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Monorails
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Monorail cars run on rubber tyres that either straddle a single rail girder or hang suspended from it. The monorail offers a number of advantages, such as: small footprint of structural components on ground; ability to negotiate relatively steep gradients and tight curves; high ride comfort; and no level crossings because track entirely elevated.
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Photo: Tokyo Monorail serving Haneda Airport
(Tokyo Monorail Co., Ltd)
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The Monorail—From Early Days to Present
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The monorail was invented much earlier than most people realize. The first record of a monorail was one patented in Britain in the 1820s, around the time the steam locomotive was first put to practical use. A motorized monorail line constructed in Ireland in 1888 carried passengers and freight over a distance of about 15 km and proved the feasibility of single-rail transport systems powered by an engine.
The suspended monorail was invented in Germany and put into operation in Wuppertal in 1901. By 1957, it was clear that the basic design of the Alweg (straddle-beam) monorail was safe and effective. This was also true for the Safege (suspended) monorail by 1960.
Japan first gave serious attention to the monorail when a suspended type was opened in 1958 in Tokyo's Ueno Park. One purpose of the project was to test monorail technology and determine how it could be used for urban transit.
During the 1960s, monorails were developed and built in different parts of the world. A number of Japanese companies developed their own systems, and this resulted in considerable variety in Japan. In the early days, monorails were considered suitable only for amusement parks, but this changed in 1964 when the Tokyo Monorail began running along the edge of Tokyo Bay between Hamamatsucho and Haneda Airport. It was constructed to serve as an urban transport system. Research continued into making the monorail more suitable for urban transport and the basic design was standardized by 1967.
The straddle-beam monorail became a composite type that borrowed from a number of designs, especially Alweg, Lockheed, and Toshiba. The suspended monorail also evolved with improvements to the Safege design. See Table 1 for further information on monorail construction in different countries.
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Table 1: World Monorails
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Straddle-beam Monorails
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Cars
Straddle-beam monorail cars have 2-axle bogies. The running wheels are rubber tyres filled with nitrogen. The bogie frame has two pairs of guide wheels on the upper side, while its lower side has one pair of stabilizing wheels. The electrical system is either 750 or 1500 Vdc.
Rail girders
Rail girders are generally made of prestressed concrete, although composite girders can be used when required. Supporting columns are generally T-shaped and made of reinforced concrete, but topographical or other conditions may dictate steel columns in the shape of a T or an inverted U. Figure 1 shows a typical example. At switches, the rail girder also serves as the turnout girder, with one end shifting to the other rail. The turnout girder is supported by a carriage that can be moved by an electric motor.
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Figure 1: Track Structure (prestressed concrete girders)
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Suspended Monorails
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Cars
Suspended monorail cars have 2-axle bogies. Each bogie has four air-filled rubber tyres for travelling and guidance. Auxiliary wheels are also provided for each wheel as a safety precaution in case a tyre loses air. The suspension system uses air springs. The suspension joins the bogies to the body, and is composed of suspension links, safety cableways, oil dampers and stoppers. The electrical system is 1500 V.
Rail girders
All rail girders are made of steel. Each standard girder is a 3-span continuous girder. The inside is hollow with the lower part slit open. The inside of the girder has travel and guidance beams, electrical wiring and signalling equipment.
Supporting columns are generally T-shaped, although topographical or other conditions may dictate an inverted-U shape or racket shape. The standard turnout is bidifferential. It is operated by a movable rail having both travel and guidance rails. The cross-section of the moveable rail forms an inverted-T shape.
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Technical Similarities Between Suspended and Straddle-beam Monorails
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Stations
Regardless of the monorail type, there are two common platform configurations—an island located between two guideways and two platforms on opposite sides of guideway(s). The chosen configuration depends on local conditions. Stations are generally located 300–1000 m apart. The distance depends on factors as such ridership, location, and connections with other transport systems.
Signalling and safety devices (ATC)
An on-board display indicates the permissible relative distance to the ahead train (the block section), and the permissible speed (which depends on guideway conditions). An Automatic Train Control (ATC) system also stops or slows the train when necessary.
