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top 10 words in brain distribution (in article): light animal drink produce species time wolf breed common hunt |
top 10 words in brain distribution (in article): city power state station street design Unite town vehicle light |
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top 10 words in brain distribution (not in article): build house store home water bus radio signal gear department |
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| Bears'" are mammals of the family "'Ursidae'". Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern Hemisphere and partially in the Southern Hemisphere. That which pertains to bears is called "ursine". Bears are found in the continents of North America, South America, Europe, and Asia. Common characteristics of modern bears include a large body with stocky legs, a long snout, shaggy hair, plantigrade paws with five nonretractile claws, and a short tail. While the polar bear is mostly carnivorous and the giant panda feeds almost entirely on bamboo, the remaining six species are omnivorous, with largely varied diets including both plants and animals. With the exceptions of courting individuals and mothers with their young, bears are typically solitary animals. They are sometimes diurnal, but are usually active during the night (nocturnal) or twilight (crepuscular). Bears are aided by an excellent sense of smell, and despite their heavy build and awkward gait, they can run quickly and are adept climbers and swimmers. In autumn some bear species forage large amounts of fermented fruits which affects their behaviour.Bears use shelters such as caves and burrows as their dens, which are occupied by most species during the winter for a long period of sleep similar to hibernation. Bears have been hunted since prehistoric times for their meat and fur. To this day, they play a prominent role in the arts, mythology, and other cultural aspects of various human societies. In modern times, the bear's existence has been pressured through the encroachment of their habitats and the illegal trade of bears and bear parts, including the Asian bile bear market. The IUCN lists six bear species as vulnerable or endangered, and even "least concern" species such as the brown bear are at risk of extirpation in certain countries. The poaching and international trade of these most threatened populations is prohibited, but still ongoing. Evolutionary relationships. Fossil of Cave bear ("Ursus spelaeus") The Ursidae family belongs to the order Carnivora and is one of nine families in the suborder Caniformia, or "doglike" carnivorans. Bears' closest living relatives are the pinnipeds, a clade of three families: Odobenidae (the walrus), Otariidae (fur seals and sea lions), and Phocidae (true or earless seals). Bears comprise eight species in three subfamilies: Ailuropodinae (monotypic with the giant panda), Tremarctinae (monotypic with the Spectacled Bear), and Ursinae (containing six species divided into one to three genera, depending upon authority). The origins of Ursidae can be traced back to the very small and graceful "Parictis" that had a skull only 7 cm (3 in) long. Parictis first occur in North America in the Late Eocene (ca. 38 million years ago), but this genus did not appear in Eurasia and Africa until the Miocene. The raccoon-sized, dog-like "Cephalogale", however, is widely regarded as the most primitive ursid and is ideally suited as a representative basal taxon for the family. "Cephalogale" first appeared during the middle Oligocene and early Miocene (approximately 20–30 million years ago) in Europe. "Cephalogale" gave rise to a lineage of early bears of the genus "Ursavus". This genus radiated in Asia and ultimately gave rise to the first true bears (genus "Ursus") in Europe, 5 million years ago. Even among its primitive species, such as "C. minor", it exhibits typical ursid synapomorphic dentition such as posteriorly oriented M2 postprotocrista molars, elongated m2 molars, and a reduction of the premolars. Living members of the ursids are morphologically well defined by their hypocarnivorous (non-strictly meat-eating) dentitions, but fossil ursids include hypercarnivorous (strictly meat-eating) taxa, although they never achieved the extreme hypercarnivory seen in mustelids. Cephalogale was a mesocarnivore (intermediate meat-eater). Other extinct bear genera include "Arctodus", "Agriarctos", "Plionarctos" and "Indarctos". It is uncertain whether ursids were in Asia during the late Eocene, although there is some suggestion that a limited immigration from Asia may have produced "Parictis" in North America due to the major sea level lowstand at ca. 37 Ma, but no "Parictis" fossils have yet to be found in East Asia. Ursids did, however, become very diversified in Asia later