Effects of traffic control regulation on Network Macroscopic Fundamental Diagram: A statistical analysis of real data

This research aims to verify the influence of traffic control strategies using signal plans at junctions on observed Network Macroscopic Fundamental Diagram (NMFD), as a variable to describe the aggregate traffic conditions of an urban road network. After establishing the theoretical basis of its existence, the research on NMFDs has been finalized for applications connected to traffic congestion control and management. The degree NMFD depends on traffic control strategies has not been fully demonstrated, nor has its relationship with different congestion levels. In the opinion of the authors, experimental NMFDs based on observed traffic data in the presence of different control strategies are key elements in supporting the understanding of this relationship. The paper has been structured into two parts. The first part presents the formulation of an optimization model for the design of signal plans at junctions which incorporates NMFD variables. The more extensive second part examines the effects of traffic control strategies on observed NMFDs, built with real traffic data. The investigation follows a procedure where observed traffic data are analysed to find variables, functions and diagrams at link and network levels (NMFD). The procedure is applied in two adjacent urban zones located in the central area of Santander (Spain). These zones were identified according to traffic characteristics and land uses. The junctions on the road sub-networks in the two zones have different control regulations, but they are used by the same road users (with the same behavioural strategy). Observed traffic data (flows, densities) from loop sensors have been collected and correlated with the signal control plans at different periods of a working day. What emerges from the analysis is that junction regulation affects traffic flow variables at a link and network level. The NMFDs are statistically different when comparing junction regulations at two homogenous adjacent zones. The results apply only to the studied area and should be confirmed in other real transport systems.