

Earlier, railroads had been among the leaders in adopting punched-card and other advanced techniques of data processing. In the 1970s and ’80s there was a strong trend toward “total information” systems built around the computer. In rail freight operation, each field reporting point, usually a freight-yard office or terminal, is equipped with a computer input device. Through this device, full information about every car movement (or other action) taking place at that point can be placed directly into the central computer, usually located at company headquarters. From data received from all the field reporting points on the railroad, the computer can be programmed to produce a variety of outputs. These include train-consist reports (listing cars) for the terminal next ahead of a train, car-location reports for the railroad’s customer-service offices, car-movement information for the car-records department, revenue information for the accounting department, plus traffic-flow data and commodity statistics useful in market research and data on the freightcar needs at each location to aid in distributing empty cars for loading. Tracing of individual car movements can be elaborated by adoption of automatic car identification systems, in which each vehicle is fitted with an individually coded transponder that is read by strategically located electronic scanners at trackside. Major customers can be equipped for direct access to the railroad computer system, so that they can instantly monitor the status of their freight consignments. Relation of real-time inputs to nonvariable data banked in computer memory enables the railroad’s central computer to generate customer invoices automatically. Data banks can be developed to identify the optimal routing and equipment required for specific freight between given terminals, so that price quotations for new business can be swiftly computer-generated.

Computers and microprocessors have found many other uses as a railroad management aid. For example, daily data on each locomotive’s mileage and any special attention it has needed can be fed by its operating depot into a central computer banking historical data on every locomotive operated by the railroad. In the past, many railroads scheduled locomotive overhauls at arbitrarily assessed intervals, but use of a computer base enables overhaul of an individual locomotive to be precisely related to need, so that it is not unnecessarily withdrawn from traffic. The same procedure can be applied to passenger cars. Systems have been developed that optimize economical use of locomotives by integrated analysis of traffic trends, the real-time location of locomotives, and the railroad’s route characteristics to generate the ideal assignment of each locomotive from day to day.

Computerization has given a railroad’s managers a complete, up-to-the-minute picture of almost every phase of its operations. Such complete information and control systems have proved a powerful tool for optimizing railroad operations, controlling costs, and producing better service.

Methods of controlling train operations evolved over many years of trial and error. A common method in the early years was to run trains on a time-interval system; i.e., a train was required to leave a station a certain number of minutes behind an earlier train moving in the same direction. The development of distance-interval systems was a great improvement. In these so-called block systems, a train is prevented from entering a specific section of track until the train already in that section has left it.

Operation of single-track routes on the basis of a timetable alone, which was common on early lines in the United States, had the disadvantage that, if one train were delayed, others also would be delayed, since it was impossible to change the meeting points. By using the telegraph, and later the telephone, the dispatcher could issue orders to keep trains moving in unusual circumstances or to operate extra trains as required. This “timetable–train order” system is still used on many lines in the United States and Canada as well as in developing countries. It is often supplemented with automatic block signals to provide an additional safety factor, and radio is increasingly the means of communication between dispatchers and train crews.


Types of signals

The earliest form of railroad signal was simply a flag by day or a lamp at night. The first movable signal was a revolving board, introduced in the 1830s, followed in 1841 by the semaphore signal. One early type of American signal consisted of a large ball that was hoisted to the top of a pole to inform the engineman that he might proceed (hence, the origin of the term highball).

The semaphore signal was nearly universal until the early years of the 20th century, when it began to be superseded by the colour-light signal, which uses powerful electric lights to display its aspects. These are usually red, green, and yellow, either singly or in simultaneous display of two colours. The different colours are obtained either by rotating appropriate roundels or colour filters in front of a single beam or by providing separate bulbs and lenses for each colour. The number of lights and the range of aspects available from one signal can vary depending on its purpose. For instance, additional lights may be installed to the left or right of the main lights to warn a driver of divergence ahead from the through track. In Britain suitably angled strips of white lights are added to signals and illuminated when a divergent track is signaled. Red (stop or danger), green (track clear), and yellow (warning) have the same basic significance worldwide, but in Europe particularly they also are used in combinations of two colours to convey meanings that can vary from one railroad to another. Colour-light signaling is now standard on all but some minor rural lines of the world’s principal railways, and its use is spreading elsewhere.


