Guidebook for Planning and Implementing Automated People Mover Systems at Airports (2010)

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40 The prior chapter concluded with a brief discussion of step 2 of the APM planning process, developing alternatives to be analyzed with the objective of best accommodating the pas- senger conveyance needs identified in step 1 (see Figure 7-1). Alternatives in their most basic form are combinations of con- veyance technology and route/alignment that connect the crit- ical airport passenger activity centers. The airside and landside passenger conveyance needs of major airports vary widely. Providing a high level of serv- ice to passengers is critical to all airports as they compete to attract customers in an increasingly competitive transporta- tion environment. Larger hubbing airports compete with each other for connecting passengers, and all airports com- pete with rail, bus, and auto (and even other area airports) for regional traffic. This chapter describes typical passenger conveyance tech- nologies used at airports, both airside and landside. It then describes the typical airport airside technology evaluation process followed by the typical airport landside technology evaluation process. Finally, the chapter presents overall guidelines or thresholds to consider when evaluating the proper technology to use in meeting an airport passenger conveyance need. 7.1 Airport Conveyance Technologies For conveying relatively large volumes of O/D airline pas- sengers between aircraft gates and terminal functions (check- in, security, and baggage claim) as well as connecting transfer passengers between aircraft gates (both intra- and inter- terminal), there are three conveyance technologies typically employed: moving walkways, buses, and APMs. (For smaller passenger volumes and shorter distances, a smaller technol- ogy called “courtesy carts” is employed within airport termi- nal buildings. This technology is described in greater detail in ACRP project 03-14, “Airport Passenger Conveyance System Usage/Throughput.”) These technology categories are listed in ascending order of system line capacity (passengers per hour per direction) for airside airport applications. They are described in terms of technical characteristics and by suppli- ers and their applications. 7.1.1 Moving Walkways Moving walkways are a means of pedestrian transport that provide a flat or inclined continuous moving surface of pal- lets that convey passengers (standing or walking) and their baggage over moderate distances. These devices are popu- larly known as moving sidewalks, moving walkways, and travelators. Typical walkway speeds range between 90 and 120 ft/min, or approximately one-half normal walking speed. The result- ing passenger speed ranges from 90 ft/min (passenger stand- ing) to 210 ft/min when passengers walk on the moving walk. Moving walkway lengths range between 30 and 500 ft, with pallet width ranges of between 24 in. and 55 in. Passenger conveyance capacities for moving walkways are a function of walkway width, passenger density, passenger passing ability, walking/standing ratio, and the moving walk- way’s speed. For a typical airside airport application with carry-on baggage only, moving walk capacities range from 4,000 to 5,000 passengers per hour. For a landside airport application with baggage carts, moving walkway capacities range between 1,600 and 3,700 passengers per hour. Although the capacity of moving walkways is high, their slow speed often results in travel times that are not acceptable. 7.1.2 Buses Rubber-tired buses are a prevalent form of transit at many airports around the world. At-grade bus operations are favor- able because they are able to reach a variety of passengers and destinations with good flexibility and lower costs. C H A P T E R 7 Matching Needs With Passenger Conveyance Technologies

Level-of-Service Decision-Making Flow Key: Process Data Output Start/ End Planning Process Decision-Making Flow APM Benefits Alignment Stations Guideway/ROW Capital Costs Operations & Maintenance Costs Cost–Benefit Analysis Financial Strategies Power Distribution Command, Control, and Communications Ridership System Capacity NEED System Level of Service Evaluate System Level of Service Evaluate System Level-of-Service Measures Environmental Final Design Procurement Defined APM System Functions Served Service Req’ts. Maintenance Facility Walk & Time Thresholds Source: Lea+Elliott, Inc. Figure 7-1. General APM planning process.

