Escalator

Escalators at Westminster tube station, London.

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, travelator, or travellator 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.

Designs

Escalators

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. 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.

Standard escalator step widths
	Inches	Millimeters	Step capacity	Applications
Very small	16 in	400 mm	One passenger, with feet together	An older design, extremely rare today
Small	24 in	600 mm	One passenger	Low-volume sites, uppermost levels of department stores, when space is limited
Medium	32 in	800 mm	One passenger + one package or one piece of luggage.	Shopping malls, department stores, smaller airports
	36 in	900 mm
Large	40 in	1000 mm	Two passengers - one may walk past another	Mainstay of metro systems, larger airports, some retail usage

Moving walkways

Moving sidewalk at Detroit's DTW airport.

Moved walkways, also known as moving sidewalks, are built in one of two basic styles:

• Pallet type -- a continuous series of flat metal plates mesh together to form a walkway. Most have a metal surface, though some models have a rubber surface for extra traction.
• Moving belt -- these are generally built with mesh metal belts or rubber walking surfaces over metal rollers. The walking surface may have a solid feel or a "bouncy" feel.

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.

High-speed walkways

Experimental 185 metre long high-speed moving walkway on the Parisian Métro.

The speed of a moving walkway is usually 3 km/h, but there is a high-speed version at Gare Montparnasse station in Paris. At first it operated at 12 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 (seen here in yellow jackets) was determining who can use it and who not. As riders must have at least one hand free to hold the handrail. Those carrying bags, shopping, etc., 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 must 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 travelling fast enough to step onto the moving walkway belt.

Once on the walkway, riders can stand or walk; there is no special sensation of travelling at speed.

At the exit, there is a deceleration zone where again riders must stand still and let the handrail pull them as they slow down, again while gliding over metal rollers. Then they just walk off.

File:Movingsidewalk.JPG

An inclined moving sidewalk at Beaudry metro station in Montreal.

Inclined moving sidewalks

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.

An assortment of escalators in the Yokohama Minato Mirai 21.

Spiral escalators

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 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 San Francisco Shopping 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.

History

In 1892, Charles A. Wheeler patented ideas for the first practical moving staircase, though it was never built. Some of its features were incorporated in the prototype built by the Otis Elevator Company in 1899.

Jesse W. Reno invented the first escalator and installed it as an amusement ride at Coney Island, New York in 1897. This particular device was little more than an inclined belt with wooden slats or cleats on the surface for traction. The incline was as steep as 25°. Reno sold this machine to the 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. Some escalators of this vintage were still being used in the Boston subway until 1994.

Around the same time that Reno's invention appeared, Charles Seeberger developed a form of escalator as well. 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. The first escalator installed on the London Underground was one such Seeberger model; it was located at Earls Court, London, UK.

For a time, Otis Elevator sold both types of escalator. The company later combined the best aspects of both the Reno (guiding slats) and Seeberger (flat steps) inventions and in 1921 produced an escalator of the type used today. These improvements in design brought the escalator into extensive use in department stores, banks and metro stations.

The German company Orenstein & Koppel (O&K) would also become a major player in escalator design and manufacture.

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 steps 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 and the St. Anna Pedestrian Tunnel underneath the Schelde in Antwerp, Belgium.

Usage

When using escalators, it is customary for passengers who wish to stand and let themselves be carried up or down to stand on one side to allow other users to walk past them. The observance of this custom varies greatly from place to place—the rule is more likely to be adhered to on, for example, the long escalators of an underground transport system than in a department store. Additionally it is customary to stand on a fixed side, so that walking people do not have to zigzag. The side for standing also varies, and does not necessarily correspond with the rules of the road: on the London Underground, and Washington Metro, and in Hong Kong, one stands on the right; in Singapore and Australia on the left. The side for standing can also vary within a country. E.g. in Japan, one stands on the left in Tokyo but on the right in Osaka. In 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.

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.

For fun, people sometimes use an escalator in opposite direction, climbing up or down the stairs faster than it moves. This can cause inconvenience for other users, so is wisest attempted during quiet periods.

Sometimes escalators help in controlling traffic flow of people. For example, an escalator to an exit effectively discourages most people from using it as entrance, hence it 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: the level of vigilance required to prevent this is therefore much lower.

Similarly, escalators are sometimes used as the exit of an airport secure area. Such an exit would generally be manned to prevent its use as an entrance.

Accidents

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: Sally Baldwin, a professor of the University of York, was crushed to death at Tiburtina Station in Rome on 28 October 2003 after a travelator collapsed and she was pulled into the cogwheels.

On December 13, 1999, 8-year-old Jyotsna Jethani was killed at New Delhi's international airport when a passenger's bag got stuck in an escalator at the arrival lounge and ripped it open. Jyotsna fell into the gaping hole that resulted. [BBC article]

In another incident, on June 15, 2002, Andrea Albright, a 24-year-old JC Penney employee in the Mall in Columbia (Columbia, Maryland), was critically injured while riding the store's escalator from the first to the second level. She somehow got her head caught between the escalator rail and a low ceiling. Albright died 10 days later of massive injuries to the brain from lack of oxygen. In 2005, her parents sued the property manager, two design firms, and the escalator company for $5 million.

