helmut schuster transportation planning techniques ... · helmut schuster transportation planning...

World Bank Reprint Series: Number Seventeen I . -

REPI 71974

Helmut Schuster

TransportationPlanning Techniques:Problems and Prospects

Reprinted from Kykios XXVII-1974-Fasc. 3

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TRANSPORTATION PLANNING TECHNIQUES:

PROBLEMS AND PROSPECTS*

This paper is concerned with giving an overview of some of the morerecent developments in transport planning techniques and tries tooutline where, to the author's mind, the thrust of future efforts infurther extending these techniques should lie. Transport planningcan be seen as consisting of four distinct, although closely inter-dependent aspects. They involve rather different conceptual issuesand different planning techniques. The paper is divided into fourparts accordingly. Part I deals with various methods of forecastingfuture traffic demand. Part II is concerned with the question ofadopting the transport facilities both hardware and software to thechanging transport requirements. Part III focuses on the locationalimpact of transport on the geographical pattern of production andconsumption. Part IV discusses the possible use of transport policyin consciously influencing the regional distribution of economic andsocial activities.

On transport forecasting a tremendous amount of both theoreticaland empirical work has been done. Essentially four approaches havebeen used, involving a successively higher degree of analytical sophis-tication: trend-extrapolation, correlation analysis, demand func-tions and equilibrium models.

Trend-extrapolation simply assumes that past growth trends orchanges in past growth trends of traffic continue into the future. Thevalidity of this assumption, especially in the long run, is alwaysquestionable.

Correlation analysis ties the expected traffic volume to some othereconomic magnitude, to which it appears to have been closely relatedin the past; such magnitudes include gross national product, popu-

* This is the revised version of a lecture given at York University, Ontario, onMarch 25, 1974. The author is indebted to T. KUHN and V.W. HOGG for valuablecriticism on an earlier version.

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lation, fuel consumption, etc. The quality of the traffic predictions isdependent on the quality of the forecast of the magnitude to whichthe traffic volume has been linked and the consistency of the cor-relation between them.

Demand models derive the expected traffic volume from the func-tional characteristics of the transport facilities provided, by relatingtransport users' utility functions of transport to different levels ofserv-ice. In the single mode models the demand is projected as a functionof the characteristics of one transport mode alone. The multi-modemodels take account of substitution effects between the modes. Themulti-modal split models relate the relative traffic volume for differ-ent modes directly to the relative levels of service. A typical exampleis the McLYNN demand model'. The multi-modal cross elasticitymodels operate with one or several resistance terms, the essentialdifference being that the volume of competing modes is not explicitlyspecified. For instance the QUANDT-BAUMOL model2 gives resistanceas a product of price, frequency and travel time. Both kinds of multi-modal demand models should be extended to include not only econ-omic factors but also sociological and institutional aspects3 .

Equilibrium models are essentially microeconomic decisionmodels incorporating both demand and supply conditions. The ex-plicit equilibrium model determines equilibrium by locating,through computer iteration, a traffic flow pattern that simul-taneously satisfies both predetermined demand and supply relations.One of the more impressive applications has been the Northeast

1. J. M. MCLYNN et al. (Consultants), Analysis and Calibration of a Modal Allo-cation Model, prepared for U. S. National Bureau of Standards, Washington 1967;J. M. McLYNN and T. WORONKA, Passenger Demand and Modal Split Models, Wash-ington 1969.

2. R.E.QUANDT and W.J.BAUMOL, 'The Demand for Abstract TransportModes: Theory and Measurement', Journal of Regional Science, Vol.6 (1966),August, pp. 13-26; see also R. E. QUANDT and K. H.YOUNG, 'Cross-SectionalTravel Demand Models: Estimates and Test', Journal of Regional Science, Vol. 9(1969), August, pp. 201-214; both reprinted in R. E. Quandt (Ed.), The Demand

for Travel: Theory and Measurement, 2nd print., Lexington, Mass., 1972.3. Organisation for Economic Cooperation and Development, Development

Center, The Status and Development of Transport Technology Studies, Technical Work-ing Group on Alternative Transport Technologies for Developing Countries,Paper No. 11, Paris, April 1974, esp. pp. 4/5.

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Corridor Study for the U.S. Department of Commerce4. The sequen-tial equilibrium models revise the demand and supply conditions insuccessive approximations of the equilibrium by breaking up theanalysis into trip generation, distribution, modal split and assign-ment. This approach is used in the Urban Transportation ModelSystem, which has been extensively applied in many cities aroundthe world.

The technique of setting up such micro-orientated models has, ina more general form, been presented adequately by LANE, POWELL

and SMITH5. The collection of information for these models may beexcessively expensive, especially for smaller scale projects. But, byand large, they at least do not seem to pose major conceptual diffi-culties.

