即時道路資料

即時道路資料會提供所選路線的最新路況和事件資訊，支援動態監控和快速回應。這類資料與 BigQuery 中定期收集的資料不同，適用於需要即時資訊的案例。

這項資料會持續串流，包括：行程時間 (顯示路線上的交通時間) 和速度讀取間隔 (顯示路段密度)。

如要存取即時道路資料，合約必須包含「即時作業」套裝組合。

建立 Cloud Pub/Sub 訂閱

專案設定完成後，即可接收即時資料，專案也會提供專屬的 Google Cloud Pub/Sub 主題。您可以在這個 Pub/Sub 主題中，找到所有已建立路線的即時資料。

以下程式碼範例顯示主題網址的格式。

projects/maps-platform-roads-management/topics/rmi-roadsinformation-PROJECT_NUMBER

您必須訂閱系統提供的 Pub/Sub 主題，才能接收即時資料訊息。如要快速瞭解如何訂閱及調用 Cloud Pub/Sub 主題的訊息，請參閱「訂閱主題」。

即時路況資料訊息結構定義

每則即時資料訊息都會納入下列資料：

• 道路詳細資料，例如 travel_duration 和 speed_reading_intervals。
• 路徑 ID，例如 selected_route_id 和 display_name。

每則訊息都會按照下列 Protobuf 格式發布。

syntax = "proto3";

// Contains the road information like travel duration and speed reading
// intervals for a selected route.
message RoadsInformation {
  message TravelDuration {
    // The duration of travel through the route based on current road conditions.
    float duration_in_seconds = 1;
    // The duration of travel through the route without taking road conditions into consideration.
    float static_duration_in_seconds = 2;
  }
  message Timestamp {
    // Represents seconds of UTC time since Unix epoch
    // 1970-01-01T00:00:00Z. Must be from 0001-01-01T00:00:00Z to
    // 9999-12-31T23:59:59Z inclusive.
    int64 seconds = 1;

    // Non-negative fractions of a second at nanosecond resolution. Negative
    // second values with fractions must still have non-negative nanos values
    // that count forward in time. Must be from 0 to 999,999,999
    // inclusive.
    int32 nanos = 2;
  }
  // Represents the latitude and longitude of a coordinate
  // within speed reading interval.
  message LatLng {
    float latitude = 1;
    float longitude = 2;
  }
  message SpeedReadingInterval {
    // The coordinates on the polyline for the speed reading interval
    repeated LatLng interval_coordinates = 1;

    // Describes the categorized current speed of road conditions. Possible values are:
    // - "NORMAL": Road is flowing smoothly, no slowdown is detected.
    // - "SLOW": Slowdown detected, but no congestion formed.
    // - "TRAFFIC_JAM": Congestion detected.
    string speed = 2;
  }
  // Id for selected_route.
  string selected_route_id = 1;
  // User provided name for the route.
  string display_name = 2;
  // Intervals representing the road density across the route.
  repeated SpeedReadingInterval speed_reading_intervals = 3;
  // Travel time information.
  TravelDuration travel_duration = 4;
  // The time the road data was collected.
  Timestamp retrieval_time = 5;
  // Contains a geojson polyline representing the optimal route determined based
  // on user's input waypoints.
  string route_geometry = 6;
}

使用 Pub/Sub 將路線資料串流至 BigQuery

您可以設定 Pub/Sub 訂閱項目，將道路資料直接串流至 BigQuery 資料表。這可確保資料儲存空間充足，並對提供的路線資訊進行強大的分析。設定這類訂閱項目之前，您必須在 BigQuery 專案中建立合適的資料集和資料表，以便寫入資料。

如需如何建立可將資料寫入 BigQuery 的 Pub/Sub 訂閱項目，請參閱「將資料串流至 BigQuery」一文。

BigQuery 資料表結構定義

發布至 Pub/Sub 主題的訊息 (也可以寫入 BigQuery 資料表) 會符合下列結構定義。建立目標 BigQuery 資料表時，請使用這個結構定義，確保資料表相容。

  {
    "mode": "NULLABLE",
    "name": "selected_route_id",
    "type": "STRING",
    "description": "Id for selected_route."
  },
  {
    "mode": "NULLABLE",
    "name": "display_name",
    "type": "STRING",
    "description": "User provided name for the route."
  },
  {
    "fields": [
      {
        "mode": "NULLABLE",
        "name": "speed",
        "type": "STRING",
        "description": "Describes the categorized current speed of traffic. Possible values are: \"NORMAL\": Traffic is flowing smoothly, no slowdown is detected.  \"SLOW\": Slowdown detected, but no traffic jam formed. \"TRAFFIC_JAM\": Traffic jam detected."
      },
      {
        "fields": [
          {
            "mode": "NULLABLE",
            "name": "latitude",
            "type": "NUMERIC"
          },
          {
            "mode": "NULLABLE",
            "name": "longitude",
            "type": "NUMERIC"
          }
        ],
        "mode": "REPEATED",
        "name": "interval_coordinates",
        "type": "RECORD",
        "description": "The geometry for this interval"
      }
    ],
    "mode": "REPEATED",
    "name": "speed_reading_intervals",
    "type": "RECORD",
    "description": "Intervals representing the traffic density across the route."
  },
  {
    "fields": [
      {
        "mode": "NULLABLE",
        "name": "duration_in_seconds",
        "type": "FLOAT",
        "description": "The duration of travel through the route based on current traffic conditions."
      },
      {
        "mode": "NULLABLE",
        "name": "static_duration_in_seconds",
        "type": "FLOAT",
        "description": "The duration of travel through the route without taking traffic conditions into consideration."
      }
    ],
    "mode": "NULLABLE",
    "name": "travel_duration",
    "type": "RECORD",
    "description": "Travel time information."
  },
  {
    "fields": [
      {
        "mode": "NULLABLE",
        "name": "seconds",
        "type": "INTEGER",
        "description": "Represents seconds of UTC time since Unix epoch 1970-01-01T00:00:00Z. Must be from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59Z inclusive."
      },
      {
        "mode": "NULLABLE",
        "name": "nanos",
        "type": "INTEGER",
        "description": "Non-negative fractions of a second at nanosecond resolution. Negative second values with fractions must still have non-negative nanos values that count forward in time. Must be from 0 to 999,999,999 inclusive."
      }
    ],
    "mode": "NULLABLE",
    "name": "retrieval_time",
    "type": "RECORD",
    "description": "The time the traffic data was collected."
  },
  {
    "mode": "NULLABLE",
    "name": "route_geometry",
    "type": "STRING",
    "description": "Contains a geojson polyline representing the optimal route determined based on user's input waypoints"
  }