What is the root of the complexity of urban system?

The root of the complexity of urban traffic flow system lies in the huge number of components and the complex interaction mechanism.

Urban traffic flow system is a dynamic and open complex giant system composed of three elements: people, vehicles and roads. The complexity research of urban traffic flow system is a frontier topic of common concern for urban traffic and complexity science.

Based on the analysis of the current situation of urban traffic congestion and the future development of traffic demand, this paper systematically studies the main causes of the complexity of urban traffic flow system from four aspects: individual travelers, urban road network, interaction mechanism among various factors and external environment.