Ulaştırma sistemlerinin bütünleşik analizi

Abstract

Bir ülkenin gelişmesi için en önemli unsurlardan birisi ulaştırma hizmetinin optimum dağılımını sağlamaktır. Bu anlamda ulaştırma planlamasındaki basan belirleyici bir etkendir. Günümüzde yaygın olarak kullanılan ulaştırma planlaması tekniklerinde, yerleşim birimlerinin oturmuş olduğu ve ulaştırma talep eğilimlerinin zamanla değişmeyeceği kabul edilip gelecekteki ulaştırma talepleri tahmin edilmeye çalışılır. Ulaştırmanın sosyoekonomik aktiviteler üzerindeki uzun vadeli yönlendirici etkisi dikkate alınmaz. Belirlenmiş hedeflere doğru gelişimi amaçlayan etken yaklaşımlar yerine mevcut durum ve eğilimleri geleceğe taşıma yaklaşımım benimseyen edilmen yöntemler kullanılır. Geleneksel modelleme tekniğinin; kaynakların kısıtlı, belirsizliklerin çok olduğu, yerleşim yerlerinin kısa süreler içinde değişime uğradığı, kararlı politikaların uygulanamadığı gelişmekte olan ülkeler için kullanımı çok fazla gerçekçi sonuçlar vermemektedir[ 1 ]. Bu çalışmada, yukarıda kısaca anlatılan geleneksel modellerin yetersizliklerini ortadan kaldırmak amacı ile oluşturulan, problemleri daha kapsamlı ve gerçeğe yakın çözmeyi hedefleyen bazı ulaştırma model ve teknikleri anlatılacaktır. Ulaştırma problemlerinin çözülmesi konusunda uygun model ve kriterleri oluşturulup, ulaştırma ile sosyoekonomik aktiviteler arasındaki ilişkiden ulaştırma talebinin oluşması incelendikten sonra ulaştırma sisteminin uzun vadede aktivite sistemim nasıl değiştirdiği açıklanmıştır. Daha sonra, ülkemiz ile birçok benzerlikleri düşünülebilecek Kore için geliştirilip uygulanmış RDRI / KİST modeli incelenmiştir. Model ile ulusal ihracat-ithalat hedeflerinin bir fonksiyonu olan bölgeler arası mal akından, her mal gurubu için üretim ve tüketim miktarları tespit edilmektedir. Birleştirilmiş input-output ve mal akım modeli, RDRI/KIST modeline bağlı olarak geliştirilmiştir. Model çok bölgeli çok ürürdü bir yapıya sahiptir. Ekonomik veriler doğrultusunda mal üretim miktarlarının, ihracat - ithalat değerlerinin, link alemdarının, başlangıç kısıtlara bağlı olarak ulusal refahı ençoklayacak şekilde dağılımının tespiti amaçlanmıştır. Ulaştırma talebi dışarıdan veri olarak değil ekonomi ile ilişkili bir şekilde modelde içsel olarak bulunmuştur. Yatırım önceliklerini belirlenmesi ve politik karar değişiklikleri durumunda yatırım öncelik sıralamasının nasıl değiştiği incelenmiştir. Görevi ulaştırma sistemleri tasarlayıp, gerekli yasal düzenlemeleri sağlayarak ülke bazında maksimum refaha ulaşmak olan devlet ile, mevcut ulaştırma sisteminden en çok faydayı hedefleyen özel sektör arasındaki karşılıklı etkileşimi ortaya koyup her iki tarafın amaç fonksiyonlarını modele dahil ederek ortak çözümler bulmak amacı ile bilevel programlama tekniği anlattıktan sonra, uzman sistemler hakkında bilgi verilmiştir. Sayısal modellerle yeterince ifade edilemeyen kompleks problemlerin çözümünde kullanılan ve daha iyi sonuçlar alman uzman sistemlerin yapısı, çalışma şekli, avantajlerı ve halledilmesi gereken sorunları üzerinde durulmuştur. Son olarak alışmadan çıkarılabilecek sonuç ve öneriler belirtilmiştir.