Automated systems

The basis of much of today’s railroad signaling is the automatic block system, introduced in 1872 and one of the first examples of automation. It uses track circuits that are short-circuited by the wheels and axles of a train, putting the signals to the rear of the train, and to the front as well on single track, at the danger aspect. A track circuit is made by the two rails of a section of track, insulated at their ends. Electric current, fed into the section at one end, flows through a relay at the opposite end. The wheels of the train will then short-circuit the current supply and de-energize the relay.

In a conventional automatic block system, permissible headway between trains is determined by the fixed length of each block system and is therefore invariable. Modern electronics has made possible a so-called “moving block” system, in which block length is determined not by fixed ground distance but by the relative speeds and distance from each other of successive trains. In a typical moving block system, track devices transmit to receivers on each train continuous coded data on the status of trains ahead. Apparatus on a train compares this data with the train’s own location and speed, projects a safe stopping distance ahead, and continuously calculates maximum speed for maintenance of that headway. Moving block has been devised essentially for urban rapid-transit rail systems with heavy peak-hour traffic and on which maximum train speeds are not high; in such applications its flexibility by comparison with fixed block increases the possible throughput of trains over one track in a given period of time.

To ensure observance of restrictive signals, a basic form of automatic train control has been used by many major railroads since the 1920s. When a signal aspect is restrictive, an electromagnetic device is activated between the rails, which in turn causes an audible warning to sound in the cab of any train passing over it. If the operator fails to respond appropriately, after a short interval the train brakes are applied automatically. A refinement, generally known as automatic train protection (ATP), has been developed since World War II to provide continuous control of train speed. It has been applied principally to busy urban commuter and rapid-transit routes and to European and Japanese intercity high-speed routes. A display in the cab reproduces either the aspects of signals ahead or up to 10 different instructions of speed to be maintained, decelerated to, or accelerated to, according to the state of the track ahead. Failure to respond to a restrictive instruction automatically initiates both power reduction and braking. The cab displays are activated by on-train processing of coded impulses passed through either the running rails or track-mounted cable loops and picked up by inductive coils on the train. On some high-speed passenger lines the ATP system obviates use of traditional trackside signals.

Among other automatic aids to railroad operation is the infrared “hotbox detector,” which, located at trackside, detects the presence of an overheated wheel bearing and alerts the train crew. The modern hotbox detector identifies the location in the train of the overheating and, employing synthesized voice recording, radios the details to the train crew. Broken flange detectors are used in major terminals to indicate the presence of damaged wheels. Dragging equipment detectors warn crews if a car’s brake rigging or other component is dragging on the track.

Interlocking and routing

The first attempts at interlocking switches and signals were made in France in 1855 and in Britain in 1856. Interlocking at crossings and junctions prevents the displaying of a clear signal for one route when clearance has already been given to a train on a conflicting route. Route-setting or route-interlocking systems are modern extensions of this principle. With them the signaling operator or dispatcher can set up a complete route through a complicated track area by simply pushing buttons on a control panel. Most interlockings employ electrical relays, but adoption of computer-based solid-state interlocking began in Europe and Japan in the 1980s. Safeguard against malfunction is obtained by duplication or triplication; parallel computer systems are arranged to examine electronic route-setting commands in different ways, and only if automatic comparison shows no discrepancy in their proof that conflicting routes have been secured will the apparatus set the required route.

Electronics have greatly widened the scope for precise but at the same time labour-saving control of a busy railroad’s traffic by making it possible to oversee extensive areas from one signaling or dispatching centre. This development is widely known as centralized traffic control (CTC). In Britain, for example, one signaling centre can cover more than 320 km (200 miles) of route with a principal city at the hub; the layout under control—used by intercity passenger, suburban passenger, and freight trains—may include 450 switch points and 1,200 possible route-settings. In the United States, the Union Pacific Railroad Company has consolidated dispatching control of its entire system in a single centre at its Omaha, Nebraska, headquarters. This concentration of signal and point control is possible because of the electronic ability to convey over a single communications channel a multitude of split-second, individually coded commands to ground apparatus and to return confirmations of compliance equally rapidly.

The functions of track circuits have been multiplied by electronics. The individual timetable number or alpha-numeric code of a train is entered into the signaling system at the track-circuited block where the train starts its journey. As the train moves from one block section to another, its occupation of successive track circuits automatically causes its number or code to move accordingly from one miniature illuminated window to another on the signaling centre’s layout displays. When the train moves from one control area to another, its code will automatically move to the next centre’s layout display. The real-time data on individual train progress generated by this system can be adapted for transmission to any interested railway office or, on a passenger railroad, to drive service information displays at stations. Particularly on rapid-transit systems, setting of junctions can be automated if train numbers or codes include an indication of routing, which is electronically detected when they occupy a track circuit at the approach to the divergence.

