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72-494: In 1922 the Interstate Commerce Commission issued a ruling requiring trains to be equipped with automatic train stop technology if they were to be operated at 80 mph or greater. The Pennsylvania Railroad decided to use this as an opportunity to implement a signaling technology that could improve both safety and operational efficiency by displaying a signal continuously in the locomotive cab. The task

144-405: A down line in the opposite direction. The signal box towards which a train travels is said to be in advance and the signal box from which it travels is said to be in rear . A block section is normally the section of track from the most advanced signal controlled by the signal box in rear, and the rearmost signal controlled by the signal box in advance. Because many signal boxes are at stations,

216-451: A (passenger) train operating company (TOC) or a freight operating company (FOC), are allocated to one of ten classes, as set out below. It is a generalized guide intended to assist signalling staff in prioritizing trains according to their importance as well as ensuring that any special instructions that may apply at a specific location are carried out. Passenger trains are generally classified in accordance with their stopping pattern while

288-515: A Restricting signal. The codes would be transmitted to the train from the block limit in front of it. This way if the rail was broken or another train entered the block, any codes would not reach the approaching train and the cab signal would again display Restricting. Trains with an insufficient number of axles will not short out (see: Shunt (electrical) ) all of the cab signal current so that following trains might receive an incorrect aspect. Trains of this type must be given absolute block protection to

360-519: A USDOT number and a Motor Carrier (MC) number that replaced the ICC numbers. The ICC served as a model for later regulatory efforts. Unlike, for example, state medical boards (historically administered by the doctors themselves), the seven Interstate Commerce Commissioners and their staffs were full-time regulators who could have no economic ties to the industries they regulated. Since 1887, some state and other federal agencies adopted this structure. And, like

432-642: A new agency, the U.S. Surface Transportation Board (STB), which reviews mergers and acquisitions, rail line abandonments and railroad corporate filings. ICC jurisdiction on rail safety (hours of service rules, equipment and inspection standards) was transferred to the Federal Railroad Administration pursuant to the Federal Railroad Safety Act of 1970. Before the ICC was abolished motor carriers (bus lines, trucking companies) had safety regulations enforced by

504-468: A passenger station). Within station limits, the signalman controls the safe movement, and in normal circumstances he can directly see the position of trains there. Usually no communication with other signalmen is needed for movements within station limits. Electrical telegraphy was the first practical use of current electricity and was developed in the 1840s and 1850s at the same time as the development of railways. The first commercial electrical telegraph

576-529: A second train was allowed to proceed; although the driver was warned that there was a train only five minutes ahead. This was insufficient to prevent a train colliding with the rear of one that had stopped unexpectedly. In absolute block working, a block section (or simply section ) is a section of railway line between one signal box and another – in the typical absolute block, lines are paired, with an up – towards London (or in Scotland, Edinburgh) – and

648-412: A signalman, who communicates with the other block sections via telegraph. This system was used on double or multiple lines where use of each line is assigned a direction of travel before the introduction of track circuits , and is still used on many lines to this day (even those with track circuits). A train approaching a section is offered by a signalman to his counterpart at the next signal box. If

720-453: Is A and the signal box in advance is C. The block indicators at B are in the Normal position. The signalman at A "offers" the train to B by sending an "Is Line Clear?" code on the block bell; for example to offer an express passenger train, he sends four beats consecutively; an ordinary passenger train is offered by sending three beats, and after a pause one more beat, usually written as 3-1. If

792-496: Is confident that the train will be able to stop at his starting (or section) signal (this is not done until the train is in view and visibly under control). Finally, his distant will not clear without both his home and starting signals being clear. As the train passes the starting signal at A, the signalman there sends the "Train Entering Section" signal (2 beats) on the block bell to B, and the signalman at B acknowledges

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864-431: Is repeated for every block section a train passes through. The absolute block system does not replace the use of any other form of signalling, such as fixed signals, hand signals, or detonators – and, in fact, usually relies on fixed signals. Prior to the introduction of block systems, time intervals were used to keep trains sufficiently far apart; typically if five minutes had passed since the first train had departed then

