Low floor

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The passenger door of a low-floor tram.
The passenger door of a low-floor tram.
The passenger door of a high-floor tram.
The passenger door of a high-floor tram.

In public transportation, low-floor is a term describing vehicles such as buses, trolleybuses, and trams whose passenger compartment has a floor which is considerably lower than that of traditional models. A recent development in the transport industry, vehicles of this type have a stepless entry and usually have an area without seating (or seating that folds up) next to at least one of the doors where wheelchairs and perambulators can be parked. In addition to improving accessibility, low floors also allow fully-mobile passengers to board more quickly, and in some cases can produce improvements in overall speeds.

The low floor may extend over the complete length of the vehicle, or some parts may be higher with ramps or steps inside the passenger compartment to allow for under-floor components. If the vehicle is entirely low-floor, there is no place for bogies or even axles connecting corresponding left and right wheels (they would be at a higher level than the floor). This is solved with single-wheel drives, motors integrated into the wheels, and (in case of trams) short carbody sections, as the axleless design constrains bogie movement, which in turn affects the minimum radius of the curve that can be negotiated. Enthusiasts frequently see these designs as a step "backwards."

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Trams traditionally had high floors. From that model the tram with a low floor centre section has arisen. Examples of this are from Amsterdam 11g/12g-trams and the Kusttrams in Belgium. The most common construction on 100% low floor vehicles is one where is shorter carbody sections for the wheels and longer suspended sections. Examples of this are the Citadis and Combino. A similar, but somewhat older technique is one that has been developed by MAN and was in 1990, the first 100% low floor tram. These trams are found in ten German cities (such as Bremen and Munich) and in the Swedish city Norrköping. In many other German cities there are trams with low floor between the outer bogies and single axle bogies under the centre section. "Light rail" type frequently vehicles have a similar configuration but with the centre bogie which is designed to accommodate a low floor situated under a short centre section. A more radical approach has been adopted for the City Class LRV (Citytram), where the main low floor section is only 300mm above the rail. The low floor runs right through the articulation of both the 29m long and 38m Super Citytram version. In both the corridor across the articulation is wide enough for seated passengers and a wheelchair to pass through.The City Class has been design to turn on 15m radius curves and climb 10% gradients.

In bus and trolleybus design, a true low-floor is difficult, as most use heavy-duty truck-type chassis that sits high off the ground. Even when lowered, it is still several steps up into the main cabin. Many manufacturers simplify the job by making rear-engined rear-wheel-drive buses with independent front wheels so that no axle needed to pass under the cabin. Van Hool has a series of "side-engine rear-drive" buses that puts the engine off to one-side of the cabin longitudinally to maximize cabin usable space.

In buses and trolleybuses, low floors can be complemented by a hydraulic or pneumatic 'kneeling device', which can be used when the bus is not in motion, tilting it to one side and thus lowering it even further towards the surface level of the road, often low enough to match the height of a normal curb. Though such technology has been available and in use on high-floor buses since the 1970s, it is only of significant utility on low floor vehicles where it enables less-mobile passengers to board and leave the vehicle without help from others. Many vehicles are also equipped with wheel-chair lifts or ramps.

Although Low-floor trams and buses are currently being further developed and are already in use in various parts of the world, generally in urban areas, some systems, such as Manchester's Metrolink, chose to use high-floor trams with level boarding platforms (possibly because parts of the network use old railway stations) to achieve the same results as low-floor trams; this simplifies the design of the vehicles, but makes stations larger and more expensive, and is not well-suited for street-side stops.

Curitiba in Brazil uses high-floor buses stopping at "tube station" bus stops. Some transit agencies refuse to order low-floor buses altogether, such as New Jersey Transit and (until recently) MUNI owing to terrain conditions in the service area or MTA Long Island Bus or DART out of preferences of high-floor vehicles. Although New York City Transit runs some 40 foot low-floors, it refuses to order D60LF buses from New Flyer, opting for D60HF's (high floors), and is currently in a dispute with New Flyer regarding this.[citation needed]

See also: Railway platform height

To put things into perspective, here are some typical floor height for public transport vehicles, old and new:

  • Ultra Low Floor tram - 180 mm (7 inches)
  • Low-floor tram - 300mm to 350 mm (11.8 to 13.78 inches)
  • High-floor tram - more than 600 mm (23.62 inches)
  • Train - 800 mm (31.5") to 1200 mm (47.25") (even 51 in or 1351 mm in the case of standard North American passenger cars.)

This list is incomplete; you can help by expanding it.

A Gillig Low Floor bus, popularly known as the "Advantage"
A Gillig Low Floor bus, popularly known as the "Advantage"
A New Flyer D40LF bus in Richmond, British Columbia, Canada.
A New Flyer D40LF bus in Richmond, British Columbia, Canada.
The Orion VII is a low floor model, built for use with diesel, and alternative fuels, hybrid, and CNG (shown).
The Orion VII is a low floor model, built for use with diesel, and alternative fuels, hybrid, and CNG (shown).
An Orion VII bus operating in San Francisco
An Orion VII bus operating in San Francisco
An Orion VII 32-footer bus operating on its first day of service in San Francisco.
An Orion VII 32-footer bus operating on its first day of service in San Francisco.

100% low-floor tram by CroTram in Zagreb, Croatia
100% low-floor tram by CroTram in Zagreb, Croatia

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