Scientific paper ID 1698 : 2018/2

Over the last few decades, the population of large cities has grown sharply, both in Bulgaria and in Europe and around the world. Cities with more than one million inhabitants have now more than 500. In their central part, these cities are mainly developed on a historically shaped urban development plan with limited road traffic. At the same time, people`s mobility - employment, training, sports, treatment and others at a considerable distance from their homes - increased sharply. There are difficult to overcome transport and environmental problems. Different ways to overcome them are sought - the use of underground spaces, the construction of overpasses, running on isolated tracks, the extension of the street network when possible and others. Realizing them to varying degrees contributes to improving the efficiency of urban transport by reducing travel time and environmental impact, increasing capacity, improving the quality of transport services and traffic safety and passengers. The practice has shown that the implementation of the above-mentioned methods is of considerable difficulty and limited effect. With a population of more than one million inhabitants, the metropolitan is the most efficient off-street mass transit.