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18 In this chapter the basic APM system is described from a com- ponent or subsystem level and from a system-configuration level. The APM components are then described in more detail in terms of the current state of the art and potential improve- ments for the different components. 4.1 APM Systems and Their Components APM systems are fully automated and driverless transit sys- tems that operate on fixed guideways in exclusive rights of way. APMs can include technologies that are also called automated guideway transit (AGT) and, when fully automated, monorails and low-speed magnetic levitation (maglev) systems. The main differences between APM systems and other transit technolo- gies are that APMs are driverless and that the vehicles are not subject to roadway-based congestion and interference. While APMs are most commonly found at airports, there are an increasing number of urban APMs and some metro systems that are fully or partially automated. An APM system is a combination of interrelated subsystems and components designed to operate as a cohesive entity that provides safe, reliable, and efficient passenger transport. APM systems are proprietary in nature and are typically not inter- changeable. This means that a system must be procured in its entirety from one supplier rather than implemented from a blend of several suppliersâ products. Thus APM system equip- ment is typically procured using a design-build (DB) or design- build-operate-maintain (DBOM) approach. At airports, the APM facilities are usually procured as separate design-bid-build (DBB) projects, although sometimes a partial or full system- facility DB or DBOM approach is used. This is discussed fur- ther in Chapter 10. An APM system consists of the operating system and fixed facilities. The operating system consists of the proprietary subsystem equipment essential to the APM system operation. Facilities are the buildings, rooms, and guideway that house or physically support the operating system equipment. There are six main components to an APM system, each with its own system and facility aspects: 1. Vehicles; 2. Guideway; 3. Propulsion and system power; 4. Command, control, and communications; 5. Stations; and 6. Maintenance and storage facility. VehiclesâAPM vehicles are fully automated, driverless, either self-propelled or cable-propelled, reliable, and provide a high degree of passenger comfort and safety. Vehicle speed, capacity, and maximum train length are dependent on the type of technology selected and the system configuration. Typical 40-ft-long APM vehicles generally carry between 50 and 75 passengers, depend- ing on passenger types and their baggage characteristics. GuidewayâThe guideway of the APM system refers to the track or other running surface (including supporting structure) that supports, contains, and physically guides APM vehicles designed to travel exclusively on it. The guideway structure itself is part of the system facilities that may be provided by the APM supplier. The guideway can be constructed at ground level (at grade), elevated (above grade), or below grade in a tunnel. Propulsion and system powerâElectric power is required to propel vehicles and energize system equipment. APM vehicles are electrically powered by either direct current (DC) or alternating current (AC) provided by a power distribution subsystem. Vehicle propulsion may be pro- vided by DC rotary motors, AC rotary motors, or AC linear induction motors (LIM), or via attached cables. Self-propelled APM vehicles are electrically powered by onboard motors using either 750 or 1500 volt DC or 480 or 600 volt AC, distributed along the guideway by a way- C H A P T E R 4 APM System Characteristics
maintenance and storage, as well as administrative offices. Items housed in the MSF include maintenance equip- ment, tools, machinery, recovery vehicle, equipment for train control and power within the MSF, and any other equipment/systems associated with maintaining (and possibly storing) the APM vehicles. Functions performed within the MSF include maintenance of vehicles and other subsystem equipment, vehicle cleaning/ washing, and storage of parts, tools, and spare equipment. 4.2 APM System Configurations This section describes overall APM system characteristics, including APM system guideway alignment and APM plat- form configurations. There are also several distinctive physical and operational characteristics of APM systems that define a systemâs alignment configuration. The physical characteristics are used to determine the best configuration to suit a particu- lar application in an airport environment. The different system alignment configurations include: â¢ Single-lane shuttle, â¢ Single-lane shuttle with bypass, â¢ Dual-lane shuttle, â¢ Dual-lane shuttle with bypass, â¢ Single Loop, â¢ Double loop, and â¢ Pinched loop. 4.2.1 Shuttle System Configurations Shuttle systems are the most basic APM configuration. Fig- ure 4.2-1 illustrates four basic types of two-station APM shuttle system configurations. 19 Source: Lea+Elliott, Inc. APM Central Control Facility Single-Lane Shuttle Single-Lane Shuttle Dual-Lane Shuttle Dual-Lane Shuttle with Bypass with Bypass Source: Lea+Elliott, Inc. Figure 4.2-1. Shuttle systems. side, rail-based power distribution subsystem. Cable- propelled vehicles are pulled by an attached cable that is driven from a fixed electrical motor drive unit located along the guideway, usually at one end of the system. Cable-propelled vehicle housekeeping power (lights, elec- tronics, HVAC, etc.) is usually provided by a 480 volt AC wayside power rail subsystem. Command, control, and communicationsâAll APM systems include command, control, and communi- cations equipment needed to operate the driverless vehicles. StationsâStations are located along the guideway to allow passenger access to the APM system. The station equip- ment typically includes automatic station platform edge doors and dynamic passenger information signs. The sta- tions also have APM equipment rooms to house com- mand, control, and communications equipment and other APM equipment. Maintenance and storage facilityâThe maintenance and storage facility (MSF) provides a location for all vehicle
