AbstractImproving the evacuation efficiency of fire stairways is conducive to ensuring the evacuation safety of underground spaces. Personnel fatigue is the main issue during ascending movement, and it is related to vertical height. During ascending evacuation, using stairway handrails is a typical behavior characteristic that may influence the fatigue and speed of pedestrians, thereby changing evacuation efficiency. Therefore, this study aims to explore the specific effect mechanism of using handrails at different heights on individual fatigue and evacuation speed during ascending evacuation. The within-subject control experiment was completed by recruiting 16 volunteers (8 males and 8 females) in a high-rise hotel building of a university in Chongqing, China. Participants’ features of using handrails, relative heart rate, evacuation time, and evacuation speed data within a range of 10 floors (33.6 m) were obtained through an observation experiment on single-person ascending evacuation. Then, the effect mechanism was analyzed through statistical methods. This study found that participants’ proportion of using handrails surged when the ascending vertical height exceeded 6.72 m and reached saturation at 20.16 m. Additionally, participants’ proportion of using handrails and handrail usage frequency showed similar changing trends and nodes throughout the whole evacuation process. Furthermore, handrails can effectively alleviate the physical fatigue of individuals after ascending over 23.52 m. In addition, the evacuation speed of using handrails during the entire ascending evacuation process was significantly improved; especially, speed attenuation slowed down in the later period. This study can help deepen the understanding of handrail usage behavior during ascending evacuation and promote the sustainable development of underground spaces.Practical ApplicationsThis study is a representative study within the interdisciplinary scope of safety science and architecture and provides a reference for the safety design of fire stairways in underground spaces. In the current underground space regulations, key parameters such as the setting principle, height, detail parameters, and surface characteristics of stairway handrails are still based on empirical research data or models developed in the ground spaces. With the large-depth and large-scale development of underground spaces and infrastructures, the inadequate applicability of the current underground regulations of fire stairway handrails may threaten the efficiency and safety of evacuation and hide potential threats. Therefore, the vertical layered design of the stair handrail should be proposed. The current standard stipulates that the number of handrails is mainly determined according to the clear width of the fire stairways. The design of fire stairway handrails should also be varied at different vertical heights based on the handrail effect mechanism, as well as the functional characteristics, human density, and evacuation difficulty of underground spaces with various depths. In addition, this study contributes to the construction of a database of individual evacuation behaviors, which provides a new perspective and support for the simulation of microscopic behavior.