Verif.2.5: Reduced visibility vs walking speed

1. Definition

A corridor of 2 m by 100 m has a 1 m wide exit at the end. One occupant has an unimpeded speed of 1.25 m/s in clear air. A constant extinction coefficient K_s of 1.0 /m is applied in the whole corridor before the run, with no light sources. The occupant walks to the exit. Models describe the effect of smoke on speed with one of five correlations (Eqs. 1-5 of TN 1822, from Ronchi et al. 2013a), which are fractional or absolute speed reductions, with or without a minimum speed in dense smoke (about 0.3 to 0.4 m/s). Only the effect of reduced visibility on walking speed is tested, not irritant or toxic effects.

Source: NIST TN 1822, Verif.2.5, pp. 21-23, Eqs. 1-5. This is a paraphrase, not the text of the standard.

Reference: Ronchi, E., Kuligowski, E. D., Reneke, P. A., Peacock, R. D., Nilsson, D. (2013). The Process of Verification and Validation of Building Fire Evacuation Models. NIST Technical Note 1822. National Institute of Standards and Technology. 10.6028/NIST.TN.1822 (Page numbers are the printed page numbers of TN 1822.)

2. Scenario

Scenario picture not available.

3. What to expect

The travel time equals the time that the tester calculates by hand with the correlation of the model, that is, with the model’s own speed reduction factor. The result is a quantitative comparison of times. TN 1822 asks to repeat the test for other combinations of clear-air speed (1.0, 0.75, 0.5 and 0.25 m/s) and extinction coefficient (10, 7.5, 3.0 and 0.5 /m). A model without a smoke-speed sub-model should describe that limitation, including that it cannot follow visibility changing over time.

Our criterion: At K_s = 1/m, simulated 100 m travel time matches the declared Equation 2 smoke-speed correlation

The smoke speed factor is applied by a test-local adapter using a declared correlation; the test checks travel time against that declared factor, not the correlation itself.

4. Our result

Status: TEST-LOCAL

Test cases of this row

• test_smoke_reduced_travel_time: bound: expected - 0.5 <= measured <= expected + 0.5, expected = 100 m / (1.25 m/s * c(K_s = 1/m)) = 160 s

5. Our implementation

Deviations from the standard:

• JuPedSim has no smoke or visibility model. A test-side adapter turns K_s into a speed factor before the run and writes it as the factor of a zone that covers the corridor. The adapter uses the form of Eq. 2, v = max(v_min, v0 c(K_s)), with c(K_s) = 1 - 0.5 K_s and v_min = 0.3 m/s. At K_s = 1 /m, c = 0.5, the speed is 0.625 m/s and the expected time over 100 m is 160 s.
• What is verified: the simulated occupant crosses a speed-factor zone at the factor’s speed. What is not verified: a smoke model, the correlation itself (c(K_s) = 1 - 0.5 K_s is the suite’s choice, not a published correlation), the dependence on K_s, or smoke that varies in space or time. At K_s = 1 /m the minimum speed does not apply, so that branch of Eq. 2 is not exercised.
• The pass rule is the suite’s own: the time over the 100 m segment must be within 0.5 s of the hand calculation. TN 1822 sets no tolerance.
• Only one of the 16 suggested combinations of clear-air speed and extinction coefficient is run, with one seed (42).
• The corridor is 120 m long, with a 10 m buffer at each end of the 100 m measurement segment. The 1 m exit is the capture area at the corridor end. The scenario is built in code (tests/vv/test_nist.py) rather than loaded from a scenario file.

Model: CollisionFreeSpeedModel

• Test function: tests/vv/test_nist.py::test_smoke_reduced_travel_time

6. Our notebook

No notebook for this test yet.