A monorail is a transportation system based on a single beam. The term is also used variously to describe the beam of the system, or the vehicles travelling on such a beam or track. The term originates from the contraction of the words mono (single) and rail, from as early as 1897, as early systems used metal rails. The transportation system is often referred to as a railway.
Differentiation from other transport systems
Monorail systems have found shared applications in the transportation market in airport transfer and some medium capacity
metro systems. To differentiate monorail systems from other transport modes, the Monorail Society further clarifies the definition of a monorail such that the beam in a monorail system is narrower than the vehicle.
Monorails are often but not exclusively elevated, sometimes leading to confusion with other elevated systems such as the Docklands Light Railway
, Vancouver SkyTrain
and the JFK AirTrain
. Monorail vehicles are often at first glance similar to other light rail
vehicles, and can be both manned and unmanned. Monorail vehicles can also be found in singular rigid format, articulated single units, or as multiple units coupled into 'trains'. In common with other advanced rapid transit
systems, some monorails are driven by linear induction motor
. In common with other dual rail systems, the vehicle bodies are connected to the beam via bogies
, allowing curves to be negotiated.
Unlike some trams
and light rail
systems, modern monorails are always partitioned from other traffic and pedestrians. Monorails are both guided and supported via interaction with the same single beam, in contrast to other guided systems such as Rubber-tyred metros
, such as the Sapporo Municipal Subway
; or guided buses
or trams, such as Translohr
. Monorails also do not use pantographs
Under the Monorail Society beam width criteria, some but not all maglev
systems are considered monorails, such as the Transrapid
. Maglevs differ from all other monorail systems in that they do not (normally) physically contact the beam.
Attempts at creating monorail alternatives to conventional railways
have been made since the latter part of the 19th century. Early designs centred on use of a double-flanged
single metal rail alternative to the double rail of conventional railways. Wheels on this rail would both guide and support the monorail car. A surviving suspended version is the Wuppertal monorail
. Into the 1900s, Gyro monorails
, with cars gyroscopically balanced on top of a single rail, were tested but never developed beyond the prototype stage. The Ewing System
, used in the Patiala State Monorail Trainways
, relies on a hybrid model with a load-bearing single rail and an external wheel for balance. One of the first systems put into practical use was that of French engineer Charles Lartigue, who built a monorail line between Ballybunion and Listowel
in Ireland, which was opened in 1888 and closed in 1924 (due to damage from Ireland's Civil War). The Lartigue system uses a load-bering single rail and two lower, external rails for balance, the three carried on triangular supports.
The first half of the 20th century saw many further proposed designs, that either never left the drawing board or remained as short lived prototypes.
In the latter half of the 20th century, monorail designs had settled on using larger beam or girder based track, with vehicles supported by one set of wheels and guided by another. These designs featured vehicles supported, suspended or cantilevered from the beams. In the 1950s the ALWEG
straddle design emerged, followed by an updated suspended type, the SAFEGE
During this period, major monorails were installed at Disneyland, California, Seattle, and Japan. Monorail systems were also heavily promoted as futuristic technology with exhibition installations and amusement park purchases, as seen by the number of legacy systems in use today. However, monorails gained little foothold compared to conventional transport systems.
Niche private enterprise uses for monorails emerged, with the emergence of air travel and shopping malls, with many shuttle type systems being built.
Perceptions of monorail as public transport
From 1950 to 1980 the monorail concept may have suffered, as with all public transport systems, from competition with the automobile
. Monorails in particular may have suffered from the reluctance of public transit authorities to invest in the perceived high cost of un-proven monorails when faced with cheaper mature alternatives. There were also many competing monorail technologies, splitting their case further.
This high cost perception was challenged most-notably in 1963, when the ALWEG consortium proposed to finance the construction of a major monorail system in Los Angeles, in return for the right of operation. This was turned down by the city authorities in favour of no system at all, and the later subway system has faced criticism as it has yet to reach the scale of the proposed monorail.
Several monorails initially conceived as transport systems survive today on revenues generated from tourism usage, benefitting from the unique views offered from the largely elevated monorail installations.
From the 1980s onwards, with the rise of traffic congestion and urbanization, monorails have experienced a resurgence in interest for mass transit usage, notable from the early use by Japan
and now Malaysia
. Monorails have also seen continuing use in niche shuttle markets, as well as amusement parks.
Modern mass transit monorail systems have settled on developments of the ALWEG beam and tyre approach, with only two suspended types in large use. Some systems have also settled on maglev technology.
Types and technical aspects
Modern monorails depend on a large solid beam as the vehicles' running surface. There are a number of competing designs divided into two broad classes, straddle-beam and suspended monorails.
