Re: [sumo-user] The mesoscopic model

[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>:

Dear SUMO team,

 

I would like to test the accuracy of the mesoscopic model in SUMO, which is based on the Eissfeldt's dissertation (2004).

The model describes that when there is a spillback (the downstream edge is completely occupied), the headway from upstream edge to the downstream edge is the time required for a space to travel upstream, which is of course theoretically correct.

However, in the case I implemented, it seems that the headway is immediately updated in the following time steps when a vehicle leaves the downstream link (the link becomes free because of the smaller number of vehicles), while the void space hasn't yet arrived at the upstream end actually.

The resulting link density evolutions are hence very different from the microsimulation ground-truth. The congestion ends earlier because spillback is not properly considered.

Attached are the case study of a simple urban corridor.

 

Could you let me know if this is a problem that was overlooked? Or is there any parameter I need to change to make the meso-simulation better?

If it indeed is a problem, I can share a solution. Please feel free to contact me via the email below to discuss.

Thank you very much. I look forward to your reply.

 

Kind regards,

Ying-Chuan Ni

 

--------------------------------

Email: ying-chuan.ni@xxxxxxxxxxxxxxxx

Traffic Engineering Group (SVT)

Institute for Transport Planning and Systems (IVT)

ETH Zurich

 

 

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