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ELSEVIER

Available online at www.sciencedirect.com MATHEMATICAL AND

8 C I IE N C I E ~ _ ~ D I R E A C T " COMPUTER MODELLING

M a t h e m a t i c a l and C o m p u t e r Modelling 39 (2004) 839-868 www.elsevier.com/locat e / m c m

A R e v i e w of Strategic Mobility M o d e l s S u p p o r t i n g the Def ense T r a n s p o r t a t i o n S y s t e m

K . M C K I N Z I E AND J . W . BARNES ETC 5.128, Graduate Program in OR/IE

The University of Texas at Austin Austin, TX 78712-1063, U.S.A.

kaye. mckinzie©us, army. mil wbarnes©mail, utexas, edu

A b s t r a c t - - T h e complexity of military logistics and force deployment modeling requires the use o f advanced c o m p u t e r models for analysis. T h e last 20 years have not only seen a concerted effort to improve t h e fidelity of these models, b u t development to improve their interconnectivity. T h e area of strategic mobility has received greater interest in t h e last decade as t h e U.S. Military has become more reliant on a force projection posture r a t h e r t h a n prepositioning its forces outside t h e continental U n i t e d States. Strategic mobility describes how forces within t h e continental U.S. are deployed in support missions outside t h e continental U.S. This posture combined with t h e ever shrinking military budget and force size has placed increased emphasis on t h e capability to efficiently deploy personnel, equipment, and support materiel. Mobility modeling is conducted at various levels of t h e mobility planning process. T h e result is a myriad of models addressing different aspects of t h e process. Current models addressing strategic mobility use aggregate network flow models, one-pass greedy approaches, and simple b o u n d i n g techniques. This paper presents an overview of these models, their operating characteristics, and t h e i r advantages and disadvantages for mobility modeling applications. (~) 2004 Elsevier Ltd. All rights reserved.

K e y w o r d s - - S t r a t e g i c mobility models, GDAS, J F A S T , MIDAS, MobSim.

1. I N T R O D U C T I O N

The United States Military has insufficient personnel and equipment to place resident forces everywhere t h e y m a y be needed. Consequently, the military employs a "capability based force projection platform" (FPP) [1]. This force structure allows the military to "rapidly alert, mo- bilize, deploy, and operate anywhere in the world" [2]. This enables the military to achieve the national military strategy with limited personnel, equipment, and support material. (For the reader's convenience, a glossary of acronyms and abbreviations is given in the Appendix.)

When forces within a given region are insufficient to complete an operation, additional forces must be deployed. Such forces cannot originate from a location outside the continental United States (OCONUS) without compromising the security of the donor. Therefore, forces from within the continental United States (CONUS) must be deployed to t h e theater and sustained during the operation. This deployment capability is critical to our national military strategy. The airlift

This p a p e r has benefited greatly from t h e support and input of persons in t h e modeling community. We specifically acknowledge from t h e assistance of: Maj. J. Hoover, B. Jones, B. Key, C. Keyfauver, T . Kowalsky, P. Loudin, J. Riveta, L T C J. Sees, and S. Young.

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T y p e s e t by ~4A4S-~X

840 K. MGKINZIE AND J. W. BARNES

and sea•if° assets used to transport forces (cargo and passengers) are procured and operated b y the military or by commercial firms under contract to the military.

In order to clarify the links between the military's strategic and tactical operations, the military defines three levels of war:

(1) tactical: employment of small combat units for a brief duration of time; (2) operational: employment, design, and organization of forces in campaigns, major opera-

tions and battles; and (3) strategic: highest level where a nation uses its resources to achieve its national objec-

tives [3] (involves movement of cargo (outsize, oversize, bulk, and total cargo) and pas- sengers (PAX) to and from CONUS and OCONUS.

The focus of this paper is on strategic mobility models (SMMs). As detailed below, strategic mobility is critical to force projection (FP) addressing six of its eight elements. SMMs enable analysts and planners to determine the methods and sequences for cargo and PAX movement at the strategic level of war by analyzing and comparing a variety of scenarios. Activities not requiring movement between CONUS and OCONUS are not the concern of SMMs because they are not at the strategic level of war. The two most recent analyses of SMMs are the Rand corporation s t u d y published in 1991 [4] and the U.S. T R A N S C O M decision report published in 1998 [5]. Significant changes and developments have occurred since these studies. This paper details the current relevant strategic mobility models and also describes several supporting models in use today.

