Train order operation
Train order operation, or more timetable and train order operation, is a obsolete system by which the railroads of North America conveyed operating instructions before the days of centralized traffic control, direct traffic control, the use of track warrants conveyed by radio. The system used a set of rules when direct communication between train dispatchers and trains was limited or non-existent. Trains would follow a predetermined operating plan, known as the timetable, unless superseded by train orders conveyed to the train from the dispatcher, through local intermediaries. Train order operation was a system that required minimum human overhead in an era before widespread use of technology-based automation, it was the most practical way for railroads with limited capital resources, or lines with limited traffic, to operate. To this day, a large number of short lines, heritage railways, railroad museums continue to use Train Order operation. On major railroads, train order operation has been completely replaced by more modern operating methods.
The Long Island Rail Road in New York is the last major railroad in North America to use a "traditional" Train Order operating practice on parts of its Greenport and Montauk Branches, as well as Train Order forms for non-standard operation on the remainder of its system. While the last traditional long hand train order form was issued on September 3, 2012, timetable and train order operating practices remain in effect; the second to last train order holdout, the Chicago South Shore and South Bend Railroad, had retired its system in 2011. The process of modernization in the 19th century involved a transition from a spatially oriented world to a time oriented world. Exact time was essential, everyone had to know what the time was, resulting in clocks towers for railway stations, clocks in public places, pocket watches for railway workers and for travelers. Trains left on time. By contrast, in the premodern era, passenger ships left. In the premodern era, local time was set at noon; every place east to west had a different time and that changed with the introduction of standard time zones.
Printed time tables were a convenience for the travelers, but more elaborate time tables, called train orders, were more essential for the train crews, the maintenance workers, the station personnel, for the repair and maintenance crews, who knew when to expect a train would come along. Most trackage was single track, with sidings and signals to allow lower priority trains to be sidetracked. Schedules told everyone what to do, where to be, when. If bad weather disrupted the system, telegraphers relayed immediate corrections and updates throughout the system. Just as railways as business organizations created the standards and models for modern big business, so too the railway timetable was adapted to myriad uses, such as schedules for buses ferries, airplanes, for radio and television programs, for school schedules, for factory time clocks; the modern world was ruled by the timetable. Timetable and train order operation was used on North American railroads that had a single main track with periodic passing sidings.
Timetable and train orders were used to determine which train had the right of way at any point along the line. A train which had the right of way over another train was said to be the superior train. Trains could be superior by class or by direction. While a train dispatcher could establish "right" via train orders, the operating timetable established scheduled trains, their class and the superior direction; the "class" designation of a train equates to its priority with passenger trains having the highest, freight trains having less and Extra trains having the least. In case of trains of the same class meeting the superior direction would apply. On single track rail lines, the timetable specifies the points at which two trains would meet and pass, it would be the responsibility of the inferior train to clear the main track a safe time before the superior train is scheduled to pass. The timetable thus provides the basic framework for train movement on a particular portion of the railroad. However, variations in traffic levels from day to day, unforeseen delays, the need to perform maintenance, other contingencies required that railroads find a way to deviate from their established schedules.
Deviations from the timetable operation would be enacted through train orders sent from the train dispatcher to block operators. These orders would override the established timetable priorities and provide trains with explicit instructions on how to run. Train orders consisted of two types and authority. Protective train orders would be used to ensure that no trains would be at risk of colliding with another along the line. Once the protective orders had been delivered to block operators, an authority could be issued to a train to move over the line where protection had been established; the timetable established both protection and authority for scheduled trains so train orders were only used for extra trains, which were not in the timetable, scheduled trains moving contrary to their normal authorities. Timetable and train order operation supplanted earlier forms of timetable only and line-of-sight running; the ability for a single dispatcher to issue train orders was enabled by the invention of the electric telegraph in the 1840s.
