Traffic Theory

This paper proposes a theory for explaining the growth of oscillations as they propagate through congested merges and diverges. The idea is that merging or diverging flows change in response to freeway oscillations, and these changes have an effect of dampening (merging) or amplifying (diverging) oscillations. In this theory, a reduction or an increase in amplitude is quantified based on a single parameter (a fraction of entering flow for the merging effect and a fraction of exiting flow for the diverging effect). The effect of merging has been verified at multiple freeway merges...

Continuum theory is used to explain why stop-and-go oscillations in congested freeway traffic change their amplitudes when they encounter the vehicular merging and diverging maneuvers that take place near ramps. The theory describes how oscillations diminish in amplitude when they propagate past a queued (and unmetered) on-ramp and how they grow when they propagate past an off-ramp. The premise is that merging (diverging) flows change in response to freeway oscillations and that these changes in flow dampen (amplify) oscillations. The theory's descriptions are simple and rational; all its...

This paper analyzes urban multimodal transportation systems in an aggregated way. To describe the aggregate behavior of traffic in cities, use is made of an idea that is now receiving some attention: the macroscopic fundamental diagram (MFD). We demonstrate through simulation how the MFD can be used to monitor and control a real network, in this case a portion of San Francisco, using readily available input data. We then show how different modes interact on the same network and discuss how these interactions might be incorporated into an MFD for multimodal networks. The work unveils two...

Macroscopic fundamental diagrams (MFDs), which relate the total time spent to the total distance traveled, are explored for freeway networks. It is proposed that these macrolevel relations should be observed if the data come from periods when all lanes on all links throughout the network are in either the congested or the uncongested regime. The theory pertains to freeway networks of any size, even when they are inhomogeneously congested and the data are variable in time. Analysis of vehicle trajectories from two freeway stretches of modest physical length supports this theory. Study...