Standard buses—Typically, these are driver-operated, diesel-powered, 30- to 40-passenger buses. Bus lengths range from 35 ft to 40 ft. System capacity can range from 400 to 500 passengers per hour, assuming five-minute headways. Articulated buses—These driver-operated, diesel-powered, 50- to 60-passenger buses typically would serve an air- port’s long-term parking. Bus lengths are typically 50 ft to 65 ft. System capacity can range from 600 to 700 passen- gers per hour, assuming five-minute headways. Buses are very flexible; routes and stations (stops) can be changed or added easily. Maintenance can occur either on- airport or off-airport. Bus lengths typically average 45 ft, and bus width is 8.5 ft for regular transit buses or up to 10 ft for spe- cialized airport apron buses. These wider apron buses are not street legal and require special operations to transport them to off-airport maintenance facilities. Buses operating on the airport apron cross active taxiways (where aircraft have the right of way) and thus can only achieve operating speeds well below their cruise speeds. Apron buses are typically 45 ft in length and can carry 80 to 100 passengers in an airside application (carry-on baggage only). For a typ- ical airside airport application, a main terminal to remote concourse bus system with two separate routes serving the con- course at three-minute headways (each route) can achieve sys- tem capacities of 3,000 to 4,000 passengers per hour. 7.1.3 Automated People Movers APMs are fully automated, driverless vehicles operating on fixed guideways along an exclusive right of way. APMs are divided into two major groups: cable-propelled and self- propelled. Monorails, rubber tire, and larger steel-wheel vehi- cles are considered within the self-propelled group. Cable-propelled—This type of technology consists of medium- to large-capacity vehicles or trains using cable propulsion with various suspension systems. System line speeds of 30 mph can be achieved with longer station- to-station distances, but typical airside station-to-station speeds average 20 mph. The fixed-grip technology is best suited for two- or three-station shuttle applications with relatively straight guideway alignments of one-half mile or less. Beyond this distance, the time between trains can exceed an airport’s desired level of service. Detachable- grip is a relatively new advancement in the technology that allows for more than two trains to operate simultaneously. Self-propelled—Self-propelled vehicles or trains use a two- rail guideway system with rubber tires on concrete or steel wheels on steel rails. Depending on the supplier’s tech- nology, system maximum speeds range between 30 and 45 mph for longer station-to-station distances, but the typical airside station-to-station speeds are 30 mph. Detailed descriptions of APM systems and technology are provided in Section 4.3. System capacity for airside APMs in a major airline hubbing operation can reach 8,500–9,000 pphpd, assuming 75 passengers per vehicle (passengers with carry-on baggage only), four-vehicle trains, and two-minute headways. Capacity requirements on the landside of an airport are typ- ically lower than the airside capacity mentioned above. The upper end of the landside capacity range can reach 3,000 pphpd assuming 50 passengers per vehicle (all baggage), three-vehicle trains, and three-minute headways. 7.2 Airside Technology Evaluation The appropriate passenger activity level at which to imple- ment an airside conveyance technology varies by airport and can be influenced by a number of different factors. For APMs, which provide high capacity and level of service at a relatively high cost, there are certain thresholds that typically must be exceeded before a system is justified. With some factors the thresholds are quantitative, while with others they are more qualitative. The importance of any single factor can vary greatly by airport. The typical factors that influence airside APM implementations include: • Terminal configuration and geometry, • Passenger level of service, • Ridership volumes, and • Costs and benefits. These implementation issues are examined in detail below. This examination is based in large part on a survey of fourteen major U.S. airports with a wide range of airside conveyance needs and technologies. 7.2.1 Terminal Configuration Geometry An airport’s terminal configuration and its geometry have significant influence on the appropriate airside conveyance technology. A terminal configuration differentiator is whether the facility is contiguous, with a single structure housing the processing (check-in, security, baggage claim) functions and all airline gates, or whether it has multiple terminals, one or more with processing functions and one or more being remote with airline gates only. Airports with contiguous terminal configurations tend to have moving walks for passenger conveyance. A limited number also employ APMs (but not buses) for passenger conveyance when an airline hubbing operation is present. Contiguous configurations are often referred to as letter- 42

43 shaped (such as “D” or “E”) or as a spoke configuration. Different contiguous terminals vary widely in their config- urations and are typically a function of property constraints and roadway access. Airport terminal configurations with concourses that are remote from check-in, security, and baggage-claim functions typically have APMs (elevated or underground), often in con- junction with moving walks. A limited number of remote con- figuration airports use apron buses to connect facilities. In all cases these inter-facility conveyance systems include O/D pas- sengers, and in some cases they include transfer passengers. The distance between the facilities influences the choice of conveyance system, with shorter distances accommodated by moving walks, medium distances by APMs or apron buses, and longer distances typically by APMs only. Some airports have both contiguous terminals and remote terminals, such as Seattle/Tacoma and Miami. Examples of remote configuration airports using only APMs include Tampa, Orlando, and Denver. The airports with the shorter connections to remote terminals (Tampa and Orlando) have elevated APMs, which cost less to construct than underground APMs. Airports with