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Page 1: Scenarios and priorities in transport planning: Application to the Sudan

Tmnspn Res., Vol. Il. pp. 343-350. Persamon Press 1977. Printed in Great Britain

SCENARIOS AND PRIORITIES IN TRANSPORT PLANNING: APPLICATION TO THE SUDANt

THOMAS L. SMTY The Wharton School, University of Pennsylvania, Philadelphia, PA 19174, U.S.A.

(Received 19 February 1976; in revised form 14 January 1977)

Abstract-This paper describes two related aspects of a transportation planning study recently completed for the Sudan-the use of scenarios and the prioritization of those scenarios and the associated transport projects. In the use of scenarios, considerable care was taken in the specifkation of diierent types of scenarios and the planning issues each is designed to highlight, and the approach should lind application to other transport problems. For the selection of a particular scenario, to be used as a basis for detailed transport project planning, a new method of evaluation or prioritization was developed, and this is presented also. Both are illustrated by the application to the Sudan.

INTRODUCTION

This paper is a summary of some of the methodology recently developed for use in preparing a transport plan for the Sudan. Particularly noteworthy is the use of scenarios in the planning and the development of a new method for evaluating alternative plans. This paper focuses on these two aspects of the research.

A formal mathematical approach to socio-political problems is, at present, difficult and often unsatisfactory and involves many risks regarding the unknown. That is one reason why the scenario approach, despite its structural shortcomings, is used as an alternative de- vice-practiced today more like an art than a science-to cope with the complexity. Another problem with the purely formal or theoretical approach is the difficulty of operationalizing or applying the results in the real world. Here again the scenario approach has been found to be better suited for modification and adaptation for planning and implementation purposes.

We shall begin by giving a brief account of those aspects of the methodology which were thought to have interesting theoretical implications in transport planning, and then indicate its application to the Sudan as a case study.

SCENARMX IN PLANNING

A useful tool rather widely employed in planning today is the method of scenario construction. Despite its wide usage, the method of scenarios has not been specified clearly in the literature and there seems to be con- siderable variation in actual practice or usage of the method. The method of scenarios as developed and used in this transportation planning study is presented below, in the form of definitions and procedures which can be used in other transportation planning efforts.

A scenario is a portrayal of the future with strong focusing on the particular idea or subject being em-

tThis study was conducted by the ADAR Corporation for the Kuwait Fund of Arab Economic Development and the Demo- cratic Republic of the Sudan. The author was the director of the project.

phasized (e.g. a transport system) with an “adequate” account of its interaction with environmental, social, political, technological and economic factors. It follows that a faithful scenario analysis must examine, in considerable depth, projections of all these factors in order to arrive at a convincing description of the state of the particular subject under various possible assump- tions. In the process of scenario construction, one must guard against free use of uninhibited or undisciplined imagination and avoid falling into a science fiction type of prognostication.

There are two general types of scenarios. They are the exploratory scenario and the anticipatory scenario.

The exploratory scenario approach is designed to explore alternative futures, in a set of trend-seeking

scenarios, by examining events that are logically neces- sary for a possible future by paramaterizing the principal components of the system under study. Its starting point is the present. Limiting scenarios are constructed in conjunction with trend-seeking scenarios to constrain the possible futures through parametric variations and by careful examination of the hypotheses of evolution from the present. The exploratory scenario is often used as a technique to spark the imagination, stimulate discussion and attract the attention of decision-makers to specific issues. The trend-seeking scenario does not make use of references to theory and methodology. Its practitioners, although they take its conclusions with a grain of salt, argue that as far as making errors in predicting the future they are in good company with all the other methods.

