Demiryolu yük taşımacılığında optimum katar yükü probleminin incelenmesi

Abstract

Demiryolları yük taşımasının ekonomik yatırım ve işletme koşullarında yapılması, genel taşıma politikası ve demiryolları açısından çok istenen bir durumdur. Bu durumun gerçekleştirilmesinde optimum katar" yükü, buna bağlı teknik ve işletme büyüklüklerinin önemli bir yeri vardır. Çalışma- - da, bu amaç gereği,. Triyaj istasyonu manevra işlemi ve toplanma,. Karşılaşma-öne geçiş istasyonu,. Katar seyir ve istasyon bekleme, işletme sonuçlarına ait yatırım ve işletme maliyetlerini dengeleyen, minimum kılan optimum katar- yükü büyüklüğünün belirlenmesi üzerinde «durulmuştur. Bu çalışma, altı bölümden oluşmaktadır. Birinci bölümde, optimum katar yükünün önemine değinilmiş, demiryolları yük taşıması özel kitlesel ve karma yük taşıması şeklinde ikiye ayrılarak genel özellikleri verilmiştir. Daha sonra bu problemin açıklanması açısından, ekonomik yük taşıması ve optimum katar yükü ile ilgili çalışmalar belirtilerek demiryolları yük taşımasındaki yeri ve çerçevesi çizilmiş, bağlı olduğu temel öğeler sıralanmış tır. İkinci bölümde, çeken-çekilen araç, katar ve trafik özellikleri incelenmiştir. Lokomotif ve vagon taşıma kapasitesi, kanca ve koşum takımı dingil yükü, katar özgül direni mi, fren düzeni ve personel yapıları belirtilerek maksimum katar yükü tanımı ile sorunları açıklanmıştır. Ayrıca demir- " yolları yük trafiği zaman değeri, başlangıç-son noktası, türel, nicel ve dalgalanma yapısı özelliklerinin taşıma özelliğine etkileri belirtilmiştir. Üçüncü bölümde, yük istasyonları yükleme-boşaltma, triyaj manevra ve toplanma, hat üzerinde araç karşılaşma-öne vı geçiş istasyonları teknik ve işletme özellikleri incelenmiş tir. Ayrıca belirli bir trafik akımı, istasyon teknik ve işletme karakteristiklerinde katar yükü ve sayısına bağlı olarak. Yükleme-boşaltma, triyaj istasyonu manevra ve toplanma süreleri, hat sayıları,. Karşılaşma-öne geçiş istasyon sayıları, bekleme süreleri,. Triyaj ve karşılaşma-öne geçiş istasyonları hat sayıları ve uzunlukları,. Katar teknik ve işletme özelliklerine bağlı katar-, saat, lokomotif ^saat, vagon- saat ve ton-saat büyük*- lükleri, tanımlanmıştır. Dördüncü bölümde, daha önceki bölümlerde incelenmiş olan katar, trafik, istasyon teknik ve işletme karakteristikleri ile bunlara bağlı işletme büyüklüklerinden hareketle yatırım ve işletme birim maliyetleri ve katar yükü değişkenine bağlı maliyet bileşenleri belirlenmeye çalışılmıştır. Burada, maliyet bileşenleri ise belirlenen bu teknik ve işletme büyüklükleri ile ilgili birim maliyetlerin çarpımların dan elde edilmiştir. Beşinci bölümde, optimum katar yükü büyüklüğü t katar taşıma verimi fonksiyonun maksimum; katar yükü değişkenine bağlı yatırım ye işletme maliyeti fonksiyonun minumum değerlerine bağlı olarak hesaplanmaya çalışılmıştır. Maliyet fonksiyonun değişim yapısı ve ekstrem "değerinin bulunmasında. Sürekli değişim ve kök bulma,. Kırıklı değişim ve sayısal seçme, çözüm şekilleri benimsenmiştir. Optimum katar yükü, uzun dönemli yatırım ve işletme, kısa dönemli taşıma işi planlama düzeylerinde değişik trafik değerleri için ayrı ayrı hesaplanmıştır. Ayrıca optimum katar yükü, hızı ile beraber katar 'taşıma verimi ve maliyet değerlerinin değişim özelliği, çözüm şekillerinin kısa bir değerlendirmesi yapılmıştır. Sonuç-altıncı bölümde ise katar taşıma verimi, yatırım ve işletme maliyeti fonksiyonları değişim yapıları ve sonuç değerleri,. Demiryolları ekonomik yük taşımasına katkı,.ileri bir çalışma için öneri vıı açılarından özetlenmeye çalışılmıştır. Bu çalışmanın önemli yanı, trafik akımı ve zaman değeri değişimi ile,. Optimum katar yükü, sayısı ye karşılaşma öne geçiş istasyon sayısı.,. Lokomotif çekim kuvveti-hız, aderans yükü,. Triyaj istasyonu manevra hattı, lokomotif ve personel sayısı,. Katar lokomotif sayısı,. Birim yatırım ve işletme maliyeti değişim yapılarını inceleme ve irdeleme olanağını daha somut sağlamış olmasıdır. Optimum katar yükü büyüklüğünün trafik hacmi, triyaj istasyonları arası hat uzunluğu, katar personeli ve lokomotif birim maliyet değiş imleriyle aynı ; hat yapım ve vagon birim maliyet değişimleriyle ters yönde değiştiği saptanmıştır. Ayrıca zaman değeri küçük -yük trafiğinde küçük-hızlı, aderans yükü büyük lokomotifleri işletmenin da ha ekonomik olabileceği görülmüştür.