Monorail tyres are rubber, so track circuits cannot be used to detect trains on the line. For this reason, signals indicating whether a train has entered or left a block are received at the trackside.
Centralized Traffic Control (CTC) devices
Centralized Traffic Control (CTC) is used to monitor traffic on all lines and control all signals and turnouts from a central location. The CTC equipment consists primarily of traffic boards, remote control consoles, television monitors showing operations, communications and alarm devices, other devices to transmit information, and peripheral equipment.
Automatic Train Operation (ATO) devices
Both types of monorail use automatic devices to ensure that all traffic follows uniform control standards and to provide a high level of safety and service.
See Table 2 for more detailed information on monorails in Japan.
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Table 2: Straddle-Beam Monorails in Japan
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Automated Guideway Transit Systems
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Automatic Guideway Transit (AGT) systems can be defined as medium-scale transport using small, lightweight rolling stock running on rubber tyres on a dedicated guideway that is usually elevated. Unmanned AGT trains are controlled by computer. A number of AGT systems have been developed worldwide, the main differences being in the guidance, switching and braking systems.
Some characteristics of Japanese AGTs are listed below:
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Hourly capacity between 2000 and 20,000 passengers bridging capacity of buses and conventional trains
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Maximum speed of 50–60 km/h
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60–70 seats per car
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4–6 cars per train |
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Computer-controlled headway
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Development history
Research and development of AGTs first began in the USA in the 1970s and resulted in practical applications in the same decade. These achievements were prompted by amendments in 1966 to the Urban Mass Transportation Act and by a number of debates and reports addressing urban transport problems. Transpo '72, an exposition held at Washington Dulles International Airport in 1972, introduced four new types of transportation systems and the featured AGT attracted interest from around the world. Later, AGT technology was introduced to a number of American cities. One example is AIRTRANS, serving Dallas/Fort Worth International Airport.
AGT systems are being developed in Europe as well, particularly in the UK, France and Germany. The French VAL is well known.
Japanese research into AGTs began in 1968 with development of the Computer Controlled Vehicle System (CVS) completed in 1976. Different manufacturers of rolling stock, steel, heavy industrial products, motor vehicles, signalling devices and other products were conducting individual or joint R&D in the field. As a result, quite a few different AGT systems were proposed and some were developed. However, most AGT systems in Japan today have 4 to 6 cars, with 60 to 70 seats per car. The first Japanese AGT urban transit system to enter service was the Port Liner opened in 1981 between Kobe and Osaka.
Japan's Ministry of Transport and Ministry of Construction established basic AGT specifications by 1983, and uniform technical standards were adopted.
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Photo: Kobe Port Liner running through city centre
(Kobe New Transit Co., Ltd.)
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AGT Structure
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Standard basic specifications
Minimum basic specifications have been established within a range that ensures future technical innovations will not be impeded. These specifications can be summed up as follows:
Basic concept:
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About 75 seats per car; unmanned operations
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Other basic specifications:
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Guidance: Lateral
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Switching: Mobile horizontal
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Electrical system: 750 V dc (in principal)
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Rolling stock clearance: Height, 3300 mm; width, 2400 mm
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Gross weight: Under 18 tonnes
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Track and bed clearance: Height, 3500 mm; width, 3000 mm
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Lateral guidance spacing: 2900 mm
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Design load (Axle load): 9 tonnes
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Rolling stock
Aluminium and fibre-reinforced plastic (FRP) are two common materials in carriage construction. The trains tyres are made of special rubber composites but auxiliary steel wheels ensure that the train can continue running for some distance if a rubber tyre fails.
Guidance and switching systems
Current specifications indicate that lateral and mobile horizontal guidance systems will become the future standard. Some previous guidance and switching systems include: a centrally-mounted beam guidance system; a central channel guidance system; a sink-and-float type switching system; a rotary switching system; and a horizontal rotary switching system. Figure 2 shows three guidance systems.