This paper is organized as follows: Section 1 introduces SMMs; Section 2 presents some histor- ical/legacy models t h a t are no longer in use t o d a y b u t were critical to the development of today's models; Section 3 describes and compares current SMMs; Section 4 discusses several supporting models t h a t can augment the SMMs; and concluding remarks are given in Section 5.

1.1. O v e r v i e w o f S t r a t e g i c M o b i l i t y

Strategic mobility is a subset of b o t h strategic logistics and force projection. Strategic logistics is broadly defined as "the art and science of harnessing the economic and societal strengths of a nation for national defense" (Basic National Defense Doctrine [6]). Force projection is '%he ability to project the military element of national power from the continental United States (CONUS)

A c q u i s i t i o n ] Requirements I Definition [ Pre-positioning I

Reconstitution . . o ~ , . • = . • • : , • " " , • " • i " ~ = ' m . O o . J ~ e e " I Mobilization I " ° •

O • • # ~ , . = ~ l l l i i J l I = i = I = i i i i i ~

~ l l , • " • • Pra-deployment • . . . . Redeployment • - I I I II . ,'- I' ...... POSt Conflict/Crisis : • • I Depl°yment I I Operations I I

% • I i EnWoperations I ' : " % , - . . . . . . . . . . . . . . . . . . .

° e ° • • ° 0 • ° [- Oe-"mo-bil'71--zzation'-V " • ° e °

e l e l l l j i l l n • m l • ~ • e l t l e l ~ J J °

m Strategic Logistics • • • • • • F o r c e Projection

• ,, Strategic Mobility

Figure 1. Strategic logistics, force projection, and strategic mobility hierarchy.

A Review of Strategic Mobility Models 841

or another theater, in response to requirements for military operations" [7]. Strategic logistics, FP, and strategic mobility have a hierarchical relationship depicted in Figure 1.

Strategic mobility consists of six of the eight components of force projection and six of the twelve components of strategic logistics.

1.2. O v e r v i e w o f Strategic Mobility Modeling

Strategic mobility models are logistics models which represent the flow of cargo and PAX from CONUS to OCONUS theaters. These models represent the movement of cargo and PAX from their origin through a p o r t of embarkation (POE) (a departure point in CONUS, Alaska, or Hawaii) and a port of debarkation (POD) (an arrival point in theater), to the designated desti- nation/employment location. Utilizing prescribed resource parameters (e.g., number of aircraft and ships) and associated routes, such models a t t e m p t to deliver all cargo a n d PAX within pre- scribed time windows. To successfully utilize these routes, various transportation methods may be used and numerous "waypoints" (temporary holding locations) m a y be required between any of the four previously-mentioned points (origin, POE, POD, destination). Graham and Dowdy [8] depict this process with t h e following diagram (Figure 2)i

THROUGHPUTNRLIFT

TC UNn'S CONUS J.Rurr - % I ~ o o AiR

SEAUFT GROUND

Figure 2. End-to-end strategic mobility model [8].

This diagram shows units mobilizing at a CONUS origin location and transitioning by ground to a P O E (air or sea). From there cargo and PAX moves across ocean by the designated trans- portation method (air or sea) to a POD. Items are then moved again by selected transportation methods to their final destinations. In this latter stage, there can be several changes of trans- portation mode prior to arriving at their destination in theater.

This process from origin to destination (end-to-end) and actions at each of the stages pictured in Figure 2 are represented in SMMs in a variety of ways. This paper will describe and compare the current SMMs. Each model is evaluated in regard to the following features: operating platform (UNIX or PC and software requirements), ease of use by analysts and planners, ability to interface with other models and doctrinal formats, level of tracking detail for both cargo and PAX and transportation assets, whether it can model multiple port pickup (p/u) and drop-off (d/o) locations for each airplane/ship modeled, and its ability to accurately model the strategic mobility environment and meet force closure times requirements.

