Print Email Facebook Twitter The impact of traffic dynamics on macroscopic fundamental diagram Title The impact of traffic dynamics on macroscopic fundamental diagram Author Knoop, V.L. Hoogendoorn, S.P. Van Lint, J.W.C. Faculty Civil Engineering and Geosciences Department Transport & Planning Date 2013-01-13 Abstract Literature shows that – under specific conditions – the macroscopic fundamental diagram (MFD) describes a crisp relationship between the average flow (production) and the average density in an entire network. The limiting condition is that traffic conditions must be homogeneous over the whole network. Recent works describe hysteresis effects: systematic deviations from the MFD as result of loading and unloading. This article proposes a two dimensional generalization of the MFD, the so-called Generalized Macroscopic Fundamental Diagram (GMFD), which relates the average flow to both the average density and the (spatial) inhomogeneity of density. The most important contribution is that we show this is a continuous function. Using this function, we can describe the mentioned hysteresis patterns. The underlying traffic phenomenon explaining the two dimensional surface described by the GMFD is that congestion concentrates (and subsequently spreads out) around the bottlenecks that oversaturate first. We call this the nucleation effect. Due to this effect, the network flow is not constant for a fixed number of vehicles as predicted by the MFD, but decreases due to local queuing and spill back processes around the congestion ”nuclei”. During this build up of congestion, the production hence decreases, which gives the hysteresis effects. To reference this document use: http://resolver.tudelft.nl/uuid:4342a18a-6175-43ad-9cd0-4d7c5b7aa458 Publisher Transportation Research Board Source 92nd Annual Meeting Transportation Research Board, Washington, USA, 13-17 January 2013; Authors version Part of collection Institutional Repository Document type conference paper Rights (c) 2012 The Author(s) Files PDF 291242.pdf 1.91 MB Close viewer /islandora/object/uuid:4342a18a-6175-43ad-9cd0-4d7c5b7aa458/datastream/OBJ/view