Herding Behavior and Exit Selection

[jaantollander]

---

layout: "post"
title: "FDS+Evac: Herding Behavior and Exit Selection"
date: "2017-05-23 09:40"

Korhonen, T., & Heliövaara, S. (2011). FDS+Evac: Herding Behavior and Exit Selection, (August), 1373–1385. https://doi.org/10.3801/IAF

Exit Selection Model

All agents use three criteria to determine preference number $P_i(k)$ for each exit $k ∈ ℰ$ which depends on the agent type. Criteria (boolean variables true or false) are

• Visible, variable
• Familiar, constant
• No-smoke, variable

Preference numbers for herding and conservative agents

P	Visible	Familiar	No-smoke
1	true	true	true
2	false	true	false
3	true	false	true
4	true	true / false	false
5	false	true	false

Preference numbers for active agents

P	Visible	Familiar	No-smoke
1	true	true/false	true
1	true/false	true	true
2	true	true/false	false
2	true/false	true	false

Agents select the exit with smallest preference number. If two of more exits share the same preference, the decisicion between the exits is made by minimizing estimated egress time.

Agent types and Preference numbers

• Herding: Herding agents use only familiar exits. If they have no familiar exits they follow other agents. Herding agents follow the movement of 5 closest agents that are withing the radius of 5 m. Only nearest neighbour that are heading away from the agent are considered ($cos(φ) < -0.2$, $φ$ is angle between agents directions).

• Conservative: Preferes familiar routes that are visible. Can get lost meaning agent does not have any visible or familiar exits. In this case they behave like herding agents until one or more exits become visible again.

• Active: Active agents prefer all visible exists familiar or not in order to find fastest exit route. Can be though as the leaders for herding agents.

Exit selection algorithm for selecting exit $k$ is formulated using a penalty function

$$ \arg\min_{k ∈ ℰ} (T_i(k) + P_i(k) M) $$

where $T_i(k)$ is the estimated evacuation time for agent $i$ through exit $k$ and $M > 0$ is sufficiently large constant. Estimated evacuation time consist of the time to walk to the door and estimated egress time of the crowd mass in front of the door.

Conclusions

Presence of active agents decreaces average egress time even in precense of large number of herding agents.

[jaantollander]

Evacuation and behaviour algorithms that needs to be implemented or updated

• Exit Selection
• Different agent behaviour types
  • Active
  • Conservative
  • Herding
• Herding + obstacle avoidance
  • Nearest neighbors search
    • Maximum distance between agents to be considered as neighbor
    • Maximum number of nearest neighbors to be followed