1.2.1. Types of strategic mobility planning

There are three types of strategic mobility planning: resource, deliberate, and crisis planning. As described below, the differing emphases of the three types of strategic mobility planning have led to the development of several different models.

Resource planning, largely synonymous with long term planning, is used to support long term budget planning and resource allocation. Resource planning focuses on improving the strategic

842 K. McKINZIE AND J. W. BARNES

mobility process by improving the flow of cargo and PAX via changes in force structure and policy to include the development of new equipment and implementation procedures. Resource planning is accomplished through two primary activities--capability assessments and requirement studies. A capability assessment analysis with a given set of transportation assets and determines the deployment capabilities of those assets under different scenarios. A requirements s t u d y seeks to determine the appropriate set of transportation assets for use in a given scenario or set of scenarios.

Deliberate planning, or midrange planning, addresses the requirements and capabilities to support a specific deployment scenario, b u t does not focus on the details of a specific deployment. Deliberate planning assesses the feasibility of a plan and provides estimates and expectations of a deployment schedule in its support of the plan. If and when the plan needs to b e employed, specific scenario dependent criteria will need to be considered prior to implementation. This is conducted in the next level of planning.

Crisis action planning, or near term planning, focuses on the actual implementation of a deploy- ment plan. While higher-level planning may be conducted over a period of months or years, crisis action planning takes place on the order of weeks or days and will be executed at the end of the planning horizon. This process can be significantly accelerated b y the deliberate planning phase. In crisis action planning, the plan is reassessed for any changes either in force structure or policy t h a t may have occurred since the deliberate plan was assessed. Specific criteria are considered such as changes due to weather, natural or man-made disaster, and international agreements. Completion of these activities leads directly to final implementation and force deployment.

1.2.2. I n p u t files

For each of the SMMs, there are typically three types of inputs: requirements prepositioned, transportation resources, and a scenario. The requirements file is provided in the form of a time phased force deployment d a t a ( T P F D D ) . Portions of a T P F D D are extracted (or constructed) for use in the SMMs.

The T P F D D contains time-phased force data, cargo and PAX data, and movement d a t a [9]. In short, the T P F D D defines when and where cargo and PAX need to be picked up and when and where t h e y need to be delivered. T P F D D d a t a includes (see Figure 3) a latest arrival time (LAD) which imposes a desired sequence of arrival at the POD. Other time constraints such as ready to load date at the origin (RLD), available to load date at the P O E (ALD), earliest arrival date at the P O D (EAD), and required delivery date to the destination (RDD) are also present. The pairing of the E A D and LAD establishes an arrival time window at the POD. Violations of these constraints m a y significantly affect the safety of the mission and of cargo and PAX in general. In many types of analysis, an early completion of a schedule m a y be the dominant consideration. However, in SMMs, early completion is not dominant b u t rather one of several considerations in achieving a multicriteria objective.

The standard descriptions for modeling level of detail for military logistics simulations are those used in joint operation planning and execution system ( J O P E S ) . The J O P E S level of detail can

Planning

I I I PoE ! PoD Dosu auo

i i i

F i g u r e 3. P l a n n i n g t i m e c o n s t r a i n t s .

A R e v i e w o f S t r a t e g i c M o b i l i t y M o d e l s 843

be an aggregation of items such as in Levels i, 2, or 3 or finer detail such as in Levels 4 or 5. Level 1 aggregates items as total number of passengers and total short tons, total measurement tons, total square feet, and/or total hundreds of barrels. Level 2 is the summary level and expresses total number of passengers, short tons, measurement tons (including barrels), total square feet of bulk, oversize, outsize, and nonair-transportable cargo and PAX. Level 3 is detailed by cargo and PAX category and is expressed as total number of passengers, short tons and/or m~asurement tons (including barrels), and total square feet of cargo. Level 4 details passengers by service specialty code and considers individual dimensional data (expressed in length, width, and height in number of inches) of cargo by equipment type (as defined by individual national stock number) by unit line number (ULN). Finally, Level 5 considers priority of shipments and expresses passengers by service specialty code in deployment sequence by ULN, plus individual weight (in pounds) and dimensional data (expressed in length, width, and height in number of inches) of equipment in deployment sequence by ULN [I0].