The anticipatory scenario approach is concerned with the conceptualization of feasible and desirable futures. Unlike the exploratory scenario which proceeds from the present to the future, anticipatory scenarios follow the inverse path by starting with the future and working backwards to the present to discover what alternatives and actions (trajectory corrections) are necessary to attain these futures. There are two types of anticipatory scenarios: The normative scenario, which determines at the start a set of given objectives to be realized and defines a path for their realization (one version is to idealize the objectives and find technologically feasible

343

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344 T. L. SAATY

means with viable descriptions to reach them); and a contrast scenario which is characterized by a sketch of a desirable and feasible future which is on the boundary of the anticipatory scenario. Each contrast scenario em- phasizes sharply a particular range of assumptions whose totality comprises the convex hull of the possible futures. Normative or contrast scenarios are synthesized into a composite scenario which retains the properties of each of the scenarios with appropriate mix or emphases. Since the future is shaped by a variety of forces or interests, each seeking the fulfdlment of its particular objectives, the synthesis of a wide ranging set of scenarios into a composite scenario must take into consideration the actors who influence the future, their objectives and the particular policies they will pursue in each scenario to fulflll their objectives. Thus, the normative process of constructing the composite scenario must reflect the priority of the actors according to importance to bring about a certain degree of fulfillment of the building blocks of each scenario. A major technical problem in scenario construction is how to construct a composite scenario from a large set of scenarios which define the “cone” of the future.

Some of the most important components of scenario construction are the following:

(1) Definition of the general system and of external and internal constraints and identification of subsystems.

(2) Hierarchical structuring of subsystems and iden- tification of regulating components.

(3) Definitions of the states of the system and modelling its historical development.

(4) Scenario treatment of the historical analysis highlighting the system’s evolution and its impacts on characteristics of the society together with examination of the internal dynamics of the model.

(5) Definition of the objectives of the scenario with a discussion of their values.

(6) Choice of the types of scenario to be used. (7) Development of a data base of past, present and

future information. (8) Identification of the structural components, factors

which offset equilibrium, evolutionary tendencies of the system.

(9) Description of the tensions inherent in the func- tional mechanisms.

(10) Analysis of the regulators of the system and of its coherence.

(11) Critique and revision of the previous analysis, refinement of the scenario by examining constraints, disequilibrium, tensions, forces, contradiction, interven- tion of the regulators and statement of the contradictions which affect the survival of the system.

(12) Production of an improved scenario. Frequently, the Delphi method of eliciting judgment

from knowledgeable people is used to make a systematic identification of the elements of a scenario. The ad- vantages and shortcomings of the method are discussed at length in Julien et al. (1974) and will not be repeated here. The method is considered by many as an indispensable tool.

Probably the best answer to the question of validation

of the scenario approach is that it is a unique aid in Forecasting the future. Its conclusions should be amenable to reasonable interpretation. The results derived from it for implementation should be categorized into urgency classes and only the most urgent projects implemented first and after a period, the planning process is then revised or iterated.

In the next section we give a summary of the general methodology of prioritization which was used to con- struct the composite scenario for the case of the Sudan and to derive priorities for the projects. These project priorities came to serve a useful role in cost-benefit analysis and subsequent decisions as to which projects should receive the earliest attention for implementation.

THE MODEL OF PRlORlTIZATlON

A major problem in a modeling approach to decision making is the scaling of judgments. Any method of scaling must stand the test of several criteria. For example, it should reflect accurately the feelings em- bodied in the judgments; it should allow for a moderate uncertainty in judgments without changing the judgment value on the scale; strong changes in judgment should be reflected in appropriate variations along the scale. The results of the model should not change drastically by making small changes in judgment values.

In performing numerical pairwise comparisons bet- ween complex activities, ordinarily one has ditIiculty in translating feeling and experience to numbers which say exactly how much more one activity impacts on a given objective than another. The business of assigning numbers seems arbitrary, and the numerical approach to prioritization acquires the semblance of artiticiality. We use a systematic way of placing the activities in various importance ranks and then assigning numerical values to each rank. With increased experience, the initial scale chosen for the pairwise comparisons can be modified until it acquires greater autonomy so that its use might be expanded.

In order to assign numerically meaningful numbers when comparing two activities, one needs a thorough understanding of both activities and the extent of the properties they have relevant to the objective or criterion being considered. The model requires that judgments be supplied by questioning experienced people who know the activities and the objectives and their interactions. These judgments indicate the relative importance of one activity over another for each objective.