during the Oligocene. Four genera representing two subfamilies (Amphicynodontinae and Hemicyoninae) have been discovered in the Oligocene of Asia: "Amphicticeps", "Amphicynodon", "Pachycynodon", and "Cephalogale". "Amphicticeps" is endemic from Asia and the other three genera are common to both Asia and Europe. This indicates migration of ursids between Asia and Europe during the Oligocene and migration of several taxa from Asia to North America likely occurred later during the late Oligocene or early Miocene. Although "Amphicticeps" is morphologically closely related to "Allocyon", and also to "Kolponomos" of North America, no single genus of the Ursidae from this time period is known to be common to both Eurasia and North America. Cephalogale, however, do appear in North America in the early Miocene. It is interesting to note that rodents, such as "Haplomys" and "Pseudotheridomys" (late Oligocene) and "Plesiosminthus" and "Palaeocastor" (early Miocene), are common to both Asia and North America and this indicates that faunal exchange did occur between Asia and North America during the late Oligocene to early Miocene. Ursid migration from Asia to North America would therefore have also been very likely to occur during this time. In the late Neogene three major carnivoran migrations that definitely included ursids are recognized between Eurasia and North America. The first (probably 21–18 Ma) was waves of intermittent dispersals including "Amphicynodon", "Cephalogale" and "Ursavus". The second migration occurred about 7–8 Ma and included "Agriotherium" – this was unusual among ursoids in that it also colonised sub-Saharan Africa. The third wave took place in the early Pliocene 4 Ma, consisting of "Ursus". The giant panda's taxonomy has long been debated. Its original classification by Armand David in 1869 was within the bear genus Ursus, but in 1870 it was reclassified by Alphonse Milne-Edwards to the raccoon family. In recent studies, the majority of DNA analyses suggest that the giant panda has a much closer relationship to other bears and should be considered a member of the family Ursidae. The status of the red panda remains uncertain, but many experts, including Wilson and Reeder, classify it as a member of the bear family. Others place it with the raccoons in Procyonidae or in its own family, the Ailuridae. Multiple similarities between the two pandas, including the presence of false thumbs, are thought to represent convergent evolution for feeding primarily on bamboo. There is also evidence that, unlike their neighbors elsewhere, the brown bears of Alaska's ABC islands are more closely related to polar bears than they are to other brown bears in the world. Researchers Gerald Shields and Sandra Talbot of the University of Alaska Fairbanks Institute of Arctic Biology studied the DNA of several samples of the species and found that their DNA is different from that of other brown bears. The researchers discovered that their DNA was unique compared to brown bears anywhere else in the world. The discovery has shown that while all other brown bears share a brown bear as their closest relative, those of Alaska's ABC Islands differ and share their closest relation with the polar bear. There is also supposed to be a very rare large bear in China called the blue bear, which presumably is a type of black bear. This animal has never been photographed. Koalas are often referred to as bears due to their appearance; they are not bears, however, but marsupials. Classification. The genera "Melursus" and "Helarctos" are sometimes also included in "Ursus". The Asiatic black bear and the polar bear used to be placed in their own genera, "Selenarctos" and "Thalarctos" which are now placed at subgenus rank. A number of hybrids have been bred between American black, brown, and polar bears (see Ursid hybrids). Biology. Despite being quadrupeds, bears can stand and sit similarly to humans. Bears are generally bulky and robust animals with relatively short legs. Unlike other land carnivorans, bears stand and walk on the soles of their feet rather than on their toes. They distribute their weight toward the hindfeet which makes then look lumbering when they walk. They are still quite fast with the brown bear reaching 30 mph although they are still slower than felines and canines. Bear can stand on their hindfeet and sit up straight with remarkable balance. Bears have non-retractable claws which are used for digging, climbing, tearing and catching prey. Their ears are rounded. Dentition. Unlike most other members of the Carnivora, bears have relatively undeveloped carnassial teeth, and their teeth are adapted for a diet that includes a significant amount of vegetable matter. The canine teeth are large, and the molar teeth flat and crushing. There is considerable variation in