II

Analyses aimed at finding the minimum cost solutions in fulfillingthe transport requirements as predicted by the forecasting modelscan be grouped under four categories: infrastructure, pricing, taxesand access restrictions. As for the planning of infrastructure varioushighway, railroad, and port cost performance models have beendeveloped. The main break-through in recent years here seems tohave been firstly the change from optimization procedures to simu-lation techniques and secondly, closely connected with it, the recog-nition that only a systems approach, involving a multitude of plan-ning parameters simultaneously, can yield satisfactory results. Atleast at the project level, the presently available models seem notonly structurally sufficiently differentiated for the study of real worldproblems but also the technical functions used in them are usuallysystematically tested so as to render these models immediately appli-

4. A. M. VooRHEss and Associates (Consultants, McLean, Virginia), TheNortheast Corridor Intercity Travel Survey, Air, Auto and Bus Modes, U.S. Depart-ment of Transportation, March 1971; for a survey on similar work in the GreaterLondon area see Transport and Road Research Laboratory, Department of theEnvironment, Transport and Road Research 1972 (Annual Report), London, HMSO,1973, pp. 30-33.

5. P. LANE, T.J. POWELL, and P. P. SMITH, Analytical Transport Planning, Duck-worth, London, 1971.

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cable in practice. Examples are the various modal cost performancemodels developed in the International Bank for Reconstruction andDevelopment6 . Typically such cost performance models includedonly operating cost and maintenance cost as endogenous variablesleaving construction as the exogenous variable. A study done byCHARLES RIVER Associates, however, also includes construction fea-tures, i.e. alignment, curvature, gradients, etc. as endogenous vari-ables, by relating them to the topographical and geographicalcharacteristics of the area under consideration 7. While providing animportant extension towards yet more comprehensive project plan-ning, the empirical validity of the construction functions, will as yethave to be tested.

Network considerations in infrastructure planning complicates themathematical structure of the infrastructure models considerably.Network planning techniques started at a rather abstract level byusing linear programming 8. To the author's mind the many attemptsof using linear programming techniques for network planning havehad limited success. For the simplest of cases, for instance planninga transport system in an agricultural area with homogeneous top-ography, the solutions provided by these linear programming models

6. C. G. HARRAL, Highway Cost Performance Model, International Bank for Re-construction and Development (IBRD), Washington, Economics DepartmentWorking Paper No.62, February 1970; L.H. MILLER, Railroad Cost PerformanceModel, IBRD, Economics Department Working Paper No.63, February 1970;C. G. HARRAL, Transfer Cost Performance Model, IBRD, Economics DepartmentWorking Paper No.64, February 1970; E.C.COMER and P.N.TABORGA, PortSimulation Model (GSM), Release (I) User's Guide, IBRD, January 1974 (mimeo-graphed); P. N. TABORGA, The Development of a Computer Modelfor the Calculation ofPort Costs, IBRD, 1974 (mimeographed).

7. CHARLEs RIVER Assoc. Inc. (Consultants, Cambridge, Mass.), A Manual ofComputer Programs for Project Analysis for Choice of Transport Technology Under VaryingFactor Endowments in Less Developed Countries, Report No. CRA-3- 138-31, preparedfor Department of Transportation, Washington, D.C., June 1973. For an earlierexposition in graphical terms see R. M. SOBERMAN, 'Economic Analysis of High-way Design in Developing Countries', Highway Research Record No. 115, Trans-portation and Economic Development, 6 Reports, Washington, 1966, pp. 44-63.

8. For a recent survey of programming techniques see S. K. AGARWAL, Opti-mizing Techniques for the Interactive Design of Transportation Networks under MultipleObjectives, doctorial thesis, mimeographed, Northwestern University, Evanston,Illinois, 1973.

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may provide some guidance to the policy maker. A recent examplefor a study under such simplified circumstances is the paper byI. OSAYIMWESE on 'An Application of Linear Programming to theEvacuation of Groundnuts in Nigeria'9. But in the majority of casesthe complexity of the real world is such that this complexity cannotbe adequately reflected in this type of model. In this sphere too,therefore, the simulation approach seems to be increasingly used. The'Systems Analysis of Rural Transportation' prepared by Meta Sys-tems may serve as an illustrative example'°. Although the simulationmodels do not provide optimal solutions in the strict sense they canusually give a fair indication as to which layout to choose from anumber of alternatives and, by sufficient iteration, approximate theoptimum adequately for practical purposes. These network studieson a simulation basis can furthermore make immediate use of pre-ceding studies done at a project level. Since the models used forinfrastructure project planning are essentially set-up at a purely tech-nical level, their aggregation does not pose the usual problems withwhich the analyst is usually faced when combining the results ofpartial analysis in the economic field. What they do require is soundtraffic forecasts, especially projections of traffic diversion, an issuetouched upon before.