longer connections to multiple remote terminals (Cincinnati, Denver, and Atlanta) have under- ground APMs that travel below aircraft taxilanes. Airports employing a combination of APMs and moving walks include Atlanta and Cincinnati. Airports using apron bus systems to connect facilities include Washington Dulles (with moving walks) and Cincinnati (with APM and moving walks). Since Washington Dulles plans to build future remote (paral- lel) concourses further from its main terminal, it has recently opened an underground APM that replaced most of its current apron bus (mobile lounge) system. The survey of fourteen major U.S. airports found a num- ber of terminal configuration and geometric thresholds in terms of the airside passenger conveyance technology. Find- ings included: Distance between Main Terminal and the Furthest Concourse • For over 3,000 ft, APMs are the only conveyance technol- ogy employed. • For 1,500 to 3,000 ft, apron buses and APMs are employed. • For under 1,500 ft, moving walks are the dominant means of conveyance. Number of Connecting (Hubbing Airline) Gates • For more than 60 gates, APMs and buses are employed to connect the gates. • For 30 to 60 gates, a mix of all conveyance technologies is employed. • For fewer than 30 gates, moving walks are predominately employed. 7.2.2 Passenger Level of Service The passenger level of service, typically measured in terms of walk distance and trip time, influences the choice of passenger conveyance technology. For O/D passengers, these distances and times are measured between security/baggage claim and the average and furthest aircraft gates. For transfer passengers, the distances and times are measured between the average and fur- thest connecting airline gates. Connect time between the two furthest-spaced connecting gates is critical because the Official Airline Guide sets a minimum connect time between arriving and departing flights that an airline can ticket a passenger as a transfer. The walk distance and trip time data from the airports sur- veyed did not present clear differentiation between conveyance technologies. A maximum walk distance between security and the furthest gate, of approximately 2,000 ft, was found among all the airports and thus appears to be a threshold of acceptable level of service. When a given airport configuration reaches this threshold and still desires growth, the solutions have included the construction of remote concourses served by either APMs or apron buses, or extending the main terminal’s curb frontage to serve the additional gates. For airports with remote concourse gates served primarily by APMs and secondarily by corridors with moving walks, the walk distance savings for the trip between security and the furthest gate is approximately 50% when using an APM, or between 1,500 and 4,000 ft of walk savings. Other differentiators among the airside conveyance tech- nologies are level changes and exposure to the elements. The use of moving walks does not require a vertical level change, while use of apron buses and underground APMs does require such a change. Elevated APMs (such as Tampa and Orlando) do not always require level changes. APMs and moving walks also have the advantage of not exposing passengers to the ele- ments while boarding or alighting the system. However, most apron busing operations do expose passengers to the elements, one exception being the mobile lounge system at Washington Dulles. 7.2.3 Ridership Volumes As described by example in Section 7.1, the maximum passenger volume capacities that the different technologies can achieve on the airside of airports is as follows: Moving walkways: 4,000 to 5,000 pphpd Apron buses: 3,000 to 4,000 pphpd Automated people movers: 8,500 to 9,000 pphpd APMs are designed to better accommodate high hourly volume with level boarding, multiple doors, and wide door widths. By comparison a bus operation is constrained by the

number and location of bus berths; also, the technology requires steps in boarding and has a much lower door-width to vehicle-length ratio. Moving walk systems are supplemented by connector or concourse walk corridors parallel to the mov- ing walks. Moving walk capacity can be substantially reduced by relatively slow passengers or passengers with baggage that block the passing lane on the moving walk. The survey of fourteen major U.S. airports found a number of passenger volume thresholds in terms of the passenger con- veyance technology employed at an airport. Findings included: MAP Connecting • For more than 20 MAP connecting, APMs are predomi- nately employed. • For more than 20 MAP connecting, moving walks are pre- dominately used. Hourly Passenger Volumes • For more than 3,000 pphpd, APMs are predominately employed [exceptions include Chicago O’Hare (moving walk)]. 7.2.4 Costs and Benefits Every airport has its own unique set of geometric constraints to growth: from existing runway locations on the airside to existing roadways and other property owners on the landside. The relative strength of each of these constraints at a given air- port, in conjunction with the passenger conveyance techno- logy’s performance characteristics, determines the best option for an airport’s facility growth plan. The capital and operating costs of any conveyance system must be financially feasible for the airport. These costs need to be considered in the short and long term as the most affordable technology (bus versus APM) can change depending on the financial time frame. The capital and operating costs of airside conveyance tech- nologies vary widely. Indirect costs can apply to the technolo- gies as well. Dual-lane moving walks increase the width of a concourse by approximately 11.0 ft, and some airports have installed four parallel moving walk lanes. Buses require a main- tenance facility, which may occupy valuable airport property. System equipment costs and annual operating costs range from relatively low for buses, to moderate/high for moving walks, to high for APMs. Facilities costs include the system’s elevated or tunnel structure (moving walk or APM), mainte- nance facility (bus or APM), and stations (bus or APM). Facil- ity costs typically exceed the system equipment costs and vary widely by region. On the revenue side of the equation, aircraft gates translate