We live in a world of rapid change. This is particularly significant for transportation systems analysis because of the strong interactions between transportation and rest of society. Trancportation is an important local public service and it has strong interactions with the private sector. All private activities require the movement of goods and people. Location of these activities, intensity of land uses, means of production, and origins and destinations are effected by the provision and pricing of transportation facilities. Coversely, locations and intensity of private activities strongly affect the demand placed on the transportation system. Finally transportation like other local public services has a strong spatial component. Thus, a model that is to be used for policy analyses must be capable of providing the interrelationship and simultaneity of interactions among urban activities explicitly. At the present time we know most about the demand for transportation and least about the desire for certain activity patterns. There for in order to cut through the complexity of the interactions between the transportation and the sosyoeconomic activity systems, the following hypothesis is used in treditional transport model: the long-run shifts in the location and scale of sosyoeconomic activity system is separated from the short-run behavior of the market for transportation. Under this hypothesis, in considering the demand for transportation, the patterns of social and economic activity are assumed fix. But this acceptance doesen't reflect real situation so we have to use the models that are include as much as posible factor. In most operational urban models the view is taken that there exists a fixed demand for services in each subdivided zone of an urban area. In transportation models, for example, it is assumed that there exists an a priori fixed number of travellers originating from each subdivision of the urban area demanding transportation services, in land use models the fixed demand for land uses is often represented by exogenously determined basic employees. Such assumptions imply that the relationship between urban land uses and transportation in particular, and interactions among urban activities in general, are undirectional. Clearly, urban land use petterns and their associated density variations are the results of complex interactions among private sectors and public sectors [3]. XI The recent development of a series of passenger transportation planning models opened new directions for modelling urban activities through their formulation as nonlinear mathematical programming problems. Using this nonlinear programming technique as the basis, one of the purpose of this thesis is to present a model that explictly addresses the interrelationship between private and public sectors in a combined urban land use transportation model in which zonal travel demand is endogenously determined. In past decades, a considerable number of urban activity models have been developed ranging from a single sector allocation model to large scale multi-sectoral econometric models. Most commonly, these are general purpose models intended to be useful in a variety of public sector's responsibilities such as transportation planing, land use control, allocation of subsidized housing, school construction, etc. In this thesis, some models which are improved in last years are introduced to find better solution. Firstly the purpose of thesis introduced then modeling technique is discussed to develop transportation models. The section after fundamental of transportation systems analysis is expresed. The transportation system of a region is tightly interrelated with the socioeconomic system. Indeed, the transportation system will usually affect the way in which the socioeconomic system grows and changes. And changes in the socioeconomic system will in turn call forth changes in the transportation system. This interrelationship is fundamental of transportation systems analysis. We can identifay three critical dimensions of change relevant to transportation. The first is change in the demand for transportation. As the population, income, and land- use patterns of metropolitan areas and states change, so do the petterns of demand for transportation both the amound of transportation desired and the spatial and temporal distribution of that demand. The second dimension of change is in technology. For example, in urban transportation, until just a few years ago the only actively considered alternatives were highways and rapid rail transit. Now we are able to consider such alternatives as lanes or even whole expressways restricyted to boses; basically new technologies such as 'dual-mode' seystems, in which vehicles operate under individual control on local streets and automaticlly on tracked interurban guideways. Change has been rapid in other areas of transportation technology as well, as exemplified by the development of freight containerization, 'jumbo' jet aircraft, vertical or short takeoff and landing aircraft, and air-cushion vehicles for water and land transport [3]. The first step in formulating a systematic analysis of transportation systems is to examine the scope of the analytical task. We shall start by setting out the basic premises of our approach, namely, the explict treatment of the total transportation system of a region and of the interrelations between transportation and its socioeconomic context. Two basic premises underlie our approach to the analysis of transportation system: xii 1) The total transportation system of a region must be viewed as a single, multimodal system. 2) Consideration of the transportation system cannot be separated from consideration of the social, economic, and political system of the region. In approaching the analysis of a transportation systems problem, initially we must consider the total transportation systems of the region: 1) All modes of transportation must be considered. 