Detection of urban traffic flow´s synchronized oscillations using spectral envelope

This paper tries to answer an interesting question: Is there any synchronized oscillation in network-wide urban traffic flow? Particularly, we apply the spectral envelope method to extract the common oscillation frequencies of a set of traffic flow time series collected from several detectors distributed on a two dimensional (2D) urban traffic network. Results show that several local synchronized oscillations are detected, which are mainly distributed surrounding an intersection or on a section between neighboring junctions. However, global synchronized oscillations are hardly observed due to the truncation effect of junctions. The proposed method is also applied to the simulation data set from Paramics. The results consist with the conclusions drawn from the detected data set.