Empirical MFDs using Google Traffic Data

The Macroscopic Fundamental Diagram (MFD) describes the relation between accumulation and speed in a zone. While theoretically expected, empirical validations have been done with limited numbers of floating car (e.g., taxi) data, and loop detectors. This paper will verify existence, shape and crispness of the MFD using Floating Car Data (FCD) from Google. Due to the large amount of users (i.e., high penetration rate), this unique data-set contains traffic information with a high spatial resolution, a high spatial scope and high reliability. We use the data for 3 purposes. First, an MFD for the city of Amsterdam is constructed, revealing a strong relationship between the average density and the average flow. It also shows that the urban road network never reaches its capacity. Secondly, inhomogeneity is analysed. Traffic is well spread over the network, hence inhomogeneity is low. Moreover, if present, the inhomogeneity has only a minor effect on the flow. Also traffic in different directions is homogeneous. Thirdly, for the first time, an MFD is created for a whole country, which turned out to be very crisp as well. This suggests that small areas or a directional split are not needed to create crisp MFDs. That, in turn, implies that a crisp MFD is not a sufficient condition to apply control without considering internal dynamics.