936-478: Is the same at the state level, though it is probably less pronounced. The Interstate Commerce Commission had a strong influence on the founders of Australia. The Constitution of Australia provides ( §§ 101-104 ; also § 73 ) for the establishment of an Inter-State Commission , modeled after the United States' Interstate Commerce Commission. However, these provisions have largely not been put into practice;

1008-744: The Consumer Product Safety Commission (1975). In recent decades, this regulatory structure of independent federal agencies has gone out of fashion. The agencies created after the 1970s generally have single heads appointed by the President and are divisions inside executive Cabinet Departments (e.g., the Occupational Safety and Health Administration (1970) or the Transportation Security Administration (2002)). The trend

1080-811: The Railroad Revitalization and Regulatory Reform Act of 1976 ("4R Act"), the Motor Carrier Act of 1980 and the Staggers Rail Act of 1980. Senator Fred R. Harris of Oklahoma strongly advocated the abolition of the Commission. In December 1995, when most of the ICC's powers had been eliminated or repealed, Congress finally abolished the agency with the ICC Termination Act of 1995 . Final Chair Gail McDonald oversaw transferring its remaining functions to

1152-411: The speedometer , as cab signals now serve a speed control function. On trains equipped with automatic train control functionality failure to properly acknowledge a restrictive cab signal change results in a 'penalty brake application', as does failure to observe the cab signal speed limit. Interstate Commerce Commission The Interstate Commerce Commission ( ICC ) was a regulatory agency in

1224-505: The 1930s. Of those lines that survived, the stronger ones were not interested in supporting the weaker ones. Congress repudiated Ripley's Plan with the Transportation Act of 1940, and the consolidation idea was scrapped. Although racial discrimination was never a major focus of its efforts, the ICC had to address civil rights issues when passengers filed complaints. The limitation on railroad rates in 1906-07 depreciated

1296-612: The 20th century, several of ICC's authorities were transferred to other federal agencies. The ICC was abolished in 1995, and its remaining functions were transferred to the Surface Transportation Board . The Commission's five members were appointed by the President with the consent of the United States Senate . This was the first independent agency (or so-called Fourth Branch ). The ICC

1368-433: The 250 Hz codes get upgraded speeds on track sections with speeds greater than 125 mph and on 80 mph high speed turnouts. Trains without simply travel at the slower speeds. The 270ppm code does break backwards compatibility with the 4-code system, but is only in use around New York Penn Station as part of a high density signaling upgrade. The 270ppm code and 60 mph speed were chosen to be compatible with

1440-409: The Commission existed between 1913–1920, and 1975–1989, but never assumed the role which Australia's founders had intended for it. Absolute block Absolute block signalling is a British signalling block system designed to ensure the safe operation of a railway by allowing only one train to occupy a defined section of track (block) at a time. Each block section is manually controlled by

1512-474: The ICC to set maximum railroad rates, and extended the agency's authority to cover bridges, terminals, ferries, sleeping cars, express companies and oil pipelines. A long-standing controversy was how to interpret language in the Act that banned long haul-short haul fare discrimination. The Mann-Elkins Act of 1910 addressed this question by strengthening ICC authority over railroad rates. This amendment also expanded

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1584-417: The ICC's jurisdiction to include regulation of telephone , telegraph and wireless companies. The Valuation Act of 1913 required the ICC to organize a Bureau of Valuation that would assess the value of railroad property. This information would be used to set rates. The Esch-Cummins Act of 1920 expanded the ICC's rate-setting responsibilities, and the agency in turn required updated valuation data from

1656-405: The ICC's powers. The ICC became the United States' investigation agency for railroad accidents. Congress expanded the commission's powers through subsequent legislation. The 1893 Railroad Safety Appliance Act gave the ICC jurisdiction over railroad safety, removing this authority from the states, and this was followed with amendments in 1903 and 1910. The Hepburn Act of 1906 authorized

1728-836: The ICC, later agencies tended to be organized as multi-headed independent commissions with staggered terms for the commissioners. At the federal level, agencies patterned after the ICC included the Federal Trade Commission (1914), the Federal Communications Commission (1934), the Securities and Exchange Commission (1934), the National Labor Relations Board (1935), the Civil Aeronautics Board (1940), Postal Regulatory Commission (1970) and

