1.
Amtrak
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Founded in 1971 to take over most of the remaining U. S. passenger rail services, it is partially government funded yet operated and managed as a for-profit corporation. Amtrak serves more than 500 destinations in 46 states and three Canadian provinces, operating more than 300 trains each day over 21,300 miles of track, some track sections allow trains to run as fast as 150 mph. In fiscal year 2015, Amtrak served 30.8 million passengers and had $2.185 billion in revenue, nearly two-thirds of passengers come from the 10 largest metropolitan areas, 83% of passengers travel on routes shorter than 400 miles. Its headquarters is at Union Station in Washington, D. C, the name Amtrak is a portmanteau of the words America and trak, the latter itself a sensational spelling of track. From the mid-19th century until about 1920, nearly all intercity travelers in the United States moved by rail, historically, U. S. passenger trains were owned and operated by the same privately owned companies that operated freight trains. About 65,000 railroad passenger cars operated in 1929, from 1920 into the later 20th century, passenger rails popularity diminished and there was a series of pullbacks and tentative recoveries. Rail passenger revenues declined dramatically between 1920 and 1934 because of the rise of the automobile, in the same period, many travelers were lost to interstate bus companies such as Greyhound Lines. However, in the mid-1930s, railroads reignited popular imagination with service improvements and new, diesel-powered streamliners, such as the gleaming silver Pioneer Zephyr and Flying Yankee. Even with the improvements, on a basis, traffic continued to decline. World War II broke the malaise, passenger traffic soared sixfold thanks to troop movements, in 1946, there remained 45 percent fewer passenger trains than in 1929, and the decline quickened despite railroad optimism. Passengers disappeared and so did trains, few trains generated profits, most produced losses. Broad-based passenger rail deficits appeared as early as 1948, and by the mid-1950s, by 1965, only 10,000 rail passenger cars were in operation,85 percent fewer than in 1929. Passenger service was provided on only 75,000 miles of track, the 1960s also saw the end of railway post office revenues, which had helped some of the remaining trains break even. The causes of the decline of rail in the United States were complex. Until 1920, rail was the practical form of intercity transport. By 1930, the companies had constructed, with private funding. In 1916, the amount of track in the United States peaked at 254,251 miles, some rail routes had been built primarily to facilitate the sale of stock in the railroad companies, they were redundant from the beginning. These were the first to be abandoned as the financial positions deteriorated
2.
Metra
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Metra is a commuter railroad in the Chicago metropolitan area. The railroad operates 241 stations on 11 different rail lines and it is the fourth busiest commuter rail system in the United States by ridership and the largest and busiest commuter rail system outside the New York City metropolitan area. There were 83.4 million passenger rides in 2014, up 1. 3% from the previous year, the estimated busiest day for Metra ridership occurred on Nov.4, 2016—the day of the Chicago Cubs 2016 World Series victory rally. Using Chicagos rail infrastructure, much of which was created in the 19th century, the Illinois General Assembly established the RTA, Metras creation was a result of the anticipated failure of commuter service operated and owned by various private railroad companies in the 1970s. Freight rail companies still operate some routes, however, these operations are guided by contracted service agreements, Metra owns all rolling stock and is responsible for all stations along with the respective municipalities. Since its inception, Metra has directed more than $5 billion into the rail system of the Chicago metropolitan area. Since its founding in the 19th century, Chicago has been a major Midwestern hub in the North American rail network and it has more trackage radiating in more directions than any other city in North America. Railroads set up their headquarters in the city and Chicago became a center for building cars, passenger cars. By the 1930s Chicago had the worlds largest public transportation system, by the mid-1970s, the commuter lines faced an uncertain future. The Burlington Northern, Milwaukee Road, Chicago and North Western, to provide stability to the commuter rail system, the Illinois General Assembly formed the Regional Transportation Authority in 1974. Its purpose was to fund and plan the Chicago regions