The connection between stress, density, and speed in crowds.

Moving around in crowds is part of our daily lives, and we are used to the associated restriction of mobility. Nevertheless, little is known about how individuals experience these limitations. Such knowledge would, however, help to predict behavior, assess crowding, and improve measures for safety and comfort. To address this research gap, we conducted two studies on how constrained mobility affects physiological arousal as measured by mobile electrodermal activity (EDA) sensors. In study 1, we constrained walking speed by externally imposing a specific walking speed without physical proximity to another person, while, in study 2, we varied walking speed by increasing the number of people in a given area. In study 1, we confirmed previous findings showing that faster speeds led to statistically significantly higher levels of physiological arousal. The external limitations of walking speed, however, even if perceived as uncomfortable, did not increase physiological arousal. In the second study, subjects' speed was gradually reduced by density in a single-lane experiment. This study shows that physiological arousal increased statistically significant with increasing density and decreasing speed, suggesting that people experience more stress when their movement is restricted by proximity to others. The result of study 2 is even more significant given the results of study 1: When there are no other people around, arousal increases with walking speed due to the physiology of walking. This effect reverses when the speed must be reduced due to other people. Then the arousal increases at lower speeds.