Automatic Train Operation (ATO) devices
Like the monorail, the AGT system can also use ATO devices. For more information on AGT systems in Japan, see Table 3.
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Figure 2: Guidance Systemsk
Table 3: Automated Guideway Transit (AGT) Systems in Japan
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Linear-Motor Subways
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The small size and relative light weight of the under-floor linear motor permits smaller carriages than conventional cars. Linear-motor subways have been developed because the smaller subway cars permit construction of networks using smaller cross-section tunnels, which greatly reduces construction costs, particularly in urban areas. Actually, cars with an even smaller cross-section could be manufactured to meet tunnelling constraints if there is no need to transport a large number of passengers.
Development history
In 1979, Japanese researchers began examining ways to reduce the cross-section of subway tunnels. Technical development began in this field in 1981 and R&D continued until 1987 with the aim of constructing a commercial linear-motor subway. By 1988, it was clear that linear-motor technology could be used on a commercial line. Soon after, the decision was made to construct linear-motor subways in Tokyo and Osaka. Tokyo's first linear-motor subway was opened as the Line No.12 (later called Oedo Line) between Hikarigaoka and Nerima in 1993, reached Shinjuku in 1997 and was then extended to Kokuritsu-kyogijo in April 2000. It became Tokyo's first loop subway on 12 December 2000. Figure 3 gives more information on the linear-motor subway in Osaka.
Structure of linear-motor subway
A linear-motor subway uses steel wheels and rails to support and guide the rolling stock. As a result, it enjoys the advantages of the track circuit control system and the linear motor propulsion system.
The linear motor permits construction of smaller tunnels and broadens the choice of where the line can be constructed because steering bogies can be used and because the non-adhesive propulsion permits use on steeper grades and sharper curves. This means that less land need be acquired to construct the line, reducing costs substantially. Some merits of this system are shown in Figure 4.
The following summarizes some of the major developments achieved in order to commercialize the linear motor subway.
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Cars with smaller cross-section dimensions
Vehicle floor height can be lowered to 700 mm by using smaller wheels and reducing the size of under-floor equipment. The result is a low-profile, lightweight car that can be used in tunnels with an internal diameter of just 4 m
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Able to negotiate tight curves
A bogie steering mechanism changes the axle angle, permitting cars to run smoothly on curves with a radius of only about 50 m.
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Able to run on steep gradients
The linear motor provides non-adhesive propulsion that does not rely on the friction between the steel rails and wheels so cars can climb steeper gradients. It can also be used as a braking system for safer operations.
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Low noise levels
The lighter cars generate less running noise and a bogie steering mechanism prevents wheel squeal on tighter curves.
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Other developments
The principle of the linear motor generates strong attractive and propulsive magnetic forces between the reaction plates on the track and the coils in the carriages. To overcome these forces, a new durable rail track was developed to attach the reaction plates to the sleepers. In addition, the motor (65-kW rated output) is mounted on the bogies using an innovative method of direct attachment and the system is controlled by a Variable Voltage Variable Frequency (VVVF) inverter. Safety is assured by four types of braking: service; emergency; security; and holding. Electrical wiring is routed to permit operation on tight curves.
Figure 5 compares the linear-motor subway with a conventional subway.
Safety evaluation
Construction of a commercial line could not have begun without determining whether the technology was sufficiently safe for a commercial railway system. Trial runs and tests were conducted to check the major safety factors as follows:
Unique features and performance of system
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Factors affecting car clearance and track clearance in small-section tunnels
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Separation of tracks; emergency procedures
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Performance on sharp curves—measures to prevent derailing at tight curves; bogie steering
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Performance on steep slopes—starting, acceleration and braking on relatively steep slopes
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New technology factors
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Linear motor technologies
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Steering bogies with small-diameter wheels
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Reaction plates—track structure, start-up strength, attachment to track
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Other factors
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Linear motor undercar clearance—flexibility of reaction plate and other components; dynamic gap change
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Safety of lighter cars
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Safety of non-adhesive linear propulsion systems
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Trial runs on the Osaka Nanko Test Track examined the above items and verified that the linear motor subway system was completely safe.