2) All elements of the transportation system must be consideret: the persons and things being transported;the vehicles in which they are conveyed; and the network of facilities through which the vehicles, passengers, and cargoes move, including terminals and transfer points as well as line-haul facilities. 3) All movements through the system must be considered, including passenger and goods flows from all origins to all destination 4) For each specific flow, the total trip, from point of origin to final destination, over all modes and facilities must be considered. The system of interest can be defined by three basic variables: T, the transportation system; A, the activity system, that is, the pattern of social and economic activities; and F, the pattern of flows in the transportation system, that is, the origins, destinations, routes, and volumes of goods and people moving through the system. Three kinds of relationships can be identified among these variables: 1) The flow pattern in the transportation system is determined by both the transportation system and the activity system. 2) The current flow pattern will cause changes over time in the activity system: through the resources consumed in providing thad service. 3) The current flow pattern will also cause changes over time in the transportation system: in response to actual or anticipated flows, entrepreneurs and governments will develop new transportation services or modify existing services. The demand for travel is a derived demand, in this sense: travel is desirable not in itself but as a means of being at certain locations, at certain times, and this goal is itself derived from the desire to undertake certain patterns of activities. Thus, to understand the basic human desires for various activitiy patterns ; from this we could derive the demand for locations of activities, especially for location of residence and workplace.and from this locational demand we could derive the demand for travel. [3] xui At the fourth section transportation models which are improved in last years are introduced. The main thesis of this section is that the charecteristics of socioeconomic activity that best describe mixed economic systems are (1) the interaction between the public and private sectors and (2) the derived nature of transportation demand. On this basis, models that are introduced explicitly describe real world situations where public and private sectors play significant roles in shaping regional economic systems. Further these models are capable of suggesting optimal levels of government investment in transportation that most enhance the market system. Thus models in this chapter are advenced in both theoretical and operational senses[7]. Also a model for formulating investment priorities for road improvements was developed and tested in this chapter. Interaction between public and private sectors is explicitly represented in the model. The model is also capable of handling changes in external and internal economic indicators and their consequent effects on transportation requirements. The model, however also has certain limitations. The foremost is that it is static in that it fails to represent the dynamic impacts of improvements of one road on others. It also fails to consider the best system, where the best is defined in terms of a national welfare function. This problem may be formulated as a bilevel programming problem, by combining a welfare maximization problem and a network equilibrium problem. Nevertheless, it was demonstrated that the model was capable of suggesting priorities for road improvements as the result of interaction between public sectors. One of the model introduced in this chapter is Bilevel programing. In mixed economic system, two parties are involved in the decision making processes: the public sector, which constructs new infrastructure systems, improves their capacities, and regulates services and prices; and users, who choose locations of residence and production modes of transportation, and shipment routes. While many have acknowledged the existence of this type of multilevel decision - making process as an important planing issue, no one has explictly incorporated it into existing development planing models. Bilevel programming models can explicitly analyze two different, conflicting objectives involved in the decision - making processes. Bilevel programming approaches have a conceptual advantage over conventional single level programming models because they can explictly simulate the interaction between different hierarchies of the decision process, such as public - private interaction [7]. At the end of the thesis, expert systems was introduced. Basic concepts of expert systems was expressed. xiv Expert system is a computer system thet attempts to replicate intelligent activities of specific human experts. Human experts make decisions and recomendations such as adjusting temperature controls in manufacturing plant. They also assist and train others to do tasks and to make decisions. A knowledge-based system enables users with a problem to consult the computer system as tehey would an expert human advisor. Like a human expert, such a computer system extract needed information from the user by asking questions related to problem during consultation. It can also answer questions asked by user about my certain formation is needed. It can make recomandations regarding the problem or decision at the end of the consultation, and it can explain the reasoning steps it used to reach its conculations. In some situations, it can analyze a problem and take corrective action directly. Expert systems are suitable for aplication to specific problems that are more amenable to treatment on the basis of rules and relationships rather than by numerical calculations. Further, these problems may be considered on the basis on incomplete or even conflicting information. Superficially at least, it would appear that transportation would be one area of study where knowledge-based system would be applicable. In particular there should be many possibilities for using knowledge-based system to enhance the quality of decision making.