[Q&A] Not getting any PT legs after replanning

[SapanTiwari]

Provide the MATSim version you are using. You can find the version in the pom.xml. E.g. 2025.0.

2025.0

Did you build a minimal example to reproduce the issue?

• Yes!

Describe the problem you are facing.

We are working on a scenario where we do not have any PT legs in the input plan file. We create a PT network with schedules and vehicles and attempt to simulate mode shifts towards PT using SwissRailRaptor.
The interesting thing we noticed is that we get mode shift among all the modes (people moving from each mode to another), but not in PT. Therefore, we do not get any PT trip in later Iterations.

This changes if we include only one trip in the Input Plan as a PT trip. We start seeing multiple PT trips in the next iterations.

We are using ChangeTripMode as the Replanning Strategy and have tried making PT attractive and other modes unattractive; however, the issue remains the same.

This is a screenshot of how the legs look when debugging this. This indicates that during the Replanning phase, the agent walks to a PT link but does not take a PT for the next leg, instead proceeding directly to the last iteration. In that sense directWalk is much faster and therefore we do not get any PT trip.

This is not the case; we can find a PT trip if we specify the same person or any other person as the PT in the input Plan.

So both the screenshots are as follows:
(1) First one showing 2 walking legs and almost equal costs of PT and directWalk
(2) The second screenshot shows the Walk and PT legs and reduced cost for the PT trip.

So, the questions are:
Why do you think it's happening?
Does the router not enable PT routes from Iteration 1 if it does not have a single PT trip at IT 0?
Are we doing something wrong?

I am happy to share the files privately if anyone is interested in exploring this further. I would appreciate it if anyone has any thoughts on this.

If possible, provide a link to your minimal example. This might be a GitHub repository.

No response

If you want, provide some background information about you and your project. This might help us understand your issue better.

No response

[paulheinr]

It is really hard to speculate what the error is without seeing at least the config. Here are some ideas

• Did you follow the pt tutorial (https://github.com/matsim-org/matsim-code-examples/wiki/pt) to set up your scenario?
• Does ChangeTripMode have a weight >0?

Please compare your config with the config from the PT tutorial. If you still get your error, please share your config with us. I'd be happy, if you could do this here publicly so that others profit from you question 🙂

[SapanTiwari]

Hi Paul,
Thank you for getting back to me. Yes, I have used the PT tutorial for this. I have worked with PT for the last few years, and this is the first time I am trying a scenario with 0 PT trips at the start and expecting PT trips after replanning.
I am attaching the config here.
Please let me know if you have any thoughts on the file or if there is any mistake that we are making within the config. I will appreciate the help.
Thanks.

Config_github.zip

[kainagel]

I would agree that this looks odd.

Having "walk" as chain-based mode in subtour mode choice looks wrong, but the way it is configured it should not use that section of the config.