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Re: [sumo-user] Vehicles stuck at priority junction
Thank you for providing example files. Here are my observations:

- your scenario is strongly affected by https://github.com/eclipse-sumo/sumo/issues/18038 (because you have elevated road speeds of 43.89 m/s in your residential network). Updating to the nightly development build will make your scenario run ~100x faster
- I am unable to replicate the deadlock at the mentioned junction but there are deadlocks that match your description in other locations. The issue is now tracked at https://github.com/eclipse-sumo/sumo/issues/18043
- Motorcycles are taking a long time to find a gap in traffic for turning left (at the junction you highlighted). This is mainly a consequence of having a lot of traffic on the main road and made worse by a very substantial fraction of left-turns which take even longer to find suitable gaps.  You can increase aggressiveness / throughput by setting a higher impatience value in your vType (impatience=1 for maximum effect) but it is still not enough to prevent build-up of queues. A reduction in traffic or more effort on traffic assignment is needed: https://sumo.dlr.de/docs/Demand/Dynamic_User_Assignment.html
- Your network defines connections with attribute keepClear=False in many parts of the net (also in the highlighted region). This causes a different kind of deadlock. Once junctions are filled by spillback, cross traffic is also blocked and traffic grinds to a halt. I recommend keeping the default of keepClear=True for clusters of closely spaced junctions with heavy traffic to avoid this.
- Your scenario contains walkingareas despite not using pedestrians or crossings. This is wasteful of simulation performance. You can get rid of the walkingareas by running netconvert -s net.net.xml --walkingareas false -o net2.net.xml

regards,
Jakob


Am Fr., 22. Mai 2026 um 08:08 Uhr schrieb Duvan Rivera via sumo-user <sumo-user@xxxxxxxxxxx>:

I am currently working on a traffic simulation and I have encountered a persistent deadlock/gridlock issue at a priority intersection that I haven't been able to resolve.

Vehicles coming from a minor road (lower priority) need to turn into a highly saturated major road but they seem to find no space to get in and clogging the intersection. As seen in the attached screenshot, completely blocking each other.

I suspect there is a direct conflict between the Sublane Model and the Junction Model logic:

  1. The sublane model allows multiple vehicles (or smaller vehicles) to stand side-by-side at the lane approach.

  2. Once at the intersection edge, the junction model seems to freeze them because they share the same exit connection or because they detect each other as lateral foes inside the junction area.

  3. This creates a permanent deadlock where no vehicle from the minor road can ever advance.

  I am attaching a screenshot of the exact moment the deadlock occurs.  
image.png
image.png

Red type vehicles which represent motorcycles seem to completely freeze until teleported. The scenario on the first image causes the second one later. Could you please provide some guidance on which parameters I should tune or what I might be doing wrong.

Thank you for your time and help.

Best regards, 

Duvan Rivera, Mateo Suarez
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