Feature Request: Add Centroid Nodes and Connectors for Each Zone

[asu-trans-ai-lab]

Feature Request: Add Centroid Nodes and Connectors for Each Zone

Requested Feature:

Introduce a feature in grid2demand to automatically generate centroid nodes and centroid connectors for each zone. This will streamline the process of building GMNS networks compatible with traffic assignment packages like TransCAD, Cube, VISUM, DTALite, and path4gmns by implementing an efficient forward star network structure.

Feature Details:

1. Centroid Node Creation:

   • For each zone, create a single centroid node with the same zone_id.
   • These centroid nodes should be listed at the beginning of the node.csv file in a sequential order, such as 1, 2, 3, ....

2. Connector Creation:

   • Add centroid connectors between each new centroid node and the activity nodes within the same zone.
   • These connectors represent links between the centroid and the corresponding activity nodes, ensuring proper connectivity within the zone.

3. Node Numbering and Sequencing:

   • After adding the centroid nodes, the physical nodes (including the original activity nodes) should be listed sequentially after the centroid node block in the node.csv file.
   • The node numbering should be updated to reflect this new order.

4. Updating Link IDs:

   • The link.csv file should be updated so that the from_node_id and to_node_id in each link are consistent with the new node IDs in the updated node.csv.
   • This ensures the network remains sorted sequentially, which is essential for efficient processing in planning packages.

5. Demand Preparation:

   • The demand.csv file should also follow the sequential zone_id structure for consistency.

Example:

In the Chicago Sketch example from DTALite, there are 934 nodes, with the first 387 nodes being zone centroids, and the rest are physical nodes. The node.csv, link.csv, and demand.csv files are structured to reflect this organization:

• node.csv: Chicago Sketch Node.csv
• link.csv: Chicago Sketch Link.csv
• demand.csv: Chicago Sketch Demand.csv

Purpose:

This structure is essential for forward star network structures, used by major planning packages. Although path4gmns and DTALite allow multiple activity nodes per zone, they internally build the centroid and connector structure. By building this structure externally in grid2demand, it would:

• Streamline the process of network building across different modes.
• Ensure consistent and efficient assignment based on the forward star network structure.

This enhancement would also improve compatibility with commercial traffic assignment packages such as TransCAD, Cube, and VISUM that require such network structures for efficient computation.

This structure is also used in the paper titled: A unified dataset for the city-scale traffic assignment model in 20 U.S. cities https://www.nature.com/articles/s41597-024-03149-8.