| Re: [sumo-user] The mesoscopic model |
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Dear Jakob and SUMO team, Thank you very much for the answer. Yes, I see the influence of the jam threshold value now although in my simulation the density evolution after changing it to -1 (see below) is quite different from the plot you showed me.
The flat density in the jam state indeed means that the propagating space is actually not considered. Then the remaining question I would like to ask is that whether the definition of this jam threshold occupancy is the same as the logic of the critical density on a fundamental diagram. Thanks a lot! Best regards, Ying-Chuan From: Jakob Erdmann <namdre.sumo@xxxxxxxxx> Hello, Your concern may be valid insofar the current algorithm possibly overestimates void space propagation (especially on short edges). However, the mismatch between microscopic and mesoscopic behavior is mainly caused by an unfortunate choice of the parameter meso-jam-threshold 0.9 With this setting, the meso model almost never enters the jammed state.
The default values from Eissfeldts dissertation was set to 0.29 (calibrated for motorways). This is unsuitable for road networks with a wide range of speed limits. For this reason the default value of -1 is used to compute a dynamic threshold for each edge (see
https://sumo.dlr.de/docs/Simulation/Meso.html#meso-jam-threshold). The default works much better than 0.9 and an even better fit is reached with -1.2 For clarity, the plot only shows the most upstream edge which also showed the highest discrepancy. Note, that the lower maximum density in sumo is an artifact of the insertion rules: there are no half cars and in micro, the next car can only enter if a full gap has traveled to the start of the edge. In contrast, meso cars are inserted
as soon as the total space on an edge permits it.
regards, Jakob Am Mi., 2. Apr. 2025 um 10:27 Uhr schrieb Ni Ying-Chuan via sumo-user <sumo-user@xxxxxxxxxxx>:
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