The fact that operational models for the planning of infrastructureare available does, of course, not imply that they are actually usedby those engaged in practical infrastructure planning. On the con-trary there appears to be a deep-rooted suspicion by some plannersagainst their application1 ". The reason can hardly lie in the difficultyin understanding the mechanism of the models. Their logical struc-ture is usually, even in the more complex cases, sufficiently simpleto be presented in the form of easily assimilable graphical flow dia-

9. I. OsAYIMvWEsE, 'An Application of Linear Programming to the Evacuationof Groundnuts in Nigeria', Journal of Transport Economics and Policy, Vol. 8 (1974),January, pp. 58-69.

10. Meta Systems Inc. (Consultants, Cambridge, Mass.), Systems Analysis ofRural Transportation, International Bank for Reconstruction and Development,Economics Department Working Paper No. 77, May 1970. A number of the laterapplications of the Harvard Transport Model, to be discussed later, also fall underthis category.

11. See also J. W. DRAKE, 77we Administration of Transport Modeling Projects,Lexington, Mass., Toronto and London 1973, pp. 39-43.

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grams; their mathematical formulation involving as a rule but thebasics of algebra, can pose no serious determent. One reason seemsto be, rather, that the models frequently force the planner to providefigures, the basis of which are mere conjecture or 'rules of thumb'.Any practical planner knows that such 'guestimates' are unavoidablefor a whole range of empirical relationships. In such cases it seemsreasonable to reduce the perfectionist claim of the model to conceptswithin which the planner does operate, for instance as regards themaintenance status of road rather than expressing it in terms of rutdepth, slope variance and percentage of cracking and patching tosimply state it in qualitative terms of good, fair and bad.

The second reason for the practitioner's reluctance to operate withplanning models is that it confronts him, by the very system approachwhich it entails, with the impact of his 'guestimates' on other partsof the model. Explicitly stating the consequences throughout thesystem makes him hesitant to give his guess in the first instance. Oneway to deal with this problem is not to confront the practitioner withthe model at all, but merely to issue him with questionnaires, which,familiar to him in the concepts used, draws upon his expertise asmuch as possible, and then calibrates the model on the basis of thesequestionnaires. Recent attempts at the World Bank in developingsuch questionnaires for the highway-cost-performance model seempromising.

As to the question of pricing, taxes and access control, the maintrend of current analysis still seems to run along quite different lines.Whereas Cost-Benefit Analysis has, especially in recourse to thesocial surplus, replaced the traditional notions of welfare economicsin the planning of infrastructure for quite some time, the pricingcontroversy still seems to take place largely in terms of the old frame-work of marginal conditions, total conditions, second-best solutions,etc. Transport economics appears to be somewhat schizophrenic atthis point. While long having abandoned the idea of utility measure-ment in favor of the social surplus or other operational concepts asfar as investment decisions go, Paretian Welfare Economics stilldominates much of the pricing discussion'2 . Since the introduction

12. For a detailed exposition, see H. SCHUSTER, Entwicklung und Stand der theo-retischen Preispolitik, Technische Universitat Berlin, Diskussionspapier aus dem In-stitut fur Wirtschaftswissenschaft, No.9, Berlin 1973.

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of total conditions, formulated in an operational way, is as contro-versial as ever, the conflict between the marginal cost and the averagecost position with all its intermediate solutions still remains unsettled.It does not appear immediately comprehensible, why with the ac-ceptance of Cost-Benefit Analysis as a criterion of decision makingin the field of infrastructure, the same criterion could or should notalso be applied to the question of pricing. Not only could this ap-proach lead the way out of the rather sterile discussion of this topicbut it would at the same time suggest the integration of the pricingand the investment question. The author's attempts in this directionof combined investment and pricing decisions in a presentation tothe European Ministers of Transport were limited to graphical sol-utions under rather highly simplified assumptions concerning thecost composition' 3 . A technically more advanced study making useof computer simulation was presented more recently by M. R. WIGAN

and T.J. G. BAMFORD at the London Transport Research Labora-tory14 . Their study too operated within a purely hypothetical net-work but research for its application to real world circumstances ispresently in progress.

Reverting now to questions of tax policy as related to transport,most of the argumentation appears to have taken place in verbal orpurely numerical form. Again, by way of example only, the studiesbe mentioned by P. EKLUND on the 'Earmarking of Taxes for High-ways in Developing Countries'"5 or the more recent paper byA. CHURCHILL on 'Road User Charges in Central America"6 . Thesomewhat non-analytical approach used for dealing with the prob-lem of taxation could be considered a reflection of the fact that taxquestions are largely debated in the field of political controversy, in

13. H. SCHUSTER, 'Pricing the Use of Infrastructure', Report on the Seventh RoundTable on Transport Economics, European Conference of Ministers of Transport, Paris1971, pp. 5 9-9 0 .