The earliest recorded usage of the telegraph to convey train orders in the United States came in 1851 on the Erie Railroad and by the time of the American Civil War, nearly every railroad had adopted th
A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is rather referred to as multiple units, motor coaches, railcars or power cars. Traditionally, locomotives pulled trains from the front. However, push-pull operation has become common, where the train may have a locomotive at the front, at the rear, or at each end; the word locomotive originates from the Latin loco – "from a place", ablative of locus "place", the Medieval Latin motivus, "causing motion", is a shortened form of the term locomotive engine, first used in 1814 to distinguish between self-propelled and stationary steam engines. Prior to locomotives, the motive force for railways had been generated by various lower-technology methods such as human power, horse power, gravity or stationary engines that drove cable systems. Few such systems are still in existence today. Locomotives may generate their power from fuel, or they may take power from an outside source of electricity.
It is common to classify locomotives by their source of energy. The common ones include: A steam locomotive is a locomotive whose primary power source is a steam engine; the most common form of steam locomotive contains a boiler to generate the steam used by the engine. The water in the boiler is heated by burning combustible material – coal, wood, or oil – to produce steam; the steam moves reciprocating pistons which are connected to the locomotive's main wheels, known as the "drivers". Both fuel and water supplies are carried with the locomotive, either on the locomotive itself or in wagons called "tenders" pulled behind; the first full-scale working railway steam locomotive was built by Richard Trevithick in 1802. It was constructed for the Coalbrookdale ironworks in Shropshire in the United Kingdom though no record of it working there has survived. On 21 February 1804, the first recorded steam-hauled railway journey took place as another of Trevithick's locomotives hauled a train from the Pen-y-darren ironworks, in Merthyr Tydfil, to Abercynon in South Wales.
Accompanied by Andrew Vivian, it ran with mixed success. The design incorporated a number of important innovations including the use of high-pressure steam which reduced the weight of the engine and increased its efficiency. In 1812, Matthew Murray's twin-cylinder rack locomotive Salamanca first ran on the edge-railed rack-and-pinion Middleton Railway. Another well-known early locomotive was Puffing Billy, built 1813–14 by engineer William Hedley for the Wylam Colliery near Newcastle upon Tyne; this locomotive is the oldest preserved, is on static display in the Science Museum, London. George Stephenson built Locomotion No. 1 for the Stockton and Darlington Railway in the north-east of England, the first public steam railway in the world. In 1829, his son Robert built The Rocket in Newcastle-upon-Tyne. Rocket was entered into, won, the Rainhill Trials; this success led to the company emerging as the pre-eminent early builder of steam locomotives used on railways in the UK, US and much of Europe.
The Liverpool and Manchester Railway, built by Stephenson, opened a year making exclusive use of steam power for passenger and goods trains. The steam locomotive remained by far the most common type of locomotive until after World War II. Steam locomotives are less efficient than modern diesel and electric locomotives, a larger workforce is required to operate and service them. British Rail figures showed that the cost of crewing and fuelling a steam locomotive was about two and a half times larger than the cost of supporting an equivalent diesel locomotive, the daily mileage they could run was lower. Between about 1950 and 1970, the majority of steam locomotives were retired from commercial service and replaced with electric and diesel-electric locomotives. While North America transitioned from steam during the 1950s, continental Europe by the 1970s, in other parts of the world, the transition happened later. Steam was a familiar technology that used widely-available fuels and in low-wage economies did not suffer as wide a cost disparity.
It continued to be used in many countries until the end of the 20th century. By the end of the 20th century the only steam power remaining in regular use around the world was on heritage railways. Internal combustion locomotives use an internal combustion engine, connected to the driving wheels by a transmission, they keep the engine running at a near-constant speed whether the locomotive is stationary or moving. Kerosene locomotives use kerosene as the fuel, they were the world's first oil locomotives, preceding diesel and other oil locomotives by some years. The first known kerosene locomotive was a draisine built by Daimler in 1887. A kerosene locomotive was built in 1894 by the Priestman Brothers of Kingston upon Hull for use on Hull docks; this locomotive was built using a 12 hp double-acting marine type engine, running at 300 rpm, mounted on a 4-wheel wagon chassis. It was only able to haul one loaded wagon at a time, due to its low power output, was not a great success; the first successful kerosene locomotive was "Lachesis" built by Richard Hornsby & Sons Ltd. and delivered to Woolwich Arsenal railway in 1896.