dental formula even within a given species. It has been suggested that this indicates bears are still in the process of evolving from a carnivorous to a predominantly herbivorous diet. Polar bears appear to have secondarily re-evolved fully functional carnassials, as their diet has switched back towards carnivory. The dental formula for living bears is: Diet & Interspecific Interactions. Their carnivorous reputation non-withstanding, most bears have adopted to a diet comprised of more plant than animal matter and are completely opportunistic omnivores. One exception is the Polar Bear, who has had to adopt a diet of mainly marine mammals to survive in the Arctic. The other exception is the Giant Panda has adapted a diet comprised mainly of bamboo. The Sloth Bear, though not as specialized as the previous two species, has lost several front teeth usually seen in bears and developed a long, suctioning tongue in order to feed on the termites and other burrowing insects that they favor. All bears will feed on any food source that becomes available. When taking warm-blooded animals, bears will typically take small or young animals, because of the endurance and potential danger that comes with attacking large prey. Although (besides Polar Bears) both species of black bear and the Brown Bear can sometimes take large prey, such as ungulates. Often, bears will feed on other large animals when they encounter a carcass, whether or not the carcass is claimed by or is the kill of another predator. This competition is the main source of interspecies conflict. Bears are typically the apex predators in their range due to their size and power, and can defend a carcass against nearly all comers. Mother bears also can usually defend their cubs against other predators. The Tiger is the only known predator known to regularly prey on adult bears, including Sloth Bears, Asiatic Black Bears, Giant Pandas, Sun Bears and small Brown Bears. Reproduction. The bear's courtship period is very brief. Bears in northern climates reproduce seasonally, usually after a period of inactivity similar to hibernation, although tropical species breed all year round. Cubs are born toothless, blind, and bald. The cubs of brown bears, usually born in litters of 1–3, will typically stay with the mother for two full seasons. They feed on their mother's milk through the duration of their relationship with their mother, although as the cubs continue to grow, nursing becomes less frequent and learn to begin hunting with the mother. They will remain with the mother for approximately three years, until she enters the next cycle of estrus and drives the cubs off. Bears will reach sexual maturity in five to seven years. Male bears, especially Polar and Brown Bears, will kill and sometimes devour cubs born to another father in order to induce a female to breed again. Female bears are often successful in driving off males in protection of their cubs, despite being rather smaller. Winter dormancy. Many bears of northern regions are assumed to hibernate in the winter. While many bear species do go into a physiological state called hibernation or winter sleep, it is not true hibernation. In true hibernators, body temperatures drop to near ambient and heart rate slows drastically, but the animals periodically rouse themselves to urinate or defecate and to eat from stored food. The body temperature of bears, on the other hand, drops only a few degrees from normal and heart rate slows only slightly. They normally do not wake during this "hibernation", and therefore do not eat, drink, urinate or defecate the entire period. Higher body heat and being easily roused may be adaptations, because females give birth to their cubs during this winter sleep. It can therefore be considered a more efficient form of hibernation because they need not awake through the entire period, but they are more quickly and easily awakened at the end of their hibernation. They have to stay in a den for the whole hibernation. Relationship with humans. Some species, such as the polar bear, American black bear, Sloth Bear and the brown bear, are dangerous to humans, especially in areas where they have become used to people. On the west coast of Canada, the American black bear has become an integral part of the silviculture industries, specifically treeplanting. The bears are coaxed into areas of harvested forest to "flush out" the other wildlife, i.e. moose, which are a far greater threat to planters. All bears are physically powerful and are likely capable of fatally attacking a person, but they, for the most part, are shy, easily frightened and will avoid humans. The danger that bears pose is often vastly exaggerated, in part by the human imagination. However, when a mother feels her cubs are threatened, she will behave ferociously. It is