14. M. R. WIGAN and T.J. G. BAMFORD, A Comparative Network Simulation of Dif-ferent Methods of Traffic Restraint, Transport and Road Research Laboratory, Re-port LR 566, London 1973.

15. P. EKLUND, Earmarking of Taxes for Highways in Developing Countries, Inter-national Bank for Reconstruction and Development, Economics Department,Working Paper No. 1, June 1967.

16. A. CHURCHILL, Road User Charges in Central America, World Bank Staff Oc-casional Paper No. 15, Johns Hopkins, Baltimore and London 1972.

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which there is little room for the economist to operate with seeminglycomplex theoretical analysis. Yet, in principle, the question of tax-ation is at least of the same relevance to the efficient construction andusage of a transport system as that of prices, in fact naturally moreso in those modes where prices in the usual sense are the exceptionrather than the rule, as in the case of roads. The systematic inte-gration of taxation questions into an analytical framework of infra-structure, prices and taxes would therefore seem to be of primeimportance. While it is somewhat doubtful that any solutions ob-tained from any such extended analysis will have any immediateimpact on the policy maker, it can at least provide him with a guide-line of the economic cost incurred by deviating from them.

Access control, finally, has received hardly any analytical treat-ment at all. While doubtless as effective an instrument of planningas prices or taxation, this may be explained by the fact that quanti-tative market controls do not, within the framework of most marketeconomies, again from a political point of view constitute a realchoice even in the otherwise frequently heavily regulated transportsector. But even in those economies where access controls are in factenforced, as for instance long distance road haulage in Germany,little analytical attention has been paid to this phenomenon. In coun-tries that do have recourse to such quantitative measures the under-lying economic analysis would seem an immediately necessary taskfor the evaluation of national policies; in countries in which suchmeasures are apparently ruled out for political reasons they mightreceive attention either to provide the economic justification for thepolitical a priori decision against them or again give at least an indi-cation of the economic cost incurred should they, from an economicpoint of view, prove to be the superior one.

The four categories, namely investment, pricing, taxes and accesscontrol form, of course, a comprehensive whole in the context oftransport coordination in reality. If they have been treated ratherindependently in planning analyses then this must be attributed tothe dimension of the problem posed in dealing with all aspects simul-taneously and up to recent years also by limitations in the analyticaltechniques available. But of late, studies which do attempt to in-corporate all aspects simultaneously are coming forth. Given thegeometric expansion of variables to be considered they must, by way

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of necessity, if individual modal aspects are to be given full treat-ment, be restricted in their regional scope, or if to be used in a widernational level, neglect some of the specific modal questions. Anexample of the former is the Singapore Mass Transit Study whichtries to give an extensive analysis of investment and traffic restraintmethods in a limited urban area"7. An example of the latter is theNew Zealand Transport Policy Study, the final report of which isnow available' 8. In view of the increasing recognition of the highdegree of interdependence between all planning parameters, it seemslikely that similar studies will emerge elsewhere.

III

Studies on the impact of changes in the transport system on the geo-graphic distribution of economic activities abound in the literature' 9.The majority of them are but simple applications of econometrics.The most ambitious analytical research program in this field isdoubtless the so called Harvard Transport Model20. It tries to set up

17. For interim reports see E. P. HOLLAND, Proposed Research on Means of TrafficRestraint for Singapore, International Bank for Reconstruction and Development(IBRD), mimeographed, January 1974; idem, Terms of Referencefor Study of TrafficRestraint in Singapore, IBRD, mimeographed, February 1974. For a similar butmore restricted application see WILBUR SiTH and Associates (Consultants), UrbanTransport Policy and Plarning Studyfor Metropolitan Kuala Lumpur, Draft Final Report,Kuala Lumpur, Dec. 1973; see also J. C. TANNER et al., Development and Calibrationof the CRISTAL Transport Planning Model, Transport and Road Research Labora-tory, Report LR 574, Growthorne, Berkshire, 1973.

18. W. SwITH and Associates (Consultants), New Zealand Transport Policy Study,prepared for the Ministry of Transport, Government of New Zealand, November1973. - See also A. W. YOUNG, 'The New Zealand Transport Policy Study', TheChartered Institute of Transport Journal, Vol.35 (1973), September, pp. 240-245.