public transportation, in the beginning the Regional Transportation Authority commuter train fleet consisted of second-hand equipment, until 1976 when the first order of new EMD F40PH locomotives arrived. That F40PH fleet is still in service today, less than a decade later the Regional Transportation Authority was already suffering from ongoing financial problems. In 1983 the Illinois Legislature reorganized the agency and that reorganization left the Regional Transportation Authority in charge of day-to-day operations of all bus, heavy rail and commuter rail services throughout the Chicago metropolitan area. It was also responsible for directing fare and service levels, setting up budgets, finding sources for capital investment, due to the broad range of responsibilities entrusted with the Regional Transportation Authority, the Commuter Rail Service Board was created in 1984. It was renamed Metra in July 1985, the newly reorganized Metra service helped to bring a single identity to the many infrastructure components serviced by the Regional Transportation Authoritys commuter rail system. Metras operating arm, the Northeast Illinois Regional Commuter Railroad Corporation, was created as a separate subsidiary which operates seven Metra owned routes. Contracts were set up with the Union Pacific and BNSF railroads to operate four other Metra routes, while Metra owns all rolling stock and is responsible for most stations on those routes, the freight carriers use their own employees and control the right-of-way for those routes. In keeping with Metras purpose to provide an identity for commuter rail in the region
3.
Chicago
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Chicago, officially the City of Chicago, is the third-most populous city in the United States. With over 2.7 million residents, it is the most populous city in the state of Illinois, and it is the county seat of Cook County. In 2012, Chicago was listed as a global city by the Globalization and World Cities Research Network. Chicago has the third-largest gross metropolitan product in the United States—about $640 billion according to 2015 estimates, the city has one of the worlds largest and most diversified economies with no single industry employing more than 14% of the workforce. In 2016, Chicago hosted over 54 million domestic and international visitors, landmarks in the city include Millennium Park, Navy Pier, the Magnificent Mile, Art Institute of Chicago, Museum Campus, the Willis Tower, Museum of Science and Industry, and Lincoln Park Zoo. Chicagos culture includes the arts, novels, film, theater, especially improvisational comedy. Chicago also has sports teams in each of the major professional leagues. The city has many nicknames, the best-known being the Windy City, the name Chicago is derived from a French rendering of the Native American word shikaakwa, known to botanists as Allium tricoccum, from the Miami-Illinois language. The first known reference to the site of the current city of Chicago as Checagou was by Robert de LaSalle around 1679 in a memoir, henri Joutel, in his journal of 1688, noted that the wild garlic, called chicagoua, grew abundantly in the area. In the mid-18th century, the area was inhabited by a Native American tribe known as the Potawatomi, the first known non-indigenous permanent settler in Chicago was Jean Baptiste Point du Sable. Du Sable was of African and French descent and arrived in the 1780s and he is commonly known as the Founder of Chicago. In 1803, the United States Army built Fort Dearborn, which was destroyed in 1812 in the Battle of Fort Dearborn, the Ottawa, Ojibwe, and Potawatomi tribes had ceded additional land to the United States in the 1816 Treaty of St. Louis. The Potawatomi were forcibly removed from their land after the Treaty of Chicago in 1833, on August 12,1833, the Town of Chicago was organized with a population of about 200. Within seven years it grew to more than 4,000 people, on June 15,1835, the first public land sales began with Edmund Dick Taylor as U. S. The City of Chicago was incorporated on Saturday, March 4,1837, as the site of the Chicago Portage, the city became an important transportation hub between the eastern and western United States. Chicagos first railway, Galena and Chicago Union Railroad, and the Illinois, the canal allowed steamboats and sailing ships on the Great Lakes to connect to the Mississippi River. A flourishing economy brought residents from rural communities and immigrants from abroad, manufacturing and retail and finance sectors became dominant, influencing the American economy. The Chicago Board of Trade listed the first ever standardized exchange traded forward contracts and these issues also helped propel another Illinoisan, Abraham Lincoln, to the national stage
4.
