An escalator is a conveyor transport device for transporting people, consisting of a staircase whose steps move up or down on tracks that keep the surfaces of the individual steps horizontal.
A moving walkway, moving sidewalk, walkalator, travelator (colloquial name, not to be confused with Trav-O-Lator®, a registered trademark of United Technologies), or moveator is a slow conveyor belt that transports people horizontally or on an incline in a similar manner to an escalator. In both cases, riders can walk or stand. The walkways are often supplied in pairs, one for each direction.
As a power-driven, continuous moving stairway designed to transport passengers up and down short vertical distances, escalators are used around the world to move pedestrian traffic in places where elevators would be impractical. Principal areas of usage include shopping centers, airports, transit systems, trade centers, hotels, and public buildings.
The benefits of escalators are many. They have the capacity to move large numbers of people, and they can be placed in the same physical space as stairs would be. They have no waiting interval, except during very heavy traffic; they can be used to guide people towards main exits or special exhibits; and they may be weather-proofed for outdoor use.
Escalators and their "cousins," moving walkways, are powered by constant speed alternating current motors and move at approximately 1–2 ft (0.3–0.6 m) per second. The maximum angle of inclination of an escalator to the horizontal is 30 degrees with a standard rise up to about 60 ft (18 m).
Modern escalators have metal steps in a continuous loop that move on tracks. Escalators are typically used in pairs with one going up and the other going down, however in some places, especially European stores and metro stations, there are no escalators going down; the escalators only go up. Some modern escalators in stores and shopping malls have glass sides that reveal their workings. Although most escalators are straight, some shopping malls use curved versions.
Most escalators have moving handrails that approximately keep pace with the movement of the steps. The direction of movement (up or down) can be permanently the same, or be controlled by personnel according to the time of day, or automatically be controlled by whomever arrives first, whether at the bottom or at the top (of course the system is programmed so that the direction is not reversed while somebody is on the escalator). In the last two cases, there has to be an alternative nearby.
A number of factors affect escalator design, including physical requirements, location, traffic patterns, safety considerations, and aesthetic preferences. Foremost, physical factors like the vertical and horizontal distance to be spanned must be considered. These factors will determine the pitch of the escalator and its actual length. The ability of the building infrastructure to support the heavy components is also a critical physical concern. Location is important because escalators should be situated where they can be easily seen by the general public. In department stores, customers should be able to view the merchandise easily. Furthermore, up and down escalator traffic should be physically separated and should not lead into confined spaces.
Traffic patterns must also be anticipated in escalator design. In some buildings the objective is simply to move people from one floor to another, but in others there may be a more specific requirement, such as funneling visitors towards a main exit or exhibit. The number of passengers is important because escalators are designed to carry a certain maximum number of people. For example, a single width escalator traveling at about 1.5 feet (0.45 m) per second can move an estimated 170 persons per five-minute period. Wider models traveling at up to 2 feet (0.6 m) per second can handle as many as 450 people in the same time period. The carrying capacity of an escalator must match the expected peak traffic demand. This is crucial for applications in which there are sudden increases in the number of passengers. For example, escalators used in train stations must be designed to cater for the peak traffic flow discharged from a train, without causing excessive bunching at the escalator entrance.
Of course, safety is also major concern in escalator design. Fire protection of an escalator floor-opening may be provided by adding automatic sprinklers or fireproof shutters to the opening, or by installing the escalator in an enclosed fire-protected hall. To limit the danger of overheating, adequate ventilation for the spaces that contain the motors and gears must be provided. It is preferred that a traditional staircase be located adjacent to the escalator if the escalator is the primary means of transport between floors. It may also be necessary to provide an elevator lift adjacent to an escalator for wheelchairs and disabled persons. Finally, consideration should be given to the aesthetics of the escalator. The architects and designers can choose from a wide range of styles and colors for the handrails and tinted side panels.
|Standard escalator step widths|
|Very small||400 mm||16 in||One passenger, with feet together||An older design, extremely rare today|
|Small||600 mm||24 in||One passenger||Low-volume sites, uppermost levels of department stores, when space is limited|
|Medium||800 mm||32 in||One passenger + one package or one piece of luggage.||Shopping malls, department stores, smaller airports|
|Large||1000 mm||40 in||Two passengers—one may walk past another||Mainstay of metro systems, larger airports, train stations, some retail usage|
Moving walkways, also known as moving sidewalks, travelators, and walkalators, are built in one of two basic styles:
Both types of moving walkway have a grooved surface to mesh with combplates at the ends. Also, all moving walkways are built with moving handrails similar to those on escalators.