In constructing a scale of importance, one customarily asks a decision-maker to state (a) which of two activities, in his opinion, is more important, and (b) his perception of this intensity of difference in importance, expressed as a rank number on a given numerical scale. Only direct effects of the activities on the objectives are considered in the judgment process. One method for dealing with indirect effects is to consider input-output types of relations between the activities. We do this elsewhere (Saaty, 1975) when considering, for example, the al- location of energy to interdependent industries according to priority.

As a preliminary step towards the construction of an

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Scenarios and priorities in transport planning 345

intensity scale of importance for activities, we have broken down the importance ranks as indicated in Table 1.

To explain the various numbers note that the integers assigned attempt to estimate a scale of values

(w I,..., w.) of the activities. Each value aij assigned in the matrix of pairwise comparison A may be regarded as an estimate of the ratio wi/wi taken to the nearest integer after appropriate scaling to make values between the (unknown) underlying scale and the approximation scale appropriately correspond through ratios.

If we assume that the values are estimated precisely, i.e. aii = wdwi, it is then sufficient to require consistency of the judgment matrix to obtain such equality. Con- sistency means QUJ~ = aa, from which we have for the main diagonal entries aii = 1 and the reciprocal relations air = I/u~J. In general, we do not expect consistency to hold everywhere in the matrix because people’s feelings do not conform to an exact formula such as the one just given. However, to improve consistency in the numerical judgments, it is recommended to those who supply the judgments that whatever value a, they may assign in comparing the ith activity with the jth one, they should consider assigning the reciprocal value to aJi, thus putting qji = l/all. It follows that clii = 1. Roughly speaking, if one activity is judged to be (r times stronger than another, then the latter is only l/a times as strong as the former. It can be easily seen that when we have consistency, the matrix has unit rank and it is sufficient to know one row of the matrix to construct the remaining entries. For eXampk, if we know the first row then aii = alJ/ali (0

rational) assuming, of course, that alif 0 for all i. We do not insist that judgments be consistent and,

hence, they need not be transitive; i.e. if the relative importance of C, is greater than that of C2 and the

relative importance of C2 is greater than that of C3, then the relation of importance of C, need not be greater than that of C1, a common occurrence in human judgments. An interesting illustration is afforded by tournaments regarding inconsistency or lack of transitivity of pre- ferences. A team CI may lose against another team CZ which has lost to a third team C,, yet C, may have won against C,. Thus, team behavior is inconsistent-a fact which has to be accepted in the formulation, and nothing can be done about it.

The treatment of the easier and more elegant case of consistency is a special case. The point is that one must develop rational means for making decisions in spite of inconsistency. We shall assume that our judgmental inputs are all provided by a single individual expert or are the collective view of several individuals as the case may be if no single individual knows enough to supply all the judgments by himself. A major difficulty lies in the large number of questions an individual must answer in order to obtain the n(n - 1)/2 judgments for each objective, where n is the number of activities, and reciprocals are used. There is room for improvement in facilitating the process of supplying these judgments.

With inconsistency we no longer have &J(WJ/W,) = 1,

i,j= 1 , . . . , n. We seek a condition on each row of the

matrix. We note that with consistency i+, aiJ(WJ,Wi) = n,

i=l , . . . , n, where the right side is the same constant II, the largest eigenvalue of A, the other eigenvalues of A are all zero since the rank of A is unity and the sum of the eigenvalues is equal to the trace Z cii = n.

It is possible to argue for the general case that the desired scale w = (w,, . . . , w.) must satisfy the eigen- value problem Aw = ,Lw where A,., is the largest eigenvalue of A, which by Perron Frobenius’ theory,

Table 1. Importance scale for prioritization

Intensity of importance Definition Explanation

2,4,6,8

Reciprocals of above non-zero

Rationals

Equal importance

Weak importance of one over another Essential or strong importance

Demonstrated importance

Absolute importance

Intermediate values between the two adjacent judgments If activity i has one of the above non-zero numbers assigned to it when compared with activity j, then j has the reciprocal value when compared with i. Ratios arising from the scale

Two activities contribute equally to the objective Experience and judgmint slightly favor one activity over another. Experience and judgment strongly favor one activity over another. An activity is strongly favored and its dominance demonstrated in practice. The evidence favoring one activity over another is of the highest pdssible order of affirmation. When compromise is needed

See text

If consistency were to be forced by obtaining n numerical values to span the matrix.

tOn occasion in 2 by 2 problems, we have used 1+ e, O<c of to indicate very slight dominance between two nearly equal activities.

