New insights on the downward evacuation speed on long-distance stairs by experiment and modelling

Current evacuation models for super high-rise buildings typically assume a fixed speed or a decrease in speed with distance traveled, which overlooks the combined effects of physical exertion, recovery after rest, and partnering behavior. In this study, we present new insights on the downward evacuation speed on long-distance stairs by experiment and modelling. First, long-distance down stairs experiments are carried out, in which the goal distance, rest, and partnering or not are used as control factors. Second, a speed formula that indicates how the speed decreases as accumulated distance and how much does the speed increase after the rest is defined according to the experimental results. Furthermore, an evacuation model with dynamic speed (Evac-DS model) for super high-rise buildings is built, in which the pedestrian's speed is determined by the factors considered in the defined formula, such as expected evacuation distance, evacuation time, rest time, goal distance, and partnering or not. The results show that whether in scenarios where pedestrians move alone or in pairs, the trend of speed changes in the evacuation process on long-distance stairs predicted by the Evac-DS model closely matches the experiment. Finally, the Evac-DS model is used to simulate the evacuation process in Shanghai Tower with 580m height, and the predicted speed is compared with the evacuation drill data, as well as two other models: one assuming a constant speed and another where speed decreases linearly with distance. The results indicate that the Evac-DS model can effectively predict the evacuation time and the variation of pedestrian's evacuation speed in actual super high-rise buildings. This study may be a key step in understanding the nonlinear changes in speed during long-distance stairs evacuation, and provide scientific reference and support for both theoretical research and model applications related to pedestrian evacuation in the stairwells of super high-rise buildings.