19. For a survey of a number of case studies, see G. W. WILsoN, 'Case Studiesof Effects of Roads on Development', Highway Research Record No. 115, Trans-portation and Economic Development, 6 Reports, Washington 1966, pp. 10-1 8. For anextensive bibliography see G. KRAFT, J. R. MEYER, and J.-P. VALETTE, The Roleof Transportation in Regional Economic Development, Lexington, Mass., Toronto andLondon 1971, pp. 9 5 -1 2 9.

20. D. T. KRESGE and P. 0. ROBERTS, 'Systems Analysis and SimulationModels', in: Y. R. MEYER (Ed.), Techniques of Transport Planning, Brookings Insti-tution, Transport Research Program, Washington, D.C., 1971.

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a model of the economy sufficiently sensitive to transport costs so asto respond to changes in the transport system, while at the same timeit incorporates the feedback effects from the changing economy onthe transport system, thus closing the loop transport system-economicsystem-transport system. The model doubtless has its merits, at leastin stating analytical objectives. The specific mode of execution, es-pecially in the Colombian case2l, has however been subjected tosevere criticism as exemplified in the review by E. P. HOLLAND andG. G. HARRAL2 2. One argument was that the data basis was quiteinsufficient to arrive at the far reaching conclusions drawn from it.Information gaps were, in a number of cases, filled with ratherarbitrary figures. Unfortunately this was, as HOLLAND demonstratesin his more extensive appraisal of the model23, done also for technicalor economic functions for which a careful perusal of the transportliterature would have yielded the desired empirical evidence. Butmost of these statistical deficiencies could in principle be overcomeby a little more time and manpower invested.

The criticism relating to the structural approach in that part ofthe model which simulates the locational impact of the transportsystem on the economy is more severe. It not only states that thenecessary empirical evidence is lacking, but that given the presentanalytical approach it can, for conceptional reasons, not be found.The level of aggregation in the model is such that empirically mean-ingful relationships in this part are impossible to establish. Broadlyspeaking the argument is based on the recognition that satisfactoryanswers for macroeconomic models can only be found at the micro-economic choice-theoretical level, a recognition that seems to havebecome quite widely accepted in the field of general economics. Inthe absence of such a choice-theoretical basis, however, the simu-

21. P. O. RoERTs, D. T. KRESGE, and J. R. MAYER, An Analysis of InvestmentAlternatives in the Colombian Transport System, Cambridge, Mass., September 1968.

22. E. P. HOLLAND and G. G. HARRAL, A Review of Systems Analysis and Simu-lation Models by D. T. KREsGE and P. O. ROBERTS, Vol. II, Techniques of Trans-port Planning, The Journal of Economic Literature, Vol. 10 (1972), December,pp. 1252/3.

23. E. P. HOLLAND, Economic System Modelsfor Transport Sector Studies, A Critiqueof the Harvard Transport Program's Multiregional Economic Model and a Pro-posal for a more practical one, International Bank for Reconstruction and Devel-opment, Economic Staff Working Paper No. 131, July 1972.

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lation of the economic system's response to the transport system mustoperate with aggregate functions with little or no statistical re-liability. Later applications of the Harvard Model, for instance thosein Dahomey2 4, Sudan25, Brazil26 and Thailand27, have avoided theseshort-comings essentially by concentrating on the transport systemrather than on the economic system part and have, somewhat re-duced in their objective, been rather successful.

As concerns more detailed research into the locational impact ofthe transport system on the economy, however, to the author'sknowledge no large scale efforts have been launched since. Thequestion hence arises, both from an operational and an analyticalpoint of view, which course to pursue from here. Given the lack ofanalytical knowledge three possibilities seem to exist, none of themmutually exclusive, but rather referring to different stages concern-ing their implementation. The immediate consequence for the oper-ational transport planner, i.e. those involved with having to reachdecisions at the present, is to accept the fact that the locational effectsof changes in the transport system are but insufficiently known andhence to explicitly reduce the analytical models in this aspect to aso-called consistency analysis. In these no attempt is made at inte-grating the economic feedback into the model structure. Rather, thepath of general economic variables is introduced exogenously or atleast is determined exclusively by factors other than the transportsystem. However, especially where a multitude of projects is underconsideration, a cross-check is made whether the combined changeeffected by the entire program can be consistent with those exogen-ously given data. If so, no further problems arise. If not, then obvi-ously the 'exogenous' data has to be adjusted. This, in principle, caninvolve all the problems of predicting the consequences of changesin the economy resulting from changes in the transport system just

24. International Bank for Reconstruction and Development, Dahomey LandTransport Models, Economics Department Working Paper No. 87, September 1970.

25. International Bank for Reconstruction and Development, Sudan TransportStudy Model, Economics Department Working Paper No. 93, November 1970.

26. International Bank for Reconstruction and Development, Brazil TransportStudy Models, Economics Department Working Paper No. 94, December 1970.