recommended to give all bears a wide berth because they are behaviorally unpredictable. Laws have been passed in many areas of the world to protect bears from hunters habitat destruction. Some populated areas with bear populations have also outlawed the feeding of bears, including allowing them access to garbage or other food waste. Bears in captivity have been trained to dance, box, or ride bicycles; however, this use of the animals became controversial in the late 20th century. Bears were kept for baiting in Europe at least since the 16th century. Bears as food and medicine. Many people enjoy hunting bears and eating them. Their meat is dark and stringy, like a tough cut of beef. In Cantonese cuisine, bear paws are considered a delicacy. The peoples of China, Japan, and Korea use bears' body parts and secretions (notably their gallbladders and bile) as part of traditional Chinese medicine. It is believed more than 12,000 bile bears are kept on farms, farmed for their bile, in China, Vietnam and South Korea. Bear meat must be cooked thoroughly as it can often be infected with trichinellosis. Myth and legend. Some evidence has been brought to light on prehistoric bear worship, see Arctic, Arcturus, Great Bear, Berserker, Kalevala. Anthropologists such as Joseph Campbell have regarded this as a common feature in most of the fishing and hunting-tribes. The prehistoric Finns, along with most Finno-Ugric peoples, considered the bear as the spirit of one's forefathers. This is why the bear was a greatly respected animal, with several euphemistic names. The bear is the national animal of Finland. This kind of attitude is reflected in the traditional Russian fairy tale "Morozko", whose arrogant protagonist Ivan tries to kill a mother bear and her cubs — and is punished and humbled by having his own head turned magically into a bear's head and being subsequently shunned by human society. "The Brown Bear of Norway" is a Scottish fairy tale telling the adventures of a girl who married a prince magically turned into a bear, and who managed to get him back into a human form by the force of her love and after many trials and difficulties. There has been evidence about early bear worship in China and among the Ainu culture as well (see Iomante). Korean people in their mythology identify the bear as their ancestor and symbolic animal. According to the Korean legend, a god imposed a difficult test on a she-bear, and when she passed it the god turned her into a woman and married her. In addition, the Proto-Indo-European word for bear, "*h₂ŕ̥tḱos" (ancestral to the Greek "arktos", Latin "ursus", Welsh "arth" (cf. Arthur), Albanian ari, Armenian arj, Sanskrit | A train'" is a connected series of vehicles that move along a track (permanent way) to transport freight or passengers from one place to another. The track usually consists of two rails, but might also be a monorail or maglev guideway. Propulsion for the train is provided by a separate locomotive, or from individual motors in self-propelled multiple units. Most modern trains are powered by diesel locomotives or by electricity supplied by overhead wires or additional rails, although historically (from the early 19th century to the mid-20th century) the steam locomotive was the dominant form of locomotive power. Other sources of power (such as horses, rope or wire, gravity, pneumatics, and gas turbines) are possible. The word 'train' comes from the Old French "trahiner", itself from the Latin "trahere" 'pull, draw'. Types of trains. An electric locomotive -hauled freight train There are various types of train designed for particular purposes. A train can consist of a combination of one or more locomotives and attached railroad cars, or a self-propelled multiple unit (or occasionally a single powered coach, called a railcar). Trains can also be hauled by horses, pulled by a cable, or run downhill by gravity. Special kinds of trains running on corresponding special 'railways' are atmospheric railways, monorails, high-speed railways, maglev, rubber-tired underground, funicular and cog railways. A passenger train may consist of one or several locomotives, and one or more coaches. Alternatively, a train may consist entirely of passenger carrying coaches, some or all of which are powered as a "multiple unit". In many parts of the world, particularly Japan and Europe, high-speed rail is utilized extensively for passenger travel. Freight trains comprise wagons or trucks rather than carriages, though some parcel and mail trains (especially Travelling Post Offices) are outwardly more like passenger trains. Trains can also be 'mixed', comprising both passenger accommodation and freight vehicles. Such mixed trains are most likely to occur where services are infrequent, and running separate passenger and freight trains is not