Articulated bus

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Articulated buses, also known as tandem buses, bendy buses, slinky buses or accordion buses in the UK and US, are buses of a type with an increased passenger capacity. Found almost exclusively in public transportation use, these buses are approximately 18 m (60 ft) long, while regular buses are 11 to 14 m (35-45 ft) long. To make them nimble enough to safely navigate streets at their increased length, they are fitted with an extra axle (set of wheels) and a joint usually located slightly behind the midpoint of the bus, behind the second axle. Some models of articulated buses have a steering arrangement on the rearmost axle which turns slightly in opposition to the front steering axle, which allows the vehicle to negotiate turns in a somewhat crab-like fashion, an arrangement similar to that used on long hook-and-ladder fire trucks operating in city environments.^[1]

Some buses have two joints, and these are called bi-articulated. Their capacity is around 200 and their length about 25 m (82 ft). These are exotic and usually run in separate and often auto-guided lanes (quasi-trams or bus rapid transit).

Contents 1 Advantages and disadvantages 2 Use 3 Types of buses 3.1 Bi-articulated buses 3.2 Double-decker articulated buses 4 References 5 External links

[edit] Advantages and disadvantages

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It has been suggested that this section be split into a new article entitled London articulated bus controversy. (Discuss)

The main benefits of an articulated bus over the double-decker bus are increased stability from a lower centre of gravity, lower roadwheel pressure, higher maximum speed, and accessibility to people with disabilities and the elderly. Accordion buses can be used in some cities with a tram network, while double-deckers sometimes cannot fit under the overhead electric cable; however, there are other cities, such as Berlin, Croydon in London, and Singapore, where double-deckers and trams coexist in some areas, and Hong Kong, where the trams are also double deckers. Accordion buses are more suitable for mass transit purposes, because they have more doors (usually three dual-lane and one single-lane door or four duals on European articulated buses) for rapid exchange of passengers.

Articulated buses also have an accessibility advantage over double-decker buses: people in wheelchairs, with baby buggies, or who are otherwise unable to climb stairs can access the whole bus, and are not limited to only a downstairs deck.

One disadvantage that appears in an articulated bus is the effective power available to it. It is common for articulated buses to use the same engine as non-articulated buses; this leads to a slower speed and acceleration, due to an increase of weight. When used in cities with many slopes (e.g. Vancouver, B.C. or San Francisco, California) the vehicle is prone to overheating, leading to stalling in the milder case and a fully fledged fire in the worst case. During 2004 in the early stages of deployment of articulated buses in London, England, there were several fires on the new Mercedes-Benz Citaro buses, which required the temporary withdrawal and modification of the entire fleet.^[2]

In London, another disadvantage to the introduction of these buses is increased fare evasion. Articulated buses in London have three separate entrances, and passengers are expected to pay for their journey in advance. Passengers can do this by validating a pre-paid card called 'Oyster', or by using pre-purchased tickets. Since the introduction of this bus type, many people opt to evade their fare by choosing not to pay for their journey. Passengers simply board the bus via the middle or rear doors. This increase in fare evasion has resulted in Transport for London recruiting an extra 150 Revenue Protection Inspectors, to police revenue collection on the bus network.

A further disadvantage in cities with older road layouts comes with difficulties caused by the length of articulated buses, and the turning radius they require in order to negotiate corners. In London, many roads in even central areas lack sufficient lane width and space, and this had led to difficulties in some areas with articulated buses blocking junctions when at bus stops, or having difficulty turning at tight intersections. Some London bus stops have had to be relocated and routes rerouted to accommodate the conversion to articulated buses.

London's articulated buses are accused by some of causing more collisions with cyclists in that city. Boris Johnson, Conservative Party candidate for Mayor of London has said that his first act as mayor of London will be to scrap bendy buses and replace them with a 'modern-day Routemaster' with an open rear platform and a conductor, describing the articulated buses as 'cyclist killing'.^[3] The incumbent, Ken Livingstone, described Mr Johnson's accusations that the articulated buses represent an extraordinary danger to cyclists as 'wicked fibs', and said that no London cyclist had ever been killed by an articulated bus.^[4] Statistics published by Transport for London show that the articulated buses have twice as many collisions per mile than other buses, but they say that the figures do not represent a 'like for like' comparison.^[5]

[edit] Use

Articulated buses have been used in most European countries for many years. Until 1980, however, they were considered illegal on British roads. Experiments by South Yorkshire PTE with buses by MAN and Leyland-DAB during 1979 led to the change, but the experiment was abandoned in 1981. Double-decker buses were generally considered less expensive to purchase and operate. The cost of the strengthened deck framing and staircase was more than offset by the added weight of the additional axle(s) and coupling mechanism of an articulated bus. Modern technology has reduced the weight issues, and the benefits of a continuous low floor allowing easier access and additional entrance doors for smoother loading have seen a reconsideration of the use of articulated buses. Notably in London, they, with their double-decker counterparts, have replaced AEC Routemasters on most routes. Elsewhere in the UK they are generally operated on specific routes to bolster patronage rather than on entire networks.

