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

Abstract

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.

Keywords:

• Traffic flow theory
• macroscopic modelling
• bi-modal urban networks
• 2D-NMFD
• 3D-NMFD

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 The employed green time for each phase is the average green time of the phase within the corresponding simulation horizon. The control plan data (e.g. average green time and the phase order) are gathered from the controller information sheets and the SCATS history viewer provided by the Christchurch city council.

2 The real time-table is employed for each bus line from Metro Information: http://m.metroinfo.co.nz/.