Los Angeles River
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Several tributaries join the once free-flowing and frequently flooding river, forming alluvial flood plains along its banks. It now flows through a channel on a fixed course. Environmental groups and park advocates support the removal of concrete and the restoration of natural vegetation, portions of the river now have earthen bottoms and restored habitat. There are also plans for a series of parks along the rivers city frontage in Los Angeles, the Los Angeles River also flows through several Los Angeles County communities and has been featured in many Hollywood films. Before the opening of the Los Angeles Aqueduct, the river was the source of fresh water for the city. Although the Los Angeles region still gets some of its water from the river and other local sources, the river suffers pollution from agricultural and urban runoff. Fed primarily by rainwater and snowmelt, the Donald C, tillman Water Reclamation Plant in Van Nuys, and urban discharge, it is one of the few low-elevation perennial rivers in Southern California. This is helped by the channel, which limits absorption of water into the earth. Flow, while low in volume, can be extremely brisk even in summer. 1952°N118. 601838°W /34.1952. Bell Creek flows east from the Simi Hills, and Arroyo Calabasas flows north from the Santa Monica Mountains, from there the river flows east through a concrete flood control channel and very soon receives Browns Canyon Wash, which flows south from the Santa Susana Mountains. The river then bends south and receives Aliso Canyon Wash. The river then flows through the district of Winnetka, then Reseda and enters the Sepulveda Basin, as the river proceeds into the usually-dry reservoir, it spills out into a channel that is similar to its historical, unchannelized form. It crosses under Balboa Boulevard and then passes through the works of Sepulveda Dam,43 miles from the mouth. It flows again into a channel and crosses under Interstate 405 as it passes through Van Nuys, Sherman Oaks. Paralleling U. S. Here, the river begins to flow over a natural riverbed, paralleling Interstate 5 for the next few miles, the river runs by the eastern side of Griffith Park and the Harding-Wilson Golf Course. It passes Silver Lake Reservoir, which is to the right and it then receives the Arroyo Seco, another major tributary, from the left. The river flows south past the Mission Junction, a railroad yard on the left. It then makes a turn east and then turns southeast, flowing a few miles before it begins to parallel Interstate 710 near Maywood, Bell, Cudahy
5.
Track (rail transport)
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The track on a railway or railroad, also known as the permanent way, is the structure consisting of the rails, fasteners, railroad ties and ballast, plus the underlying subgrade. It enables trains to move by providing a surface for their wheels to roll upon. For clarity it is referred to as railway track or railroad track. Tracks where electric trains or electric trams run are equipped with a system such as an overhead electrical power line or an additional electrified rail. The term permanent way also refers to the track in addition to structures such as fences etc. Most railroads with heavy traffic use continuously welded rails supported by sleepers attached via baseplates that spread the load, a plastic or rubber pad is usually placed between the rail and the tieplate where concrete sleepers are used. The rail is held down to the sleeper with resilient fastenings. For much of the 20th century, rail track used softwood timber sleepers and jointed rails, jointed rails were used at first because contemporary technology did not offer any alternative. The joints also needed to be lubricated, and wear at the mating surfaces needed to be rectified by shimming. For this reason jointed track is not financially appropriate for heavily operated railroads, timber sleepers are of many available timbers, and are often treated with creosote, copper-chrome-arsenic, or other wood preservative. Pre-stressed concrete sleepers are used where timber is scarce and where tonnage or speeds are high. Steel is used in some applications, the track ballast is customarily crushed stone, and the purpose of this is to support the sleepers and allow some adjustment of their position, while allowing free drainage. A disadvantage of traditional track structures is the demand for maintenance, particularly surfacing and lining to restore the desired track geometry. Weakness of the subgrade and drainage deficiencies also lead to maintenance costs. This can be overcome by using ballastless track, in its simplest form this consists of a continuous slab of concrete with the rails supported directly on its upper surface. There are a number of systems, and variations include a continuous reinforced concrete slab. Many permutations of design have been put forward, however, ballastless track has a high initial cost, and in the case of existing railroads the upgrade to such requires closure of the route for a long period. Its whole-life cost can be lower because of the reduction in maintenance, some rubber-tyred metros use ballastless tracks
6.
