Experimental study on mechanical transfer regularity and step distance of individuals under different collision impulse

In the process of emergency evacuation, the fall of an individual may lead to the instability of surrounding pedestrians. The evacuation routes would be obstructed by fallen pedestrians, thereby diminishing the evacuation efficiency and increasing the overall crowd risk. The purpose of this study is to explore the balance-recovery process of pedestrians under collision. The study conducted a series of experiments to obtain the total step distance and number of steps taken by individuals during the balance-recovery process under different impulses. The impulse applied by the unstable individual to the obstacle ahead for balance recovery was also measured. The gait characteristics and mechanical principles of the individuals in the balance-recovery process after collision force were analyzed. The results indicate that individuals can recover balance within a 90 cm step distance if the impulse received is in the range of 20–160 N s. The relationship between the step distance of an individual and the impulse received can be expressed as a quadratic function. When stepping is prohibited, the impulse applied by the individual to the obstacle ahead is approximately 1.85 times the impulse he received. However, if stepping is allowed, the dispersion of the impulse applied to the obstacle gradually decreases with increasing step space. Additionally, logistic regression models were constructed to calculate individual instability probabilities for different conditions based on the experimental data. These results can serve as a foundation method for evaluating the individual and group instability risk during emergency evacuation scenarios.