Moving walkways are often used in airports, where there is a long distance to walk between terminals, and in metro stations.
A first attempt at an accelerated walkway in the 1980s, was the TRAX (Trottoir Roulant Accéléré), which was developed by Dassault and RATP and whose prototype was installed in the Paris Invalides metro station. It was a technical failure due to its complexity, and was never commercially exploited.
In 2002, the first successful high-speed walkway was installed in the Montparnasse—Bienvenüe Métro station in Paris. At first, it operated at 12 kilometers per hour (km/h) but too many people were falling over, so the speed was reduced to 9 km/h. It has been estimated that commuters using a walkway such as this twice a day would save 11.5 hours a year.
Using the high-speed walkway is like using any other moving walkway, except that for safety there are special procedures to follow when joining or leaving. When this walkway was introduced, staff determined who could and who could not use it. As riders must have at least one hand free to hold the handrail, those carrying bags, shopping, and so forth, or who are infirm, must use the ordinary walkway nearby.
On entering, there is a 10 m acceleration zone where the "ground" is a series of metal rollers. Riders stand still with both feet on these rollers and use one hand to hold the handrail and let it pull them so that they glide over the rollers. The idea is to accelerate the riders so that they will be traveling fast enough to step onto the moving walkway belt. Riders who try to walk on these rollers are at significant risk of falling over.
Once on the walkway, riders can stand or walk. Owing to Newton's laws of motion, there is no special sensation of traveling at speed, except for headwind.
At the exit, the same technique is used to decelerate the riders. Users step on to a series of rollers which decelerate them slowly, rather than the abrupt halt which would otherwise take place.
An inclined moving sidewalk, also called a movator, travelator, or moving ramp, is used in airports and supermarkets to move people to another floor with the convenience of an elevator (people can take along their suitcase trolley or shopping cart) and the capacity of an escalator. The carts have either a brake that is automatically applied when the cart handle is released, or specially designed wheels that secure the cart within the grooves of the ramp, so that it does not run away down the ramp. Some department stores instead use an escalator with a specially-designed chain, similar to those used on roller coasters, to move specially-designed carts up and down a steeper slope beside and at the same speed as the passenger escalator. The Central-Mid-levels escalator system on Hong Kong Island, Hong Kong, also has several inclined moving sidewalks. In the Melbourne suburb of Carlton, another inclined moving sidewalk can be found at Lygon Court.
Spiral escalators take up much less horizontal space than straight escalators. However, early spiral designs were failures. For example, one spiral escalator constructed by Reno in conjunction with William Henry Aston and Scott Kietzman at London's Holloway Road Underground station in 1906, was dismantled almost immediately and little of the mechanism survives. The Mitsubishi Electric Corporation has developed successful commercial designs and has manufactured curved and spiral escalators since the 1980s.
Notable sets of spiral escalators are located in the Westfield San Francisco Centre in San Francisco, California, and at Forum Shops at Caesars Palace in Las Vegas, Nevada. The Times Square shopping mall in Causeway Bay, Hong Kong, also features four curved escalators, as does Wheelock Place in Singapore.
Nathan Ames, a patent solicitor from Saugus, Massachusetts, is credited with patenting the first "escalator" in 1859, despite the fact that no working model of his design was ever built. His invention, the "revolving stairs," is largely speculative and the patent specifications indicate that he had no preference for materials or potential use (he noted that steps could be upholstered or made of wood, and suggested that the units might benefit the infirm within a household use), though the mechanization was suggested to run either by manual or hydraulic power.
Jesse W. Reno, an 1883 engineering graduate of Lehigh University, invented the first escalator (he actually called it the "inclined elevator") and installed it alongside the Old Iron Pier at Coney Island, New York, in 1896. (His patent was issued in January 1892.) This particular device was little more than an inclined belt with cast-iron slats or cleats on the surface for traction, and traveled along a 25° incline. A few months later, the same prototype was used for a month long trial period on the Manhattan side of the Brooklyn Bridge. By 1898, the first of these "inclined elevators" was incorporated into the Bloomingale Bros. store at Third Avenue and 59th Street. (This was the first retail application of the devices, and no small coincidence, considering that Reno's primary financier was Lyman Bloomingdale.) Reno eventually joined forces with Otis Elevator Company, and left the company after his patents were purchased outright. Some escalators of this vintage were still being used in the Boston subway until 1994-1997.
In 1892, a few months after Reno's patent was approved, George A. Wheeler patented ideas for a more recognizable moving staircase, though it was never built. Some of its features were incorporated in the prototype built by the Otis Elevator Company in 1899.