Railroad car
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A railroad car or railcar, railway wagon or railway carriage, also called a train car or train wagon, is a vehicle used for the carrying of cargo or passengers on a rail transport system. Such cars, when coupled together and hauled by one or more locomotives, alternatively, some passenger cars are self-propelled in which case they may be either single railcars or make up multiple units. The term car is used by itself in American English when a rail context is implicit. Indian English sometimes uses bogie in the manner, though the term has other meanings in other variants of English. In American English, railcar is a term for a railway vehicle, in other countries railcar refers specifically to a self-propelled, powered. Tables may be provided between seats facing one another, alternatively, seats facing in the same direction may have access to a fold-down ledge on the back of the seat in front. If the aisle is located between seats, seat rows may face the direction, or be grouped, with twin rows facing each other. In some vehicles intended for services, seats are positioned with their backs to the side walls. This gives a wide accessway and allows room for standing passengers at peak times, if the aisle is at the side, the car is usually divided into small compartments. These usually contain six seats, although sometimes in second class they contain eight, modern cars usually have either air-conditioning or windows that can be opened, or sometimes both. Various types of onboard train toilet facilities may also be provided, other types of passenger car exist, especially for long journeys, such as the dining car, parlor car, disco car, and in rare cases theater and movie theater car. In some cases another type of car is converted to one of these for an event. Observation cars were built for the rear of many trains to allow the passengers to view the scenery. Sleeping cars outfitted with small bedrooms allow passengers to sleep through their night-time trips, long-distance trains often require baggage cars for the passengers luggage. In European practice it used to be common for day coaches to be formed of compartments seating 6 or 8 passengers, in the UK, Corridor coaches fell into disfavor in the 1960s and 1970s partially because open coaches are considered more secure by women traveling alone. Another distinction is between single- and double deck train cars, an example of a double decker is the Amtrak superliner. A trainset is a semi-permanently arranged formation of cars, rather than one created ad hoc out of cars are available. These are only broken up and reshuffled on shed, trains are then built of one or more of these sets coupled together as needed for the capacity of that train
7.
Locomotive
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A locomotive or engine is a rail transport vehicle that provides the motive power for a train. A locomotive has no payload capacity of its own, and its purpose is to move the train along the tracks. In contrast, some trains have self-propelled payload-carrying vehicles and these are not normally considered locomotives, and may be referred to as multiple units, motor coaches or railcars. The use of these vehicles is increasingly common for passenger trains. 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. Prior to locomotives, the force for railroads had been generated by various lower-technology methods such as human power, horse power. The first successful locomotives were built by Cornish inventor Richard Trevithick, in 1804 his unnamed steam locomotive hauled a train along the tramway of the Penydarren ironworks, near Merthyr Tydfil in Wales. Although the locomotive hauled a train of 10 long tons of iron and 70 passengers in five wagons over nine miles, the locomotive only ran three trips before it was abandoned. Trevithick built a series of locomotives after the Penydarren experiment, including one which ran at a colliery in Tyneside in northern England, the first commercially successful steam locomotive was Matthew Murrays rack locomotive, Salamanca, built for the narrow gauge Middleton Railway in 1812. This was followed in 1813 by the Puffing Billy built by Christopher Blackett and William Hedley for the Wylam Colliery Railway, Puffing Billy is now on display in the Science Museum in London, the oldest locomotive in existence. In 1814 George Stephenson, inspired by the locomotives of Trevithick. He built the Blücher, one of the first successful flanged-wheel adhesion locomotives, Stephenson played a pivotal role in the development and widespread adoption of steam locomotives. His designs improved on the work of the pioneers, in 1825 he built the Locomotion for the Stockton and Darlington Railway, north east England, which became the first public steam railway. In 1829 he built The Rocket which was entered in and won the Rainhill Trials and this success led to Stephenson establishing his company as the pre-eminent builder of steam locomotives used on railways in the United Kingdom, the United States and much of Europe. The first inter city passenger railway, Liverpool and Manchester Railway, opened in 1830, there are a few basic reasons to isolate locomotive train power, as compared to self-propelled vehicles. Maximum utilization of power cars Separate locomotives facilitate movement of costly motive power assets as needed, flexibility Large locomotives can substitute for small locomotives when more power is required, for example, where grades are steeper. As needed, a locomotive can be used for freight duties. Obsolescence cycles Separating motive power from payload-hauling cars enables replacement without affecting the other, to illustrate, locomotives might become obsolete when their associated cars did not, and vice versa
8.