The company built a series of kerosene locomotives between 1896 and 1903, for use by the British military. Petrol locomotives use petrol as their fuel. Most petrol locomotives built were petrol-mechanical, using a mechanical transmission to deliver the power output of the engine t
A brakeman is a rail transport worker whose original job was to assist the braking of a train by applying brakes on individual wagons. The earliest known use of the term to describe this occupation occurred in 1833; the advent of through brakes, brakes on every wagon which could be controlled by the driver, made this role redundant, although the name lives on in the United States where brakemen carry out a variety of functions both on the track and within trains. In the United States, the brakeman was a member of a railroad train's crew responsible for assisting with braking a train when the conductor wanted the train to slow down or stop. A brakeman's duties included ensuring that the couplings between cars were properly set, lining switches, signaling to the train operators while performing switching operations; the brakemen rode in the caboose, the last car in the train, built specially to allow a crew member to apply the brakes of the caboose and which would help to slow the train. In rare cases, such as descending a long, steep grade, brakemen might be assigned to several cars and be required to operate the brakes from atop the train while the train was moving.
By the start of the 20th century, some local U. S. labor laws noted that enough brakemen would be staffed on every train such that a brakeman would be responsible for no more than two cars. Brakemen were required to watch the train when it was underway to look for signs of hot boxes or other damage to rolling stock, as well as for people trying to ride the train for free and cargo shifting or falling off. A brakeman's job was very dangerous with numerous reports of brakemen falling from trains, colliding with lineside structures or being run over or crushed by rolling stock; as rail transport technology has improved, a brakeman's duties have been reduced and altered to match the updated technology, the brakeman's job has become much safer than it was in the early days of railroading. Individually operated car brakes were replaced by remotely-operated air brakes, eliminating the need for the brakeman to walk atop a moving train to set the brakes. Link and pin couplings were replaced with automatic couplings, hand signals are now supplemented by two-way radio communication.
As of 2012, 24,380 brakeman jobs were staffed in the U. S. with 93% of them employed in the rail transport industry with much of the remainder employed by supporting companies. By 2016, the total number had dropped to 19,860, with the highest employment rates in Texas, Pennsylvania and Georgia, respectively. In Germany, the brakemen occupied brakeman's cabins on several or all wagons in a train and would operate the wagon brakes when signaled by the engine driver, it was a dangerous and uncomfortable role in winter when it was not uncommon for brakemen to freeze to death in the unheated cabins. The function was abolished in the 1920s with the introduction of air brakes, which could be controlled by the engine driver. Freight and yard crews consisting of conductor and brakeman employ the brakeman in throwing hand operated track switches to line up for switching moves and assisting in cuts and hitches as cars are dropped off and picked up. A brakeman is sometimes seen as an assistant to the conductor in a train's operations.
In passenger service, the brakeman collects revenue, may operate door "through switches" for specific platforming needs, makes announcements, operates trainline door open and close controls when required to assist the conductor. A passenger service trainman is required to qualify as a conductor after 1 to 2 years experience; the rear end trainman signals to the conductor when all the train's doors are safely closed boards and closes his/her door. Scenic railways in the form of side friction roller coasters, require a brakeman to ride with the train around the track to slow it down at certain points on the layout bends; the brakeman is responsible for slowing the train down when necessary and stopping it in the station at the end of the ride. There are only a few examples of such rides now left in existence. Jimmie Rodgers, "the Singing Brakeman"
Atchison, Topeka and Santa Fe Railway
The Atchison and Santa Fe Railway referred to as the Santa Fe or AT&SF, was one of the larger railroads in the United States. Chartered in February 1859, the railroad reached the Kansas-Colorado border in 1873 and Pueblo, Colorado, in 1876. To create a demand for its services, the railroad set up real estate offices and sold farm land from the land grants that it was awarded by Congress. Despite the name, its main line never served New Mexico, as the terrain was too difficult; the Santa Fe was a pioneer in intermodal freight transport, an enterprise that included a tugboat fleet and an airline. Its bus line extended passenger transportation to areas not accessible by rail, ferryboats on the San Francisco Bay allowed travelers to complete their westward journeys to the Pacific Ocean; the AT&SF was the subject of a popular song, Harry Warren and Johnny Mercer's "On the Atchison and the Santa Fe", written for the film, The Harvey Girls. The railroad ceased operations on December 31, 1996, when it merged with the Burlington Northern Railroad to form the Burlington Northern and Santa Fe Railway.