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Photo: TMG Oedo Line
(TMG)
Figure 3: Comparison of Osaka Linear Motor Subway (Nagahori Tsurumiryokuchi Line) and Conventional Osaka Subway Line
Figure 4: Linear Motor Subway
Figure 5: Linear Motor Subway
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Flexible Intelligent Transportation System
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The extensive system of expressways, shinkansen trains, and other advanced surface transport modes has dramatically boosted the Japanese economy, raised the standard of living and expanded travel opportunities. However, there are still serious problems, including road congestion in cities, rush-hour overcrowding on urban railways, widespread air pollution, etc.
To counter these problems, Japan has developed and constructed the various urban transit systems described in this article. Strides are also being taken in other areas, including more efficient buses and promotion of ‘park and ride’ systems. But these measures are still not enough to solve the problems.
As a result, some quite futuristic systems have been proposed in the last few years. They aim to combine the advantages offered by tracks—speed, large capacity and accurate scheduling—with the door-to-door convenience of the car. The last part of this article examines one proposal called the Flexible Intelligent Transportation System (FITS).
What is FITS?
Although they are not physically coupled, FITS vehicles run something like a train in a dedicated lane at high speed in single file (Figure 6). The FITS concept envisions an intelligent transportation system that is safe and reliable, can carry large volumes of passengers at high speed, and operates in accordance with demand. Passengers may transfer at points that correspond to today's stations, or may proceed without making a transfer to a place close to their destination. Such a system would offer flexibility and expanded choice.
The basic concept proposes a system that will:
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Span wide areas and increase mobility for all, especially the elderly
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Permit passengers to travel directly and easily to their destinations
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Be responsive with reasonable fares
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Complement existing local and inter-regional transport systems, ensuring mutually profitable operations
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Benefit local economies
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Have low construction, maintenance and management costs
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Be environment friendly
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Transport method
The envisioned dedicated lane will serve as a main line on which vehicles will operate at high speed in single file, much like a train, but at a fixed distance from each other. At nodes (stations), some vehicles may leave the file and enter an expressway or ordinary road to carry passengers to their destinations like a bus serving a local route. Capacity will be from 8000 to 14,000 people per hour, one way, with a service every 3 minutes.
Vehicles
As presently envisioned, a gasoline engine will drive a generator to store electricity in batteries. This electricity will power the vehicle's two electric motors. The low-floor vehicle will follow a dedicated lane marked by magnetic pins. Sensors on the vehicle will detect the magnetic pins to control the steering. Switching the polarity of the magnetic lane markers will permit control of vehicles leaving and entering the dedicated lane. The distance between vehicles will be controlled by a front radar and vehicle interval control system that can apply the brakes when necessary. At high speeds, the distance between vehicles will be about 15 m. Figure 7 shows a diagram of the vehicle and the proposed specifications.
Lane structure
A single row of columns will bear the lane girders at a height of 5 m. The proposed concrete or asphalt road will have a width of 7.5 m and the construction methods will take durability, maintenance, and cost effectiveness into consideration. The vehicle wheels will be strengthened with steel fibers or other materials. There will be no need for special electrical or signalling equipment, nor for a vehicle shed. Figure 8 shows some more details.
The future
Once FITS is operational, it could spread to many areas; it offers great promise not only for conventional transport industries but also for new types of industry. The Society for New Transportation Systems is presently examining various issues with a view to promoting FITS.
The Japanese government has restructured its ministries and agencies this year. The Ministry of Land, Infrastructure and Transport has jurisdiction over all land, sea and air transport. Hopefully, this new administrative environment will make it easier to develop systems (like FITS) that exploit the advantages of both road and rail, and to propose, develop and construct new transportation systems based on new technologies.
With new technology, the transport sector can help society serve aging populations, combat global pollution, and develop even better lifestyles for all
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Figure 6: Illustration of FITS
Figure 7: FITS Specifications
Figure 8: FITS Infrastructure Concept
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