Single-Lane Shuttle A single train shuttles back and forth between two endpoints on a single guideway. Two stations are most common, but additional stations can be accommodated. This simple shuttle is best suited to transporting passengers between two points in a low-demand environment. Because a single point failure along the guideway will shut down the single-lane shuttle, this configuration should only be used where passengers have the alternative of walking or where a standby means of conveyance is available. Single-Lane Shuttle with Bypass Two synchronized trains pass each other in the bypass area of the guideway. Because each train can be independently pro- pelled, there is the potential for a degree of redundancy and failure management capability. A third station can be added in the bypass area. Single lane shuttles with bypass are limited to two trains. This configuration is slightly more complex opera- tionally than the single-lane shuttle because the trains must be synchronized to avoid delays at the bypass. This configuration has a role in relatively low-demand situations to transport pas- sengers between two points. Dual-Lane Shuttle Two trains shuttle back and forth independently in a syn- chronized manner on separate guideways. During non-peak times this configuration can be operated as a single-lane shut- tle to allow for maintenance on the other lane/train, or in an on-call mode, like elevators. Two stations are most common, but additional stations can be accommodated. Dual-lane shuttles provide both vehicle and wayside redundancy for good failure management and are limited to two trains. This configuration serves higher demand levels than the single- lane shuttles for passengers traveling between two points. To provide APM system configurations in the context of the dif- ferent APM components, Figure 4.2-2 shows the plan view of a two-station, self-propelled APM shuttle above a profile view of the same shuttle configuration. A cable-propelled APM shuttle is similar in configuration to a self-propelled shuttle, but there are differences with a num- ber of the APM components, as shown in Figure 4.2-3. Pro- pulsion is a clear difference between cable- and self-propelled systems. Propulsion is provided at the station (bullwheel) for a cable system, while it is provided in the vehicle (onboard motor) for a self-propelled system. Dual-Lane Shuttle with Bypasses Two synchronized trains pass each other on each lane in the bypass area of the guideway. This configuration doubles the capacity potential of the dual-lane shuttle configuration by allowing a maximum of four trains without requiring four full guideway lanes. This configuration is suitable for higher demand levels than the other shuttle configuration for trans- porting passengers between two points. 20 Figure 4.2-2. Typical APM self-propelled shuttle. Source: Lea+Elliott, Inc.
4.2.2 Loop System Configurations Loop and pinched-loop system configurations differ from shuttle configurations and are described below. Figure 4.2-4 illustrates the range of loop-type APM system configurations. Single Loop/Double Loop Loop configurations allow multiple stations to be served with a self-propelled (but typically not cable-propelled) vehi- cle fleet. Distances and number of trains are not limited. As the scale of a single-loop system increases, the one-way movement of its trains becomes problematic. For example, in a multi- station loop, if the passengerâs destination is the adjacent sta- tion in the opposite direction of the one-way train movement, the passenger must ride through the entire system and all other stations to reach the destination. Failures on a single loop can cause a shutdown of the entire system unless there are pre-planned backup shuttle routes between unaffected stations. The single loop should only be used for nonessential services that can provide an alternative means of conveyance in the event of failures. Even then it has serious operational drawbacks. The double-loop configuration solves these problems by offering trains traveling in both directions. Passengers can be instructed as to the shortest route to their destination station. Double loops provide redundancy to lessen the impact of failures. Double-loop configurations are suitable for non- linear applications that serve multiple stations and have higher demand levels than can be served by single-loop or shuttle systems. Pinched Loop Although having the visual appearance of a dual-lane shut- tle, the trains in a pinched-loop configuration travel in a loop by reversing direction and changing lanes via switches at the 21 Figure 4.2-3. Typical APM cable-propelled shuttle. Figure 4.2-4. Loop systems. Source: Lea+Elliott, Inc. Single Loop Double Loop Pinched Loop Source: Lea+Elliott, Inc.