In railway freight transportation, one of the impor tant problems is the determination of the economic charac teristics of that system which will lead to higher produc tivity and lower cost in the short and long term planning. In order to acheive this, a number of policy problems as a sequence of decisions aiming to meeting demand by a suitable allocation of resources and facilities available to the rail ways should,, be solved. Among these is the problem of the op timum train load which is related to the short and long term Level of decision-making. In this study, the problem of the optimum train load and speed is examined under varying traffic, technical and operational conditions. The objective function to be mini mized is the sum of the operation costs of the railway fre ight transport and the depreciation cost of the investment required in the long-term. This study consists of six chapters. In the first chapter^ the railway freight transporta tion is discussed within two general categories, one being the operation of the special by-pass unit trains hauling special bulk, traffic between the origin and destination points, and the other being the operation of the regular yard and local trains hauling multicommodity traffic between the qrigin and destination points, and the other - being the operation of the regular yard and local trains hauling multicommodity traffic between the local stations and the marshalling yards. Later, in order to get the exclusive concept of the optimum train load studies concerning the line capacity, the hauling productivity of the trains and lines, the handling and assembling process in the yards are examined and the problem of the optimum train load is der scribed: KONDRATCHENKO and TURBIN (1980) present a method for determining gradual increase of the line capacity in rela tion to the increasing traffic leading to the optimum in vestment and operation productivity on a single track rail way line. For this purpose, the number and location of the wayside stations where trains cross and overtake are formu lated depending on the load and the speed of the freight trains under given freight and passenger traffic |l8[. RAMA RAO (1978) deals with the decision criteria for an optimal selection of the civil engineering parametres which provide maximum productivity of the railway line. The deci sion criteria depend on the optimizationof the fixed in vestment costs and the direct operation costs at the ap propriate traffic volume. The same study also explains that the. number of the crossing and overtaking events is direct ly proportional with the product of the number of trains at each direction, thus, the economic line capacity is less than the maximum practical line capacity. In addition, the variation of the transport capacity of a train which is defined as the product of the load and speed of the train is examined, and how the length of train, station spacing and length of the wayside stations affect the economic line capacity is explained |7|. BECKMANN et al. (1956) discuss the handling times of trains or of car strings such as re ceiving, sorting, accumulating and making-up in yards de pending on the train lentgh, traffic volume, yard technol ogy and. policy. Their study is fundamentally a method of train scheduling in order to minimize the accumulation time which depends on the train length and car traffic |ll|. PETERSEN (1977) examines the yard types, and the effects of train lengths on the sorting and making-up times | 20 |. AREA COMMITTE 16 (1972) defines the optimum train length as the length which maximizes profit and economic effi ciency under given traffic and operation conditions. It briefly examines the factors affecting the optimum train load and economic operation conditions. Among these are the number of motived axles of locomotives, brake operation car equipment, yard operation, the number and the length of sidings, etc. It concludes that the determination of an optimum is extremely complicated in real life, but is worth resolving for maximum profit and maximum efficiency to, the economy as a- whole -| 21|. KLUVANEK and BRANDALIK (1977) discuss the method of determining decisive criteria in the assembling process of a marshalling yard for the planning of railway service. They establish the economically opti mum load of the set-up good trains which is to be used in drawing up long-term plans as well as in the operational management. In their study, the optimum train load is given as a function of the traffic volume, fixed train hauling cost on the line, and the unit cost of car waiting in the yards | 11 |. In the light of above studies, the problem of de termining the optimum train load between two successive main line stations is described^ and the underlying assump tions and basic parameters included in the problem are given. In the. second chapter, the technical and operational characteristics of locomotives and cars such as axle load, coupler-drawbar, ^rain resistance, brake operation and maximum train load are discussed and basic formulae are given. The advantage and disadvantage of making up long trains are also explained. Later, the lentgh of haul, the value of time, car flows, the volume and fluctuation properties of freight traffic, and the