Re: [sumo-user] Significant Capacity Drop on Multi-lane basic segments

[Jakob Erdmann <namdre.sumo@xxxxxxxxx>]

Hello,

to be honest I'm not sure what exactly is going on in your scenario. However, here are some observations:

- replacing all carFollowModels with Krauss or W99 makes the issue disappear (flow on the rightmost lane roughly doubles)

- using lcAssertive=1 instead of 2 also makes the issue disappear

- setting option --lanechange.overtake-right also makes the issue disappear

- replacing ACC with CACC looks a lot better than the original version but the drop is still quite large

The ACC and CACC models are rather novel additions to the SUMO carFollowing model list (added within the TransAID project, https://www.transaid.eu/)  and are still undergoing changes. Bluntly speaking, I have not had enough experience in using these models to let me recommend them to your use.

There are also some known issues with these models:

https://github.com/eclipse/sumo/issues?uatf8=✓&q=is%3Aissue+is%3Aopen+cacc

https://github.com/eclipse/sumo/issues?uatf8=✓&q=is%3Aissue+is%3Aopen+acc

I'm pretty sure the above flow issue is unrelated to the bug you cited as that was about merging effects and not specific to a particular car-following model.

regards,

Jakob

Am Di., 1. Okt. 2019 um 16:27 Uhr schrieb MS Sam <ssatncsu@xxxxxxxxx>:

 Hi Jakob and the team,

I am studying the impact of ACC and CACC equipped vehicles on basic segment capacity and simulated them in a mixed traffic stream where human-driven vehicles are modeled via W99. A (2 km) (3 lanes) basic freeway segment is simulated using the latest version of SUMO. A clear and significant drop in capacity (defined as the maximum 5-minute flow rate) is witnessed between the lanes. Moving from left most lane to the middle and from middle lane to the rightmost lane, the capacity decreases by as much as 50%. While a small (up to 15%) capacity drop is expected (happens in real life) between the left and right lanes, the drop in capacity obtained from SUMO is extremely large and not defensible. 

The output of the simulation and other necessary files to run it are attached to this email for your reference.

While investigating the issue, I bumped into the following question from another user (https://www.eclipse.org/lists/sumo-user/msg03973.html  ). Jakob mentions:

- there is a known issue with the current dynamics model that can lead to a strong separation of vehicle speeds between the lanes (rightmost lane is very slow and leftmost lane is still at maximum speed). This lowers the observed capacity drop effect because there is no spill-over jamming effect to the left lanes. The speed seperation can be avoided with careful tuning of the lane-changing gap acceptance parameter (lcAssertive) distribution across the vehicle fleet but I anticipate that there will be model extensions in the future to adress this.  

* Am I witnessing the issue because of a SUMO bug as highlighted by Jacok above?

* Are there any workarounds to solving this issue? I tried to carefully tune lcAssertive and other lane-changing parameters to no avail.

Thanks,

Shoaib

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