From the foregoing it is apparent that the means for complete automation of train operation exist. It has been applied to some private industrial rail systems since the early 1970s, and most of the capability has been built into some city metro systems. Extension of computer processing to the real-time data on train movement generated from track circuitry has further benefited control of major railroads’ traffic. In Europe’s latest centres controlling intensive passenger operations, operators can call up graphic video comparisons of actual train performance with schedule, projections of likely conflict at junctions where trains are not running on schedule, and recommendations for revision of train priorities to minimize disruption of scheduled operation. In North America, where many main lines are single-track, the Computer-Assisted Dispatching System (CADS) can relieve the operator of much routine work. At Union Pacific’s Omaha centre, once the dispatcher has entered a train’s identity and priority, the system automatically routes it accordingly, arranging its passing of other trains in loops as befits its priority. CADS automatically updates and modifies its determinations based on actual train movements and changing track conditions. The operator can intervene and override the system.

In early CTC installations the layout under a centre’s control was shown only on one panoramic display, in which appropriately located lights indicated the setting of each switch point and signal, the track-circuited sections occupied by trains, and in windows at each occupied section the identifying code of the train in question. In some installations route-setting buttons were incorporated in this display. In the most recent CTC centres the overall panoramic display is generally retained, but operators have colour video screens portraying close-ups of the areas under their specific control. In many such cases, a light-pencil or tracker-ball movement of a cursor is used to identify on the screen the route to be changed. Alternatively, the operators may have alphanumeric keyboards on which reset route codes may be entered.

On the main lines of North America, precise control of train movement is more difficult than in Europe, because block sections are much longer. To overcome the problem, the principal railroads of the United States and Canada combined in the 1980s to develop an Advanced Train Control Systems (ATCS) project, which integrated the potential of the latest microelectronics and communications technologies. In fully realized ATCS, trains continuously and automatically radio to the dispatching centre their exact location and speed; both would be determined by a locomotive-mounted scanner as well as signals received from global positioning system (GPS) satellites. In the dispatching centre, this input is processed to arrive at the optimal speed for each train in relation to its priority, the proximity of other trains it must pass, and route characteristics. From this analysis, continuously updated instructions can be radio-transmitted to train locomotives and processed by onboard computers for reproduction on cab displays so that trains can be driven with maximum regard for operating and fuel-consumption efficiency. ATCS can be developed in several stages, or levels, up to full implementation.

The marshaling yard

A major area for automation techniques in railroading is the large classification, or marshaling, yard. In such yards, freight cars from many different origins are sorted out and placed in new trains going to the appropriate destinations. Marshaling yards are frequently called “hump yards” because the large installations have a “hump” over which cars are pushed. The cars then roll down from the hump by gravity, and each is routed into a classification or “bowl” track corresponding to its destination or where the train for the next stage of its transit is being formed.

Operations in classification yards have reached a high degree of automation. The heart of the yard is a central computer, into which is fed information concerning all cars in the yard or en route to it. As the cars are pushed up the hump (in some yards, by locomotives that are crewless and under remote radio control from the yard’s operations centre), electronic scanners confirm their identity by means of a light-reflective label, place the data (car owner, number, and type) in a computer, and then set switches to direct each car into the proper bowl track. Electronic speed-control equipment measures such factors as the weight, speed, and rolling friction of each car and operates electric or electropneumatic “retarders” to control the speed of each car as it rolls down from the hump. Every phase of the yard’s operations is monitored by a computerized management control and information system. With hand-held computers, ground staff can input data directly into the yard’s central computer.

Because such electronically equipped yards can sort cars with great efficiency, they eliminate the need to do such work at other, smaller yards. Thus, one large electronic yard usually permits the closing or curtailing of a dozen or more other yards. Most modern electronic yards have quickly paid for themselves out of operating savings—and this takes no account of the benefits of improved service to shippers.

Intermodal freight vehicles and systems

An important competitive development has been the perfection of intermodal freight transport systems, in which highway truck trailers or marine shipping containers are set on railroad flatcars. In North America and Europe they have been the outstanding growth area of rail freight activity since World War II. For the largest U.S. railroads, only coal now generates more carloadings per annum than intermodal traffic.

In overload intermodal transport the economy of the railroad as a bulk long-distance hauler is married to the superior efficiency and flexibility of highway transport for shorter-distance collection and delivery of individual consignments. Intermodal transportation also makes use of rail for the long haul accessible and viable to a manufacturer that is not directly rail-served and has no private siding.