The most common type of monorail in use today is the straddle-beam monorail, in which the train straddles a reinforced concrete beam in the range of two to three feet (~0.6-0.9 m) wide. A rubber-tired carriage contacts the beam on the top and both sides for traction and to stabilize the vehicle. The straddle-beam style was popularized by the German company ALWEG.
There is also a form of suspended monorail developed by the French company SAFEGE in which the train cars are suspended beneath the wheel carriage. In this design the carriage wheels ride inside the single beam. The Chiba Urban Monorail is presently the world's largest suspended monorail network.
Almost all modern monorails are powered by electric motors
fed by dual third rails
, contact wires or electrified channels attached to or enclosed in their guidance beams. There is a startup called Metrail
that has built a hybrid prototype using diesel power to generate electricity for the motors.
Magnetic levitation train (maglev) systems by the German Transrapid were built as straddle-type monorails, as they are highly stable and allow rapid deceleration from great speed. When in full-speed operation maglev trains hover over the track and are thus not in physical contact with it. The maglev is the fastest train of any type, the experimental JR-Maglev having recorded a speed of 581 km/h (361 mph). The commercial Shanghai Maglev Train has run at 501 km/h (311 mph).
In addition, Linimo was inaugurated in Japan in 2003.
UniModal has patented the SkyTran "pod monorail" which would use an Inductrack passive maglev monorail track for personal rapid transit. The system remains in the conceptual stage.
Some early monorail systems--notably the suspended monorail of Wuppertal
), dating from 1901 and still in operation--have a design that makes it difficult to switch from one line to another. Some other monorail systems avoid switching as much as possible, by operating in a continuous loop or between two fixed stations, as in Seattle, Washington
Current operating monorails are capable of more efficient switching than in the past. In the case of suspended monorails, switching may be accomplished by moving flanges inside the beamway to shift trains to one line or another.
Straddle-beam monorails require that the beam structure itself be moved to accomplish switching, which originally was an almost prohibitively ponderous procedure. Now, however, the most common way of achieving this is to place a moving apparatus on top of a sturdy platform capable of bearing the weight of vehicles, beams and its own mechanism. Multiple-segmented beams move into place on rollers to smoothly align one beam with another to send the train in its desired direction, with the design originally developed by ALWEG capable of completing a switch in 12 seconds. Some of these beam turnouts are quite elaborate, capable of switching between several beams or even simulating a railroad double-crossover.
In cases where it must be possible to move a monorail train from one beam to any of a number of other beams, as in storage or repair shops, a traveling beam not unlike a railroad transfer table may be employed. A single beam, at least long enough to carry a single monorail vehicle, is aligned at an entry beam to be mounted by the monorail cars. The entire beam then rolls with the vehicle to align with the desired storage beam.
Advantages and disadvantages
- The primary advantage of monorails over conventional rail systems is that they require minimal space, both horizontally and vertically. Monorail vehicles are wider than the beam, and monorail systems are commonly elevated, requiring only a minimal footprint for support pillars.
- A monorail track is usually less expensive to build than a comparable elevated conventional rail line of equal capacity.
- Due to a smaller footprint they are seen as more attractive than conventional elevated rail lines and block only a minimal amount of sky.
- Monorail is, by design, a grade-separated system. They do not interfere with existing transport modes.
- They are quieter, as modern monorails use rubber wheels on a concrete track (though some non-monorail subway systems, like certain lines of the Paris Métro and all of the Montreal metro, use the same technique and are equally quiet)
- Unlike conventional rail systems, straddle monorails wrap around their track and are thus not physically capable of derailing, unless the track itself suffers a catastrophic failure.
- Rubber-tired monorails can climb steeper grades better than ordinary steel wheel trains, with Hitachi monorails designed to cope with 6% grade.
- Monorail vehicles are not compatible with any other type of rail infrastructure, which makes (for example) through services onto mainline tracks impossible.
- Monorail tracks do not allow at-grade intersections.
- In an emergency, passengers may not be able to immediately exit because the monorail vehicle is high above ground and not all systems have emergency walkways. The passengers must sometimes wait until a rescue train, fire engine or a cherry picker comes to the rescue. Newer monorail systems resolve this by building emergency walkways alongside the entire track, at the expense of visual intrusion. Suspended railways resolve this by building aircraft style evacuation slides into the vehicles. Japanese systems use the next train to tow broken down trains to the next station, but this has yet to occur .
- Turnouts, especially high speed ones tend to be difficult. Traversers might be substituted.
- Monorail infrastructure and vehicles are often made by separate manufacturers, with different manufacturers using incompatible designs.
: List of monorail systems
Monorails in general
Monorail advocacy groups
- 2045 Seattle - a grassroots movement that supports the construction of rapid transit monorail in Seattle, WA
- Austin Monorail Project - a non-profit advocating monorail transit for Austin, TX
- The Monorail Society - an all-volunteer organization founded to foster more awareness and promote this unique method of transportation
Organizations/views opposing monorails