1800-696: The Interstate Commerce Act banned "personal discrimination" and required shipping rates to be "just and reasonable." President Cleveland appointed Thomas M. Cooley as the first chairman of the ICC. Cooley had been Dean of the University of Michigan Law School and Chief Justice of the Michigan Supreme Court . The Commission had a troubled start because the law that created it failed to give it adequate enforcement powers. The Commission is, or can be made, of great use to

1872-576: The Interstate Commerce Commission to prepare and adopt a plan for the consolidation of the railway properties of the United States into a limited number of systems. Between 1920 and 1923, William Z. Ripley , a professor of political economy at Harvard University, wrote up ICC's plan for the regional consolidation of the U.S. railways. His plan became known as the Ripley Plan . In 1929 the ICC published Ripley's Plan under

1944-802: The Office of Motor Carriers (OMC) under the Federal Highway Administration (FHWA). The OMC inherited many of the "Economic" regulations enforced by the ICC in addition to the safety regulations imposed on motor carriers. In January 2000 the OMC became the Federal Motor Carrier Safety Administration (FMCSA), within the U.S. Department of Transportation . Prior to its abolition, the ICC gave identification numbers to motor carriers for which it issued licenses. The identification numbers were generally in

2016-509: The PRR installed cab signals over much of its eastern system from Pittsburgh to Philadelphia, New York to Washington. This system was then inherited by Conrail and Amtrak and various commuter agencies running on former PRR territory such as SEPTA and New Jersey Transit . Because all trains running in cab signal territory had to be equipped with cab signals, most locomotives of the aforementioned roads were equipped with cab signal equipment. Due to

2088-491: The United States created by the Interstate Commerce Act of 1887 . The agency's original purpose was to regulate railroads (and later trucking ) to ensure fair rates, to eliminate rate discrimination, and to regulate other aspects of common carriers , including interstate bus lines and telephone companies. Congress expanded ICC authority to regulate other modes of commerce beginning in 1906. Throughout

2160-517: The basis for the absolute block system. By 1872 it was used on 44% of lines in Britain, rising to 75% by the end of the decade and was made mandatory on passenger-carrying lines in 1889. It successfully managed train control over most of the British railway system until generally superseded by more sophisticated systems from 1950. Block instruments are located in signal boxes. They show the state of

2232-412: The bell a request from box A to take an up train. The other block instrument will do the same for box C for a down train. The commutator and lower display on the two instruments relate to the up line and the down line respectively. The upper display is a repeater from the signal box of the block ahead. The signalling bell , also known as a block bell , is used in conjunction with the block instruments if

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2304-427: The bell is not integrated with them. It is a single stroke design that is used to communicate from one signal box to an adjacent one. Each bell has its own distinctive sound so that the signalman knows which box is communicating with him. There are a set of standard bell codes . Each communication starts with a single strike of the bell meaning “Call attention”. The recipient signalman then shows that he has received

2376-439: The bicycle railroad. Based on his own testimony and that of a Massachusetts congressman, Boynton won release on May 28, 1920, overcoming testimony of the ICC's chief clerk that Boynton was virtually a daily visitor at ICC offices, seeking Commission adoption of his proposal to revolutionize the railroad industry. Congress passed various deregulation measures in the 1970s and early 1980s which diminished ICC authority, including

2448-403: The block indicator to "Normal". Bell codes are used to communicate with adjacent signal boxes. They can communicate information regarding the type of train being offered, the status of trains within sections or emergency information. A bell code is acknowledged as being understood by repetition. Nearly all bell codes are preceded by a single stroke on the bell, referred to as Call Attention —

2520-411: The block sections before and after the signal box. Originally the different displays and commutator handle were in a variety of cabinets. The standard British Railways block instrument brought them together in a single small cabinet; its front face displaying two indicators, a commutator handle, a bell and a tapper. The upper indicator shows the state of the forward block – along the line leading away from

2592-469: The cab signaling system only acted as a form of automatic train stop where the engineer would have to acknowledge any drop in the cab signal to a more restrictive aspect to prevent the brakes from automatically applying. Later, passenger engines were upgraded with speed control which enforced the rulebook speed associated with each cab signal (Clear = No Restriction, Approach Medium = 45 mph, Approach = 30 mph, Restricting = 20 mph). Over time