end stations. Intermediate switches between selected stations are often provided for failure management purposes, allow- ing trains to be temporarily rerouted around a problem area that would otherwise disrupt service. Stations along the align- ment are served in both directions of travel. Distances and number of trains are typically not limited. This configuration is well suited to linear, must-ride applications requiring high- capacity frequent service, multiple stations, multiple trains, and high reliability. Advances in cable-grip subsystems (detachable grips) now allow cable-propelled technologies to be used in limited pinched-loop configurations with multiple cables/cable drives, typically serving two or three stations and with cable transfer done at stations. There are two such cable-grip APM systems currently in operation at airports. Figure 4.2-5 shows the pinched-loop configuration within the context of the different APM system components. It is important to note that the pinched-loop system includes switch machines for crossovers and yard access, as well as an expanded central control equipment room, which typically includes train control functions for the yard access and depar- ture testing. 4.3 State-of-the-Art APM Components This section discusses APMs at the component or subsys- tem level. It focuses on the current state of APM systems that are now operating at airports. There continue to be significant advances in many subsystems and components, particularly those associated with command/control and power distribu- tion, so that aspects of the current state of the art may be quickly superseded. An APM system is a combination of interrelated, interacting subsystems and elements designed to operate together as a cohesive system. The primary elements of an APM consist of the operating system and fixed facilities. The operating system consists of proprietary subsystems and is typically provided as a complete system by a single APM supplier. This is not neces- sarily the case in Japan, where the standard Japanese APM can have subsystems provided by several entities. Facilities are the buildings, rooms, and guideway that house or physically sup- port the operating system equipment, and may be provided by the APM system supplier, depending on the projectâs procure- ment strategy. Figure 4.3-1 illustrates the organization of APM system components. Each is discussed in detail in the subse- quent sections. 4.3.1 Vehicles APM vehicles are fully automated, either self-propelled or cable-propelled, and provide a high level of passenger comfort and safety. Vehicle speed, capacity, and maximum train length are dependent on the type of technology selected. The major- ity of APM vehicles have capacities of 50â75 passengers at air- ports, depending on their baggage characteristics. Landside systems have the lower end of the capacity range (passengers having all their bags), while airside systems have the upper end of the range (passengers having carry-on bags only). Self-propelled vehicles are powered by either DC or by AC. Vehicle propulsion is provided by DC rotary motors, AC rotary motors, or AC LIM. With LIM, the motorâs stator is 22 Source: Lea+Elliott, Inc. Figure 4.2-5. Typical APM pinched-loop system.
typically installed on the vehicle and the rotor is installed on the guideway. Cable-propelled vehicles are attached to a cable and are pulled along the alignment. Most cable systems have the vehicles permanently attached to the cable, while more recent systems are detachable, which allows multiple trains to operate in pinched-loop operations. The typical airport APM single vehicle is approximately 40-ft long and 10-ft wide and can be coupled into trains as long as four to six vehicles. APM vehicles are typically equipped with a ventilation and air conditioning system, automatically con- trolled doors, a public address system, passenger intercom, a pre-programmed audio and video message display, fire detec- tion and suppression equipment, seats, and passenger hand- holds. Some APM vehicles are designed to accommodate baggage carts. APM vehicles can be supported by rubber tires, steel wheels, air levitation, or magnetic levitation. A detailed description of each type of APM vehicle suspension follows: Rubber tiresâAPMs using a rubber-tire suspension bogie also use concrete or steel guidance structures. The run- ning surfaces are attached to a primary surface (concrete or steel) in a manner that maintains proper alignment. When climate conditions require, heating may be pro- vided on sections of the guideway exposed to the elements to aid in maintaining good tire adhesion. Steel wheelsâSome APM vehicle types use steel-wheel bogie suspension. The primary advantages of steel wheels on rail tracks are simplified vehicle guidance, low rolling resist- ance, and faster switching. Rail tracks are typically directly 23 Figure 4.3-1. Organization of APM system components. APM System FacilitiesOperating System Vehicles Guideway Equipment Power Equipment Command, Control and Communications Equipment (Including Central Control Equipment) Station Equipment Maintenance Facility Equipment Vehicle Storage Yard/Facility Guideway Structure Maintenance Facility Power Facilities Command, Control and Communications Facilities (Including Central Control Facility) Station Facilities Source: Lea+Elliott, Inc. Photo: www.bombardier.com Two-Car APM Shuttle Photo: www.bombardier.com Steel-Wheel APM Train
fixed to concrete cross ties. Steel-wheel technologies can achieve higher operating speeds. Air levitatedâAir-levitated APM vehicles ride on a cushion of air, allowing them to travel without friction on the run- ning surface. The vehicle and the concrete guideway âfly- ingâ surface are separated by an air gap. Low-pressure air flows from blowers in the vehicle chassis to air pads. Spe- cial surface finishing requirements are needed to provide a smooth surface texture since any unusual roughness can contribute to rapid wearing of the pads. Magnetic levitationâMaglev vehicles are magnetically lev- itated and propelled by linear motors. Electromagnetic maglev systems use permanent magnets or electromag- nets and have a relatively small gap between the car and the running surface. There are high-speed (200+ mph) and low-speed (30â60 mph) maglev systems, but only low-speed maglev is applicable to airport APMs. The initial Birmingham (UK) Airport landside APM was a maglev system. The APM vehicle steering and guidance mechanisms vary by technology. Steering inputs are provided to vehicle bogies through lateral guidance wheels that travel in continuous con- tact with guideway-mounted guide