The Atchison, Topeka & Santa Fe Railway was chartered on February 11, 1859, to join Atchison and Topeka, with Santa Fe, New Mexico. In its early years, the railroad opened Kansas to settlement. Much of its revenue came from wheat grown there and from cattle driven north from Texas to Wichita and Dodge City by September 1872. Rather than turn its survey southward at Dodge City, AT&SF headed southwest over Raton Pass because of coal deposits near Trinidad and Raton, New Mexico; the Denver & Rio Grande Railroad was aiming at Raton Pass, but AT&SF crews arose early one morning in 1878 and were hard at work with picks and shovels when the D&RGW crews showed up for breakfast. At the same time the two railroads had a series of skirmishes over occupancy of the Royal Gorge west of Cañon City, Colorado. Federal intervention prompted an out-of-court settlement on February 2, 1880, in the form of the so-called "Treaty of Boston", wherein D&RG was allowed to complete its line and lease it for use by Santa Fe.
D&RG paid an estimated $1.4 million to Santa Fe for its work within the Gorge and agreed not to extend its line to Santa Fe, while Santa Fe agreed to forego its planned routes to Denver and Leadville. Building across Kansas and eastern Colorado was simple, with few natural obstacles, but the railroad found it economically impossible because of the sparse population, it set up real estate offices in the area and promoted settlement across Kansas on the land, granted to it by Congress in 1863. It offered discounted fares to anyone. AT&SF reached Albuquerque in 1880. In March 1881 AT&SF connected with the Southern Pacific at Deming, New Mexico, forming the second transcontinental rail route; the railroad built southwest from Benson, Arizona, to Nogales on the Mexican border where it connected with the Sonora Railway, which the AT&SF had built north from the Mexican port of Guaymas. AT&SF purchased the Southern California Railway on Jan. 17, 1906. The Atlantic & Pacific Railroad was chartered in 1866 to build west from Springfield, along the 35th parallel of latitude to a junction with SP at the Colorado River.
The infant A&P had no rail connections. The line, to become the St. Louis–San Francisco Railway would not reach Springfield for another four years, SP did not build east from Mojave to the Colorado River until 1883. A&P started construction in 1868, built southwest into what would become Oklahoma, promptly entered receivership. In 1879 A&P struck a deal with the Santa Frisco railroads to construct a rail line for each; the railroads would jointly own the A&P railroad west of Albuquerque. In 1883 A&P reached Needles, where it connected with an SP line. A&P built a line between Tulsa, Oklahoma and St. Louis, Missouri for the Frisco, but the Tulsa-Albuquerque portion remained unbuilt; the Santa Fe began to expand: a line from Barstow, California, to San Diego in 1885 and to Los Angeles in 1887. By January 1890, the entire system consisted of some 7,500 miles of track; the Panic of 1893 had the same effect on the AT&SF. In 1895 AT&SF sold the Frisco and the Colorado Midland and wrote off the losses, but it still retained control of the A&P.