2664-539: The cab signals installed on the Long Island Rail Road trains that also use Penn Station. Cab signals are presented to the locomotive by means of a cab signal display unit. The earliest CDUs consisted of miniature signals of the type visible along the track, back lit by light bulbs. These could be found in both color light and position light varieties depending on the railroad's native signaling system. Modern CDUs on passenger trains are often integrated with

2736-411: The effect of interoperability lock in, the 4-aspect PRR cab signal system has become a de facto standard and almost all new cab signaling installations have been of this type or a compatible type. Pulse code cab signals work by sending metered pulses along an existing AC track circuit operating at a chosen carrier frequency . The pulses are detected via induction by a sensor hanging a few inches above

2808-446: The form of "ICC MC-000000". When the ICC was dissolved, the function of licensing interstate motor carriers was transferred to FMCSA. All interstate motor carriers that transport freight moving across state lines have a USDOT number, such as "USDOT 000000." There are private carriers, e.g. Walmart that move their own freight requiring only a USDOT number, and carriers with authority that haul freight for hire that are still required to have

2880-409: The home signal of the next signal box on the same line in the same direction of travel is the absolute block section. To clear the intermediate block home signal a "line clear" is required from the signal box in advance. An intermediate block section means that a train can approach the intermediate block home signal while there is a train between the intermediate block home signal and the home signal of

2952-553: The home signal, which will only show a clear aspect if all stop signals under a signal box's control are clear, and will otherwise show caution – this gives a driver advance warning of a need to stop. Some signal boxes have an intermediate block section , or IBS . This normally takes the place of an old absolute block section, and is commonly found where former absolute block sections and their associated signal boxes have been removed. Essentially an intermediate block section allows two block sections, and therefore two trains, to be on

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3024-431: The last signal controlled by the rear box is called the starter signal , whether or not there is a station at which trains stop. This signal, and the rearmost signal controlled by the box ahead, are stop signals , which a train should not pass if they are in the on position, showing a red light. The first stop signal controlled by a box is called the home signal . A distant signal is also provided some distance from

3096-421: The line is not clear, B simply does not acknowledge A's "Is Line Clear?", and leaves the commutator in the Normal position. At this point, B will not clear any of his signals. Firstly, he cannot clear his starting signal without a "Line Clear" from C. As a result, B will not clear his home signal – he can only clear it when he either has a clear run through (which he does not have without a "Line Clear" from C), or

3168-477: The loop signal and switched to 100 Hz for the track signal. The pivotal change was that now it would come on above Restricting merely as a carrier and 1.25 to 3 Hz on-off pulsing of it would be used as a code to convey the aspects. The presence of the carrier alone was not meaningful, no pulsing would still mean a Restricting aspect. This new system allowed four signal aspects: Restricting; Approach; Approach (next signal at) Medium (speed); and Clear. Initially

3240-479: The main exception being Train Entering Section . The Is Line Clear? bell signal describes the train, distinguishing between ordinary and express passenger trains, and various categories of goods train. In some locations, routing information is included in the bell code, such an ordinary passenger train to be routed to a branch at the signal box in advance would be offered by the bell code 1-3 instead of 3-1. These often vary by location. All trains, whether operated by

3312-419: The message by repeating it back to the sender. All subsequent bell messages are acknowledged promptly by repeating back to the sender – with the single exception of six strikes which indicate “Obstruction danger” which is not echoed back until all relevant signals have been set to “Stop”. An example is the process of signalling a train in the up direction (from A to C) past a signal box B. The signal box in rear

3384-413: The next signal box on the same line in the same direction of travel. Generally, all intermediate block home signals and their respective distants are colour light signals, normally showing two aspects. The extent of the line from the rearmost home signal to the most advanced starting signal controlled from the same signal box is called station limits at that signal box (this does not necessarily refer to

3456-415: The other rail. The pickup just ahead of the wheels would sum the approaching current from one side with the returning current on the other. The externally returned ”loop” signal was fed into and out of the mid tap of a resistor across each end of the track circuit. The pickup would sum the approaching current on each side as it carried on past to the far end of the track. This signal was shifted 90 degrees from

3528-483: The other. The signals were applied one or both continuously to give Approach or Clear aspects while no signal was a Restricting aspect. The test installation eliminated wayside block signals, and trains relied solely on cab signals. For its next installation, on the Northern Central line between Baltimore, MD and Harrisburg, PA in 1926 (1927?), the PRR tested another variation of cab signals which dropped