Initially, the emphasis in North America was on the rail piggybacking of highway trailers on flatcars (TOFC), which the Southern Pacific Railroad pioneered in 1953. By 1958 the practice had been adopted by 42 railroads; and by the beginning of the 1980s U.S. railroads were recording more than two million piggyback carloadings a year. In Europe, few railroads had clearances ample enough to accept a highway box trailer piggybacked on a flatcar of normal frame height. As shipping lines developed their container transport business in the early 1960s, European railroads concentrated initially on container-on-flatcar (COFC) intermodal systems. A few offered a range of small containers of their own design for internal traffic, but until the 1980s domestic as well as deep-sea COFC in Europe was dominated by the standard sizes of maritime containers. In the 1980s an increasing proportion of Europe’s internal COFC traffic used the swapbody, or demountable, which is similar in principle to, but more lightly constructed, cheaper, and easier to transship than the maritime container; the latter has to withstand stacking several deep on board ship and at ports, which is not a requisite for the swapbody. As its name suggests, the swapbody has highway truck or trailer body characteristics

The container took on a growing role in North American intermodal transportation in the 1980s. American President Intermodal decided that containers originating from Pacific Rim countries to destinations in the Midwest and eastern United States were better sent by rail from western seaboard ports than shipped through the Panama Canal. To optimize the economics of rail landbridging, the shipping line furthered development of lightweight railcars articulating five low-slung well frames on each of which containers could be double-stacked within, or with minimal modification of, the vertical clearances of the principal route between West Coast ports and Chicago. At the same time, the shipping line marketed containers off-loaded in the east as the medium for rail shipment of merchandise from the east to the western states. This was influential in stimulating new interest in the container as a medium for domestic door-to-door transportation. Other shipping lines copied American President’s lead; railroads enlarged clearances to extend the scope of double-stack container transportation to the eastern and southern seaboards (Canadian railroads followed suit); and in the later 1980s both double-stack operation and the container’s share of total North American intermodal traffic rapidly expanded.


The overhead costs of COFC and TOFC are considerable. Both require terminals with high-capacity transshipment cranage and considerable space for internal traffic movement and storage. TOFC also has a cost penalty in the deadweight of the highway trailers’ running gear that has to be included in a TOFC train’s payload. Two principal courses have been taken by railroads to improve the economics of their intermodal operations. One is to limit their transshipment terminals to strategically located and well-equipped hubs, from which highway collection and delivery services radiate over longer distances; as a result, the railroad can carry the greater part of its intermodal traffic in full terminal-to-terminal trainloads, or unit trains. The other course has been to minimize the tare weight of rail intermodal vehicles by such techniques as skeletal frame construction and, as in the double-stack COFC units described above, articulation of car frames over a single truck. Even so, North American railroads have not been able to make competitively priced TOFC remunerative unless the rail component of the transit is more than about 1,000 km (600 miles).

Two different managerial approaches to intermodal freight service have developed in the United States. Some of the major railroads have organized to manage and market complete door-to-door transits themselves; others prefer simply to wholesale intermodal train space to third parties. These third parties organize, manage, and bill the whole door-to-door transit for an individual consignor.

Given the shorter intercity distances, European railroads have found it more difficult to operate viable TOFC services. The loading of a highway box trailer on a railcar of normal frame height without infringing European railroads’ reduced vertical clearances was solved by French National Railways in the 1950s. The answer was a railcar with floor pockets into which the trailer’s wheels could be slotted, so that the trailer’s floor ended up parallel with that of the railcar. Even so, there were limitations on the acceptable height of box trailers. Other railroads were prompted to begin TOFC in the 1960s when the availability of heavy tonnage cranes at new container terminals simplified the placing of trailers in the so-called “pocket” cars. Initial TOFC service development was primarily over long and mostly international trade routes, such as from the Netherlands, Belgium, and northern Germany to southern Germany, Austria, and Italy.

In 1978 the West German government decided to step up investment in its railways for environmental and energy-saving reasons. Its plans included a considerable subsidy of railroad intermodal operation, including TOFC. Similar support of intermodal development, for the same reasons, was subsequently provided for their national railways by the Austrian and Swiss governments. The German railroad (and also Scandinavian railroads) has more generous vertical clearances than the European norm. Whereas other European mainland railroads, even with pocket cars, can only operate TOFC over a few key trunk routes, the German Federal Railway Authority could use the financial support to launch TOFC as well as COFC service between most of its major production and consumption areas.