Around May 1895, Charles Seeberger began drawings on a form of escalator similar to those patented by Wheeler in 1892. This device actually consisted of flat, moving stairs, not unlike the escalators of today, except for one important detail: The step surface was smooth, with no comb effect to safely guide the rider's feet off at the ends. Instead, the passenger had to step off sideways. To facilitate this, at the top or bottom of the escalator the steps continued moving horizontally beyond the end of the handrail (like a mini-moving sidewalk) until they disappeared under a triangular "divider" which guided the passenger to either side. Seeberger teamed with Otis Elevator Company in 1899, and together they produced the first commercial escalator, which won a first prize at the Paris 1900 Exposition Universelle, in France. Also on display at the Exposition were Reno's "inclined elevator," a similar model by James M. Dodge, and two like devices by French manufacturers, including Hallé-Piat.
The first standard escalator installed on the London Underground was one such Seeberger model; it was located at Earls Court, London, UK. (London's Underground installed a rare spiral escalator designed by Jesse Reno in 1906; it was run for a short time but was taken out of service the same day it debuted.)
For a time, Otis Elevator sold both types of escalator, referring to the Seeberger model as "step-type" and the Reno model as "cleat-type." The company later combined the best aspects of both inventions (guiding slats and flat steps) and in 1921, produced an escalator similar to the type used today: They called it the "L-type" escalator.
The older lines of the London Underground had many escalators with wooden steps until they were rapidly replaced following the fire at King's Cross St. Pancras tube station in 1987. Old escalators with wooden cleated treads are still in use in some places, however, such as the Tyne Cyclist and Pedestrian Tunnel in Tyne and Wear, England, the Macy's department store in New York City, some floors of the Macy's department store in downtown Pittsburgh, Town Hall Railway Station in Sydney, and the St. Anna Pedestrian Tunnel underneath the Schelde in Antwerp, Belgium.
An escalator user may choose to stand and ride at the speed of the escalator, or walk in the same direction to arrive faster. In many places—particularly on the longer escalators, used daily by commuters, found on rapid transit systems—passengers who stand customarily stay on one particular side of the escalator, leaving the other side free for walkers. The proper side for walking does not necessarily correspond with the passing lane in road traffic: Passengers stand on the right and walk on the left on the London Underground as well as the Washington, Boston, Hong Kong, Toronto, and Moscow subway systems; but in Singapore and Australia, they stand on the left. In Japan, riders stand on the left in Tokyo but on the right in Osaka. On the Montreal Metro, while walking on escalators is theoretically forbidden, this rule is scarcely observed and not at all enforced, and passengers tend to stand on the right. In some countries there is no convention and people stand on either side, randomly, as they please.
A mnemonic for the U.S./British convention on this point is that stand and right each have five letters, while walk and left have four.
Sometimes, escalators help in controlling traffic flow of people. For example, an escalator to an exit effectively discourages most people from using it as an entrance, and therefore does not require a regular ticket check. As with turnstile jumping, this can be physically defeated by someone able-bodied and determined to do so, but at the price of making themselves conspicuous. Similarly, escalators often are used as the exit of an airport secure area. Such an exit would generally be manned to prevent its use as an entrance.
For fun, people sometimes use an escalator running in the opposite direction, climbing up or down the stairs faster than it moves. This is forbidden in some places, notably the Paris Métro, where running in the opposite direction can lead to being fined.
Escalators have recently been used by various media agencies in advertising campaigns with the handrails, side panels, or steps used for advertising. Escasite is one example of an advertising company that specializes in this.
There have been various reports of people actually falling off a moving escalator or getting their shoe stuck in part of the escalator. A few fatal accidents are known to have involved escalators and travelators. Of these accidents, they usually involved a structural failure of the escalator.
To reduce accidents, newer models of escalators are equipped with one or more of the following safety devices:
While some escalator accidents are caused by a mechanical failure, most can be avoided by following some simple safety precautions.
In Hong Kong, tens of thousands of commuters travel each work day between Central, the central business district, and the Mid-levels, a residential district hundreds of feet uphill, using a long distance system of escalators and moving sidewalks called the Central-Mid-Levels escalator. It is the world's longest outdoor escalator system (not a single escalator span), at a total length of 800 meters (m). It goes only one way at a time; the direction reverses depending on rush hour traffic direction. The Ocean Park, in Hong Kong, also has a long escalator system connecting two parts of the Park, with an overall length of 224 m (745 feet). In the Times Square shopping center in Causeway Bay there is a bank of four spiral escalators, each of which turns through about 180 degrees—by necessity, the undersides of these escalators are thicker as the step return mechanism needs to be more complex than on a straight escalator.
