How to generate the actual geometry of line variant elements using "GTFS To Public Transit Data Model" tool?

Allenlai · ‎01-26-2022

The length and shape of the line feature aren't used by the Public Transit evaluator to calculate the travel time. When I create my data model tables from GTFS data using the GTFS To Public Transit Data Model tool, the line variant elements will be simple straight lines connecting adjacent transit stops.

However, it is really matter to show the actual geometry of line variant elements using the service area analysis tool. It doesn't make straightforward to display the coverage of the public transit lines and stops using the simple straight lines.

Therefore, my question is how to generate the actual geometry of line variant elements. Maybe it will be good choice to replace the shape of line variant elements using "GTFS To Public Transit Data Model" tool. However, I could not find the available methods to achieve that.

Give me some hits or anything suggestions, plz. Thanks a lot!

MelindaMorang · ‎01-26-2022

You have understood the software's behavior correctly: GTFS To Public Transit Data Model generates straight-line connections between stops rather than attempting to create geometry that follows the streets traveled by buses. Fundamentally, the geometry is not needed for the network analysis, but the reason we built the tool this way has more to do with the fact that it is difficult or impossible to extract this information reliably from GTFS datasets. The geographic shapes of routes are stored in shapes.txt, which is an optional file that ties in only tangentially with the schedule data.

If including the actual route geometry in your network dataset is important to you, you can try using the GTFS Shapes To Features tool, which creates a line feature class from the information in the shapes.txt file of your GTFS dataset. You would then need to carefully swap out the LineVariantElement geometry for the geometry from the feature class of shapes, all the while being very careful to maintain proper network connectivity (snapping the stops to the shape features and splitting them, etc.). I do not expect this to be straightforward or automatable, and often the quality of the data in shapes.txt is not great.

You could also try using the Conflation tools to try to make the LineVariantElements match the shapes of the streets where the transit travels.

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MelindaMorang · ‎01-26-2022

You have understood the software's behavior correctly: GTFS To Public Transit Data Model generates straight-line connections between stops rather than attempting to create geometry that follows the streets traveled by buses. Fundamentally, the geometry is not needed for the network analysis, but the reason we built the tool this way has more to do with the fact that it is difficult or impossible to extract this information reliably from GTFS datasets. The geographic shapes of routes are stored in shapes.txt, which is an optional file that ties in only tangentially with the schedule data.

If including the actual route geometry in your network dataset is important to you, you can try using the GTFS Shapes To Features tool, which creates a line feature class from the information in the shapes.txt file of your GTFS dataset. You would then need to carefully swap out the LineVariantElement geometry for the geometry from the feature class of shapes, all the while being very careful to maintain proper network connectivity (snapping the stops to the shape features and splitting them, etc.). I do not expect this to be straightforward or automatable, and often the quality of the data in shapes.txt is not great.

You could also try using the Conflation tools to try to make the LineVariantElements match the shapes of the streets where the transit travels.

Allenlai · ‎01-26-2022

Thx!!!! Your suggestion helps me a lot. I will try to swap out the LineVariantElement geometry for the geometry from the feature class of shapes.