Bağdat Caddesi'nde trafik akımı incelenmesi

Abstract

Günümüzde, göç nüfusları ile hızla artan nüfusları için gerekli alt yapı ve donanıma sahip olmayan büyük kentler, çarpık arazi kullanımları sonucunda büyük sorun ları olan yerleşmeler haline gelmişlerdir. Bu sorunlar içinde ulaşım sorunları başı çekmektedir. Türkiye'nin en büyük kenti olan İstanbul'da da bu sorun büyük ölçüde ya şanmaktadır. Teze konu olan Bağdat caddesi istanbul'un en büyük ve sorunlu caddelerinden biridir. Cadde çevresinde ki bölgenin arazi kullanışı bakımından oldukça doygun ol ması, caddenin geniş ve tek yönlü olması ilk bakışta bura sının sorunsuz olması gerektiğini düşündürmektedir. Ancak İstanbul'da görülen trafik sıkışıklıkları burada da mevcut tur. Bu zıt ikilem Bağdat caddesinin örneklem alanı seçil mesine sebep olmuştur. Tezin amacı, cadde üzerindeki akı mı etkileyen unsurları araştırmaktır. Cadde üzerinden top lanan sayısal ve görsel verileri değerlendirerek burası ile ilgili akım eğrilerini ve modellerini tespit etmek ve bunları yorumlayarak tıkanıklığı yaratan sebepleri ortaya koymak tezin kapsamını oluşturmaktadır. Tezin giriş bölümünde, tezin amaçlarının yanı sıra sorunun çeşitli boyutları vurgulanmaktadır. Tezin ikinci bölümünde, çalışma alanının tanıtımı yapılmakta, İstanbul ve Kadıköy'ün demografik gelişmesinin yanı sıra Bağdat caddesinin tarihsel gelişimi anlatılmak tadır. Modelin tanımlanması ve seçimi, trafik akım teorisi ve trafik akımının ana öğeleri üçüncü bölümün konusunu oluşturmaktadır. Dördüncü bölüm yapılan uygulamaları kapsamakta, görsel ve sayısal veriler karşılaştırılıp yorumlanmaktadır. Beşinci bölümde ise tezin sonuçları bildirilmekte, Bağdat caddesi üzerinde tıkanmaya yol açan unsurlar orta ya konmakta ve bunlara bazı öneriler getirilmektedir.