rails. The steering inputs cause the bogies, usually located at both ends of each vehicle, to rotate so that vehicle tires do not âscrubâ as they go through alignment curves. Side and center guidance mechanisms are used by different manufacturers, and each type has unique characteristics. Side guidance is generally provided by steel or concrete ele- ments located along the sides of each guideway lane. The side guidebeams/rails may be located outside the main wheel paths and can be located either above or below the top of the primary running surface. Side guidance gener- ally requires special mechanisms and trackwork to main- tain positive guidance through track switches. Center guidance systems generally use a structural steel guidebeam along the guideway centerline to provide guidance and steering inputs. Guide wheel configura- tions and materials generally roll along both sides of the center guidebeam, trapping the beam between the guide wheels. Center guidebeams are located at various elevations relative to the top of primary running surfaces. Special movable replacement-beam type switches are usually employed at track switch areas. These types of switches replace a straight guidebeam with a curved turnout guidebeam. 4.3.2 Guideway The guideway of the APM system refers to the track or other running surface (including supporting structure) that supports and physically guides vehicles that are specially designed to travel exclusively on it. The guideway structure may be pro- vided by the APM supplier, as discussed in Chapter 10 (APM System Procurement). 24 Photo: Lea+Elliott, Inc. Side Guidance Photo: www.Doppelmayr.com Guideway Running Surface The guideway can be constructed at grade, above grade, or below grade in tunnels. Depending on the selected supplier and other considerations, the guideway may be constructed of steel or reinforced concrete. For elevated guideways, the size of the structure (columns) varies with span length, train loads, and any applicable seismic requirements. Spans typically range from 50 ft to 120 ft in length. The APM supplier provides guideway equipment that gen- erally includes running surfaces, guidance and/or running rails, power distribution rails, signal rails or antennas, commu- nications rails or antennas, and switches. For technologies that
employ linear induction motors for propulsion, guideway equipment may also include either reaction rail (called the rotor) or the powered element of the motor, called the stator. An emergency walkway along the guideway is sometimes required to provide emergency egress from a disabled train. It is typically continuous, preferably at vehicle floor height, and provides an unobstructed exit path to a station or other place of refuge or escape. The adjacent photo shows the emergency walkway between two guideway lanes for an elevated airside shuttle at Las Vegas McCarran Airport. Some APM systems allow for emergency egress along the guideway itself with pas- sengers evacuating from the front or rear of the train. 4.3.3 Propulsion and System Power Electric power is required to propel vehicles (propulsion/ traction power) and energize system equipment. Propulsion and system power are typically configured such that power will be supplied by substations spaced along the guideway. The substations house transformers, rectifiers (if required), and the primary and secondary switchgear power-conditioning equip- ment. Power distribution can be provided either as three-phase AC or DC. The distance between substations for AC systems is limited to about 2,000 ft, whereas for DC systems the distance is typically limited to one mile. Vehicles are either self-propelled or cable-propelled. A more detailed description of both types of propulsion follows: Self-propelledâThese APMs may use electric traction motors or LIM. Self-propelled APMs are electrically pow- ered by onboard AC or DC motors using (typically) either 750- or 1,300-volt DC or 480- or 600-volt AC wayside rail-based power distribution subsystems. Self-propelled APMs are not limited in guideway length. These tech- nologies can be used for shuttle, loop, pinched loop, and network guideway configurations. Cable-propelledâThese APMs use a steel cable or âropeâ to pull vehicles along the guideway. The cable is driven from a fixed electrical drive motor located along the guideway. Prior to the advent of the detachable grip, cable-propelled systems had typically been limited to use for shorter shut- tle systems up to 4,000 ft. Onboard equipment power is usually provided by a 480-volt AC wayside power. There has been recent interest among airport owners/ operators in reducing power requirements for APM systems. Heightened cost awareness, the variable price of energy, and a focus on sustainability have created a strong interest in lowering power requirements. At the time of this guidebookâs publication, a comparative analysis of regenerative braking energy-capture technologies was being performed at a number of airports with operating APM systems. These analyses were taking into account the physical space requirements of the equipment, the space availability along the APM system to accommodate such equipment, and the cost/benefit ratio of various equipment (technology) alternatives. While analyses findings were not available at the time of the guidebook publi- cation, energy savings is expected to be an important issue for APMs in the future. 4.3.4 Command, Control, and Communications All APM systems include command, control, and commu- nications equipment to operate the driverless vehicles. Each 25 Photo: Lea+Elliott, Inc. Emergency Walkway Crossovers provide the means for trains to move between guideway lanes. They are required for pinched-loop operations and are desirable for failure management purposes on such system configurations. Crossover requirements vary signifi- cantly among APM system suppliers and each supplierâs switch and crossover requirements are discrete in that their geomet- ric and other requirements are largely inflexible. Many guide- way configurations have guideway switches that allow trains to switch between parallel guideway lanes or between different routes on a system. Different APM technologies have different types of switches, including: â¢ Rail-like, â¢ Side, â¢ Beam replacement, and â¢ Rotary. Because of the guidance systems of most rubber-tired APMs, a crossover is generally composed of two switches (one on each guideway lane) connected by a short length of special track- work. Steel wheel/rail APMs use rail switches, and the Siemens VAL systems use a slot-follower switch that is similar to a tra- ditional rail crossover switch.