Page 4: Scenarios and priorities in transport planning: Application to the Sudan

346 T. L. SAATY

turns out to have an essentially unique non-negative solution w if A is non-negative and irreducible.

To see how one arrives at this eigenvalue formulation for the general problem, note first that in the consistent case if we take a typical row ail, ui2,. . . , a. and multiply ai, by WI, ui2 by ~2,. . . , ai. by wn we would obtain

. . wi. this all values exact therefore we the Aw obtain

vector and as stated, solve problem = to the w we

by each its by wi

obtain desired i-l

the case process multiplying ith as does yield values . . , wi but

deviations about them which amount to perturbations of the exact values. It is known in matrix theory that the eigenvalues of a matrix are continuous functions of the coefficients. If we perturb the coefficients of a consistent matrix, we are interested in the case where the largest eigenvalue remains near n and the remaining ones near zero. Thus, our problem becomes: fmd w which satisfies Aw = hmnxw and the results would be the more valid the closer A,., is to n. This requirement corresponds to finding Wi, i=l,..., n which minimizes sums: u,pX;‘+ (l/aij)xixi_’ in the expression for A. It is known that A,, is a monotone increasing function of ail and error in ulj is compensated for by a,, = l/n,,. For this reason use of the relation aji = l/ni, helps to improve consistency. The relative deviation of A,., from n is used as a “global” measure of the consistency and hence usefulness of the results. It is worth noting that we have a ratio scale (invariant under positive similarity transformations) as our approach can be shown to satisfy the axioms and representation theorems for a ratio scale.

Once ratio judgments are elicited from the subjects to form one row or column, the use of paired comparisons can make further contributions to locating the stimuli by possibly enhancing stability where the data are nearly but not quite perfectly consistent. More importantly, requiring each subject to rate each pair of stimuli separately permits tests of dimensionality to be under- taken.

To summarize: the process begins with a listing of the activities against themselves in a matrix. A referrent attribute or objective is chosen for the comparison and numerical values are supplied from the amount of evidence available that any activity dominates or is more important than another, thus tilling out the matrix. Reciprocal values are entered automatically and the eigenvalue problem is solved. Consider

A mpl-n n-l =-&A,

where Ai are the remaining eigenvalues of A. If this index is large when compared with its average value from a sample of size 50 matrices of order n with random entries from the l-9 scale and using their reciprocals in appropriate positions, the judgments are re-examined for improvement particularly in positions

where ai1 differs significantly from wl/wi. The process is repeated for each objective, resulting in several matrices. The objectives themselves are expressed pairwise in the same way with respect to a general overriding objective such as economic and social development. The theory is then applied.

The solution w for each judgment matrix A gives (after dividing by the sum of its entries) the priority weights representing the impact of the activities being compared on one of the objectives. After doing this for each objective and then in a separate matrix comparing the objectives, we weight each priority vector of the activities with the corresponding priority of its objective and add the resulting weight vectors of objectives to obtain the overall priority measure. Thus, to obtain the weighted priority vector, its matrix of eigenvalues is multiplied on the right by the weighted vector of the adjacent upper level.

Our method has several significant virtues: (1) It is natural; that is, it provides a fairly direct

translation from the knowledge of qualified observers (used to determine A) to the derivation of priorities.

(2) It is easy to compute with, and in various test applications, has yielded results which agree nicely with observed data.

(3) It satisfies various technical restrictions; e.g., a small change in the Q’S produces a small change in the answer.

(4) Most importantly, it provides a useful tool to deal with inconsistency and a measure of the overall de- parture of judgments from consistency.

(5) It offers an opportunity to study priorities in hierarchical structures quantitatively.