relations between operation and traffic characteristics are briefly explained. In the third chapter, the technical and operational characteristics of the loading-unloading stations marshal ling yards, and the crossing-overtaking stations on the line are examined in relation to the train load. The times required for loading-unloading in the stations, and for handling and accumulating in marshalling yards are given as the linear functions of the number of cars per train, the daily traffic volume, and. the operational character istics of the stations. The delay time experienced by the cargo and the cars in train, and shunting locomotives and crews in yards are defined. Furthermore, depending on the required capacity for single line operation between two successive yards, the number of the wayside stations is formulated, and the crossing and overtaking delays are given as the functions of the number of trains and unit- tirae per circulation. Then, the minimum length of siding is defined as the sum of train length and a fixed length XI which depends one operational safety and circulation of trains. In the fourth chapter, the depreciation cost of investment» and the operation costs of trains are formulated depending on the train load and the traffic volume. In ad dition, fixed investment costs which are to be faced in the long-term are defined. The investment costs are calculated on the daily-cost basis by multiplying the length and the number of stations oil the line with associated unit cast. The operation cost are calculated on the basis of train- hours, car-hours, locomotive-hours. These variable costs are divided into the following groups :. Train costs comprise the costs associated with the crew, the locomotive-motive power, the cars and the delay time of the freight traffic.. Yard costs comprise the investment and maintenance costs of the shunting track, the operation costs of the shunting crew and locomotives, and the handling and accumulating costs öf cars in the mar°- shall ing yards.. The costs of the crossing and overtaking stations comprise the investment and maintenance costs, the crew and operation costs of these stations. In the fifth chapter, the transport capacity of the train which is defined as the product of the train load and speed, is obtained as a function of such parametres âs the tractive force of the locomotive the train resistance and the grade of line. Similarly, line transport capacity which is defined as the product of the number of trains and the train load is formulated. The optimum train speed and load can be obtained by maximising the train transport capacity. Then, the optimum train speed is substituted in the cost relationship given in the fourth chapter, and the unit cost function is obtained from the total cost by the traffic volume and transport live length between marshalling yards. The optimum train load in the criteria of minimum cost value is to be determined by the following two solution process.. In the first solution process, the unit cost function is obtained as a jump-piecewise smooth function which varies depending on the train load, and the number of locomotives per train. The Xll solution process used to determine the optimum train load is as follows : ' 1. Set, the number of locomotives, N^= 1, 2. Calculate G^ (Ni), 3. Calculate G (Ni) by differentiating the continuous unit cost function, 4. If Gw (Ni) < Gwo (Nx), set G^ = G^Nx), otherwise calculate Cu (Gwo (Nj^)), 5. If Nx < Nim increase Ni by 1 and return. to step (2), otherwise select the mini mum unit cost and the optimum train load by comparing the unit costs calculated in step (4). In the second solution process, the unit cost func tion is obtained as a discrete point unsmooth func tion which varies depending on the train load and the number of locomotives per train. In order to calculate the optimum train load, first the unit cost values are calculated for each (G^, Nm) pair in which the number of trains, 1^, is chosen as an integer variable.. Then, the optimum train load is selected on the basis 'of unit cost values calculated» The sixth chapter is devoted to conclusions. The results derived from the study are as follows ;. The value of the optimum train load is directly proportional to such parameters as the traffic vol ume, the distance between two major stations,- the unit delay time per trains for crossing-overtaking circulation, and also the unit costs associated.with train crew, locomotives, and the handling work independent of train loed per train in yards.. The value of the optimum train load is inversely proportional to the unit time costs of freight traffic and car, and to the unit investment cost of siding tracks in stations.. The unit cost per the train load varies depending on the number of locomotives per train, the motived axle load, and the characteristics of the tractive force-speed curve. Xlll. Locomotives should be operated with maximum hauling productivity. They must be selected according to the optimum train load and the traffic character istics. The formulae expressing the coefficient of the unit cost function, the computer programs.developed to determine the optimum train load, the flow-charts of the programs, and the outputs of the solution are given in the Appendix.