The TPFDD lists items by ULN which may contain multiple quantities of a given item. A ULN may be composed of multiple pallets of material, unpalletized materiel, or multiple personnel. Other ULN restrictions such as size and weight restrictions may also be present.

The primary classifications for aircraft are PAX and cargo where cargo is further classified as bulk, oversize, outsize, and nonair transportable. PAX must be assigned to aircraft. Bulk cargo is palletized and fits on a "pallet of 88 inches by 108 inches, or with tie-down devices that occupies a space not greater than 84 inches by 104 inches" [II]. Oversize cargo is larger than bulk and is "loaded to a design height of 96 inches but is equal to or less than 1,090 inches in length, 117 inches in width, and 105 inches in height" and is nonpalletized rolling stock [ii]. Outsize cargo, the largest cargo category, is not palletized and less than "1,453 inches in length, 144 inches in width, and 156 inches in height" or less than "1,453 inches in length, 216 inches in width, and 114 inches in height" [Ii]. Nonair transportable cargo is any single item that exceeds the dimensions of outsize cargo. Ships also use these cargo categories, but due to the larger capacity of a ship it is more common to use the larger load measurements of 20 foot containers (TEUs), breakbulk (roll on roll off--RORO), or square feet rather than inches.

Table 1 presents a small portion of a TPFDD [12]. The military has prepositioned equipment and support material around the world on land and

sea for deployment use. This reduces the distance the equipment and support material must be

T a b l e i . T P F D D s a m p l e .

L i n e I D O n l o a d O f l l o a d L o a d R e q u i r e d B u l k O v e r s i z e O u t s i z e

U N I T 1 4 8 6 K B L V R K P S 10 24 292 1009 59

U N I T 1 4 8 7 K W R I R K P S 10 24 116 349 35

U N I T 1 4 8 8 K T I K R K P S 10 . 24 6 9 2

U N I T 1 4 8 9 K T C M R K P K 10 2 4 0 0 15

U N I T 1 4 9 0 K T I K R K P S 10 24 0 41 85

U N I T 1 4 9 1 P A E I R K P S 11 24 0 110 5

U N I T 1 4 9 2 K S U U R K P K 11 24 133 32 7

U N I T 1 4 9 3 K T I K R K P S [ 11 24 29 764 9

U N I T 1 4 9 4 P H I K R K P S 11 25 63 182 7

U N I T 1 4 9 5 K S U U R K T Y 11 25 634 562 8 8 0

U N I T 1 4 9 6 K D O V R K J K 11 25 220 208 212

U N I T 1 4 9 7 K T I K R K S O 11 25 0 190 83

U N I T 1 4 9 8 K H O P R O D N 11 25 4 7 44 12

U N I T 1 4 9 9 K L F I P H I K 11 25 0 0 0

U N I T 1 5 0 0 K O F F P H I K 11 25 0 0 0

P a s s e n g e r s O w n e r T y p e

0 9

0 23

0 2

0 5

0 5

19 2

59 18

0 18

0 18

0 4

0 1

402 1

44 1

1876 2

814 2

844 K. MCKINZIE AND J. W. BARNES

transported. If there are prepositioned stocks available, their locations and quantities are also provided as inputs.

Transportation resources input includes availability and constraints on transportation vehicles, ports, and routes. Among these restrictions are constraints associated with fuel usage, cargo and PAX capacities, loading practices, and maintenance.

The scenario file includes any additional d a t a for a particular version of a scenario, such as availability of ports and canals and varying time driven constraints.

1.2.3. N o d e a n d l i n k c o v e r a g e

As depicted in Figure 2, the modeling process is performed in a network environment with nodes and arcs. Each node may require the completion of several activities. Transport of cargo and PAX occurs on the arcs. All b u t one of the current models implement activities b y conducting deterministic activity simulations. The primary nodes of interest include: home station, POD, P O E , and destination.