into airport revenues. All three conveyance technologies help to connect distant gates with main terminal processing and/or other connecting gates by reducing the walk distance and travel time between the two locations. Thus the technologies allow for more gates to be used while still adhering to level-of-service thresholds for walk distance and trip time. The faster the tech- nology conveys passengers, the more gates a technology allows an airport to use. For hubbing operations, a strong correlation was found between the number of connecting gates and the conveyance technology, as summarized below. Aircraft gates for a hubbing airline operation have higher gate utilization and therefore generate greater revenues for the airline and airport. Also, hubbing (connecting) passengers do not require landside facilities. Hence, many airlines/airports have been able to justify remote terminals connected by APMs on a cost/benefit basis. The APMs have allowed an airport to turn otherwise nonperforming land into revenue-generating property, placing more terminals farther away and handling greater numbers of annual passengers. APMs have also allowed contiguous terminal configurations to be converted into major hubbing operations (Dallas/Fort Worth and Miami). Chicago O’Hare and Newark use landside APMs to connect international terminals with domestic ones and increase both their international and domestic traffic volumes. 7.3 Landside Technology Evaluation Just as no two airports are exactly alike, the appropriate time or activity level to implement a specific landside conveyance technology varies by airport and can be influenced by a num- ber of different factors. For APMs, which provide high capac- ity and level of service at a relatively high cost, there are certain thresholds that typically must be exceeded before a system is justified. With some factors the thresholds are quantitative, while with others they are more qualitative. The importance of any single factor can vary greatly by airport. The typical factors that influence landside APM implementations include: • Passenger/employee volumes, • Facility spacing, • Terminal access spacing, • Terminal roadway capacity, • Regional rail station proximity, • Costs and revenues, • Airport land use and revenues, • The airport’s desired transport level of service, and • Competitive position to rival airport. 7.3.1 Passenger/Employee Volumes and Facility Spacing In surveying airports that have implemented landside APMs, an overall measure such as MAP for O/D passengers does not 44

45 provide a clear threshold for implementations. Airports with landside APMs range between 12 MAP and 30 MAP of O/D passengers at the time of implementation, with a concentration around 22 MAP. A better passenger metric is the design hour volume. APMs are designed to better accommodate high hourly volume with level boarding, multiple doors, and wide door widths. By com- parison, a bus operation is constrained by the number and location of bus berths, and the technology requires steps in boarding and has a much lower door width to vehicle length ratio. As shown in the Figure 7.3-1, landside APMs can poten- tially move over 6,000 pphpd, while a bus system often has dif- ficulty accommodating flows over 2,000 pphpd at a single location with any fewer than four bus berths. For current APM systems connecting a main terminal with (1) other terminals, (2) car rental, (3) long-term parking, and (4) regional rail, system demands are in the hourly range of 2,500 to 3,500 pphpd. APM systems serving all these groups tend to be longer systems of between 2 and 3 miles. Systems serving fewer than the four groups listed above have propor- tionately lower demands and are typically shorter in length. Systems serving only car rental and long-term parking may have hourly demands from 1,000 to 2,500 pphpd and range from 1,500 ft to 2 miles. For remote facilities located more than three miles from the main terminal, buses are the more typical transport technology. It should be noted that for the purposes of the survey, the nine-mile Airtrain at New York’s JFK Inter- national is considered a regional rail system extension rather than an airport landside APM. For existing landside systems, the hourly number of passen- gers per mile of dual-lane guideway is another threshold to apply. The longer 2- to 3-mile systems tend to have design hour flows of 500 to 700 passengers per mile. Shorter systems of 1,500 ft to 2 miles, though serving fewer rider groups, typically have higher flows of 700 to 1,200 passengers per mile. 7.3.2 Terminal Access Spacing Longer landside APM systems (length of guideway) typically serve multiple landside terminals, each having their own tick- eting and baggage-claim functions. One of the APM’s main functions is to connect these terminals. Connecting a terminal with international service to one or more domestic terminals occurs at a number of landside applications, including Chicago O’Hare, Newark, Frankfurt, San Francisco, and Paris–CDG. For those gate-to-gate connections, passengers must go out of and then back through security screening. As an implementa- tion criterion, when terminal access locations are spaced 1,000 ft or more from one another, APMs or buses, as opposed to moving walkway connections, are typically used to provide connections between the terminals. ACRP Report 25: Airport Passenger Terminal Planning and Design is a helpful resource on this topic. 7.3.3 Terminal Roadway Capacity Terminal roadways can quickly become a landside bottle- neck, resulting in long delays for buses and autos. Lengthening or widening terminal roadways eventually becomes physically impossible, if not cost prohibitive. At airports such as Newark, Chicago O’Hare, Düsseldorf, and Birmingham (UK), landside APMs provide an efficient means of supplementing the termi- nal roadways, thus improving access to and from the terminal buildings. These landside APMs allow the airport to increase passenger volumes without having to increase roadway capac- ity. With this factor there is probably not a universal roadway 9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000 0 1 2 3 Distance (Miles) Automated People Mover Bus 4 5 Ca pa ci ty (p as se ng er s/h ou r) Source: Lea+Elliott, Inc. Figure 7.3-1. APM and bus capacities.

