Re: [sumo-user] How to get high densities?

[Jakob Erdmann <namdre.sumo@xxxxxxxxx>]

The spacing of 90m is unexpected for your setup, With the above configuration, you should see an average spacing of roadSpeed + vehLength + minGap (i.e. ~20m for 13.89/ms = 50km/h road and 7.5m length+minGap).

Depending on road speed you should be seeing 1800 - 2000 v/h/lane.

If you use departSpeed="avg" instead of "max", capacity goes up to 2400 v/h/lane

see also https://sumo.dlr.de/docs/Simulation/RoadCapacity.html

Please post your (zipped) scenario files to figure out why you are not seeing this.

However, insertion flow alone will never lead to a breakdown of the flow. For that you need some sort of speed disturbance downstream.

If you set sigma="1" you will see occasional breakdowns but they will be short-lived (and due to a known issue with the Krauss model, this only works at 1s step length).

An alternative for inducing break-down would be a variable-speed-sign

https://sumo.dlr.de/docs/Simulation/Variable_Speed_Signs.html

https://sumo.dlr.de/docs/Tutorials/FundamentalDiagram.html

regards,

Jakob

Am Di., 8. Feb. 2022 um 17:23 Uhr schrieb Ste Millington <stemillington@xxxxxxxxx>:

I'm struggling to get high flow rates in a simple model, just a straight 5km stretch of 4 lane highway.

I'm using multiple flow elements with probability set close to 1. However i can't seem to get the flow rate to ever go above 4000 vehicles per hour. This only gives me 1000 vehicles per hour per lane and an average vehicle spacing of 90 metres. I was hoping to be able to achieve a breakdown of the flow.

I've tried tried setting step length to 0.1 and using multiple copies of

<flow id="flow_0" type="DEFAULT_VEHTYPE" begin="0.00" departSpeed="max" departPos="last" departLane="best" route="route_0" end="3600.00" probability="0.9"/>

But after a certain point nothing seems to make much difference. I'm sure I'm doing something wrong or not perhaps just misunderstanding the traffic dynamics somehow.

Should I be able to ramp up the flow rate to a point where the traffic flow breaks down?

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