In the 20th century, administrators and planners must be carefull about the facts of urbanisation. The overpopulations in the big cities cause social, environ mental, economic, sub-structural and transport problems and these above mentioned subjects can be faced much more in developing countries then developed ones. Because, they use limited sources while they are solving their problems. Wrong plannings, wrong land-use and insuf f icient transportation networks in rapidly populating big cities cause these problems. With approximately 360 000 registered vehicles in Istanbul and this number expected to increase, street and road traffic will continue to be an important social and economic problem. Although there is a growing interest in public transit systems, the automobile may be expected to continue as the dominant form of urban transportation for many years to come0 The main reasons causing these problems - Increase in population due to the immigration from the rural areas to big cities, - Adaptation difficulties of old city centers to the new developments, - Response difficulties to demands due to insuf ficient transport sub-structure and its wrong application, - Great amount of automobile usage rather then public transport during daily travels, - Difficulties in compensation of increasing demands and updating problems of available transport plans, - The high number of establishments related with subject, lack of cooperation and comunication among these establishments, insufficient number of specialists and experts working in these organizations, viii - Reduced number of transport investments because of insufficient economical sources, - Driver and pedestrian faults of immigrated rural population because of adaptation difficulties to urban areas. Bağdat Street is one of the problematic roads of Istanbul. This study analyses the problems of Bağdat Street using numerical and visual data. Steps of the research are» - The research of the available data in the street, - Counting of the vehicles passing on the road and determination of the vehicles speeds, - The calculation of the speed-flow, speed-con centration and flow-concentration curves, - Calculation of the correlation coefficient of these curves, - The comparison and interpretation of the available data and the traffic curves. In the first chapter, the study field has been presented. The demographic evolution of Istanbul and Kadıköy, and the historical development of Bağdat Street are the sub-titles of this part. Since 1950, the population of Istanbul has increased rapidly because of the immigration from rural regions. The short- term, economically-motivated decisions made in this growth phase often have undesirable long-term effects. The original housing deteriorates and new affluence and the availability of cars and other forms of transportation enable the managerial and skilled labour classes to build a new ring of houses outside the old city» The squatter settlements without sub -structure. This invasion of the urban area complicates the available city plans. The roads and the sub -structure s of the city are incapable for increasing requests. The resi dential area of Bağdat Street is approximately saturated, because it is an ancient suburb of Kadıköy. In other words, its land -use is stopped by the saturation of the area. But the principal traffic problems can be estab lished on Bağdat Street. This is the fundamental choice reason of Bağdat Street as the study field. IX In this summary the number of chapter is begun after the introduction. Chapter 2 contains the description and the selection of the traffic model. It is important to be able to design and operate streets and roads with the greatest possible efficiency. Traffic flow theory is one tool to aid in attaining this end. It serves the dual purposes of aiding the under standing of traffic behavior and predicting future per formance. One may take as a working definition of traffic flow theory, "The description of traffic behavior by appli cation of the laws of physics and mathematics". At present as indicated by the definition, there is no unified theory of traffic flowi rather there are several theoretical approaches to describe the phenomena. Traffic flow theory had its beginnigs in the 1930s with applications of probability theory and the first models relating volume and speed. During the 1940s, there were few theoretical developments, presumably because of the interruption caused by World War II, The early 1950s saw theoretical developments based on a variety of approaches, principally car-following, traffic wave theory (hydrodynamic analogy), and queueing theory. Investigators came from a variety of disciplines, including theoretical physics, applied mathematics, control theory, psychology, economics and engineering. By 1959 traffic flow theory had developed to the point where it appeared desirable to hold an international conference. Accordingly, at the invitation of General Motors Research Laboratories a sym posium was held in Detroit, It was generally agreed that the benefits of this symposium were substantial and that additional symposia should be convened in the future. Before one attempts to model the fundamental traffic characteristics of flow, speed and concentration, it is important to have unambiguous definitions of these charac teristics in relationship to the methods of measurement, as well as the appropriate methods of averaging the measurements. The only instruments available for the earliest tests of traffic behavior were stopwatches and manual counters. Thus flows past a point and headways were the important measurements. These were supplemented by measurements of speed by means of timing each car's transit across a "trap". As other methods of measurement have been developed, it has become evident that the nu merical results depend on the method of measurement. Various methods of measurements currently available to the traffic engineer are considered and the definitions of characteristics are related to these methods of measurement. Specifically, the methods of measurement include measure ment at a point, along a length and by a moving observer. Traditionally, the traffic engineer has used volume or flow as one of the primary measures of traffic condition or state. This has been because flow is the easiest of all characteristics to obtain. Then if N cars cross line AA' in a time T, the flow is computed as q=N/T. The average speed is an important measure of the traffic performance at a particular point or along a par ticular route» in addition, it is one of the fundamental characteristics of traffic flow. There are two principal average speeds, the time mean speed and the space mean speed. In the past, it has been common practice among traffic engineers to report the "spot speed" for a given location. This is computed as the arithmetic mean of the observed speeds. In theorical discussions of traffic flow this value is referred to as the "time mean speed". The speed that represents average travel time is the harmonic mean of speeds observed at a point. Further more, it will be noted that the harmonic mean speed is lower than the time mean speed. The harmonic mean of speeds observed at a point is known as the space mean speed. Although concentration (the number of vehicles per unit length) implies measurement along a distance, traffic engineers have traditionally estimated concentration from point measurements, using the relationship k=q/üs« The relationship among the three variables u, k and q is called a traffic stream model. It is an observable fact that drivers decrease their speeds as the number of cars around them increases. Because of this close inter action between concentration and speed, and knowing both concentration and speed, from which flow can be computed, it is not surprising that early investigators explored relationships between speed and concentration. Once a speed-concentration model has been determined, a speed- flow model can be determined from it. In all realistic u-k models, the free-flow speed at zero concentration is the maximum attainable speed. The flow-concentration curve is called as the basic diagram of traffic. In the curve of q-k, the free-flow speed can be calculate from the ratio q/k at zero point. Chapter 4 is the application of this thesis. Nu meric data was collected from Bağdat Street. Observations were done at five different points on Bağdat street. A cam-recorder was used during the observations. Later, cassette was watched on television and 5-minute vehicle counting was performed. xx Depending on the real referance points taken, spot speeds were calculated by measuring time with digital chronometer. Collected q and u values were fitted to stream models, u-k» u-q and q-k curves were calculated for five different observation points and Bağdat Street in general. The lines and curves with the highest correlation coefficients were considered as Bağdat Street stream models. Collected visual data were evaluated in sketches, u and q values were tested by using Newton Divided Difference program. Chapter 5 covers the conclusion. Pocket parking places, randomly parked vehicles on the road, bus stops ı traffic-lights queueings, refuges, great number of side entries and driver faults on Bağdat Street are the main problems of the street. The places where these above problems occuring togather are the traffic jam points on Bağdat street. Places where couple of these problems are missing have easy flow