Roadnet File Format

Roadnet file defines the roadnet structure. CityFlow’s roadnet mainly consists of intersections and roads (see them as nodes and edges of a graph).

• Road represents a directional road from one intersection to another intersection with road-specific properties. A road may contain multiple lanes.
• Intersection is where roads intersects. An intersection contains several roadlinks. Each roadlink connects two roads of the intersection and can be controlled by traffic signals.
• A roadlink may contain several lanelinks. Each lanelink represents a specific path from one lane of incoming road to one lane of outgoing road.

Now let’s see a sample roadnet file and we’ll explain the meaning of each components. Relax, the definition of field is quite straight forward, if you are familiar with modern road networks. For the following json file, [] means this field is an array, but we will only show one object for demonstration.

Note

Runnable sample roadnet files can be found in examples folder.

Sample roadnet.json with explanation.

{
  "intersections": [
    {
      // id of the intersection
      "id": "intersection_1_0",
      // coordinate of center of intersection
      "point": {
        "x": 0,
        "y": 0
      },
      // width of the intersection
      "width": 10,
      // roads connected to the intersection
      "roads": [
        "road_1",
        "road_2"
      ],
      // roadLinks of the intersection
      "roadLinks": [
        {
          // 'turn_left', 'turn_right', 'go_straight'
          "type": "go_straight",
          // id of starting road
          "startRoad": "road_1",
          // id of ending road
          "endRoad": "road_2",
          // lanelinks of roadlink
          "laneLinks": [
            {
              // from startRoad's startLaneIndex lane to endRoad's endLaneIndex lane
              "startLaneIndex": 0,
              "endLaneIndex": 1,
              // points along the laneLink which describe the shape of laneLink
              "points": [
                {
                  "x": -10,
                  "y": 2
                },
                {
                  "x": 10,
                  "y": -2
                }
              ]
            }
          ]
        }
      ],
      // traffic light plan of the intersection
      "trafficLight": {
        "lightphases": [
          {
            // default duration of the phase
            "time": 30,
            // available roadLinks of current phase, index is the no. of roadlinks defined above.
            "availableRoadLinks": [
              0,
              2
            ]
          }
        ]
      },
      // true if it's a peripheral intersection (if it only connects to one road)
      "virtual": false
    }
  ],
  "roads": [
    {
      // id of road
      "id": "road_1",
      // id of start intersection
      "startIntersection": "intersection_1",
      // id of end intersection
      "endIntersection": "intersection_2",
      // points along the road which describe the shape of the road
      "points": [
        {
          "x": -200,
          "y": 0
        },
        {
          "x": 0,
          "y": 0
        }
      ],
      // property of each lane
      "lanes": [
        {
          "width": 4,
          "maxSpeed": 16.67
        }
      ]
    }
  ]
}

Illustration of a 1x2 grid roadnet.

You can convert SUMO roadnet files into CityFlow format using tools/Converter/converter.py

For example, the following code converts a sumo roadnet file, atlanta.net.xml, to CityFlow format.

python converter.py --sumonet atlanta_sumo.net.xml --cityflownet atlanta_cityflow.json