The Santa Fe Railway still wanted to reach California on its own rails, the state of California eagerly courted the railroad to break SP's monopoly. In 1897 the railroad traded the Sonora Railway of Mexico to SP for their line between Needles and Barstow, giving AT&SF its own line from Chicago to the Pac
Public transport timetable
A public transport timetable is a document setting out information on service times, to assist passengers with planning a trip. The timetable will list the times when a service is scheduled to arrive at and depart from specified locations, it may show all movements at a particular location or all movements on a particular route or for a particular stop. Traditionally this information was provided in printed form, for example as a poster, it is now often available in a variety of electronic formats. In the 2000s public transport route planners / intermodal journey planners have proliferated and offer traveller the convenience that the computer program looks at all timetables so the traveller doesn't need to. A "timetable" may refer to the same information in abstract form, not published, e.g. "A new timetable has been introduced". The first compilation of railway timetables in the United Kingdom was produced in 1839 by George Bradshaw. Greater speeds and the need for more accurate timings led to the introduction of standard railway time in Great Western Railway timetables in 1840, when all their trains were scheduled to "London time", i.e. Greenwich Mean Time, which replaced solar time.
Until railway time was introduced, local times for London, Birmingham and Manchester could differ by as much as 16 to 20 minutes. The European Rail Timetable, a compendium of the schedules of major European railway services, has been in publication since 1873, and for most of its history, it was published by Thomas Cook & Son and included Thomas Cook or Cook's in its title. Although Thomas Cook Group plc ceased publication in 2013, the Thomas Cook European Rail Timetable was revived by a new company in early 2014 as the European Rail Timetable. From 1981 to 2010, Cook produced a similar bi-monthly Overseas volume covering the rest of the world, some of that content was moved into the European Timetable in 2011. A timetable can be produced dynamically, on request, for a particular journey on a particular day around a particular time, or in a timetable that gives an overview of all services in a particular category and is valid for a specified period; the latter could take the form of a book, billboard, or a computer file, makes it much easier to find out, for example, whether a transport service at a particular time is offered every day at that time, if not, on which days.
Many timetables comprise tables with services shown in columns, stations or stops on the rows of the table. There will be separate tables for each direction of travel, separate tables for weekdays and Sundays; the times shown against each station or stop will be the departure time, except for the last stop of the service which will be the arrival time. The left hand column will list the stations in route order, the other columns are arranged from left to right in chronological order. If the service is scheduled to wait, both arrival and departure times might be shown on consecutive rows. If a slow service is overtaken by a fast service, the slow service will occupy more than one column, to keep the times in order. There may be additional rows showing connecting services. In most parts of the world times are shown using the 24-hour clock. If services run at the same minutes past each hour for part of the day, the legend "and at the same minutes past each hour" or similar wording may be shown instead of individual timings.
Other information may be shown at the tops of the columns, such as day of operation, validity of tickets for each service, whether seat reservations are required, the type of vehicle used, the availability of on-board facilities such as refreshments, availability of classes, a service number. Timetables with services arranged in rows of tables and stops or stations in columns are less common but otherwise similar to timetables with services in columns; some timetables at railway stations and bus stops, list the times that services depart from that location, sometimes with other information such as destinations and stopping conditions. Again, there may be separate lists for different days of the week. There may be a combined chronological list. In parts of mainland Europe train departures are listed on a yellow poster, arrivals on a white poster; these posters are placed at entrances on platforms. Dynamic electronic displays in stations may be at a central place and list the next few departures for each line, or all departures in the next hour.
Displays on platforms just show the next departure from that platform. Timetables may be printed as books, folded or plain cards or paper, posters, or hand-written on posters or blackboards, shown on back-lit displays, or published on-line or as SMS or text messages. With the development of the internet and electronic systems, conventional thick paper timetables are being replaced by website searching or CD-ROM style timetables, the publication of comprehensive printed timetables is decreasing. Transport schedule data itself is being made available to the public digitally, as specified in the General Transit Feed Specification format. In many modern public transport systems, timet
Rail transport is a means of transferring of passengers and goods on wheeled vehicles running on rails known as tracks. It is commonly referred to as train transport. In contrast to road transport, where vehicles run on a prepared flat surface, rail vehicles are directionally guided by the tracks on which they run. Tracks consist of steel rails, installed on ties and ballast, on which the rolling stock fitted with metal wheels, moves. Other variations are possible, such as slab track, where the rails are fastened to a concrete foundation resting on a prepared subsurface. Rolling stock in a rail transport system encounters lower frictional resistance than road vehicles, so passenger and freight cars can be coupled into longer trains; the operation is carried out by a railway company, providing transport between train stations or freight customer facilities. Power is provided by locomotives which either draw electric power from a railway electrification system or produce their own power by diesel engines.