27. A. ISRAEL, Reappraisal of Rail Project in Thailand, An Application of the HarvardTransport Models, International Bank for Reconstruction and Development, Econ-omic Staff Working Paper No. 132, July 1972.

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discussed. But for many practical purposes, the problems will not bequite so severe. For in many cases the inconsistencies detected willrefer but to one or two economic variables. For example, the analysismay suggest that the transport program under review will cause theprice of labor to change from the figure predicted assuming the ab-sence of the program. A simple adjustment can then be made inrealigning the expected cost. Similar considerations may hold for themarket prices of individual commodities, individual productionfigures, etc. Of course neither the further impact of such changes ofindividual variables on the rest of the economic performance, norinterdependencies between them can be given sufficient treatment.The consistency model must thus be unsatisfactory to the analyticalpurist. But for the operational planner, who can hardly be expectedto wait for further research to provide more comprehensive answers,it would appear as the immediate course to pursue in the evaluationof larger scale programs.

The second course of action would be to turn to so called dynamicplanning methods. Dynamic in this context refers not to the ana-lytical set-up of these models - following the course of variablesthrough time by computer simulation - but to the time-consecutiveway in which changes in the transport system are staggered toachieve given objectives. The economic objectives, broken down byregions or zones, are stated at the outset. Again it is recognized thatno precise statements as to the effect of changes in the transportsystem towards the approximation of those objectives can be given.But use is made of conjectures and qualitative indications concerningthe direction in which the impact in relation to those economicobjectives will occur. The changes in the transport system are thendevised in small steps, each successive one dependent on the effectof the preceding one. The subsequent steps are only undertaken ifthe objectives stated at the outset have not already been achieved bythe preceding one. The analysis must thus be closely connected to amonitoring system, keeping track of the economic changes that havetaken place. A more detailed description of this type of dynamicplanning has, although at a rather theoretical level, been givenrecently by H. L. BEENHAKKER 2 8 . An application at the more practi-

28. H. L. BEENHAKKER, 'Approaches to Dynamic Transport Planning', Transpor-tation, Vol. 2 (1973), pp. 245-280.

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cal level would be for instance opening up a hitherto untouchedregion for development, firstly by constructing a gravel road, ex-tending it by feeder earth roads, followed by paving of the gravelroad, then gravelling the feeder roads, extending the feeder roadsystem by a secondary system of earth feeder roads, then furtherupgrading the main road, etc. Any such dynamic plan need, ofcourse, not be confined to the transport system itself but may includeagricultural, industrial, public utility projects, etc.

Staggered investment programs in transportation have factuallybeen put into effect in some developing countries in the sense thatinvestments in infrastructure, insufficient in generating the desireddevelopment effect, have been followed up by further investment inthe same sector, frequently flanked by simultaneous investment pro-grams in other economic activities. The disadvantage of such a 'fac-tual' i.e. unplanned procedure is two-fold. Firstly considerable timeis lost between the successive investment stages both, because of theabsence of an appropriate statistical monitoring system and becausepreparation of the succeeding investment is normally not even starteduntil it has become obvious that the preceding step did not achievethe desired effects. Secondly because when planning the initial in-vestment the possibility of the subsequent steps are not given system-atic consideration. Construction work is then frequently undertakenwhich is of limited value, often causes high cost for its removal, whenextensions become necessary. Systematic planning of such extensionswould constitute a major improvement over the traditional ap-proach. Its main advantage is the flexibility of the investment pro-grams. The staggered plan may, of course, involve the loss of someeconomies of scale, but if part of a long-term plan these losses canbe kept relatively small. They should in any case be outweighed bythe advantages occasioned by avoiding either bottleneck situationsin case the development effects were overestimated or underutiliz-ation of infrastructure in case they were underestimated.

The third possibility in trying to account for the feedback effectsfrom the transport system in the economic system, to be consideredonly on a long-term basis, would be to redivert attention to the ana-lysis of precisely those locational phenomena that seem to haveeluded satisfactory explanation so far. There seems to be a consensusamongst transport planners, that the only way to deal with the

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locational aspect is first to go out into the field and gather extensivedetailed base line data. In the absence of reliable analytical guide-lines, essentially information is to be collected on any magnitudesthat could relate to the locational pattern. As a first classification itmight prove useful to fall back on a suggestion by G. W. WILSON29 ,

to differentiate between magnitudes indicating what he calls 'econ-omic opportunity' and 'responses to economic opportunity'. Theformer would include geological and topographical conditions, avail-ability of inputs, access to markets, etc., the latter actual productionpattern, behavioral characteristics, social structures, etc. It is import-ant in this context that effects of migration should also be taken intoconsideration. The Harvard Model, for instance, completely ignoresthis aspect. While perhaps indeed the most difficult component inanalyzing the locational impact of changes in the transport system,past experience seems to suggest that the movement of populationcan be of major importance in the assessment of development effects.

