Kerner’s three-phase theory of traffic flows and its comparison with classical two-phase theories

Introduction. This publication provides a comparative analysis of two-phase and three-phase theories of traffic flows. It considers the key differences between these theories and their applicability to real transport systems as well as the phase transitions taken into account by the theories’ models. The main focus is made on empirical data and modeling complex dynamic phenomena on roads. The article highlights the scientific novelty of Kerner’s threephase theory and its advantages in congestion forecasting and managing traffic flows.

Materials and methods. The study examines and analyses classical theories of traffic flow, including two-phase models based on the fundamental diagram and the three-phase theory of traffic developed by B. Kerner. Main attention is paid to theoretical aspects, comparative analysis, and interpretation of key provisions of these theories. Study is based on analysis of scientific literature. The main sources of information have been peer-reviewed articles published in leading scientific journals on transport, monographs devoted to the traffic flow theory and its application in traffic management, reports and materials of the international conferences, and other sources covering both classic approaches and current trends in traffic flow modeling.

Results. A comparative analysis of the general two-phase theory of traffic flow and Kerner’s three-phase traffic flow theory has been made. In two-phase model, based on the fundamental traffic diagram, the main phases are free flow and dense flows. These phases are characterized by the relationship between density, flow, and vehicle speed. In two-phase model the phase transition occurs when the critical vehicle density is exceeded. The threephase model describes several fundamental properties of phase transitions: from free flow to synchronized flow, from synchronized flow to wide clusters and reverse transitions and their variants.

Discussion and conclusion. The main results of the study include a detailed comparison between two theories, allowing us to identify critical aspects and potential directions for further development. Specifically, it has been shown that Kerner’s three-phase model offers greater capabilities for describing metastable states and complex transitions between phases, making it more suitable for analyzing traffic flows in modern megacities.

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