Articulated buses became popular in mainland Europe as a means of increasing capacity, In many cities lower railway bridge clearances have precluded the use of double deck vehicles and they have never gained great popularity there. Overhead wires for trams. trolleybuses etc. are not really relevant as the minimum normal clearance above road level is standard across the EU and is well clear of a double deck vehicle (otherwise many goods vehicles would have severe problems).

The recent popularity of articulated buses in the UK is because any double deck vehicle must be full seated upstairs. This limits the capacity to around 80 - 90 depending on the seating layout downstairs. An articulated single deck vehicle can be mainly of 'standee' configuration with a much lower percentage of people seated than a double deck vehicle. This however gives it a much higher capacity (120 - 140) for an 18 metre vehicle. With the same one driver, this should notionally reduce the cost per passenger kilometre, although their multi door design does present very real challenges in ensuring that all revenue is actually collected due to passengers in London entering through all three doors. The vehicles are also more expensive to buy and maintain and use more fuel than conventional double deck buses so it may be some time before the true economics of their operation can be assessed.

In Israel, the use of articulated buses—commonly called long buses—is widespread, particularly in Gush Dan and Jerusalem, the two great urban centers of the country. The long buses are considered reliable and useful and they served in Israel since the mid-seventies. During the Israeli-Palestinian conflict, such buses were often targeted by Palestinian terrorists and suicide bombers during rush hours, since a crowded long bus can contain more than 100 passengers. Due to the al-Aqsa Intifada wave of mass bombings, security measures were enforced and today many long buses in Israel are accompanied by a security guard.

An articulated bus is a long vehicle and usually requires a specially trained driver, as maneuvering (particularly reversing) can be difficult. Articulated electric trolleybuses can be difficult to control with engines having momentary peak power in excess of 500 kW (800 hp). The trailer section of a "puller" bus can be subject to unusual centripetal forces, which can be a discomfort for many people although this is not an issue in "pushers." Nonetheless the articulated bus is a total success in Budapest, Hungary, where the BKV city transit company has been running more than one thousand of them every single day since the early 1970s. The Hungarian company Volan also runs hundreds of articulated buses on intercity lines. They are common fare in the US urban centres such as Boston, Chicago, Columbus, Los Angeles, New York City, Orange County, California, Philadelphia, the Quad Cities, San Francisco, Seattle, and Washington, DC. In Canada they are used in Vancouver, Ottawa, Edmonton, Halifax, suburban Montreal, and Mississauga, although Mississauga Transit intends to replace them with single units running more frequently. In Asia, many major Chinese cities had fleets of articulated buses prior to the late 1990s. Many of these fleets have since been replaced by single section units, with the exception of a few cities, namely Beijing.

In Adelaide, Australia, articulated buses are used on the O-Bahn guided busway. The first Articulated buses to use it were the Mercedes Benz O305G buses, however three MAN SG280H buses are also fitted for O-Bahn use. Trouble has been encountered in recent years trying to find suitable low-floor articulated buses as replacements for the 1984-built Mercedes buses. Unfortunately the design of the O-Bahn track prohibits most modern type of articulated bus.

[edit] Types of buses

Articulated buses can be of pusher or puller configuration.^[1] In pusher buses only the rear C-axle is powered by a rear-mounted engine and the longitudinal stability of the vehicle is maintained by active hydraulics mounted under the turntable. This modern system makes it possible to build entire length low-floor buses without any steps, which simplifies access for passengers with limited mobility. In puller articulated buses, the engine is mounted under the floor between the front and middle A- and B-axles, and only the B-axle is powered. This is an outdated design, which prohibits floor levels lower than approximately 750 mm (30 in) and causes passengers discomfort due to high noise and vibration levels. On the other hand, the puller bus is cheaper to make and can be used in very narrow or severely pot-holed streets. Also, modern, low-floor pusher articulated buses usually suffer from suspension problems, because their wheels lack ample travel to absorb street unevenness, leading to passenger discomfort and relatively rapid disintegration of the superstructure. During late 2003, early 2004, a series of onboard fires on newly delivered Mercedes-Benz Citaros led to Londoners humorously nicknaming the vehicles chariots of fire. Mercedes-Benz quickly addressed the problem, although the vehicles were out of service for a period.^[2]

Although the majority of bendy buses are diesel powered, a number of operators (primarily outside of North America and by LACMTA) are adopting compressed natural gas power to reduce pollution. Many other transit authorities in the United States and Canada are adopting bendy buses that are diesel-electric hybrids such as the New Flyer DE60LF.