APM system supplier, based on its unique requirements, pro- vides different components to house the automatic train con- trol (ATC) equipment. ATC functions are accomplished by automatic train protection (ATP), automatic train operation (ATO), and automatic train supervision (ATS) equipment. ATP equipment functions to ensure absolute enforcement of safety criteria and constraints. ATO equipment performs basic operating functions within the safety constraints imposed by the ATP. ATS equipment provides for automatic system supervision by central control computers and permits manual interventions/overrides by central control operators using con- trol interfaces. The APM system includes a communications network mon- itored and supervised by the central control facility (CCF). This network typically includes station public address systems, operation and management (O&M) radio systems, emergency telephones, and closed-circuit televisions. The bases for many of these communication requirements are emergency egress codes such as NFPA 130. The CCF is the focal point of the con- trol system and can vary in size from a simple room with one or two operator positions and a minimal number of computer and CCTV monitor screens (simple APM shuttle) to a large room with multiple operator and supervisor positions and a large array of screens and other information devices (complex pinched-loop APMs). 4.3.5 Stations Stations are located along the guideway to provide passen- ger access to the APM system. Stations for airport APMs are typically online, with all trains stopping at all stations. The sta- tion equipment provided by the APM system supplier typically includes automatic station platform edge doors and dynamic passenger information signs. The stations typically have station APM equipment rooms to house command, control, and com- munications equipment and other APM equipment. The station platforms and vertical circulation are sized to accommodate the system ridership and station flow estimates. Since it is difficult and costly to expand APM station platforms once constructed, it is usually recommended that stations ini- tially be designed and constructed to meet the estimated ulti- mate airport APM ridership demand. Dimensions defining the minimum width of the APM plat- forms and stations are developed based on analyses that take into account the train lengths of the ultimate design vehicle, reasonable allowance for passenger circulation and queuing at the platform doors and escalators, passenger queuing and circulation requirements based on ridership flow assump- tions, and reasonable spatial proportions and other good design practices. In addition to the APM train doors, the station has doors that align with a stopped/berthed train and the two-door systems operate in tandem. The automatic station platform doors are integrated into a platform edge wall and provide a barrier between the passengers and the trains operating on the guideway. The station platform doors provide protection and insula- tion from the guideway noise, heat, and exposed power sources in the guideway. The interface between the station platform and the APM guideway is defined by the platform edge wall and automated station doors. This wall and door system is designed to allow evacuation of the APM vehicles in the event of a misalignment of the vehicle with the station doors. This requirement is accommodated by either a castellated wall con- figuration or a straight wall with opening panels. All airport APMs have station platform walls and doors for safety reasons as well as climate control. Some urban APMs do not have such walls and doors, as riders are familiar with the danger at platform edges and do not tend to have baggage/ strollers that could exacerbate potential safety problems. 26 Photo: Lea+Elliott, Inc. Center Platform of a Dual-Lane Shuttle Photo: Lea+Elliott, Inc. APM Vehicle Dwelling at Station
Dynamic passenger information signs are typically installed above the platform doors and/or suspended from the ceiling at the center of the station to assist passengers using the system. These dynamic signs provide information regarding train des- tinations, door status, and other operational information. The barrier wall, doors sets, and passenger circulation/ queuing area within the APM station and adjacent to the APM berthing position are commonly referred to as the platform. A single station can have multiple platforms. The type of platforms used depends on the type of APM configuration, physical space constraints, and any passenger separation requirements. An examination of the roles each platform type serves is needed to determine the best configuration to suit a particular application in an airport environment. Based on station size along with ridership and circula- tion parameters, the platform configuration can take two basic forms. The first is flow through, where the station has a center platform for boarding passengers located between the two APM guideway lanes that are in turn flanked by two exterior or side platforms for alighting passengers. This configuration can reduce dwell times by having the doors on the alighting (side) platform open first and then several seconds later having the doors on the boarding platform open. This separates conflict- ing passenger flows and allows the arriving passengers to begin to clear the vehicle before departing passengers begin to board the vehicle. The second configuration is cross flow, where there is a single center platform or two side platforms where board- ing and alighting occurs through the same set of APM train doors. In this instance, passengers are encouraged to allow the arriving passengers to alight before boarding