1.2.4. T a s k c o v e r a g e

In [4], nine tasks were addressed for the SMMs: merge files, aggregate records, prioritize records, select modes, schedule cargo and PAX, simulate movements, prepare textual output, prepare graphical output, and check and correct. For comparison purposes, we will consider the same nine tasks. In [4] all of the SMMs were deterministic simulations, with most tasks taking place within the models. In the last 11 years the models have evolved to interfacing with other models. This leverages the capabilities of supporting models so t h a t many SMM tasks are performed by calling these models. The models also allow some probabilistic considerations. However, these are usually specified deterministic failure rates. All of the current models are characterized as a "simulation models" since t h e y simulate (emulate) movement of cargo and PAX, even if t h e y are not stochastic in nature.

1.2.5. S o l u t i o n c h a r a c t e r i s t i c s

The solutions provided by an SMMs are multitiered and comprise the item level schedule of the cargo and PAX, to include the transportation asset schedule and force closure profiles. Many criteria are considered including: time constraints, cargo and PAX delivered (on time, late, not delivered), cargo t y p e (bulk, oversize, outsize) to include PAX, transportation assets used (type, number, distance traveled), and ports usage frequency. The objective is a cost driven function t h a t is measured in terms of monetary costs, time, cargo and PAX delivery, a n d / o r asset usage.

1.3. S t r a t e g i c M o d e l i n g

The above discussion gives only an overview of the more important factors t h a t analysts and planners consider when choosing an SMM to use. Military analysts would prefer t h a t models depict every aspect of their modeled environment. The size and scope of the scenarios associated with an SMM precludes this preference with the modeling capabilities currently available. As a consequence, many of the detailed aspects of strategic mobility are represented, b u t not fully modeled. Many such aspects are discussed in more detail in supporting models. A selected set of such supporting models are addressed later in this paper. This additionM capability for detailed analysis supports enhanced interoperability and further development of supporting models a n d SMMs.

2. L E G A C Y M O D E L S

Many of the defense transportation system (DTS) SMMs t h a t were developed and used b y the Department of Defense (DoD) are no longer in use. This section provides a brief description of some of the more important of these legacy models.

A Review of Strategic Mobility Models 845

Some models have become obsolete due to a change in operating strategies, others have been replaced by more capable models, and others have been replaced due to their failure to meet COE standards. This ongoing, dynamic improvement process will continue in the future. As part of this process, the DoD has implemented guidelines to ensure new and developing models comply with interoperability standards (COE). This has led to the development of a system for integrat- ing models into one command and control (C2) system and for insuring the interoperability of transport ation/logistical systems.

"The end of the Cold War combined with a maturing simulation technology environment created an enviromnent for change" [13]. This dynamic was enhanced by a draw down of the military forces and funding which resulted in a modified DoD simulation acquisition strategy. Stand alone models and simulation models were identified for replacement b y models that were COE compliant. Today, most standMone models are legacy systems and the models in use today are interoperable with many other models [14].

2.1. Rapid Intertheater Deployment Simulation Model ( R A P I D S I M )

This transportation flow model is the predecessor of the model for intertheater deployment by air and sea (MIDAS). RAPIDSIM does not model specific items; rather it aggregates all items and capacities into common units of flow. RAPIDSIM only modeled the movement of cargo and PAX from P O E to POD. The cargo and PAX records required a priority sorting b y the analyst prior to the model execution. This very cumbersome model required an expert to operate [4,15].

2.2. Transportation Feasibility Estimator ( T F E )

TFE, a transportation flow model, was the predecessor of the joint flow and analysis system for transportation (JFAST). T F E was used to determine the gross feasibility of a T P F D D ' s transportation requirement. It had the capability to model ten times as many requirements as the MIDAS of that era in a typical run because of the flow nature of the model rather than performing a detailed simulation [4,15].

2.3. World Wide Military Command and Control S y s t e m ( W W M C C S )

W W M C C S provided "the means for operational direction and technical administrative support involved in the function" of C2 of U.S. Military Forces [16]. In 1996, this system was replaced by the global command and control system (CCCS) as part of the initiative towards interoperability of military models and systems [i7]. Although neither WV~rMCCS nor GCCS simulate a specific aspect of military operations, they integrate models and systems to improve the information flow and decision making capabilities for military leaders.

2.4. Computer Aided L o a d M a n i f e s t i n g ( C A L M )

Primarily used b y the U.S. Air Force (USAF), CALM was replaced by automated air load planning system (AALPS) [18]. CALM was an automated air load planner that printed manifests and produced load plans to support aircraft loading [19].