The Germans, followed by the Austrians and Swiss and then other European countries, developed a particularly costly intermodal technology called “Rolling Highway” (Rollende Landstrasse), because it employs low-floor cars that, coupled into a train, form an uninterrupted drive-on, drive-off roadway for highway trucks or tractor-trailer rigs. Rolling Highway cars are carried on four- or six-axle trucks with wheels of only 36-cm (14-inch) diameter so as to lower their floors sufficiently to secure the extra vertical clearance for highway vehicles loaded without their wheels pocketed. Platforms bridge the gap between the close-coupled railcars. To allow highway vehicles to drive on or off the train yet enable a locomotive to couple to it without difficulty, the train-end low-floor cars have normal-height draft-gear headstocks that are hinged and can be swung aside to open up the train’s roadway. Truck drivers travel in a passenger car added to the train.

In the face of growing trade between northwestern and southeastern Europe, Austria and Switzerland have imposed restraints on use of their countries as a transit corridor by over-the-highway freight to safeguard their environments. Primarily to provide for increase in intermodal traffic, and in particular Rolling Highway trains, the Swiss parliament approved a government plan to bore new rail tunnels on each of its key north-south transalpine routes, the Gotthard and the Lötschen. The Lötschberg Base Tunnel, the world’s longest overland tunnel—a 34.6-km (21.5-mile) rail link—took eight years to build, and when full rail service began in 2007, it slashed the train journey between Germany and Italy from 3.5 hours to less than 2 hours. The 57-km (35-mile) Gotthard Base Tunnel—an even more ambitious project—was opened June 1, 2016, and was the longest and most deeply set rail tunnel in the world. Both tunnels are much longer than older tunnels located higher up in the summit passes, and their tracks are free of the summit routes’ steep gradients and sharp curves on either side of their tunnels.

Passenger intermodals

To save motorists the negotiation of mountain passes, especially in winter, two Swiss railroads shuttle drive-on, drive-off trains for automobiles between terminals at the extremities of their transalpine tunnels. This practice has been elaborated for Channel Tunnel rail transport of private automobiles, buses, and trucks between Britain and France. The tunnel’s rail traffic is partly conventional trains, but it has been bored to dimensions that allow auto transporter trains to employ cars of unprecedented size. Consequently, these trains are limited to shuttle operation between terminals on the British and French coasts. The fully enclosed double-deck cars for automobile traffic measure 5.5 metres (18 feet 4 inches) high and 4 metres (13 feet 5 inches) wide; the latter dimension allows room for automobile passengers, who are carried in their vehicle, to dismount and use the car’s toilet or auto-buffet while the train threads the tunnel. The transporter cars for buses and trucks are single-deck.

Thomas Clark Shedd

Geoffrey Freeman Allen

Railroad History

Source in inland water transport

The earliest railroads reinforced transportation patterns that had developed centuries before. During the Middle Ages most heavy or bulky items were carried by water wherever possible. Where natural interconnection among navigable rivers was lacking, gaps in trade were likely to develop, most notably at watersheds. By the 16th century canal building was being widely used in Europe to integrate waterway systems based on natural streams. During the Industrial Revolution canal networks became urgent necessities in western Europe and the western Mediterranean. In Britain and France the increased use of coal for raising steam and for iron smelting greatly increased the need for canal transportation. In the 50 years after 1775 England and Wales were webbed with canals to provide reasonably inexpensive transport of coal. But in areas of concentrated industry in hilly country, such as around Birmingham and in the “Black Country” of England, or areas of heavy coal production in droughty uplands, as in western County Durham, the transporting of coal by water seemed impracticable.

A development of the late Middle Ages, the plateway, suggested a means to make steam-powered land transport practicable. In central Europe most of the common metals were being mined by the 16th and 17th centuries, but, because they occurred in low concentrations, great tonnages of ore had to be mined to produce small yields of usable material. In that situation it was helpful to provide a supporting pavement on which wheels might run with somewhat reduced friction. Recourse was had to the minimum pavement possible, that provided by two parallel rails or plates supporting the wheels of a wagon. The wheels were guided by a flange either on the rail or on the wheel. The latter was ultimately preferred, because with the flange on the wheel debris was less likely to lodge on the rail. In the Harz Mountains, the Black Forest, the Ore Mountains, the Vosges, Steiermark, and other mining areas such railroads or plateways were widespread before the 18th century.