Switcher
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They do this in classification yards. Switchers may also make short runs and even be the only motive power on branch lines and switching. The term can also be used to describe the workers operating these engines or engaged in directing shunting operations, the typical switcher is optimised for its job, being relatively low-powered but with a high starting tractive effort for getting heavy cars rolling quickly. Switchers are geared to produce high torque but are restricted to low top speeds and have small diameter driving wheels, switchers are rail analogs to tugboats. US switchers tend to be larger, with bogies to allow them to be used on tight radiuses, European shunters tend to be smaller and more often have fixed axles. They also often maintained coupling rods for longer than other types, although bogie types have long been used where very heavy loads are involved. Switching is hard work, and heavily used switch engines wear out quickly from the abuse of constant hard contacts with cars, nevertheless, some types have been remarkably long-lived. Diesel switchers tend to have a cab and often lower and/or narrower hoods containing the diesel engines. Slugs are often used because they allow even greater effort to be applied. Nearly all slugs used for switching are of the low hood, good visibility in both directions is critical, because a switcher may be running in either direction, turning the locomotive is time-consuming. Some earlier diesel switchers used cow-calf configurations of two powered units in order to provide greater power, the vast majority of modern switchers are diesels, but countries with near-total electrification, like Switzerland, use electric switchers. Prior to the introduction of locomotives, electric shunting locomotives were used to an extent in Great Britain where heavy trains needed to be started on steep gradients. The steeply-graded Quayside Branch in Newcastle upon Tyne was electrified by the North Eastern Railway in 1905,1, is now part of the National Collection and resides at Locomotion in Shildon. A number of the early German locomotives built for use on lines have been preserved. These specialised locomotives were tall steeple-cab types not seen anywhere else, one example built by Greenwood and Batley in Armley, Leeds is preserved at the Middleton Railway, not far from where it was built. Small industrial shunters are sometimes of the battery-electric type, an early battery-electric shunting locomotive is shown here. The Tyne and Wear Metro has three battery electric shunters built by Hunslet, which are used to haul engineering trains when the supply is switched off. Flywheel energy storage was used experimentally by Sentinel
9.
Centralized traffic control
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Centralized traffic control is a form of railway signalling that originated in North America. CTC consolidates train routing decisions that were carried out by local signal operators or the train crews themselves. The system consists of a train dispatchers office that controls railroad interlockings. One hallmark of CTC is a panel with a graphical depiction of the railroad. On this panel the dispatcher can keep track of trains locations across the territory that the dispatcher controls, larger railroads may have multiple dispatchers offices and even multiple dispatchers for each operating division. These offices are located near the busiest yards or stations. Key to the concept of CTC is the notion of control as it applies to railroads. Trains moving in opposite directions on the same track cannot pass each other without special infrastructure such as sidings, the starting point of each system was the railroad timetable that would form the advanced routing plan for train movements. Trains following the timetable would know when to take sidings, switch tracks, however if train movements did not go as planned the timetable would then fail to represent reality, and attempting to follow the printed schedule could lead to routing errors or even accidents. This was especially common on single-track lines that comprised the majority of railroad route miles in North America, therefore, timetable operation was supplemented with train orders, which superseded the instructions in the timetable. The development of Direct Traffic Control via radio or telephone between dispatchers and train crews made telegraph orders largely obsolete by the 1970s. Where traffic density warranted it, multiple tracks could be provided, trains running counter to this flow of traffic would still require train orders, but other trains would not. Such a Mexican standoff not only represents a safety hazard, before the advent of CTC there were a number of solutions to this problem that did not require the construction of multiple single direction tracks. In areas of traffic density, sometimes bi-directional operation would be established between manned interlocking towers. Each section of track would have a traffic control lever associated with it to establish the direction of traffic on that track. Often, both towers would need to set their traffic levers in the way before a direction of travel could be established. Block signals in the direction of travel would display according to track conditions, furthermore, no train could be routed into a section of track against its flow of traffic and the traffic levers would not be able to be changed until the track section was clear of trains. Both APB and manual control would still require train orders in certain situations
10.
