Traffic dynamics in bi-modal urban networks: a cross-comparison of outflow 2D-NMFD and 3D-NMFD

Network macroscopic fundamental diagram (NMFD) has provided practical convenience to simulate network-level traffic dynamics using NMFD-based models. Nevertheless, only a few works have been conducted on traffic dynamics in bi-modal urban networks. This paper provides a comparison of the application of outflow 2D-NMFD and 3D-NMFD through simulating different scenarios using accumulation-based model in a single reservoir system. The models are verified using micro-simulation data as ground truth performed on a Manhattan-style grid network and a real network. The results reveal the outflow 2D-NMFD can provide accurate traffic state evolution, while the goodness of fit is the main challenge in the application of outflow 3D-NMFD. Besides, the accumulation-based model needs modifications to construct the bus accumulation profile in the test-bed with a low share of buses. Last but not least, the accuracy of the existing network-level speed models in mixed-traffic condition and its effects on traffic dynamics simulation are validated and discussed.