cost-effective, though the differing needs of passengers and freight usually means this is avoided where possible. Special trains are also used for track maintenance; in some places, this is called maintenance of way. In the United Kingdom, a train hauled by two locomotives is said to be "double-headed", and in Canada and the United States it is quite common for a long freight train to be headed by three or more locomotives. A train with a locomotive attached at each end is described as 'top and tailed', this practice typically being used when there are no reversing facilities available. Where a second locomotive is attached temporarily to assist a train up steep banks or grades (or down them by providing braking power) it is referred to as 'banking' in the UK, or 'helper service' in North America. Recently, many loaded trains in the US have been made up with one or more locomotives in the middle or at the rear of the train, operated remotely from the lead cab. This is referred to as "DP" or "Distributed Power." Official terminology. The railway terminology that is used to describe a 'train' varies between countries. In the United Kingdom, the interchangeable terms set'" and "'unit'" are used to refer to a group of permanently or semi-permanently coupled vehicles, such as those of a multiple unit. While when referring to a train made up of a variety of vehicles, or of several sets units, the term "'formation'" is used. (Although the UK public and media often forgo 'formation', for simply 'train'.) The word "'rake'" is also used for a group of coaches or wagons. In the United Kingdom Section 83(1) of the Railways Act 1993 defines "train" as follows: In the United States, the term "'consist'" is used to describe the group of rail vehicles which make up a train. When referring to motive power, "'consist'" refers to the group of locomotives powering the train. Similarly, the term "'trainset'" refers to a group of rolling stock that is permanently or semi-permanently coupled together to form a unified set of equipment (the term is most often applied to passenger train configurations). The Atchison, Topeka and Santa Fe Railway's 1948 operating rules define a train as: "An engine or more than one engine coupled, with or without cars, displaying markers." Motive power. The first trains were rope-hauled, gravity powered or pulled by horses, but from the early 19th century almost all were powered by steam locomotives. From the 1920s onwards they began to be replaced by less labour intensive and cleaner (but more complex and expensive) diesel locomotives and electric locomotives, while at about the same time self-propelled multiple unit vehicles of either power system became much more common in passenger service. In most countries dieselisation of locomotives in day-to-day use was completed by the 1970s. A few countries, most notably the People's Republic of China, where coal and labour are cheap, still use steam locomotives, but this is being gradually phased out. Historic steam trains still run in many other countries, for the leisure and enthusiast market. Electric traction offers a lower cost per mile of train operation but at a higher initial cost, which can only be justified on high traffic lines. Since the cost per mile of construction is much higher, electric traction is less favored on long-distance lines with the exception of long-distance high speed lines. Electric trains receive their current via overhead lines or through a third rail electric system. Passenger trains. A passenger train is one which includes passenger-carrying vehicles. It may be a self-powered multiple unit or railcar, or else a combination of one or more locomotives and one or more unpowered trailers known as coaches, cars or carriages. Passenger trains travel between stations where passengers may join or leave the train. The oversight of the train is the duty of a staff called the conductor. Many of the more prestigious passenger train services have been given a specific name, some of which have become famous in literature and fiction. India has the largest passenger density in the world. Some passenger trains, both long distance and short distanced, may use Bilevel car (double-decker) to hold more passengers per car. Designs and safety of passenger trains has changed dramatically over time. Long-distance trains. Long-distance trains travel between many cities and or regions of a country, and sometimes cross several countries. They often have a dining car or restaurant car to allow passengers to have a meal during the course of their journey. Trains traveling overnight may also have sleeping cars. High-speed trains. Russian Velaro high speed passenger train (a form of multiple unit) One notable and growing long-distance train category in the world is High-speed train. Generally they are