Goods wagon
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Goods wagons or freight wagons are unpowered railway vehicles that are used for the transportation of cargo. At the beginning of the era, the vast majority of goods wagons were four-wheeled vehicles of simple construction. These were almost exclusively small covered wagons, open wagons with side-boards, over the course of time, an increasing number of specialised wagons were developed. Special wagons for specific purposes or wagons with special features were already being introduced around 1850 by private companies, amongst these were tank wagons and numerous refrigerated vans. In countries like Germany, wagon hire firms procured large numbers of these wagons, in the early days of the railway, goods trains still ran at top speeds of only about 20 mph. However, the introduction of through brakes using air pipes from the 1920s enabled higher speeds to be safely achieved, the Deutsche Bahn even has goods wagons cleared for high-speed rail travel at up to 100 mph. In Europe, the first agreements were struck early on between the national state railways and private companies for the mutual use of each other’s goods wagons. Around 1850, the Union of German Railway Administrations drew up regulations for the standardisation of dimensions, the formation of the Prussian State Railway Union in 1881 encouraged the emergence of wagon classes built to standard norms. One further European milestone was the formation of the German State Railway Wagon Association on 1 April 1909. With the participation of all the German state railways, it created a pool of goods wagons. In addition, they all had standardised inscriptions and red-brown livery, in order to standardise future procurements, a total of 11 wagon classes were defined. From 1939, wagons were developed primarily from a point of view and were known as wartime classes. After the war, in East Germany, some pre-war goods wagon classes were given a new lease of life as ‘reconstructed goods wagons’, since the Union of Private Goods Wagon Companies was founded in 1921, the interests of private transport organisations in Germany has been jointly represented. The Union has around 100 members who own 50,000 goods wagons, in 2007, they transported 361,000,000 t of goods. Since 1922, the agreement for the use of goods wagons in international traffic has regulated the exchange of goods wagons in Europe. In addition, international goods wagon fleets were created in 1953 in Western Europe with the Europ-Verband, during the second half of the 20th century, national goods wagon classes in Europe were increasingly replaced by Union internationale des chemins de fer standard wagons. Since 1964, all goods wagons in Germany, for example, have had to be classified using the UIC goods wagon classification system, lowmacs Covered wagons or vans have a fixed roof and are mainly used for the transportation of part-load goods or parcels. Today these are divided into, Ordinary classes Special classes, which are distinguished by their large loading volumes
11.