Figure 1 illustrates the use of a hierarchy to structure large, complex problems such as the Sudan transportation problem to be discussed in detail. The first hierarchy level has a single objective used as a criterion below. Its priority value is assumed to equal unity. The second hierarchy level objectives have priorities derived from their matrix of comparison of their impact on the objective given in the first level. The third hierarchy level consists of the regions considered as to their contributions to the scenarios. The fourth hierarchy level objectives fall in groups according to which element of the third hierarchy level they contribute. Their overall priority is obtained from the matrix of comparison of their impact on the relevant objective of the third level multiplied by nJm (the fraction of elements in their group with ): ni = m where i is the index of groupings) and by the priority of the element from the third level class they fall under. The sum of the priorities in each level must add up to unity. This is achieved by a normalization process of dividing the priority of each objective by the sum of all priorities in the level. Lower hierarchy level priorities are similarly derived based on the immediately preceding level.

An elementary example Rather than presenting over-simplified transportation

examples to illustrate application of the method with numerical judgments and accompanying calculations, we

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Scenarios and priorities in transport planning 341

present an elementary practical example, which is simple the future of the Sudan taking into consideration detailed and direct. It ilhrstrates calculations in a hierarchy. information regarding its agriculture, industry, politics

Three highschools-A, B, C-were analyzed from the and transportation. Based on the idea of hierarchical standpoint of a candidate according to their desirability. prioritization applied to the scenarios with regard to their Six characteristics were selected for the comparison. feasibility and desirability, a composite scenario was They are: learning, friends, school lie, vocational constructed reflecting these weights of the individual training, college preparation and music classes. The scenarios within which the priorities of the important pairwise judgment matrices were as follows: regions of the Sudan were studied according to their

Comparison of characteristics with respect to overall satisfaction with school

School Vocational College Music Learning Friends life training preparation classes

Erg 1 4 3 1 3 4

l/4 1 I 3 115 1 School life l/3 l/7 1 l/3 l/5 l/6 vocational training 1 l/3 5 1 1 l/3 College preparation l/3 5 5

: 1 3

Music classes l/4 1 6 l/3 1

Comparison of schools with respect to the six characteristics

Vocational College Music Learning Friends School life training preparation classes

A B C A B C A B C A B C A B C A B C

A 1 l/3 l/2 A 1 1 1 A 151 A 191 A 1 l/2 1 A 1 6 4 B 313 Bill B l/5 1 l/5 B l/9 1 l/S B 2 1 2 B l/6 1 l/3 c 2 l/3 1 c 1 1 1 c 1 5 1 c l/7 5 1 c 1 l/2 1 c l/4 3 1

The eigenvector of the first matrix is given by: potential contributions to that scenario. Transport supply and demand were determined and inadequacies in the

(0.32, 0.14, 0.04, 0.13, 0.24, 0.14) existing system-termed gaps-identified (using a linear programming model) within the context of this scenario.

and its corresponding eigenvalue is A = 7.49 which is far The transportation gaps were parameterized under three from the consistent value 6. different NGP growth rates-4.3, 6 and 7.3%. These

The eigenvalues and eigenvectors of the other six rates not only determined demand but also whether matrices are: sufficient capital would be generated to afford the total

A = 3.05 A=3 1\=3 A = 3.21 A=3.00 A = 3.05 vocational College

Leaming friends School lie training preparation Music

0.16 0.33 0.45 0.77 0.25 0.69 0.59 0.33 0.09 0.05 0.50 0.09 0.25 0.33 0.46 0.17 0.25 0.22

To obtain the overall ranking of the schools, we multiply the last matrix on the right by the transpose of the vector of weights of the characteristics. This yields:

A = 0.37 B = 0.38 c = 0.25

The individual went to school A because it had almost the same rank as school B. Previously, he had been attending school B.

THEWDANzACASESl’UDY

The planning began with the construction of econometric models of the Sudan projecting to 1985. It was followed by the construction of a set of scenarios of

plan. With the aid of a set of guidelines (called a doctrine) concerned with social, political, technological and other factors relating to the Sudan, the projects were prioritized. This was done according to their con- tributions to the regional development in the context of the composite scenario, thus receiving an overall set of weights. The cost of each project was divided by its priority, thereby obtaining a measure of the effectiveness of investment.

The set of projects was divided essentially according to priority into three time phases for implementation. By way of validation, results of the priorities tended to coincide rather closely with what had been regarded as of great importance in the five year plan which preceded this study by a few years.