Most tracks are accompanied by a signalling system. Railways are a safe land transport system. Railway transport is capable of high levels of passenger and cargo utilization and energy efficiency, but is less flexible and more capital-intensive than road transport, when lower traffic levels are considered; the oldest known, man/animal-hauled railways date back to the 6th century BC in Greece. Rail transport commenced in mid 16th century in Germany in the form of horse-powered funiculars and wagonways. Modern rail transport commenced with the British development of the steam locomotives in the early 19th century, thus the railway system in Great Britain is the oldest in the world. Built by George Stephenson and his son Robert's company Robert Stephenson and Company, the Locomotion No. 1 is the first steam locomotive to carry passengers on a public rail line, the Stockton and Darlington Railway in 1825. George Stephenson built the first public inter-city railway line in the world to use only the steam locomotives all the time, the Liverpool and Manchester Railway which opened in 1830.
With steam engines, one could construct mainline railways, which were a key component of the Industrial Revolution. Railways reduced the costs of shipping, allowed for fewer lost goods, compared with water transport, which faced occasional sinking of ships; the change from canals to railways allowed for "national markets" in which prices varied little from city to city. The spread of the railway network and the use of railway timetables, led to the standardisation of time in Britain based on Greenwich Mean Time. Prior to this, major towns and cities varied their local time relative to GMT; the invention and development of the railway in the United Kingdom was one of the most important technological inventions of the 19th century. The world's first underground railway, the Metropolitan Railway, opened in 1863. In the 1880s, electrified trains were introduced, leading to electrification of tramways and rapid transit systems. Starting during the 1940s, the non-electrified railways in most countries had their steam locomotives replaced by diesel-electric locomotives, with the process being complete by the 2000s.
During the 1960s, electrified high-speed railway systems were introduced in Japan and in some other countries. Many countries are in the process of replacing diesel locomotives with electric locomotives due to environmental concerns, a notable example being Switzerland, which has electrified its network. Other forms of guided ground transport outside the traditional railway definitions, such as monorail or maglev, have been tried but have seen limited use. Following a decline after World War II due to competition from cars, rail transport has had a revival in recent decades due to road congestion and rising fuel prices, as well as governments investing in rail as a means of reducing CO2 emissions in the context of concerns about global warming; the history of rail transport began in the 6th century BC in Ancient Greece. It can be divided up into several discrete periods defined by the principal means of track material and motive power used. Evidence indicates that there was 6 to 8.5 km long Diolkos paved trackway, which transported boats across the Isthmus of Corinth in Greece from around 600 BC.
Wheeled vehicles pulled by men and animals ran in grooves in limestone, which provided the track element, preventing the wagons from leaving the intended route. The Diolkos was in use for over 650 years, until at least the 1st century AD; the paved trackways were later built in Roman Egypt. In 1515, Cardinal Matthäus Lang wrote a description of the Reisszug, a funicular railway at the Hohensalzburg Fortress in Austria; the line used wooden rails and a hemp haulage rope and was operated by human or animal power, through a treadwheel. The line still exists and is operational, although in updated form and is the oldest operational railway. Wagonways using wooden rails, hauled by horses, started appearing in the 1550s to facilitate the transport of ore tubs to and from mines, soon became popular in Europe; such an operation was illustrated in Germany in 1556 by Georgius Agricola in his work De re metallica. This line used "Hund" carts with unflanged wheels running on wooden planks and a vertical pin on the truck fitting into the gap between the planks to keep it going the right way.