takes place. Center Platforms with Cross-Flow Movements A center platform configuration mixes both boarding and alighting passengers in cross-flow movements. Center plat- forms may be used in the bypass area of a single-lane shuttle with bypass alignment configuration, and may also be used with dual-lane shuttles, pinched loops, double loops, and some network APM configurations. Center platforms typically require vertical circulation to move passengers up and over (or down and under) the guideways. Vertical circulation is not required at the end-of-line station configurations of the shut- tle or pinched loop if passengers can circulate beyond the ends of the guideways. Side Platforms with Cross-Flow Movements A single-side platform is a single loaded platform that requires mixing of boarding and alighting passengers, again in cross-flow movement. A potential advantage of a single- side platform (depending on the associated architecture) is the ability to be on the same level as the facility that it serves and not require vertical circulation to go up and over the guideway. However, a single-side platform provides a rela- tively low level of service and can increase dwell time at stations because board/deboard times will be high. By providing two side platforms, the level of service for the station can be greatly increased, and board/deboard times reduced. However, providing two side platforms is more costly and demands more physical space, which may outweigh the benefits of bet- ter passenger service. Two side platforms, one on either side of a single guideway, can provide simultaneous flow-through boarding and alighting. Side platforms (single or double) are the only platform type that can be used with a single-shuttle APM configuration. Triple Platforms with Flow-Through Movements A triple-platform configuration is a combination of both side and center platforms. Sometimes referred to as flow- through platforms, triple platforms allow for simultaneous boarding and alighting. For example, boarding passengers move into the APM vehicle from the center platform while alighting passengers depart the vehicle and move onto the side platforms. Other uses are also possible such as segregating pas- senger types (for instance secure and non-secure passengers) on a single train. Consideration needs to be made for the cost and physical space needs of triple platforms and the require- ment for potentially three independent sets of vertical circu- lation elements. Although triple-platform configurations are the most demanding in terms of cost and space requirements, they provide the highest level of service to passengers. The three types of APM platform configurations are pro- vided in profile view in Figure 4.3-2 below. 4.3.6 Maintenance and Storage Facility The maintenance and storage facility provides a location for vehicle maintenance and storage as well as administrative offices and central control. The maintenance functions include vehicle maintenance, cleaning, and washing; shipping, receiv- ing, and storage of parts, tools, and spare equipment; fabrica- tion of parts; and storage of spare vehicles. For larger APM systems (non-shuttles), the MSF is typically a facility located independent from the operating alignment. When in this configuration, vehicle testing and test track func- tions can generally be performed on the guideway approach- ing the MSF. Meanwhile, simple shuttle systems often have the MSF located under one of the system stations. An example of main- tenance below a shuttle station is provided in the photo of the Las Vegas McCarran airport airside APM shuttle system. 27
cles in transitioning from concept to a service-proven product. These obstacles are met in steps, including: 1. Developing the concept through stages of engineering, and refining the design to make it meet performance and budget (weight, size, cost, etc.) requirements, 2. Developing a prototype of the system or component, 3. Testing the prototype thoroughly (for operation, perfor- mance, safety, and other aspects) on a test track/facility (which could be computer simulation for train control systems), 4. Refining the design/prototype based on the testing program and then testing it further, 5. Formalizing the design and packaging of the product, and 6. Promoting the new product to prospective customers. This process can take years, particularly for a completely new product. Some suppliers have attempted to bring new products to the market without undertaking all of these steps, often with negative consequences: either no one buys it or there are additional research, development, and re-engineering efforts required during product production, resulting in con- siderable cost and schedule impacts. Few airports are willing to accept a new system or major new subsystem without it being fully service proven. Airports are typically not in the research and development business, and they prefer a system that will meet all performance require- ments from the first day of operation. Several airports have, in the past, taken on new systems. Currently one airport owner/ operator, British Airports Authority, is a partner in the devel- opment of a new APM technology (PRT) for use at London Heathrow. Most airport managements, however, do not want 28 Source: Lea+Elliott, Inc. Figure 4.3-2. Platform configurations. Source: Lea+Elliott, Inc. MSF Located Below Station 4.4 Prospective APM Components A number of APM system and component concepts have emerged since APMs first began operating at airports in 1971. Some concepts never advanced beyond the conceptual phase, while others were developed into prototype systems. The proto- type systems were, in some cases, implemented and became industry standards, while others were discontinued. The suc- cessful systems currently available for airport APM systems have been discussed in the prior section of the guidebook. This section focuses on prospective APM systems and their components. Prospective systems are defined as those that have not yet been implemented at airports but might have potential for future implementation. A new concept for an APM system, component, or subsys- tem faces considerable technical, schedule, and financial obsta-