2.5. Strategic Sealift Analysis System (SEASTRAT)

SEASTRAT was replaced b y JFAST 7. It was designed for sealiR analysis contingency plan- ning. Consisting of two primary functional modules, ship file and route generation, it revolution- ized the methods for calculating ship routes [20].

2.6. Air Mobility Command (AMC) Deployment Analysis System ( A D A N S )

ADANS, used by deliberate planners, managed information on cargo and PAX, scheduled air missions, and analyzed schedules. Prior to ADANS, air flow planners were limited to planning

846 K. McKINzm AND J. W. BARNES

their missions b y hand and typing them into the existing command and control system [21]. ADANS was replaced by the consolidated air mobility planning system (CAMPS) which joined two models, ADANS and the combined mating and ranging planning system (CMARPS), adding a tanker refueling capability to ADANS [22] in February 2002 [23].

2.7. C o m b i n e d M a t i n g and R a n g i n g P l a n n i n g S y s t e m ( C M A R P S )

C M A R P S was the second of the two models replaced by CAMPS as a part of the suite of GCCS models. C M A R P S was used to schedule specific tanker aircraft to refueling points. The model takes a given mission for aircraft then determines the fuel t h a t mission will need. Next, it determines where the mission aircraft will need to be refueled and schedules refueling points consistent with other parameters such as "minimizing use of tankers, minimizing tanker fuel consumption, using air refuelable tankers, regenerating tankers for tanker reuse and satisfying abort base requirements" [24].

3. S T R A T E G I C M O B I L I T Y M O D E L S All of the SMMs in use today are COE compliant and are under continual development.

Some SMMs improvements are designed to provide greater fidelity in modeling capability and algorithms. Other SMM developments attempt to improve interfaces and transitions to more deployable platforms.

Although there are many models which interface with SMMs, none are used throughout the DoD. Each of the SMMs is used by one or more organizations that find an SMM's capabilities uniquely suited to their required level of planning. In the descriptions presented below, the SMMs are described in regard to their task coverage, node and link coverage, and solution characteristics. Following a separate description of each SMM, they are compared.

Only one of the models being used today, MIDAS, was covered by Shank et al. [4]. For this reason, an additional discussion is provided on the changes in MIDAS since that study.

The four major SMMs in current use today are the global deployment analysis system (GDAS), JFAST, MIDAS, and the mobility simulation model (MobSim©). Each section is prefaced with a short description of the model provided by the model user/developer. This is followed by our assessment of the model.

3.1. G l o b a l D e p l o y m e n t A n a l y s i s S y s t e m ( G D A S )

GDAS was developed by Noetics, Inc. in cooperation with the Center for Army Analysis (CAA), the U.S. Transportation Command (USTRANSCOM), Stanley Associates Inc., and the U.S. Department of Transportation's John A. Volpe National Transportation Systems Center (Volpe Center). GDAS is used to perform analyses of transportation policy issues and opera- tional planning tasks for large or small scale force deployments. The transportation requirements represented by these deployments may be aggregated or may be very specific. The latest version of GDAS runs on standard personal computers (PCs) running Microsoft Windows and Office 2000 [25].

3.1.1. D a t a p r e p a r a t i o n GDAS allows users to model new technology, define new units of measure, as well as add

new ports and capabilities, all without programmer support. This ability significantly assists in resource planning b y providing the means to analyze future capabilities prior to their development and acquisition. Results from this analysis may be used to influence future production and acquisition decisions and policy decisions.

GDAS allows the user to import the T P F D D in J O P E S Menu B Level 8 formatted file (the standard for DOD models), the associated t y p e unit characteristics (TUCHA) file, and the geo- graphic location file (Geoloc) directly from the J O P E S system to build movement requirements.

A Review of Strategic Mobility Models 847

The model merges the T P F D D (both unit and nonunit requirements) with the TUCHA to de- velop individual unit requirements (ULN level) at JOPES Levels 3 (default), 4, or 5 detail if available. GDAS then translates the requirement types, Geoloc, and cargo and PAX category codes to GDAS formatted nodes and …