Examples of detailed field investigations of the kind described arethe study on feeder roads in Yemen (Arab Republic of Yemen)undertaken by 0. DUNANT and others30, and the feeder road surveyon Ethiopia as prepared by G.J. GILL3 1. Both these studies have sofar yielded a host of highly interesting information, but unconnectedas they are, the results are of course difficult to compare. To get moreinformation on a cross-sectional basis a study group has been set upby the International Bank for Reconstruction and Development,whose objective is to examine a larger number of cases trying to usestandard terms of reference so as to make them comparable. Thedifficulty with this undertaking is of course that since it is reallyunknown which information is to be collected, the only consequenceseems to be to collect all the information available. Some facts willprove useful, others not. It stands to reason that such a rather ex-

29. G. W. WILSON, 'Towards a Theory of Transport and Development', in:G. W. WILSON (Ed.), The Impact of Highway Investment in Development, The BrookingsInstitution, Transport Research Program, Washington, D.C., 1966, pp. 190-218.

30. 0. DUNANT et al., Yemen Arab Republic Feeder Road Study, Report on Phase I,Zurich, April 1973 (mimeographed).

31. G.J. GILL, Agaro-Chira Feeder Road Survey, Part I: Transportation andTrading Patterns, Institute of Development Research, Haile Selassie I University,Working Paper No.8, July 1973.

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tensive approach is fairly costly and will therefore have to be re-stricted to a limited number of cases.

The object of these very detailed field surveys is, to state it again,not the gathering of information as such, but to gain conceptualinsights. Reading through the two above mentioned reports, alreadya number of unconventional working hypotheses spring to mind.Naturally, as more such hypotheses emerge it would be possible andperhaps tempting to the analyst to try and assemble them in somesort of model. Whether the model approach at this highly disaggre-gate microeconomic level is appropriate for practical planning pur-poses appears questionable. For if the microeconomic approach wereto be applied at a wider regional, let alone national level, the stat-istical requirements for the calibration of such large models wouldfor all practical purposes lie beyond the limits of reasonable planningcosts. The objective must be, after the completion of some morehighly detailed empirical studies, to first sift the large amounts ofdata available from them by way of the sensitivity studies on aqualitative or simple correlation basis. Then, only after the mostimportant factors of influence have been detected, should efforts beredirected towards building more aggregate and hopefully morerealistic models of locational impact.

IV

If the economic system responds to changes in the transport system,and not knowing the precise format of those responses does of coursenot preclude the existence of such responses, then it is clear thatplanning the transport system can be used as a policy tool in in-fluencing that system. The effectiveness of this tool may be smallerin the so called mature economies, in Western Europe and NorthAmerica in which the geographical pattern of economic activities isonly marginally variable both for economic reasons, the factual pat-tern constituting a large element of sunk cost, and for political con-siderations. It seems of greater immediate relevance in developingcountries whose economies are only now taking shape, or in devel-oped economies with large underdeveloped areas. While plans existin most of these countries for development as such, the absence of

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any conscious planning of the geographical location of developmentleads to bringing about the problems, which the developed countries,already confronted with them, have difficulty in solving. England isfinding it excessively costly to decongest the South East region,Germany is faced with similar problems in the 'Ruhrgebiet', to quotebut two examples. At the same time the very unchecked growth thatgave rise to the present regional problems in the developed countries,is allowed to occur in the Sao Paulo region of Brazil, in Lagos,Teheran, etc.

Hardly any studies involving the conscious use of the transportsystem in shaping the economy exist. The insufficient knowledge con-cerning the precise locational effect of changes in the transport systemmay have been one of the reasons. Also using the transport systemas a conscious tool of guiding economic development geographically,requires of course geographically specified objectives. Given the im-portance of the issue, these can only be formulated at the highestpolitical level. But as a matter of fact, other than the purely enumer-ative and frequently antinomous statement of various goals, such aformulation is usually not obtainable. Finally the fact that the resultsof systematic analysis would in mariy cases have but marginal impacton the political decision process as concerns the regional pattern ofeconomic development - if in fact explicit decisions are taken at all -may have deterred the researcher from indulging in this field32. Butin view of the fact that it would in many cases be easy to preventthe problems, the solution of which in the future will cause high costor which may in fact prove to be insoluble once they have arisen, itwould seem of primary importance to devote more efforts in trans-portation economics towards the systematic analyzation of such re-gional policy models.

International Bank for Reconstruction HELMUT SCHUSTER

and Development,Washington, D.C.

32. For a more detailed exposition see N.WENGERT, 'Political and Admninis-trative Realities of Regional Transport Planning', in: J. S. DESALVO (Ed.), Per-spectives on Regional Transport Planning, Lexington, Mass., Toronto and London1973, pp. 39 7-43 0 .