faster than 200 km h and often use new separate passenger-only line of high grade standard. Shinkansen in Japan opened in 1964 is the first successful example of newly constructed High-speed train. The fastest train on rails is the French TGV (Train à Grande Vitesse) (French for High Speed Train) which achieved a speed of 574.8 km h (356 mph) in testing in 2007. The fastest commercial speed on rail is currently 350km h of Beijing–Tianjin Intercity Rail in China. TGV runs at a maximum commercial speed of 300-320 km h, as does the German ICE. Generally, High-speed rail is very competitive in less than 3 or 4 hours distance (ex; Tokyo – Osaka in Japan, 500km, 2h 30min, Paris- Lyon in France, 500 km, 2h) in corridor of dense population, but often air has advantage in longer journey. Very fast trains sometimes tilt, like the APT, the Pendolino, or the Talgo. Tilting is a system where the passenger cars automatically lean into curves, reducing the sideways g-forces on passengers and permitting higher speeds on curves in the track with greater passenger comfort. Maglev. In order to achieve much faster operation over 500 km h, innovative Maglev technology has been researched for years. Shanghai Maglev Train, opened in 2003, is the fastest one of 430km h operation. But Maglev has never operated to serve mass inter-city transit so far. Inter-city trains. Trains connecting cities can be distinguished into two groups, inter-city trains, which do not halt at small stations, and trains that serve all stations, usually known as local trains or "stoppers" (and sometimes an intermediate type, usually known as limited-stop). Regional trains. Regional trains usually connect between towns and cities, rather than purely linking major population hubs like inter-city train, and serve local traffic demand in relatively rural area. Commuter trains. For shorter distances many cities have networks of commuter trains, serving the city and its suburbs. Train is very efficient mode of transportation to cope with large traffic demand in metropolis. Compared with road transport, it carries many people with much smaller land area and little air pollution. Some carriages may be laid out to have more standing room than seats, or to facilitate the carrying of prams, cycles or wheelchairs. Some countries have double-decked passenger trains for use in conurbations. Double deck high speed and sleeper trains are becoming more common in mainland Europe. Sometimes extreme congestion of commuter trains becomes a problem. For example, an estimated 3.5 million passengers ride every day on Yamanote Line in Tokyo, Japan, with its 29 stations. For comparison, the New York City Subway carries 4.8 million passengers per day on 26 lines serving 468 stations. To cope with large traffic, special cars in which the bench seats fold up to provide standing room only during the morning rush hour (until 10 a.m.) are operated in Tokyo (E231 series train). This train has as many as six sets of doors on each side to shorten the time for passengers to get on and off at station. Passenger trains usually have emergency brake handles (or a "communication cord") that the public can operate. Misuse is punished by a heavy fine. Rapid transit. Large cities often have a metro system, also called underground, subway or tube. The trains are electrically powered, usually by third rail, and their railroads are separate from other traffic, without level crossings. Usually they run in tunnels in the city center and sometimes on elevated structures in the outer parts of the city. They can accelerate and decelerate faster than heavier, long-distance trains. The term "'rapid transit'" is used for public transport such as commuter trains, metro and light rail. However, in New York City, lines on the New York City Subway have been referred to as "trains". Tram. A light one- or two-car rail vehicle running through the streets is by convention not considered a train but rather a tram, trolley, light-rail vehicle or streetcar, but the distinction is not always strict. In some countries such as the United Kingdom the distinction between a tramway and a railway is precise and defined in law. Light rail. The term light rail is sometimes used for a modern tram, but it may also mean an intermediate form between a tram and a train, similar to metro except that it may have level crossings. These are often protected with crossing gates. They may also be called a trolley. Monorail. Monorail is developed to meet medium-demand traffic in urban transit, buts represent minor technologies in the train field. Named trains. Railway companies often give a name to a train service as a marketing exercise, to raise the profile of the service and hence attract more passengers (and also to gain kudos for the company). Usually, naming is reserved for the most