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The Zone Activity Check evaluates conditions at the zone level — how many tracks are in a zone and whether they meet threshold criteria. Unlike the Track Checks which evaluate individual track behavior, this node answers the question “what is happening in this zone right now?”

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When to use

Use the Zone Activity Check when your workflow is triggered by zone state signals and you care about aggregate zone activity rather than individual track behavior:
  • Congestion — too many vehicles in an aisle zone
  • Congregation — multiple people gathering in an area
  • Occupancy limits — zone exceeds a maximum track count
  • Zone monitoring — any scenario where the number of objects in a zone matters
This node is designed for zone state data from the Detection Webhook Trigger with signal type set to Zone State. For track-level checks, use the Track Checks node instead.

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How it works

  1. The node reads the zone state from the input, including the list of active tracks in the zone
  2. For each active track, it evaluates the enabled threshold conditions (dwell time, intersection)
  3. Tracks that meet all enabled thresholds are counted as qualified tracks
  4. The check passes if the number of qualified tracks meets the minimum track count

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Configuration

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Site

Select the Worlds site. This loads available zones for reference.

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Threshold groups

Each group defines the conditions tracks must meet to be counted:
ParameterTypeDescription
Zone IDsMulti-selectWhich zones this group applies to. Use ={{$json.zone_state.zone_id}} to dynamically match the incoming zone.
Min Track CountNumberMinimum number of qualified tracks for the check to pass
Dwell TimeToggle + valueMinimum time (seconds) a track must have been in the zone to be counted
IntersectionToggle + valueMinimum overlap percentage between the track’s bounding box and the zone polygon
Setting the zone ID dynamically with ={{$json.zone_state.zone_id}} means the same threshold configuration applies to every zone your trigger is monitoring. This is the most common approach.

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Example configuration

For a congestion workflow detecting 4+ vehicles lingering in aisle zones:
ParameterValue
Zone IDs={{$json.zone_state.zone_id}}
Min Track Count4
Dwell TimeEnabled, >= 5 seconds
IntersectionEnabled, >= 10%
This means: the check passes when 4 or more tracks in the zone each have at least 5 seconds of dwell time and at least 10% intersection with the zone polygon.

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Output

{
  "zone_state": { ... },
  "checks": {
    "zoneActivity": {
      "passed": true,
      "zone_id": "92",
      "zone_name": "Aisle-Zone-West",
      "qualified_track_ids": ["track-uuid-1", "track-uuid-2", "track-uuid-3", "track-uuid-4"],
      "qualified_track_count": 4,
      "total_active_tracks": 6,
      "track_details": {
        "track-uuid-1": {
          "tag": "forklift",
          "dwell_time": 25.0,
          "intersection": 45.3,
          "qualified": true
        }
      }
    }
  }
}

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Key output fields

FieldDescription
passedWhether the qualified track count met the minimum threshold
zone_idThe zone that was evaluated
qualified_track_idsTrack IDs that met all threshold conditions — use these downstream for image capture and event metadata
qualified_track_countNumber of qualifying tracks
total_active_tracksTotal tracks in the zone (including those that didn’t meet thresholds)
track_detailsPer-track breakdown showing dwell time, intersection, and whether it qualified

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Downstream usage

The qualified_track_ids output is commonly used by downstream nodes:
  • Closest Frame — find the timestamp where qualified tracks are closest together for the best image
  • Process Detection Image — generate a still or GIF showing the qualified tracks
  • Event Manager — attach qualified track IDs to the created event

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Credentials

Requires GraphQL Subscription API credentials (for loading site/zone options).

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Business use case examples

Detect when multiple vehicles are lingering in a factory aisle zone, creating traffic congestion that blocks material flow.
ParameterValuePurpose
Zone IDs={{$json.zone_state.zone_id}}Dynamically matches incoming zone
Min Track Count4At least 4 vehicles to constitute congestion
Dwell Time>= 5 secondsVehicles must be lingering, not just passing through
Intersection>= 10%Vehicles must be meaningfully inside the zone
Mode: Streaming, zone state — receives updates whenever zone occupancy changes.The workflow uses an Event Orchestrator scoped by zone (not track) to prevent duplicate congestion events. The qualified_track_ids output feeds downstream into Closest Frame (to find the best multi-track image) and Create Still (to show all qualifying vehicles with bounding boxes and zone overlay).A VLM analyzes the captured image to add context metadata (e.g., “Four vehicles visible in the aisle. Two forklifts are positioned side by side blocking the travel path…”). When vehicles leave and the count drops below 4, the orchestrator routes to the Close Event path with the congestion duration.See the Congestion Workflow guide for the full end-to-end walkthrough.
Zone Activity Check works for any aggregate zone monitoring scenario:
Use CaseMin Track CountDwell TimeIntersectionNotes
Aisle congestion4>= 5s>= 10%Vehicles blocking traffic
Congregation5>= 30s>= 15%People gathering in restricted areas
Occupancy limitSite-specific>= 10s>= 5%Maximum capacity enforcement
Loading dock queue3>= 60s>= 20%Vehicles waiting too long at dock
Higher dwell time thresholds filter out transient tracks (objects passing through), while higher intersection thresholds ensure the objects are meaningfully inside the zone rather than just at the boundary.