to be the first to implement a new product, and it usually takes a considerable effort to convince them to accept an APM that has not already been proven through previous implementa- tion(s) or extensive testing. This section discusses some of the prospective APM systems and/or subsystems that are currently emerging and vying to become future industry standards. 4.4.1 Vehicles Small vehicles, holding just two to four passengers, are a prospective APM system component not currently in opera- tion at any airport or urban application. Such small vehicles could be part of a PRT system that would have different sys- tem characteristics from current APM systems (see also Sec- tion 4.4.7). PRT is not a new concept. The Lea Transit Compendium (Volume II, No. 4) provided detailed information on ten sep- arate PRT supplier technologies in 1975, none of which devel- oped into industry standards. land values and office space rentals, congestion relief, and acci- dent reduction. PRT vehicle capacity for this landside implementation will be between two and three passengers (as compared with a max- imum of four passengers for an airside application). Depend- ing on their baggage characteristics, this capacity limitation could pose challenges for larger groups traveling together, requiring them to divide into multiple groups. Distinct from PRT, a prospective APM vehicle subsystem currently being developed is active steering. In this concept, the vehicle utilizes an alignment database, a travel database, and a vehicle positioning actuator to correlate the two databases. The actuator actively steers by cross-referencing the real-time vehi- cle position with desired/future position (travel database). The vehicle also has a simple failsafe mechanical guidance system to be used in the event of failure of the active steering system. The ULTra PRT system is proposed to use this guidance approach. Mitsubishi is also undertaking prototype testing for this prospective vehicle guidance system on its Crystal Mover APM technology. Incorporation of active steering concepts into commercial APM systems will require rigorous safety analyses and certifications to ensure passenger safety. Other technological advances are also finding their way onto APM vehicles. Onboard CCTV systems are now com- monplace, and airports are increasingly requiring that cell phone service, wireless internet access, and other amenities be provided on APM vehicles. APM suppliers are continually advancing their offerings to meet these needs and provide a competitive advantage for their technology. 4.4.2 Guideway The active steering concept described above has APM guide- way implications. The concept would not need side or center guidance rails (or power rails, as described in section 4.4.3), which would simplify the guideway equipment and possibly structure. Without the guidance and power equipment on the guideway, the running surface could potentially serve as the egress walkway (replacing the need for a separate walkway sys- tem). This would reduce the facility (guideway) capital cost, while the reduced equipment requirements would reduce the system capital cost. 4.4.3 Propulsion and System Power Significant advancements in battery technologies and other types of energy storage and distribution are expected to find their way into APM systems. APM suppliers are developing systems that more effectively manage the way APM systems consume electrical energy. Some are developing energy man- agement algorithms and subsystems that more effectively man- age train movements and propulsion power consumption, 29 Photo: British Airports Authority BAA Demonstration PRT Project The British Airport Authority (BAA) is currently imple- menting a pilot demonstration project to evaluate a landside PRT system at London Heathrow. The system will connect Terminal 5 with a remote parking area and includes 2.6 miles of guideway and 18 vehicles. The demonstration system is scheduled to open for passenger service in late 2009. The full- scale project could consist of a 20-mile guideway network with 50 stations and approximately 300 vehicles. BAA selected and became partners with Advanced Transport Systems Ltd. for the project, which will utilize the ULTra vehicle concept (shown in BAA Demonstration PRT Project photo). Some of the external benefits of this project identified by BAA include increased