prestigious trains: the high-speed express trains between major cities, stopping at few intermediate stations. The names of services such as the Orient Express, the Flying Scotsman, the Flèche d’Or and the Royal Scot have passed into popular culture. A somewhat less common practice is the naming of freight trains, for the same commercial reasons. The "Condor" was an overnight London-Glasgow express goods train, in the 1960s, hauled by pairs of "Metrovick" diesel locomotives. In the mid-1960s, British Rail introduced the "Freightliner" brand, for the new train services carrying containers between dedicated terminals around the rail network. The Rev. W. Awdry also named freight trains, coining the term "The Flying Kipper" for the overnight express fish train that appeared in his stories in The Railway Series books. Other trains of specific kinds. Heritage trains are operated by volunteers, often railfans, as a tourist attraction. Usually trains are a kind of historic value and retired practical operation. Most of them run weekend and vacation seasons. Airport trains are trains within airport buildings that transport people between terminals. Mine trains are operated in large mine and carry both workers and goods. Freight trains. A freight train (also known as goods train) uses "'freight cars (also known as wagons or trucks) to transport goods or materials (cargo) – essentially any train that is not used for carrying passengers. Much of the world's freight is transported by train, and in the USA the rail system is used more for transporting freight than passengers. Under the right circumstances, transporting freight by train is highly economic, and also more energy efficient than transporting freight by road. Rail freight is most economic when freight is being carried in bulk and over long distances, but is less suited to short distances and small loads. Bulk aggregate movements of a mere twenty miles (32 km) can be cost effective even allowing for trans-shipment costs. These trans-shipment costs dominate in many cases and many modern practices such as container freight are aimed at minimizing these. The main disadvantage of rail freight is its lack of flexibility. For this reason, rail has lost much of the freight business to road competition. Many governments are now trying to encourage more freight onto trains, because of the benefits that it would bring. There are many different types of freight trains, which are used to carry many different kinds of freight, with many different types of wagons. One of the most common types on modern railways are container trains, where containers can be lifted on and off the train by cranes and loaded off or onto trucks or ships. This type of freight train has largely superseded the traditional boxcar (wagon-load) type of freight train, with which the cargo has to be loaded or unloaded manually. In some countries "piggy-back" trains are used: trucks can drive straight onto the train and drive off again when the end destination is reached. A system like this is used through the Channel Tunnel between England and France, and for the trans-Alpine service between France and Italy (this service uses Modalohr road trailer carriers). 'Piggy-back' trains are the fastest growing type of freight trains in the United States, where they are also known as 'trailer on flatcar' or TOFC trains. 'Piggy-back' trains require no special modifications to the vehicles being carried. An alternative type of "inter-modal" vehicle, known as a Roadrailer, is designed to be physically attached to the train. The original trailers were fitted with two sets of wheels: one set flanged, for the trailer to run connected to other such trailers as a rail vehicle in a train; and one set tyred, for use as the semi-trailer of a road vehicle. More modern trailers have only road wheels and are designed to be carried on specially adapted bogies (trucks) when moving on rails. There are also many other types of wagons, such as "low loader" wagons for transporting road vehicles. There are refrigerator cars for transporting foods such as ice cream. There are simple types of open-topped wagons for transporting minerals and bulk material such as coal, and tankers for transporting liquids and gases. Today however most coal and aggregates are moved in hopper wagons that can be filled and discharged rapidly, to enable efficient handling of the materials. Freight trains are sometimes illegally boarded by passengers who do not wish to pay money, or do not have the money to travel by ordinary means. This is referred to as "hopping" and is considered by some communities to be a viable form of transport. Most hoppers sneak into train yards and stow away in boxcars. More bold hoppers will catch a train "on the fly", that is, as it is moving, leading to occasional fatalities. |