Test 15: Social influence on exit choice

1. Definition

A room of 10 m by 15 m has two 1 m exits on the 15 m walls, centred 12 m from the short end wall. In Scenario 1 one occupant (occupant 1), with no preferred exit, no pre-evacuation time and a speed of 1 m/s, starts 1 m from the bottom wall at a position equidistant from both exits. The run is repeated until the exit usage changes by less than 1 % with an additional run. In Scenario 2 a second occupant starts 2 m from the bottom wall and is deterministically assigned to Exit 2. The runs are again repeated until usage is stable. Exit usage is recorded. A model whose exit choice is user-defined, so that occupants always take the closest exit, documents that limitation.

Source: ISO 20414:2020, Test 15, Table 17, pp. 26-27, Fig. 11. This is a paraphrase, not the text of the standard.

Reference: ISO (2020). ISO 20414:2020, Fire safety engineering - Verification and validation protocol for building fire evacuation models. First edition. International Organization for Standardization, Geneva. https://www.iso.org/standard/78348.html (Page numbers are the printed page numbers of ISO 20414:2020 (the copy read is a proof, so numbers can differ by a page in the published edition). ISO states that its tests are examples and that a tester may use different tests that verify the same component equivalently.)

2. Scenario

Scenario figure from the executed notebook.

3. What to expect

Occupant 1 uses Exit 2 more often in Scenario 2 than in Scenario 1.

Our criterion: A deterministic exit-2 occupant raises free occupants’ exit-2 usage

CollisionFreeSpeedModel has no social-influence model; exit-2 usage is unchanged.

4. Our result

Status: FAIL

Limitation: CollisionFreeSpeedModel has no social-influence model; exit-2 usage is unchanged.

Test cases of this row

• test_social_influence_raises_exit2_usage: comparison: measured[0] (free occupants with an exit-2 occupant present) > measured[1] (baseline, Iso-15-social-influence-1.zip); expected failure

Result figure from the executed notebook.

5. Our implementation

Deviations from the standard:

• Scenario 1 has two free occupants instead of one, each assigned by journey weights of 50 / 50 to the two exits. The exit of the free occupants is set by these input weights, not by a choice the model makes. Their start positions are drawn inside a small box and are not fixed.
• Scenario 2 adds a third occupant, bound to Exit 2, starting about 2 m from the bottom wall. The occupants that start closest to the bottom wall (below 1.5 m) are counted as the free ones.
• ISO’s rule of repeating until the exit usage varies by less than 1 % is replaced by 40 fixed seeds.
• The pass rule is the suite’s own: the Exit-2 fraction of the free occupants in Scenario 2 must be higher than in Scenario 1.

Model: CollisionFreeSpeedModel

• Test function: tests/vv/test_iso.py::test_social_influence_raises_exit2_usage
• Scenario file: Iso-15-social-influence-1.zip
• Scenario file: Iso-15-social-influence-2.zip

6. Our notebook

• Executed notebook (HTML)
• Notebook source (.ipynb) on GitHub