capacity threshold. At individual airports a high demand/ capacity ratio over a sustained period is probably a better metric. 7.3.4 Regional Rail Station Proximity Most major airports desire to have a regional rail station located within the terminal complex, allowing an easy connec- tion between the rail station and ticketing and baggage-claim functions. However, many major airport terminal functions are not served well by a single rail station location. Also, regional rail’s geometric constraints (curves and grades) do not easily allow multiple station locations in the terminal area. As a con- sequence, the cost and constructability impacts of in-terminal station location(s) have led some airports to locate a regional rail station remote from the terminal area. With the more distant locations from the terminal, APMs and buses provide the connection to the terminal. Passenger arrival patterns at the regional rail station depend on that ser- vice’s train frequency and train size. Long trains arrive period- ically and unload a large group of passengers in a very short time period. Such surged demand is well suited to the high capacity provided by APMs. The majority of airports surveyed have their existing or planned (future) regional rail station between 200 and 1,000 ft from their terminals. These are almost exclusively served by walkways. APMs serve a small number of airport rail stations over distances between 1,000 ft and 2 miles between the station and the terminal. Buses serve a larger number of airport rail stations, with the distance between the station and the termi- nals ranging from one-half mile to 3 miles for most of these systems. The maximum distance served by relatively frequent bus service (30-minute headways) was approximately 12 miles. ACRP Report 4: Ground Access to Major Airports by Public Transportation is an excellent resource on this topic. 7.3.5 Costs and Revenues The capital and operating costs of any conveyance system must be financially feasible to the airport. These costs need to be considered in the short and long term because the most affordable technology (bus versus APM) can change depending on the financial time frame. The implementation of a landside APM can positively impact costs and revenues for an airport. The following are examples of indirect financial benefits: • APMs can lower construction costs and shorten schedules of terminal roadway expansion or short-term parking expan- sion by allowing remote garages to temporarily serve short- term parkers. • APMs can reduce costs of regional rail service to an airport by allowing for a remote/at-grade airport station, as opposed to a terminal/below-grade airport station. • Given the high correlation between an airport’s parking pricing and parking proximity (time/distance/ease of access) to the terminal, the same remote garage could be viewed as closer and more convenient if served by APM as opposed to bus. Directness of route, shorter headways, and exclusive right of way all contribute to the APM’s quicker connect times. This faster service can translate into greater parking revenues for a given garage. 7.3.6 Airport Land Use and Revenues Major international airports have a wide variety of land uses on their premises. With airport growth, the expansion of ter- minals and roadways often force other facilities to relocate to more remote locations. Landside APMs have been used to facilitate such relocations at airports including Minneapolis/ St. Paul, Düsseldorf, and Chicago O’Hare. APMs are most effi- cient when such facility relocations have high densities, such as with consolidated car rental and/or multi-story long-term parking structures. The higher densities allow a single APM station to serve a large number of facility users. Commercial development opportunities on airport and adjacent properties are a revenue-generating land use that is under consideration for planned landside systems at Oakland and Phoenix. The ability of a landside APM to connect the air- port facilities and a regional rail station with a commercial development property can enhance that property’s value to the tenant, and hence, revenues to the airport. The relocation of check-in and security processing away from the aircraft gates and baggage-claim functions is a new land-use issue under consideration at a number of major air- ports. Again, APMs are in the planning stage for this type of high-capacity facility. 7.3.7 Airport’s Desired Conveyance Level of Service The level of service provided by a landside conveyance technology can be measured in many different ways. Level- of-service measures typically include trip time, wait time, walk distance, weather protection, mode changes, level changes, and bag cart accommodation. For example, weather protection was a major reason that Minneapolis/St. Paul implemented a relatively short 1,000-ft landside APM to car rental and parking garages in its extremely cold climate. The ability to accommodate baggage carts has been a very positive factor for APMs in comparison to buses for south Florida airports that handle high volumes of baggage- laden tourists bound for cruise ships. A rider of a landside APM system can reasonably expect to save about half of the overall trip time between point A (e.g., station in parking garage) and point B (e.g., airport terminal 46