Page 6: Scenarios and priorities in transport planning: Application to the Sudan

348 T. L. SMP

I st Level:

projects in regions

Fig. 1.

Scenarios of the Sudan’s future In planning alternative strategies for the future of the

Sudan’s transport system, the method of anticipatory scenario construction was used. A stti of nearly twenty people was intermittently occupied over a period of four months in scenario definition, analysis and construction. Occasional participants were the Foreign Minister, the Minister of Transport and officials from the Siudan Planning Commission. This part of the study followed a period of eight months in a vast attempt to gather data and information and to construct econometric models of the Sudan. The result was a composite scenario which provided the basis for determining transport require- ments and priorities.

The construction of the composite scenario was based on the use of the method of priorities to compare the individual scenarios as to their feasibility and desirability to the various forces which will shape changes in the Sudanese society. First, a reference scenario of the state of the Sudan was constructed to include all major economic, political, social and transport parameters. The other scenarios comprise variations in the values of these parameters (some of which were given in qualitative terms). Thus, diagnosis of the resource endowment, the social and political factors, and potentialities for change, led to the development of four plausible scenarios for the Sudan of 1985. New possibilities such as industrialization or a service-oriented economy, which do not seem feasible at this time, may be incorporated in a revision. All the scenarios are based in part on information derived from the econometric study and the estimations of present and projected production and consumption patterns. Hence the scenarios are all considered feasible on the basis of currently available information. The attainment of any scenario will depend on the policies adopted by the government and the availability of the indicated resources.

The scenarios and their transport implications are summarized in Table 2

Pairwise comparison of the four scenarios according to their feasibility and desirability by 1985 (revision of the plan could separate these two criteria) gave rise to the matrix and its corresponding eigenvector of weights presented above.

Priorities of the scenarios I II III IV

status quo I 1 l/7 l/5 l/3 Agricultural export II 7 1 5 5 Balanced regional growth III 5 l/5 1 5 Arab-African regional expansion IV 3 l/5 l/5 1

The priorities of the scenarios in the order they are listed are:

(0.05, 0.61, 0.25, 0.09).

This shows the perceived importance of each scenario relative to the other scenarios as well as the final priority ratings assigned to each. As can be seen, Scenario II dominates, with Scenario III next in importance. Since the future is likely to be not one or the other, but rather a composition of these scenarios-with emphasis indicated by the priorities-this information was used to construct a composite scenario of the Sudan of 1985, which is presented in Table 3.

This scenario is intended as the anticipated actual state of the future, it being a proportionate mix of the forces which make up the four scenarios just described above. The Composite Scenario takes the main thrust of Scenario II, the future given by far the highest priority, and is enlarged and balanced with certain elements from Scenarios III and IV. This composition indicates the likelihood of a synergistic amplification of individual features.

Sectoral investment strategies Total investment requirements to achieve the Com-

posite Scenario projected growth of real GNP at 7.3% per year are estimated to be approximately ES 2042 million (one fS is approximately $2.5) at 1974 price levels, or fS 3058 million at current price levels. The latter figure represents approximately 10% of the GNP each year over the planning period, 1972-85. This will be divided among the major sectors as shown in Table 4, for three possible rates of growth.

In terms of 1974 prices, we have the following investments in transport: 762.32, 533.56 and 262.32 million fS corresponding respectively to 7.3, 6 and 4.3% GNP annual growth rates. (These figures give costs of projects and fleet except for trucks, buses and air transport. They also do not include operating costs.) The corresponding total investment at 1974 price levels are fS 1703 million at the 6% GNP growth rate and fS 1410 million at the 4.3% GNP growth rate. The allocation of investment is a critical consideration in achieving development targets. Since the econometric model calculations do not directly measure sectoral capital stock requirements and consequent investment needs, subsidiary computations have been made to develop the required investment allocations.