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SUMMARY

The paper reviews and assesses recent developments in transport planning tech-niques and makes suggestions on those aspects on which further research couldmost productively focus. Part I deals with various traffic forecasting methods, afield in which newer microeconomic decision models appear to provide promisingresults. Part II analyzes the use and limits of various planning techniques at theproject, modal network and intermodal level, with particular emphasis on multi-parametric simulation models; special attention is directed at the interdependenceof investment, pricing, taxes/subsidies and access control. Part III is concernedwith some ambitious but rather unsatisfactory attempts of predicting the locationalimpact of changes in the transport sector on other sectors of the economy; consist-ency analysis, dynamic planning and further basic line data collection, necessaryto formulate models of higher predictive value, are suggested. Part IV discusses theimplications of using transport policy as an instrument for explicitly influencingthe desired regional pattern of economical and social activities, an area to whichpriority of further research should be given.

ZUSAMMENFASSUNG

Der Beitrag gibt einen tJberblick uiber neuere Entwicklungen in Techniken derVerkehrsplanung und setzt Akzente fur weitere Forschungsaufgaben. Teil I be-schaftigt sich mit Verkehrsprognosen. tYber einfache Extrapolationen und Kor-relationsanalysen hinausgehend, scheinen mikrookonomische Entscheidungs-modelle jungeren Datums auf diesem Gebiet befriedigende Ergebnisse zu erbrin-gen. Teil II analysiert Planungstechniken fur Einzelprojekte, modale Verkehrs-netze und den intermodalen Vergleich verschiedener Verkehrstrfiger, vor allemunter Verwendung von mehrparametrigen Simulationsmodellen. Die Inter-dependenz von Investitionen, Preisen, Steuern/Subventionen und Zugangskon-trollen wird besonders betont. Teil III behandelt die ehrgeizigen, jedoch wenigerfolgreichen Versuche, den raumlichen Einfluss von Veranderungen im Ver-kehrssektor auf andere Wirtschaftssektoren zu erfassen. Konsistenzanalyse, dyna-misches Planen und die Erfassung weitergehenden Grundlagenmaterials zur For-mulierung von Modellen mit besserem Prognosewert werden vorgeschlagen.Teil IV diskutiert den moglichen Einsatz der Verkehrspolitik als Instrument zurexpliziten Beeinflussung der regionalen Verteilung bkonomischer und sozialerAktivitaten, ein Gebiet, auf dem weitere Forschungsarbeiten dringend gebotenerscheinen.

RESUMA

L'article passe en revue les developpements recents des techniques de la planifica-tion du trafic et propose des recherches a poursuivre. Partie I s'occupe des pronos-tiques du trafic: c'est un domaine de recherche oCb les modeles de decision micro-

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economiques recents semblent donner des resultats promettants. Partie II analysel'emploi et les limites de differentes tdchniques de planification pour un projetparticulier, reseaux de communications modales et la comparaison intermodalede plusieurs niveaux de trafic; ceci en employant des modees de simulation multi-parame&riques. L'accent est mis sur l'interdependance des investissements, desprix, des taxes, des subventions et des contr6les d'acces. Partie III traite les essais- ambitieux mais peu promettants - de saisir l'influence spatiale que des change-ments dans le secteur du trafic exercent sur d'autres secteurs economiques; analysede consistance, planification dynamique et la collection de nouvelles donneesfondamentales sont proposees afin de formuler de modees permettant des pronos-tiques plus prdcises. Partie IV discute l'application de la politique du trafic dansun champ ous des recherches plus pouss6es semblent urgentes et desirables: il s'agitde son influence explicdte sur la repartition regionale des activits economiqueset sociales.

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WORLD BANK1818 H Street, N.W.Washington, D.C. 20433, U.S.A.

Other World Bank reprints

No. 11. Hollis B. Chenery and Helen Hughes, "The International Division of Labor: TheCase of Industry," El Trimestre Economico [available in Spanish as publishedand in English translation]

No. 12. Bension Varon and Kenji Takeuchi, "Developing Countries and Non-fuelMinerals," Foreign Affairs

No. 1 3. P.B.R. Hazell and P.L. Scandizzo, "Competitive Demand Structures under Risk inAgricultural Linear Programming Models," American Journal of AgriculturalEconomics

No. 14. Gabriel J. Roth, "Regulation of Buses in Cities," Highway Research Record

No. 1 5. Bela Belassa, "Estimating the Shadow Price of Foreign Exchange in Project Ap-praisal," Oxford Economic Papers

No. 1 6. Hollis B. Chenery, "Restructuring the World Economy," Foreign Affairs

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