Overview

The Tailgating node analyses line crossings from a prior Line crossing node to detect tailgating events.

Inputs & Outputs

Inputs: 1, Media Format: Raw Video
Outputs: 1, Media Format: Raw Video
Output Metadata: Tailgating Metadata

Pipeline usage

Place a detector, Track Objects, and Annotate Line Counter before this node. Set line_id to the upstream line label, optionally followed by :dir1 or :dir2 to monitor one direction; using only the line label monitors both directions. The interval rule flags objects that cross too close together. The correlating-trigger rule instead consumes an upstream event such as a badge swipe and permits crossing_allowance crossings during its buffer. Violating objects receive a tailgating attribute, so downstream filters and events can match that class.

Properties

Property	Description	Type	Default	Required
`object_types`	ex. `car`,`person`,`face.mask`. Comma-separated list of object types to consider. Empty list processes all objects.	model-labels	`person`	No
`line_id`	ex. front_entrance or front_entrance:dir1 or front_entrance+vestibule. Line ID from a preeceding Line or MultiLine node to monitor for tailgating.	`string`	`null`	Yes
`tailgating_rule`	Tailgating rule. Options: Interval (`interval`): Require a minimum interval between objects crossing the line; Correlating Trigger (`trigger`): Require an external trigger (such as badge swipe) before each object that crosses the line.	`enum`	`interval`	Yes
`tailgating_interval`	Minimum time between objects crossing the specified line to be considered valid. A `tailgating` event will be triggered for objects that cross within a smaller interval. Conditional on `tailgating_rule` being `interval`. Unit: seconds.	`number`	`5`	Yes
`correlating_trigger`	If specified, each object that crosses must be preceeded by a trigger event that satisfies this condition. If not, a `tailgating` event will be triggered. Conditional on `tailgating_rule` being `trigger`.	trigger-condition	`null`	Yes
`correlating_trigger_buffer`	Each correlating trigger will be matched with an object crossing within this interval. After the interval elapses, the trigger will be discarded. Conditional on `tailgating_rule` being `trigger`. Unit: seconds.	`number`	`5`	Yes
`crossing_allowance`	Number of objects allowed to cross per interval or trigger. Unit: objects.	`number`	`1`	Yes
`display`	Display. Options: None (`none`); Basic (`basic`): Highlight violating objects; Full (`full`): Display stats, highlight violating objects.	`enum`	`basic`	No

Output Metadata

The fields below are declared by this node's metadata schema; the JSON values are representative examples.

Path	Type	Description
`nodes.<node_id>.tailgating_delta`	`integer`	When one or more instances of tailgating are detected
`nodes.<node_id>.lines.<line_id>.tailgating_delta`	`integer`	When one or more instances of tailgating are detected on a specific line
`nodes.<node_id>.lines.<line_id>.tailgating_objects`	`array`	Array of tracking IDs of objects involved in a tailgating event.
`nodes.<node_id>.events`	`array`	Array of event names generated by this node for the current frame.
`nodes.<node_id>.type`	`string`	Identifies the node type that produced this metadata.

JSON example

{
  "nodes": {
    "tailgating1": {
      "events": [],
      "lines": {
        "line1": {
          "tailgating_delta": 0,
          "tailgating_objects": []
        }
      },
      "tailgating_delta": 0,
      "type": "tailgating"
    }
  }
}

Object labels and attributes

Object labels/classes added: None.
Object attribute labels/classes added: tailgating, with class 17001.