Generalized Fundamental Diagram with Implications of Congestion Mitigation

Abstract

The classic triangular fundamental diagram describes the functional relationship between flow rate and traffic density for longitudinal movements of homogeneous traffic. This study generalized the classic triangular fundamental diagram in the congestion regime to consider lateral lane-changing and heterogeneous traffic. F-test results indicated that the generalized model fit and predicted flow rate better than the classic model. The inconsistency in the literature regarding the impacts of lane changing was reconciled as follows. Lane changes decreased flow rate when traffic was both slightly and severely congested but increased flow rate when traffic was moderately congested. Motivated by this finding, a dynamic lane-changing management strategy was developed to mitigate congestion. Results showed that the proposed strategy improved throughput by 10.3%, average speed by 9.7%, and average delay by 19.2%. The findings from this study advance knowledge of the classic two-dimensional fundamental diagram, reveal the nonlinear effects of lane changes, and provide policy implications for congestion mitigation.