Low visibility caused by smoke in fire can greatly affect movement speed and it should be taken into consideration in the fire performance-based design and evacuation calculation models. This paper aims to study evacuation performance of individuals and small groups under normal and visually handicapped condition. The evacuation experiment was conducted in a 5-layer office building with 75 subjects. Movement speed including horizontal speed and descending speed, and route choice of individuals and small groups were analysed and discussed in this paper. It can be concluded that horizontal speed was considerably higher than descending speed in good visibility condition and the speed differences among different participants were very great, but the gap between horizontal speed and descending speed narrowed significantly and the speed differences grew smaller with reduced visibility. The small group behaviour could make negative effect on movement speed when people evacuated under normal visibility condition but it could make positive impact in bad visibility condition since people's fear of disorienting was relieved and message exchange rate was improved in a group. Both individuals and small groups generally tended to choose the most familiar route in normal visibility condition but ignored the shortest and unfamiliar route. People were more afraid to move vertically on stairs in low visibility compared to horizontal motion on flat surface such as corridor. It is suggested that proper evacuation guidance should be taken to improve the utilization of each exit in building in case of emergency.
Xie, W., Zhang, Y. C., Cheng, Y. Y., Chen, S. M., Liang, X. W., & Zhang, W. B. (2018). Experimental Study on Movement Speed and Route Choice of Individuals and Small Groups under Different Visibility Conditions. In Procedia Engineering (Vol. 211, pp. 830–836). Elsevier Ltd. https://doi.org/10.1016/j.proeng.2017.12.081