3600-406: The overlay codes, backwards compatibility could be maintained so that any train unable to detect the new codes would never receive a signal more favorable than had it would otherwise detect. In addition to the use of 250 Hz codes, a 5th, 270ppm code was incorporated from rapid transit and Long Island Rail Road use. The mapping of codes to speeds is as follows: Trains with the ability to get

3672-471: The position of the upper needle indicator in B's block instrument to repeat that indication. B may now clear his signals for the train. After an interval, the train will arrive and pass B; as it does so, B sends "Train Entering Section" on the block bell to C. Then C acknowledges the bell signal and places the block instrument to "Train On Line". As the train passes, he restores his signals to danger, and when

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3744-472: The problem and avoid a complete rebuild of the signaling system, impair lower speed service, break backwards compatibility with existing cab signals or place too high a reliance on the human operator, an overlay pulse code system was devised for use on Amtrak's Northeast Corridor. By operating with a different carrier frequency of 250 Hz, additional pulse codes could be sent to the train without interfering with legacy 100 Hz codes. By carefully designing

3816-421: The rail before the leading set of wheels. The codes are measured in pulses per minute and for the 4-aspect PRR system are set at 180 ppm for Clear, 120 ppm for Approach Medium, 75 ppm for Approach and 0 for Restricting. The pulse rates are chosen to avoid any one rate being a multiple of another leading to reflected harmonics causing false indications. The system is failsafe in that the lack of code would display

3888-575: The railroads. In March 1920, the ICC had Eben Moody Boynton, the inventor of the Boynton Bicycle Railroad , committed as a lunatic to an institution in Washington, D.C. Boynton's monorail electric light rail system, it was reported, had the potential to revolutionize transportation, superseding then-current train travel. ICC officials said that they had Boynton committed because he was "worrying them to death" in his promotion of

3960-590: The railroads. The enlarged process led to a major increase in ICC staff, and the valuations continued for almost 20 years. The valuation process turned out to be of limited use in helping the ICC set rates fairly. In 1934, Congress transferred the telecommunications authority to the new Federal Communications Commission . In 1935, Congress passed the Motor Carrier Act, which extended ICC authority to regulate interstate bus lines and trucking as common carriers. The Transportation Act of 1920 directed

4032-406: The railroads. It satisfies the popular clamor for a government supervision of the railroads, while at the same time that supervision is almost entirely nominal. Following the passage of the 1887 act, the ICC proceeded to set maximum shipping rates for railroads. However, in the late 1890s, several railroads challenged the agency's ratemaking authority in litigation , and the courts severely limited

4104-475: The rear. Where DC and 25 Hz AC electrification co-exist, the standard 100 Hz frequency is changed to 91⅔ Hz (next available M-G set frequency). This avoids even harmonics created by the return rail's DC traction current offsetting the AC return sine wave in the same rail. 70 years after pulse code cab signals had been introduced, the 4 speed design was found to be insufficient for speeds not envisioned when

4176-431: The same line but controlled by the same signal box. Typically, a signal box with an intermediate block section will have a home signal (and associated distant signal), starting signal and an intermediate block home signal which has its own distant signal. The line from the starting signal to the intermediate block home signal is called the intermediate block home section. The line from the intermediate block home signal to

4248-428: The section is clear, the latter accepts the train, and the first signalman may clear his signals to give permission for the train to enter the section. This communication traditionally takes place by bell codes and status indications transmitted over a simple telegraph wire circuit between signalmen using a device called a block instrument , although some contemporary block working is operated wirelessly. This process

4320-431: The signal and moves the commutator to "Train On Line". His lower indicator on the block indicator to A repeats the position of the commutator. B immediately offers the train on to C, after calling for attention, by sending the "Is Line Clear?" bell signal (repeating the same steps A had done while offering the train to B); if C accepts it, he repeats the bell signal and places his block indicator to "Line Clear", which moves

4392-454: The signal box. The commutator is used by the signalman to indicate the state of his block, and the lower indicator displays this state, which is also displayed on a repeater indicator in the box for the block from which a train will come. At the bottom is a single-stroke bell and the tapper to sound the bell in the next box. The commutator and each of the two indicators has three positions: normal (or line blocked), line clear, and train on line. In

