Evacuation speed in full-scale darkened tunnel filled with smoke

Tunnel fires create dense black smoke that covers ceiling lights and darkens tunnel spaces. The present study investigates experimentally the evacuation speed in a full-scale tunnel filled with smoke and clarifies the relation between the extinction coefficient (up to 1.6m−1) and normal walking speed. In this study, participants were exposed to smoke in a full-scale experimental tunnel that was darkened by turning off the ceiling lights, and the extinction coefficient was varied from 0.18 to 1.6m−1. The maximum, minimum, and mean normal walking speeds were almost constant up to 1.0m−1 but decreased slightly at higher extinction coefficients. At 0.30m−1, the maximum emergency-evacuation speed through the dark tunnel is less than that when the ceiling lights are on and corresponds to 2.6m/s, thereby indicating a fast walking speed even at small extinction coefficients. However, the maximum emergency-evacuation speeds at coefficients exceeding 0.48m−1 for light and dark conditions are almost identical. The minimum and mean emergency-evacuation speeds decrease at extinction coefficients of approximately 1.0m−1. Additionally, normal walking speed and emergency-evacuation curves are calculated from the current experimental results to compare the effect of ceiling lights with that of a darkened space. The results indicate that the normal walking speed and emergency-evacuation speed are influenced by the darkened space. •We measured normal walking and evacuation speeds in a smoke-filled full-scale darkened tunnel.•Both normal walking and emergency-evacuation speed probability distributions in the darkened case in extinction coefficients up to Cs =1.0m−1 are less than those in the case with ceiling lights on.