47 station) compared to a similar trip using a landside bus. The trip time savings come from shorter headways, faster average speeds, and more direct routes (APM alignment vs. airport roadway system). 7.3.8 Competitive Position to Rival Airport For multiple airports run by the same agency or for multi- ple airports served by a single regional rail system, there may be political pressure for the airports to be served equally. Exam- ples of this in the United States are in New York City and the Bay Area in California, where the decision of one airport to implement a landside APM helped lead another airport to an implementation of its own. For multiple airports in a single region run by separate agen- cies, often there is fierce competition to attract passengers. Once again, when one airport implements a landside APM, the competing airport soon follows. For example, in a tourist- destination region of the United States, where two major airports compete for the same tourist/cruise passengers, two airports are currently in the planning or implementa- tion stages of landside APMs that would help connect the airport to the seaport. 7.4 Airport Conveyance Technology Guidelines While this chapter attempts to quantify some general imple- mentation thresholds for different passenger conveyance tech- nologies, the most appropriate technology at a given airport is always the technology that best meets the goals and objectives of the airport. Given the many components of an airport’s environment, the framing of these goals and objectives in a technology assessment must be comprehensive and inclusive. By properly framing the passenger conveyance analysis with full integration of the airport’s goals and objectives, the best technology for the airport will emerge. The most basic comparison of passenger conveyance tech- nologies looks at the connection time between two locations for different separation distances. This connection time com- parison is a typical level-of-service metric used in comparing the different technologies. Although such a comparison is very site-specific, results of a typical airside comparison are pro- vided in Figure 7.4-1; the longer the distance, the greater the connect time advantage of an APM. The speed advantage of APM systems has brought new expansion possibilities to existing airports and has allowed new terminal design concepts to develop, including increas- ing the number of gates and the distance between facilities while still meeting the airport’s threshold for walk distance and connect time. APMs also provide greater system capacity flexibility, mea- sured in pphpd, than competing conveyance technologies. Greater alighting/boarding rates at a station compared to apron bus and conventional rail is one aspect of improved overall system capacity for APMs. In Figure 7.4-2, the ratio of a vehicle’s door width to train consist length (vehicles making up a train) and the issue of level boarding versus step boarding are compared for APMs versus apron buses. The typical APM train has a considerably higher ratio of door width to vehicle length; it also allows alighting/boarding on both sides of a vehicle, unlike an apron (or landside) bus, Figure 7.4-1. Airside technologies—travel time vs. distance comparison. Source: Lea+Elliott, Inc.

which typically can only access one side. The APM also has level boarding, which allows faster boarding compared to the step boarding of apron buses. From the survey of fourteen major U.S. airports, some inter- esting airside correlations were found between the conveyance technology and the distance between facilities served. The type of airport terminal configuration was also found to influence the conveyance technology. A comparison of the number of gates used by hubbing air- lines against the type of airside conveyance technology is pro- vided in Figure 7.4-3. As the figure shows, airside APMs allow greater airline hubbing (connecting) operations to take place 48 Figure 7.4-2. Door width and boarding level comparison. Source: Lea+Elliott, Inc. Source: Lea+Elliott, Inc. Figure 7.4-3. Connecting gates vs. terminal type by airside technology. Fig. 7.4-3

regardless of the terminal configuration. For both contigu- ous and remote terminal configurations, APMs allowed for approximately 50% more gates. A number of interesting trends and correlations have devel- oped in the airside APM field since the first shuttle system opened at Tampa in 1971. The earlier airside applications tended to be shuttles, serving airports with mostly O/D passen- ger operations. Since the early 1990s, however, there has been a mix of shuttles and pinched-loop systems serving O/D oper- ations as well as transfer or hubbing operations. With the pinched-loop operations have come longer APM systems with multiple airside stations. 49