Recently, it has been found that Macroscopic Fundamental Diagrams (MFD) exist on large urban networks in which traffic conditions are in homogenousstate. MFDs can be used to estimate the level-of-service of road networks, for perimeter control and to model traffic on a macroscopic level. However, before the concept of MFD can be used in reality, the question which factors influence the shape of an MFD should be answered. To change variousconditions, we use a microscopic simulation model to derive MFDs in different conditions and for different types of networks. This paper indeed shows that a relation exists between production and accumulation for the whole network as well as for parts of the network focused on either freeway links or urban links. It is shown that the shape of the MFD is not only a property of the network itself, but also of the applied traffic control measures. At the same time the on-set and resolving of congestion leads to heterogeneous traffic conditions with congestion at specific locations in thenetwork, resulting in loops in the congested parts of the MFD. In addition, the impact of traffic demand on MFD has been investigated, showing thatrapidly changing traffic demands drastically affect the shape of the MFD curves.
Abstract