The miners called the wagons Hunde from the noise. There are many references to their use in central Europe in the 16th century; such a transport system was used by German miners at Cal
A train horn is a powerful air horn that serves as an audible warning device on electric and Diesel locomotives. The horn's primary purpose is to alert persons and animals to an oncoming train when approaching a grade crossing; the horn is used for acknowledging signals given by railroad employees, such as during switching operations. Trains move on fixed rails; this susceptibility is exacerbated by the enormous weight and inertia of a train, which make it difficult to stop when encountering an obstacle. Trains do not stop at grade crossings, instead relying upon pedestrians and vehicles to clear the tracks when they pass. Therefore, from their beginnings locomotives have been equipped with loud horns or bells to warn vehicles or pedestrians that they are coming. Steam locomotives had steam whistles, operated from steam produced by their boilers; as Diesel locomotives began to replace steam on most railroads during the mid-20th century, it was realized that the new locomotives were unable to utilize the steam whistles in use.
Early internal combustion locomotives were fitted with small truck horns or exhaust-powered whistles, but these were found to be unsuitable and hence the air horn design was scaled up and modified for railroad use. Early train horns were tonally similar to the air horns still heard on road-going trucks today, it was found that this caused some confusion among people who were accustomed to steam locomotives and the sound of their whistles. So, locomotive air horns were created that had a much higher, more musical note, tonally much more like a steam whistle; this is why most train horns have a unique sound, different from that of road going trucks, although many switch engines, which didn't see road service, retained the deeper truck-like horns. Strict regulations specific to each country specify how loud horns must be, how far in advance of grade crossings and other locations locomotive engineers are required to sound their horns to give adequate time to clear the tracks. Standard signals consisting of different sequences of horn blasts must be given in different circumstances.
Due to the encroachment of development, some suburban dwellers have opposed railroad use of the air horn as a trackside warning device. Residents in some communities have attempted to establish quiet zones, in which train crews are instructed not to sound their horns, except in case of emergency. Recent years have seen an increase of horn theft from railroad property. Train horns are operated by compressed air 125-140 psi, fed from a locomotive main air reservoir; when the engineer opens the horn valve, air flows through a supply line into the power chamber at the base of the horn. It passes through a narrow opening between a nozzle and a circular diaphragm in the power chamber out through the flaring horn bell; the flow of air past the diaphragm causes it to vibrate or oscillate against the nozzle, producing sound. Keep in mind that when an air horn is not operating and has no fluid pressure flowing through it, the interior of the power chamber housing is air tight, as the diaphragm disc creates a full air tight seal against the nozzle surface.
Referring to the cut-away blueprint diagram of a conventional air horn power chamber on the right, when a constant stream of pressurised fluid enters through the small inlet at the bottom, the pressure in the power chamber increases as it is air tight internally. The pressure continues rising in Chamber'A' until the air pressure overcomes the spring tension of the Diaphragm. Once this occurs, the Diaphragm is deflected back, in such, is no longer sealed against the nozzle. From this, the interior of the power chamber is now no longer air tight, as the Diaphragm has deflected off the nozzle; as a result, the pressurised Fluid now escapes out of the horn bell. Because the pressurised Fluid exits through the horn bell at a much faster rate than the fluid enters into the power chamber through the base air inlet, the air pressure in the power chamber drops rapidly; as such, the Diaphragm re-seats itself against the nozzle surface. This entire process is one cycle of the Diaphragm operating. In reality, this operation process occurs much faster in accordance to the frequency produced by the horn.
The constant back and forth Oscillation of the Diaphragm creates sound waves, which are amplified by the large flared horn bell. The length and diameter of the horn bell contribute to the frequency of the note produced by the horn; when vibrated by the diaphragm, the column of air in the bell oscillates with standing waves. The length of the bell determines the wavelength of the sound waves, thus the fundamental frequency of the note produced by the horn; the longer the horn bell, the lower the note. North American diesel locomotives manufactured prior to the 1990s utilized an air valve actuated by the engineer through the manipulation of a lever or pull cord. Use of this method made possible a practice known as "feathering", meaning that modulation of the horn's volume was possible through finer regulation of the air valve. Many locomotives manufactured during the 1990s made use of pushbutton controls. In addition, several North American locomotives incorporated a sequencer pedal built into the cab floor beneath the operators position.
Locomotives of European origin have featured pushbutton control of air horns since the mid-1960s. Current production locomotives from GE Transportation