Classification yard
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A classification yard or marshalling yard is a railway yard found at some freight train stations, used to separate railway cars on to one of several tracks. First the cars are taken to a track, sometimes called a lead or a drill, from there the cars are sent through a series of switches called a ladder onto the classification tracks. Larger yards tend to put the lead on an artificially built hill called a hump to use the force of gravity to propel the cars through the ladder, freight trains that consist of isolated cars must be made into trains and divided according to their destinations. Thus the cars must be shunted several times along their route in contrast to a unit train and this shunting is done partly at the starting and final destinations and partly in classification yards. Flat yards are constructed on ground, or on a gentle slope. Freight cars are pushed by a locomotive and coast to their required location, hump yards are the largest and most effective classification yards, with the largest shunting capacity, often several thousand cars a day. The heart of these yards is the lead track on a small hill over which an engine pushes the cars. As concerns speed regulation, there are two types of hump yards—without or with mechanisation by retarders, in the old non-retarder yards braking was usually done in Europe by railroaders who laid skates onto the tracks. The skate or chock was manually placed on one or both of the rails so that the treadles or rims of the wheel or wheels caused frictional retardation, in the United States this braking was done by riders on the cars. In the modern retarder yards this work is done by mechanized rail brakes called retarders and they are operated either pneumatically or hydraulically. Pneumatic systems are prevalent in the United States, France, Belgium, Russia and China, while hydraulic systems are used in Germany, Italy and the Netherlands. In the United States, many classification bowls have more than 40 tracks—up to 72—which are often divided into six to ten tracks in each balloon loop. Bailey Yard in North Platte, Nebraska, United States, the worlds largest classification yard, is a hump yard, notably, in Europe, Russia and China, all major classification yards are hump yards. Europes largest hump yard is that of Maschen near Hamburg, Germany, the second largest is in the port of Antwerp, Belgium. According to the PRRT&HS PRR Chronology, the first hump yard in the United States was opened May 11,1903 as part of the Altoona Yards at Bells Mills. Other sources report the PRR yard at Youngwood, PA which opened in the 1880s to serve the Connellsville coke fields as the first U. S. hump yard. Gravity yards are operated similarly to hump yards but, in contrast to the latter, thus, only few gravity yards were ever built, sometimes requiring massive earthwork. Most gravity yards were built in Germany and Great Britain, a few also in some other European countries, in the USA, there were only very few old gravity yards, one of the few gravity yards in operation today is CSXs Readville Yard south of Boston, Massachusetts
12.
Weighing scale
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Weighing scales are devices to measure weight or calculate mass. Scales and balances are used in commerce, as many products are sold. Very accurate balances, called analytical balances, are used in fields such as chemistry. Although records dating to the 1700s refer to spring scales for measuring weight, the earliest design for such a device dates to 1770 and credits Richard Salter, an early scale-maker. Postal workers could work quickly with spring scales than balance scales because they could be read instantaneously. By the 1940s various electronic devices were being attached to these designs to make more accurate. A spring scale measures weight by reporting the distance that a spring deflects under a load and this contrasts to a balance, which compares the torque on the arm due to a sample weight to the torque on the arm due to a standard reference weight using a horizontal lever. Spring scales measure force, which is the force of constraint acting on an object. They are usually calibrated so that measured force translates to mass at earths gravity, the object to be weighed can be simply hung from the spring or set on a pivot and bearing platform. In a spring scale, the spring either stretches or compresses, by Hookes law, every spring has a proportionality constant that relates how hard it is pulled to how far it stretches. Rack and pinion mechanisms are used to convert the linear spring motion to a dial reading. With proper manufacturing and setup, however, spring scales can be rated as legal for commerce, to remove the temperature error, a commerce-legal spring scale must either have temperature-compensated springs or be used at a fairly constant temperature. To eliminate the effect of gravity variations, a spring scale must be calibrated where it is used. It is also common in high-capacity applications such as crane scales to use force to sense weight. The test force is applied to a piston or diaphragm and transmitted through hydraulic lines to an indicator based on a Bourdon tube or electronic sensor. A digital bathroom scale is a type of electronic weighing machine, the digital bathroom scale is a smart scale which has many functions like smartphone integration, cloud storage, fitness tracking, etc. In electronic versions of spring scales, the deflection of a beam supporting the weight is measured using a strain gauge. The capacity of such devices is only limited by the resistance of the beam to deflection and these scales are used in the modern bakery, grocery, delicatessen, seafood, meat, produce and other perishable goods departments
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