Istanbul is a big city with its 15+ million people living on an area of 5200 square kilometers (2000 square miles) divided by the Bosphorus Strait into two continents. Undoubtedly, in a city of this dimensions the traffic is one of the biggest problems. The continuous increase in the population because of the emigration and the number of motor vehicles make the city traffic a nightmare.
Most of the transportation in Istanbul is based on buses, minibuses, taxis and private automobiles, which creates a big pressure on the city traffic. Like in other big metropolitan cities of the world, the best solution of this problem would be the railway system which also helps to lower environmental pollution problems as well. In the last decade, many tramlines are built to lessen the traffic and also the subway is being extended somehow, but still new public transportation projects are essential.
Rail transport systems contribute to the solution of the traffic congestion and environmental pollution. Today, Istanbul has several railway systems long about 170 km. The plans for 2023 is to take it up to 641 km. The first light metro line was opened in 1989 and is running through the districts of Aksaray, Otogar, Esenler, Yenibosna and Ataturk Airport. The first subway line was opened in 2000 with 5 stops only, which today is extended significantly. The metro (subway) has a capacity of 70 thousand passengers per hour, one way. The rail lines in Istanbul carry about 480-500 million passengers a year.
There are huge rail system projects ongoing in Istanbul today. Marmaray project is the biggest and the most expensive project in the city's public transportation system. The underwater tunnel passing underneath the Bosphorus Strait thus connecting both continents was opened in October 2013. This rail tunnel connects to a new Yenikapi - Halkali rail line on the European side and to a new Üsküdar - Gebze rail line on the Asian side. The second tunnel, called as Eurasia Tunnel, is for motor vehicles and was completed by the end of 2016. The 3rd tunnel project is called as Great Istanbul Tunnel and will be a 3-levels tunnel for both motor vehicles and subway.
Sea transportation is another important way of commuting in Istanbul, since the city is divided on two continents. Besides private passenger boats, also local municipality boats carry passengers from one side to the other. There are regular passenger ferries and also fast ferries operating between the shores of the Bosphorus.
For the public transportation in Istanbul, people use a "smart card" (Istanbul Kart) system with an electronic chip inside, this brings many savings for connections between different types of public transportation. The use of the smart ticket has been encouraged, over 90% of passengers now use this electronic cards.