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4464-405: The signalman at B can accept the train safely (if the line is clear up to B's clearing point and will not need to be blocked by another train ) he "accepts" the train by repeating the bell signal, and placing the commutator on his block instrument for the section from A to "Line Clear". The "Line Clear" is repeated at box A, and allows the signalman at A to clear, or "pull off", his signals. In case

4536-497: The simplest case of a signal box serving a two-track section, there will be two block instruments, one for communicating with each of the neighbouring boxes. In a simple double line configuration, where the signal boxes are A, B and C in succession in the up direction, the signal box at B will have two block instruments, one for communicating with box A for trains on the up line and one for box C for down trains. The block instrument for communicating with box A will be used to receive on

4608-645: The state of each stage. In 1842 he published these ideas in a book entitled Telegraphic Railways: Or the Single Way Recommended by Safety, Economy, and Efficiency, Under the Safeguard and Control of the Electric Telegraph . Cooke's ideas were not taken up by the railway companies until the 1850s and 1860s. When they were developed into a practical system, it provided the ability for signalmen to communicate with each other and provided

4680-441: The system was designed. The two most pressing problems were the use of high speed turnouts , which allowed trains to take a diverging route faster than the normal 30 or 45 mph covered by the existing cab signals. The introduction of Amtrak's Acela Express service with its 135 mph to 150 mph maximum speeds would also exceed the capabilities of the legacy signaling system and its 125 mph design speed. To address

4752-593: The title Complete Plan of Consolidation . Numerous hearings were held by ICC regarding the plan under the topic "In the Matter of Consolidation of the Railways of the United States into a Limited Number of Systems". The proposed 21 regional railroads were as follows: There were 100 terminal railroads that were also proposed. Below is a sample: Many small railroads failed during the Great Depression of

4824-528: The value of railroad securities, a factor in causing the panic of 1907 . Some economists and historians, such as Milton Friedman assert that existing railroad interests took advantage of ICC regulations to strengthen their control of the industry and prevent competition, constituting regulatory capture . Economist David D. Friedman argues that the ICC always served the railroads as a cartelizing agent and used its authority over other forms of transportation to prevent them, where possible, from undercutting

4896-490: The whole of the train passes B complete with tail lamp attached, B sends the "Train Out Of Section" bell signal (2-1) to A and when A acknowledges it, he places his block indicator to "Normal". The block section between A and B is now normal and A can offer B another train, if he has one. When the train has reached C, the signalman there sends "Train Out Of Section" on the block bell and when B acknowledges it, C places

4968-408: Was assigned to Union Switch and Signal corporation, the PRR's preferred signal supplier. The first test installation between Sunbury and Lewistown, PA in 1923 used the tracks as an inductive loop coupled to the locomotive's receiver. The system had two 60 Hz signals. The break-sensing “track” signal was fed down one rail towards the oncoming train and crossed through its wheels, returning in

5040-549: Was established by the Interstate Commerce Act of 1887, which was signed into law by President Grover Cleveland . The creation of the commission was the result of widespread and longstanding anti-railroad agitation. Western farmers, specifically those of the Grange Movement , were the dominant force behind the unrest, but Westerners generally — especially those in rural areas — believed that the railroads possessed economic power that they systematically abused. A central issue

5112-439: Was rate discrimination between similarly situated customers and communities. Other potent issues included alleged attempts by railroads to obtain influence over city and state governments and the widespread practice of granting free transportation in the form of yearly passes to opinion leaders (elected officials, newspaper editors, ministers, and so on) so as to dampen any opposition to railroad practices. Various sections of

5184-692: Was the Cooke and Wheatstone system . In July 1837 William Fothergill Cooke installed a demonstration system on the Euston to Camden Town section of Robert Stephenson 's London and Birmingham Railway for signalling rope-hauling of carriages (as the locomotives could not cope with the steep incline). Cooke also put forward the idea of dividing a single line into grand divisions of between 15 and 20 miles (24 and 32 km), each subdivided into stages 2 to 5 miles (3.2 to 8.0 km) long that were to be connected together by telegraph, with instruments that showed

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