Priorities of the projects The method of priorities was then used to determine

the overall priorities of the projects in the plan. The process was carried out as follows. We have seen earlier

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Scenarios and priorities in transport planning 349

Table 2. The scenarios

Scenario I: Reference projection

The reference projection describes the likely state of the Sudanese economy and transport system in 1985 if no purposeful intervention takes place at present. We assume that the factors governing the evolution of the Sudan over the next ten years are similar to those that have influenced the country’s development in the recent past. The main characteristic of the reference projection is a conservative 3.5% annual expansion rate in the economy. The economy will remain centered on agriculture, and the crops and methods of farming will not change very much. Since production for export will not have increased greatly, the Sudan will still suffer from a lack of foreign exchange, and consequently, from a shortage of imports needed for mechanization and modernization.

Scenario II: Agricultural export-oriented development

In this scenario, the Sudan’s development is oriented through government policy towards greatly strengthening the agricultural sector for export. In the short run, other requirements, such as capital goods, technological inputs and most consumer goods unrelated to agriculture, will be satisfied through imports. This scenario shows a considerable strengthening of the Sudan’s hard currency position and a resulting stimulation of the entire economy.

In contrast to the reference projection, this scenario visualizes an annual growth of from 7-8% over the next ten years. This implies a more rapid development of all sectors of the economy by 1985 than would take place under Scenario I.

Under an agriculturally-based, export-oriented economic policy, the emphasis in transportation planning will be towards increasing the quality and number of feeder roads to railway junctions and improving the capacity and operation of the rail to and from Port Sudan, the country’s main export outlet on the Red Sea. Air connections among all major cities will be improved.

Scenario III: Balanced regional growth

Scenario III recognizes that the unequal development of the several regions of the Sudan is a source of some social strain and a resource waste as well. Certain of the Sudan’s less developed regions have a tremendous potential for agriculture. This scenario presupposes calculated intervention into the processes of the reference projection of Scenario I for the purpose of stimulating growth, primarily based on increased agricultural production and aimed at raising the level of economic activity in the poorly-developed regions to a point where it is somewhat similar to that of the better-developed regions. This policy also aims at self-sufficiency by 1985 in terms of internal consumption of food and clothing.

In this scenario, the major transportation emphasis would be placed on the creation of a limited number of efficient corridors connecting the various regions. Although none of the Sudanese regions will become entirely self-sufficient by 1985, regional development would reduce the movement of basic goods. There will also be an increase in the movement of manufactured goods as against raw products. In addition to improving regional links, secondary networks serving each of the regions and designed to meet local needs would have been constructed. These networks are given high priority in planning during the decade.

Scenario IV: Arab and African orientation

Scenario IV is based on Sudan’s possible interest in serving as a link between the Arab and African worlds. This interest arises naturally since the Sudan has long been associated with both worlds in a cultural and a political sense. The internal cohesion of the country should be enhanced by policies building upon both identifications, particularly because Sudan’s geographic position makes her proposed interface role a natural one.

More emphasis will be placed upon focd processing and upon other intermediate activities than in the other scenarios. In transport, the scenario presupposes the opening of new transport links to Egypt and other neighbors. Consequently, it entails by far the most ambitious transport plan of any scenario.

Scenario IV is perhaps the boldest of the scenarios in that it proposes very large initial investments, generated externally, for payoffs, some of which are social and political rather than economic and some of which depend on new markets whose existence may be speculative.

how priorities were developed for the scenarios (the physically belonged. A project may belong to several second hierarchy level) from a matrix of pairwise regions and this had to be considered. The resulting comparison of their impact on the future as far as their matrix of eigenvectors, was again weighted by the vector feasibility and desirability (the first level of the of regional weights to obtain a measure of the overall hierarchy) are concerned. impact of each project on the future.

The Sudan has twelve regions (whose individual economic and geographic identity more or less justifies political division into distinct entities). The regions were compared pairwise in separate matrices according to their impact on each of the scenarios. They comprise the third hierarchy level. The resulting eigenvectors are arranged as the columns of a matrix which, when multiplied by the eigenvector of weights or priorities of the scenarios, gave a weighted average for the impact of the regions. Now the projects, the fourth level of the hierarchy, were compared pairwise in twelve matrices according to their impact on the regions to which they

The priorities of the projects could have been done separately according to economic, social and political impacts. However, these attributes were considered jointly in the judgment dbbate. A number of refinements of the approach along these lines are possible for future revisions of the plan.

