Istanbul is located on both sides of the Bosporus strait, straddling Europe and Asia. It has a population of 16 million people, accounting for 18.71 percent of Turkey's total population , and is both Europe's and Turkey's most populated metropolis. Istanbul, a fast expanding city, is confronted with substantial urban issues such as major urban transport problems leading to persistent traffic congestion, car crashes, air pollution and noise pollution, and energy and time waste . In , the authors stated that traffic congestion, particularly the Istanbul Strait crossings, is one of the city's most persistent difficulties, according to social studies.
Annual motorization rates in Turkey are increasing at a rate of 4.5 percent per year, in accordance with economic and demographic expansion . As a solution to this problem, Istanbul Metropolitan Municipality (IMM), responsible for Istanbul's urban mobility planning, has devoted a significant portion of its funds to expanding public transportation capacity over the previous decade. One of these projects is to expand the rail system network aiming to make it the city's transportation system's backbone.
Between 2004 and 2018, IMM extended the city rail network from 45.1 kilometers to 158 kilometers. IMM intends to significantly expand the rail system of Istanbul to 495.35 kilometers by 2019 and 710.95 kilometers by 2023 .
The extension of Istanbul's metro system is transforming the city's transportation infrastructure and significantly influences the city's urban development .
In , the authors studied the spatial impact of the Istanbul Metro network by considering a 2 km buffer around it. They state that the existing rail system serves 46% of the population. While this amount will increase to 71% and 87% in 2019 and 2023, respectively . Paper  mentioned that the Istanbul Metro provided indirect economic advantages, particularly in corporate investment and industry shifts from industrial and manufacturing-related industries to high-profile service-based enterprises within its catchment regions.
The Istanbul Metro is a rapid transit railway network that serves Istanbul's European and Asian (Anatolian) sides. The system consists of eight lines and 107 stations. Also, the Istanbul Metro is connected to the underground systems of the Marmaray. The Marmaray Mass Rapid Transit railway system connects the railway tracks on both sides of Istanbul through a tunnel under the Istanbul Strait. It has 43 stations and starts from Halkalı on the European side and ends in the Gebze district of Kocaeli. The study area (Fig. 1) covers the metro and Marmaray systems, located on the European side of Istanbul. It consists of seven lines and 77 stations. The three main metro lines of Istanbul, shown in Fig. 2, were built in different periods. The starting and destination points of these lines; socio-economic development of the neighborhoods where the metro stops are connected along the line; and land use patterns also differ. Undoubtedly, this differentiation causes the rates of activity types that fall under the influence of metro areas to differ.
The Hacıosman-Yenikapı metro line (Yenikapı, Vezneciler, Şişhane, Taksim, Osmanbey, Haliç, Şişli, Gayrettepe, Levent); Hacıosman, the starting station, is connected to the Central Business District of Istanbul, and Yenikapı station is connected to the intercity passenger port. Most of the stops on the line are connected with the central business district (Taksim, Osmanbey, Haliç, Şişli, Gayrettepe, Levent) and white-collar workplaces, including mixed-use, and establish a relationship with the Historic Peninsula. In addition, the world-famous Taksim Square is also located on this line.
The Yenikapı-Bağcılar-Şirinevler metro line (Aksaray, Bakırkoy, Ataköy, Yenibosna); is one of the oldest metro lines, connecting with the starting station, Sirkeci Historical Peninsula. The destination stop is linked to Yenibosna and the former airport (Atatürk Airport). Some of the stops on this line are connected with old neighborhoods (some of them transformed from squatter areas into apartments, such as Terazidere, Bağcılar, Güngören).
The Marmaray line (Sirkeci) is parallel to the Marmara coast, connecting the Anatolian and European Sides. The line, which starts with the Sirkeci stop on the European side, ends with Küçükçekmece, which is one of the highly populated residential areas.