The topic of this diploma paper is Traffic in big cities – current problems, new solutions. Traffic is an indispensable part of our lives nowadays, but at the same time it is one of the most serious factors that influence environmental pollution. Traffic complexity in cities is big today. Nowadays every city organizes city traffic according to its possibilities and requirements. With the increased growth of cities and the population associated with cities, traffic – related challenges are growing. Traffic jams, safety, speed of travelling and pollution significantly affect the quality of life. This paper consists of nine chapters which deal with traffic in big cities, historical development of traffic, types of means of transport, and the special emphasis is placed on urban transport problems and possible solutions of city traffic which are also the main factors of environmental pollution and have a negative impact on human health, then with sustainable development of cities and urban transport which implies a holistic approach to environmental protection. The last chapter is named “The strategy for transport development of the Republic of Croatia for the period from 2017 to 2030” which represents a shift from the current situation and realization of the new phase, which is to increase the quality of the traffic system and the same traffic infrastructure.