A double decker is a bus, airplane, train, tram, or ferry that has two levels for passengers, one deck above the other.
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4 Cable Car (Aerial Tramway)
Double-decker buses are almost twice as tall as other buses. Most famous is the Routemaster used in London. Most of the buses in Hong Kong are double deckers.
The most popular double deck airplane is the Boeing 747, although the top deck is smaller than the lower level. The new Airbus A380, however, has two decks extending the full length of the airplane.
Because of the standard height of tunnels and overhead power wires, many double-decker trains set the bottom deck lower down between the bogies. At the entrance platforms of the train there is just a single deck, above the bogies. From there one can go upstairs or downstairs. For example, for the DD-IRM (see below) it is one step up from the station platform to the entrance platform, and from there 7 steps up or 4 steps down.
France runs double-decker cars on highly loaded high-speed TGV lines and commuter lines such as the Paris suburban RER.
Other double-decker railcars do not have a full upper deck but on the left and on the right a gallery, each with a row of single seats. An example are the bilevel cars provided and leased in the U.S. by Midwest Transportation & Development Corporation of Chicago. They are of a design, proven in service and steadily refined, since their initial introduction in the 1950s. (Midwest Transportation & Development's website is ). These cars, known as "bilevel gallery cars", are among the most successful designs ever developed in the U.S. and are currently in daily use in Chicago, San Francisco and Montreal, Canada. They provide high capacity (155 to 169 passengers each) and use standard, off-the-shelf components, without relying on proprietary, expensive and hard to get replacement parts. Chicago's commuter rail system Metra is currently receiving new versions of these cars and the San Francisco area commuter rail authority, known as CalTrain, has recently overhauled its fleet of bilevel gallery cars.
Another advantage of bilevel gallery cars is the relatively low first step of the vestibule entrance to the car, which is 14 5/8 inches above the head of the rail. The advantage of this design feature is that commuter rail operators do not have to unnecessarily spend scarce funds on building high level platforms; rather, a low level platform is all that is necessary, at a far lower cost.
Other designs include rolling stock made by Colorado Railcar Manufacturing, house the entrance on the lower deck rather than an intermediate level. The Amtrak Superliners are also double-decker trains of this variety, housing the entrance about a step or so up from the (generally low) platform of the railroad stations, and allowing passage from car to car through the upper corridors of the train. (Colorado Railcar Manufacturing, responsible for constructing the Princess cars on the Alaska Railroad, can be located online at .
In some countries such as the United Kingdom, the railway system cannot accommodate double decker trains because the loading gauge is too small (i.e. bridges, tunnels, etc. are too low). An intermediate form of two-level seating arrangement has been tried in Britain, where the bottoms of the upper seats are above the heads of the people on the lower level, but the feet of the people above are not, see .
Double decker trains often have curved windows upstairs. In the evening and in tunnels children love this for the distorting mirror effect.
In the Netherlands, there are two types of double decker trains, the DDM and the DD-IRM, also called Regiorunner, see Trains in the Netherlands.
Cable Car (Aerial Tramway)
The double decker Vanoise Express cable car carries 200 people in each cabin at a height of 380 metres (1250 feet) over the Ponturin gorge - see aerial tramway
There are also double-decker trams. Hong Kong Tramways is the only tram company that operates exclusively double-decker trams.
They are also in some places, aimed at tourists, e.g. in summer only, e.g in Blackpool and the Isle of Man.
See also: transport.