A typical puller model is the Ikarus 280, the articulated version of the Ikarus 260, from Hungary, with more than 200,000 buses manufactured between 1973 and 2000, mostly for Soviet bloc customers. Well-known makers of pusher-type articulated buses include Mercedes-Benz, New Flyer Industries, and Scania. In the past, Volvo and MAN produced puller bendies but both manufacturers have since abandoned these designs for more modern pusher designs. The Renault PR 180 and PR 180.2 (articulated versions of the PR 100 and PR 100.2) were a special variation of the pusher design where both the B-axle and C-axle were driven, with a driveshaft passing through the turntable between the two driving axles. There are very few companies that specialize in manufacturing the articulated section for the buses. One company that does is ATG Autotechnik GmbH in Siek near Hamburg.

[edit] Bi-articulated buses

The first city in the world to use the bi-articulated bus is Curitiba, Brazil. They began in 1992 with buses, manufactured by Volvo chassis and Marcopolo body, can carry 270 passengers. Each bi-articulated bus is constructed with five doors where passengers can quickly load and unload. These buses (along with other bus routes in Curitiba) were the first to stop on tube stations. These stations allow passengers to pre-pay the fare and enter the vehicle at level, allowing Curitiba's bus system to be a much more affordable solution compared to subway. Curitiba has over 170 bi-articulated buses circulating the city along five major structural axis of dedicated bus lanes. These buses run on an average frequency of fifty seconds during peak hours.

The Brazilian bus body manufacturer Marcopolo and CAIO have made many bi-articulated buses on top of Volvo chassis. They are currently used in São Paulo (without air conditioning) and Curitiba (with air conditioning). Those buses, called Top Bus by Induscar, were nicknamed metrô sobre pneus (metro over tires) in Curitiba, and Martão (Big Marta) in São Paulo, referencing the mayor, Marta Suplicy, whose public transport program, Interligado, included those buses.

Volvo have made a few bi-articulated buses running in Gothenburg. They are based on their pusher articulated low-floor bus model with the engine mounted on the floor on the side of the bus, and the cooling system on the roof.

The Belgian manufacturer Van Hool offers a 25 m (82 ft) bi-articulated bus with a capacity of about 180 passengers. In September 2002, fifteen were deployed on lines 11 and 12 in the Dutch city of Utrecht, connecting the downtown railway station to office, college and university buildings at the edge of the city.^[6] More have been added since. These buses are also used in the German cities of Hamburg (Metrobus 5) and Aachen (lines 5 and 45), where single articulated buses alone were not able to handle the huge number of passengers per day.

The French manufacturers Renault and Heuliez developed the "Mégabus" (officially the Heuliez GX237), a bi-articulated high-floor bus, in the late 1980s. The demonstrator Mégabus visited transit agencies throughout France, but the only city to order them was Bordeaux (for an order of 10 buses, built in 1989.) These buses, now retired, operated Bordeaux's heavily-used bus route 7 until the city's tramway was built in 2004 over the previous route of the Mégabuses. [1]

The Chinese manufacturer Zhejiang Youngman (Jinhua Neoplan) has developed the 25-meter JNP6280G bi-articulated bus, deemed the "world's largest", with assistance from Neoplan. These buses will be put into service on Beijing and Hangzhou's Bus Rapid Transit lines. [2]

[edit] Double-decker articulated buses

A few attempts have been made to create a double-decker articulated bus. Neoplan built a handful of Jumbocruisers between 1975 and 1992. In these models, it is only possible to move between the two parts via the upper deck, so they have separate doors and two sets of stairs.

[edit] References

[edit] External links

• Steering Considerations & Engine Placements

Types of buses
Articulated bus – Double-decker bus - Dual-mode bus – Guided bus – Gyrobus – Low-floor bus – Midibus – Minibus Motorcoach – Party bus – School bus - Transit bus – Trolleybus

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