The longest individual escalators in the world are found on the metro systems in several cities in Eastern Europe; those in St. Petersburg, Kiev, and Prague have Soviet-era escalators up to approximately 100 m (330ft) long. The longest of all these are in the famously deep Moscow Metro, in the Park Pobedy station. Opened in 2003, these escalators are 126 m long and take nearly three minutes to transit.
The longest single span uninterrupted escalator in the Americas is at the Wheaton station of the Washington Metro system. It is 70 m (230 ft) long, and takes almost 2 minutes and 45 seconds to ascend or descend without walking.
The longest escalator on the London Underground system, and indeed in Western Europe, is at Angel station with a length of 60 m, and a vertical rise of 27.5 m. The longest escalator on the Helsinki Metro is at Kamppi metro station with a length of 65 m, and a vertical rise of 29.7 m, including 334 steps.
The longest freestanding escalator in the world is inside a huge atrium at CNN Center in Atlanta, Georgia. It rises 8 stories and is 205 ft (62 m) long. Originally built as the entrance to the Krofft-themed indoor amusement park, The World of Sid and Marty Krofft, the escalator is now used for CNN studio tours.
The concept of a megalopolis based on high-speed walkways is common in science fiction. The first work set in such a location is When The Sleeper Wakes (1899) written by H. G. Wells (also republished as The Sleeper Awakes), and takes place in London around the year 2100. In the 1927 silent film, Metropolis, there are several scenes showing moving sidewalks and escalators between skyscrapers at high levels. Later, The Roads Must Roll (1940), written by Robert A. Heinlein, depicts the risk of a transportation strike in a society based on similar-speed sidewalks. The novel is part of the Future History saga, and takes place in 1976. Isaac Asimov, in the novel, The Caves of Steel (1954), and its sequels in the Robot Series, uses similar enormous underground cities with a similar sidewalk system. The period described is about the year 3000.
In each of these cases there is a massive network of parallel moving belts, the inner ones faster. Passengers are screened from wind, and there are chairs and even shops on the belt. In the Heinlein work the fast lane runs at 180 km/h, and the first "mechanical road" was built in 1960 between Cincinnati and Cleveland. The relative speed of two adjacent belts is an unrealistic 20 km/h (in the book the fast lane stops, and the second lane keeps running at 160 km/h). In the Wells and Asimov works, there are more steps in the speed scale and the speeds are less extreme.
In Arthur C. Clarke's novel, Against the Fall of Night (later rewritten as The City and the Stars) the Megacity of Diaspar is interwoven with "moving ways" which, unlike Heinlein's conveyor belts, are solid floors that can mysteriously move as a fluid. On pages 11-13 of the novel, Clarke writes,
An engineer of the ancient world would have gone slowly mad trying to understand how a solid roadway could be fixed at both ends while its center traveled at a hundred miles an hour… The corridor still inclined upwards, and in a few hundred feet had curved through a complete right-angle. But only logic knew this: To the senses it was now as if one were being hurried along an absolutely level corridor. The fact that he was in reality traveling up a vertical shaft thousands of feet deep gave Alvin no sense of insecurity, for a failure of the polarizing field was unthinkable.
It is reputed that the first escalator was designed and partially built by Reese Williams, great grandfather of Jim Williams, co-owner of Gennesee Valley Water Bottling Company, and an immigrant from Wales. He owned a small carpentry shop where he originally got the idea for the escalator. Unfortunately, he did not think to patent his idea before finishing his prototype, and openly talked to his local community about his project. One day, he went to open the shop, and found that it had been burned to the ground, with none of his plans intact. Within the next week the patent for the escalator was filed with the U.S. patent office. It is unknown as to whether or not the plans were stolen or this was simply a coincidence.
Escalator was originally a combination of the word "scala," which is Latin for steps, and the word "elevator," which had already been invented. The verb form of the word is (to) escalate and is commonly applied to the use of increased force in warfare.
The word Escalator started out as a trademark of the Otis Elevator Company. Otis, however, failed to police its usage sufficiently, so escalator became a generic term in 1950. But until then, other manufacturers had to market their escalators under different names. The Peelle Company called theirs a Motorstair, and Westinghouse called their model an Electric Stairway. The Haughton Elevator company (now part of Schindler Group) referred to their product as simply, Moving Stairs.
All links retrieved October 3, 2013.
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