such as regenerative breaking that uses the energy required to slow one train to drive or accelerate others. Some APM suppliers are developing onboard battery technologies that promise to eliminate power distribution and power rails along the guideway. Magnetic levitation, combined with linear induction motor propulsion systems, have begun to compete with more con- ventional rubber-tired, onboard rotary traction motor APMs. Results in the UK and United States have been mixed, but tech- nological advancements in Japan have brought this technology to fruition. The promise of no moving parts in vehicle propul- sion systems and resulting reductions in maintenance costs makes these technologies very attractive to airport operators. Good ride quality, low noise, strong performance, and the abil- ity to operate in all weather conditions are also touted as advan- tages of these technologies. 4.4.4 Command, Control, and Communications As the procurement of APM systems is primarily based on the DBOM approach, the vehicle suppliers usually provide their own ATC system technology or have long-term relation- ships with a specific ATC system supplier. Historically, APM systems have used fixed-block ATC systemsâfirst relay-based, and more recently, microprocessor-based. Beginning in the 1980s, a new type of control system called communications- based train control (CBTC) was developed, which uses a moving block approach to achieve considerably closer vehicle headways. CBTC systems are now widely used and are largely supplanting fixed-block technology in APM applications. It seems likely that prospective APM systems will rely even more heavily on CBTC train control systems, except perhaps in certain long-distance applications, where fixed block techno- logy may offer cost savings. Advancement in CBTC technology will likely further shorten the headways between successive trains. While this is a very desirable goal, there are design lim- its currently imposed on ATC systems (no physical contact of vehicles or trains, online stations, and the undesirability of stopping trains on the guideway to wait for a train stopped in the station ahead) that, unless modified, will limit the practical time-separation of following trains. 4.4.5 Stations Offline stations, located on guideways parallel to the main- line guideway, are a prospective APM system improvement. These were used on the initial Airtrans system at the DFW Air- port but have not been used on airport APMs since. They are also used on the Morgantown urban APM that, although it has larger vehicles, operates like a PRT system. They are part of the 30 Photo: British Airports Authority Rendition of Future PRT Station at London Heathrow PRT system concept but could also be part of a conventional APM system. Station length is a critical planning and design issue for off-line stations. For example, a PRT station would typically accommodate multiple vehicle berths (docking locations); the exact number will depend on the forecasted passenger demand for that station. However, for the current PRT concepts, each station configuration has a maximum berth number beyond which the station throughput begins to decline. For loca- tions where demand requires more than the optimal number of berthing locations, it is recommended that two or more offline stations be constructed. 4.4.6 Maintenance Facility New maintenance procedures and equipment are typically developed by manufacturers concurrently with development of new subsystem equipment. Consequently, such prospec- tive maintenance aspects are subsystem-specific and not a characteristic of APM systems in general. A major goal of all manufacturers (and APM system owners) is to minimize maintenance in every form as a means of achieving lower sys- tem operating costs. 4.4.7 APM System Characteristics Route Networks A prospective APM system characteristic is a network align- ment configuration in contrast to the linear nature of currently operating airport APMs. The network alignment configuration allows specific trains to serve specific routes (combinations of stations). Overlapping routes allow different levels of capacity to be provided over different parts of the network. This could allow the system to match capacity with demand better than linear alignments, which typically provide a constant capacity over the entire system.
An example of a route network system (with routes illus- trated) is shown in Figure 4.4-1. This example reflects the operations of the AIRTRANS system at Dallas/Fort Worth International Airport prior to its decommissioning in 2005. Offline stations are often assumed with a network align- ment and allow trains to bypass stations that are not assigned to that particular route. PRT Networks A PRT network operation is a prospective APM operational characteristic. PRT networks contemplate nonstop service between the origin station and the destination station; this is different from route networks where each train stops at each station along the route. Individual vehicles are available (wait- ing empty) at offline stations, thus minimizing wait times by passengers. Proper positioning of PRT vehicles at stations requires empty vehicles to be routed through the network as part of an empty-vehicle management system. The combination of empty-vehicle management, empty-vehicle waiting at stations, and in-use vehicle load factors of 50% (average party size of two passengers) will likely result in higher levels of unused sys- tem capacity even during peak demand periods. An example of a hypothetical PRT network is shown in Figure 4.4-2. 4.4.8 Summary of Prospective Components/Characteristics No predictions are made in this section as to which prospec- tive APM component or system characteristic will successfully transition into operational, service-proven status. Of the com- ponents and characteristics listed above, many already have transitioned and some seem well on their way, while others are coming back in a several-decade cycle. Advances in the APM industry are often incremental. Components in the APM field have sometimes migrated to the standard urban rail technolo- gies of light rail and rapid (heavy) rail. This is especially true in the train control (signal) subsystem. Technological advances in APM components and subsystems have been continuous since their introduction to airports in 1971, and such advances are expected to continue in the future. 31 Source: Lea+Elliott, Inc. Figure 4.4-1. Route network system. Source: Lea+Elliott, Inc. Figure 4.4-2. Hypothetical PRT network.