The bulk and weight of the steam engine suggested its being mounted on a railway. This occurred in Britain where, in the 17th century, coal mining had become common in the northeast in Tyneside and in South Wales. By 1800 each of these areas also had an extensive plateway system depending on gravity-induced movement or animal traction. The substitution of steam-engine traction was logical. The timing of this shift during the first decade of the 19th century was dictated by improvements in the steam engine. The weight-to-power ratio was unfavourable until 1804, when a Cornish engineer, Richard Trevithick, constructed a steam engine of his own design. In 1802 at Coalbrookdale in Shropshire he built a steam-pumping engine that operated at 145 pounds per square inch (roughly 1,000 kilopascals) pressure. He mounted the high-pressure engine on a car with wheels set to operate on the rails of a cast-iron tramroad located at Pen-y-Darren, Wales.


Railroad signals are a form of communication designed to inform the train crew, particularly the engine crew, of track conditions ahead and to tell it how to operate the train.

In the United States Oliver Evans, a Delaware wheelwright, in 1805 built an engine with steam pressure well above the single atmosphere that Watt used in his early engines. Evans was commissioned to construct a steam-powered dredge to be used on the docks in Philadelphia. He built his dredge away from the Schuylkill River, having it move itself, ponderously, to its destination by rail.

Early European railroads


The Stockton and Darlington Railway

George Stephenson was the son of a mechanic and, because of his skill at operating Newcomen engines, served as chief mechanic at the Killingworth colliery northwest of Newcastle upon Tyne, Eng. In 1813 he examined the first practical and successful steam locomotive, that of John Blenkinsop, and, convinced that he could offer improvements, designed and built the Blücher in 1814. Later he introduced the “steam blast,” by which exhaust was directed up the chimney, pulling air after it and increasing the draft. His success in designing several more locomotives brought him to the attention of the planners of a proposed railway linking the port of Stockton with Darlington, eight miles inland.

Investment in the Bishop Auckland coalfield of western County Durham was heavily concentrated in Darlington, where there was agitation for improvement in the outward shipment of the increasing tonnages produced. The region had become the most extensive producer of coal, most of which was sent by coastal sloop to the London market. The mining moved inland toward the Pennine ridge and thus farther from the port at Stockton-on-Tees, which in 1810 had been made a true seaport by completion of the Tees Navigation. A canal linking the cities had been proposed in a survey by James Brindley as early as 1769 but was rejected because of cost, and by the early 19th century several of the gravity tramways or railways on Tyneside had been fitted with primitive locomotives. In 1818 the promoters settled on the construction of a railway, and in April 1821 parliamentary authorization was gained and George IV gave his assent.

While construction was under way on the 40-km (25-mile) single-track line, it was decided to use locomotive engines as well as horse traction. Construction began on May 13, 1822, using both malleable iron rails (for two-thirds the distance) and cast iron and set at a track gauge of 1,422 mm (4 feet 8 inches). This gauge was subsequently standardized, with 13 mm (one-half inch) added at a date and for reasons unknown.

On September 27, 1825, the Stockton and Darlington Railway was completed and opened for common carrier service between docks at Stockton and the Witton Park colliery in the western part of the county of Durham. It was authorized to carry both passengers and freight. From the beginning it was the first railroad to operate as a common carrier open to all shippers. Coal brought to Stockton for sale in the coastal trade dropped in price from 18 shillings to 12 shillings a ton. At that price the demand for coal was greater than the initial fabric of the Stockton and Darlington could handle.

This was an experimental line. Passenger service, offered by contractors who placed coach bodies on flatcars, did not become permanent until 1833, and horse traction was commonly used for passenger haulage at first. But after two years’ operation the trade between Stockton and Darlington had grown tenfold.

The Liverpool and Manchester Railway

The Liverpool and Manchester, Stephenson’s second project, can logically be thought of as the first fully evolved railway to be built. It was intended to provide an extensive passenger service and to rely on locomotive traction alone. The Rainhill locomotive trials were conducted in 1829 to assure that those prime movers would be adequate to the demands placed on them and that adhesion was practicable. Stephenson’s entry, the Rocket, which he built with his son, Robert, won the trials owing to the increased power provided by its multiple fire-tube boiler. The rail line began in a long tunnel from the docks in Liverpool, and the Edgehill Cutting through which it passed dropped the line to a lower elevation across the low plateau above the city. Embankments were raised above the level of the Lancashire Plain to improve the drainage of the line and to reduce grades on a gently rolling natural surface. A firm causeway was pushed across Chat Moss (swamp) to complete the line’s quite considerable engineering works.

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