Francisco Portillo, a Salvadorian man living in Boston, died after getting his hood stuck in an MBTA escalator on 21 February, 2005.

Safety features

An escalator receiving maintenance. The steps have been removed, showing internal workings.

To reduce accidents, newer models of escalators are equipped with one or more of the following safety devices:

• Step demarcation lights -- a fluorescent light, traditionally colored green, is located inside the escalator mechanism under the steps at the boarding point. The resulting illumination between the steps improves the passengers' awareness of the step divisions.
• Step demarcation lines -- the front and/or sides of the steps are colored a bright yellow as a warning. Earlier models had the yellow color painted on; many newer steps are designed to take yellow plastic inserts.
• Combplate impact sensors -- will stop the escalator if a foreign object gets caught between the steps and the combplate on either end.
• Handrail inlet sensors -- located at the bottom and top of the unit. These sensors guard the opening where the handrail enters and exits the escalator. If something gets caught between the handrail and the opening, a hard fault is generated in the controller and the escalator shuts down.
• Skirt brush -- a long continuous brush made of stiff bristles runs up the sides of the escalator just above the step level. This helps keep loose garments and curious hands away from the dangerous gap between the moving stairs and the side panel.
• Raised edges -- the sides of the steps are raised slightly to discourage standing too close to the edge.
• Flat steps -- the first two or three steps at either end of the escalator are flat, like a moving walkway. This gives the passenger extra time to orient him/herself when boarding, and more level time to maintain balance when exiting. Longer escalators, especially those used to enter a subterranean metro station, often have four or more flat steps.
• Antislide devices -- these are raised circular objects that often stud the escalator balustrade. They are sometimes informally called "hockey pucks" by their appearance. Their purpose is to prevent objects (and people) from precariously sliding down the otherwise smooth metallic surface.
• Emergency Stop button -- At each end of the escalator, a large red button can be pressed to stop the escalator. A transparent plastic guardplate (usually alarmed) often covers the button, to avoid that the button is pressed accidentally, or for fun by children and casual vandals. Restarting requires turning a key.
• Safety instructions -- posted on the balustrades at either end. Formerly, the only warning usually given was "PLEASE HOLD HANDRAIL" or some variation thereof (and, in models that used now-rare smooth step risers, had such a message right on the step face). Now, a series of instructions are given (see below).

Safety tips

While some escalator accidents are caused by a mechanical failure, most can be avoided by following some simple safety precautions.

• Hold the handrail.
• Use the elevator when transporting any large package or when pushing a device with wheels (moving sidewalks and ramps usually excepted - look for signs). This includes: baby strollers, baggage carts, hand trucks, or shopping carts. Also, the elevator should be used by someone with a walker or on crutches.
• Check for loose garments. These may include: long dresses, scarves, trench coats, or loose belts. Also, loose shoelaces are particularly notorious for getting caught in escalator machinery, so make sure that shoes are tied.
• Keep footwear away from the side panels - especially shoes with traction like sneakers.
• Children under the age of 7 should be accompanied by an adult when riding.
• Do not ride barefoot.
• Face forward.
• Carry dogs up or down (or use the elevator).
• Keep walking after exiting the escalator to prevent a pile-up.

Longest escalators and systems

A long escalator in the Washington Metro.

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 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 (745ft). In the Times Square shopping centre 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 single span uninterrupted escalator in the world is at the Wheaton station of the Washington Metro subway system. It is 155 m (508ft) long, and takes almost 3 and a half minutes to ascend or descend without walking. Four of the five longest escalators in the Western Hemisphere are in the Washington Metro system (the fifth is at Porter Square station in Boston) including what was formerly the longest escalator in the Western Hemisphere, located at the Bethesda station (475 ft), and also those at Woodley Park - Zoo (456 ft) and Medical Center (453 ft, or 138 m).

The metro systems in several cities in Eastern Europe (including St. Petersburg, Kiev and Prague) have Soviet-era escalators up to approximately 100 m (330ft) long. Those at the Náměstí Míru station in Prague were rebuilt to the same length in 1998–9 by ThyssenKrupp. The longest in the famously deep Moscow Metro is the Park Pobedy station. Opened in 2003, these escalators are 126 m long and take nearly three minutes to transit, making them the longest single-section escalators in Europe.

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 a Krofft-themed indoor amusement park that opened and closed in 1976, the escalator is now used for CNN studio tours.

Etymology

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.

See also

• Central-Mid-Levels escalator (Hong Kong)
• People mover
• Slidewalk
• Vermaport
• International Union of Elevator Constructors

External links

• The first Escalator in a London Store
• Moving Stairways/Escalators at www.theelevatormuseum.org
• The Elevator Escalator Safety Foundation
• Walkway propels Paris metro into future, a BBC article on the high-speed travelator at Gare Montparnasse station in Paris. (provided by CNIM)
• Briton dies in Rome station accident, BBC
• Man is strangled after clothing snags in MBTA escalator, news article about Francisco Portillo's death, with mention of other escalator accidents
• Escalator troubles rooted in Metro's original design
• Why does it take so long to mend an escalator?, London Review of Books