Scenario data format

If you want to import your own travel demand model, you can use this JSON file.

Specification

Until we switch to using protobufs or similar, there's no formal spec. The JSON deserialization happens from Rust code. It's easiest to follow the example below.

Example

This defines a scenario containing a single person, who takes one trip. They begin at midnight at the building nearest to the origin, then at 3AM (10800 is seconds after midnight), they drive to the building nearest to the destination. The mode field could also be Walk, Bike, or Transit. The purpose field is mostly unused; you could pick other values that show up in the UI. You could add more trips to this person, with increasing departure time. And of course, you can add as many people as you like.

{
  "scenario_name": "monday",
  "people": [
    {
      "origin": {
        "Position": {
          "longitude": -122.303723,
          "latitude": 47.6372834
        }
      },
      "trips": [
        {
          "departure": 10800.0,
          "destination": {
            "Position": {
              "longitude": -122.3075948,
              "latitude": 47.6394773
	    }
          },
          "mode": "Drive",
          "purpose": "Shopping"
        }
      ]
    }
  ]
}

Tools

To import this JSON file into A/B Street:

cargo run --bin import_traffic -- --map=data/system/us/seattle/maps/montlake.bin --input=/path/to/input.json

This tool matches input positions to the nearest building, within 100 meters. If the point lies outside the map boundary, it's snapped to the nearest map border. The tool will fail if any point doesn't match to a building. If you pass --skip_problems, those people will be logged and skipped instead.

There are also a few tools that produce this JSON file:

• https://github.com/a-b-street/abstreet/blob/master/headless/examples/generate_traffic.py
• https://github.com/dabreegster/grid2demand/blob/scenario_script/src/demand_to_abst_scenario.py

Future requests

• A way to specify some kind of numeric ID for each person, so you can later correlate results from the simulation with your input
• A way to specify the purpose of a trip (unused for now, in the distant future may affect willingness to pay tolls)