Traffic State Evaluation based on Macroscopic Fundamental Diagram of Urban Road Network

The premise of relieving urban traffic congestion is to quantitatively master and evaluate the traffic operating performance of urban road network. In the paper, an observation-based model Macroscopic Fundamental Diagram (MFD) is applied to describe and evaluate the traffic state, which connecting the accumulation and production. It should be highlighted that a traffic parameter, network operation efficiency, is introduced to divide the traffic state into three categories: free flow conditions, optimal accumulation and congestion. The empirical analysis is carried out on a core urban road network located in Haizhu District of Guangzhou, China. The results verify that an MFD exists for the complete network and can be used to evaluate the traffic operation of the district. The results also show that the road network being saturated only when the accumulation reaching 477pcu and the production being 600pcu/h. Moreover, the weighted free-flow speed is 43.9 km/h, and the weighted jam density is 72.1 vehicles/km.