The results of prioritization not only showed the relative importance of the regions for possible in- vestment purposes, but also those of the projects as to which of the three phases of implementation they should belong: the first phase-to remove bottlenecks; the second phase-to open up the agricultural areas and ship

TR Vol. II. No. 5-D

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350 T. L. SAATY

Table 3. Tbe composite scenario

The central theme of the Composite Scenario is agricultural production for export, which is the theme of Scenario II with all that it implies for growth in the northeast, which is the transport funnel to the outside world. But the massive initial funding and continuous rechanneling of internal resources by the Sudanese government will provide sutlicient resources to allow much of the regional economic development of Scenario III. This scenario depicts a 1985 in which all regions are progressing at plausible accelerated rates. It uses population projections which foresee success in halting runaway migration to the urban areas through the government’s regional development policies.

The Composite Scenario contemplates an annual rate of increase in GNP of 6% during the decade 1975-85-nearly double that of the reference projection. Total production will have increased at a somewhat more rapid rate, and production per capita will have risen. Internal consumption as a percentage of output will have declined considerably as one would expect under a policy which gives high priority to agricultural exports.

In 1985, considerable industrial development would have taken place under this scenario. Food processing industries, as in Scenario II, would be active. Most of the processing would be located in Khartoum and in other cities in the northeast. Exports wit1 have greatly increased, but the regional emphasis wiIl have been maintained so that the east no longer so dominates both the agricultural export sector and the economy at large.

The importance of transport in the projected development implies a large investment in capital goods for the rail system, such as rolling stock and communication equipment. An extensive portion of the main line would have been doubletracked, and a new western spur line constructed.

The road system would be well developed, extensively, and all-weather roads would connect the major cities, and the highway to Port Sudan would be in operation. Many feeder roads to the railway will have been built throughout the agricultural areas. In general, it would have been found possible to reach the transport objective of both Scenarios II and III as far as the highway system is concerned.

The Nile waterway would have been improved and would be navigated by a modern fleet, backed up by excellent maintenance and docking facilities. The airway system would be as in Scenario II, with an operating air freight export service. Most air traBic and all international traffic would use the Khartoum airport. The secondary port at Suakin would have been opened and connected to the rail and road systems.

Table 4. Investment requirements of composite scenario, fS million current prices

4.3% 6% 1.3%

Transportt 391.33 Agriculture 549.10 Industry 235.31 Services 522.94 Total 1.69868

tExcludii air transport.

715.95 1159.98 678.21 873.32 385.33 582.43 417.83 442.88

2251.32 3058.61

goods to the outside world; and the third phase-to encourage balanced regional growth and transport between regions whose contribution to the composite scenario is not as visibly urgent as those of other regions and hence will probably receive less of the overall investment.

CONCLUSION

The methodology adopted in the Sudan Transport Study began with a general study of the country on the basis of which a composite scenario for the Sudan of 1985 was constructed. A macro-economic analysis was performed to test the feasibility of the scenario and to study related major economic consequences along with the transportation requirements of associated activities. This was done with the guidance of a transportation doctrine consisting of a set of principles relating the geographical, economic, social, institutional and

managerial factors to the transportation needs of the country. The resulting transportation requirements were translated into specific projects which were prioritized according to their contribution to the objectives of the scenario. The priorities were then used as a basis for time phasing of the projects. The resulting transport is directed towards the achievement of rapid economic growth and integration of the different regions of the country.

A presentation of the study in Sudan before a council of ministers and transport officials, as well as the represen- tative of the sponsor produced mostly favorable reac- tion. This suggests that this approach to planning, using scenarios and the prioritization procedure described above, yields plans which are satisfactory from the standpoint of the ultimate user of these plans. While many more applications of these methods are required to provide an adequate test of their efficacy, the results in this study are encouraging.

Acknowledgement-I am grateful to the referees for helpful suggestions and recommendations in rewriting this highly abbre- viated version of the original paper.

REFERENCES

Julien P. A. and Latouch D. (1974) La Methode Des Scenarios. University of Quebec, Canada.

Saaty T. L. (1977) A scaling method for priorities in hierarchical systems. Jour. Math. Psych. (to appear).