Fire is a great calamity. For example, the 1115 fire in Shanghai killed 58 people 11. Due to the rapid progress of urbanization, rapid development of commercial economy, the scale of a single building is constantly expanding, and the internal structure is becoming more and more complex. To improve the efficiency of evacuation and reduce casualties, the problem of evacuation in emergency has become a research hotpot.
The efficiency of evacuation in emergency depends on the completeness of spatial knowledge19.Having good spatial knowledge helps to reduce evacuation time and distance23,35.The influence of spatial knowledge integrity on evacuation is mainly reflected in the following aspects: first, the evacuation efficiency of participants with different spatial knowledge integrity is different. Participants with complete spatial knowledge were able to find evacuation routes more quickly23.The participants with incomplete spatial knowledge cannot identify the environment, which leads to the difficulty of evacuation35.Therefore, participants with complete spatial knowledge are more likely to reach the safe area than participants with incomplete spatial knowledge16.Secondly, people with different spatial knowledge have different evacuation characteristics, such as: people with complete spatial knowledge rely on autonomous evacuation43.People with incomplete spatial knowledge were evacuated with the surrounding crowd19.Thirdly, people with different levels of spatial knowledge tend to choose familiar evacuation routes36.People in emergency situations tend to choose familiar routes and exits rather than unfamiliar routes1,34.However, depending only on the spatial knowledge integrity of individuals to choose evacuation routes may lead to crowd congestion46, outlet blockage5, evacuation efficiency reduced1,34and issues et al. Therefore, some scholars in the study of spatial knowledge based on the integrity of leaders, signs and crowd flow patterns and other factors to solve the existing problems in crowd evacuation19,23.However, the impact of spatial knowledge integrity on population evacuation under different dangerous emergency degrees is unclear.
Effective intervention can improve the efficiency of crowd evacuation. Intervention refers to the behavior that the leader himself or the leader provides the security information to the crowd in the emergency situation through the equipment42,46.There are two kinds of intervention: leader intervention and scope intervention42,46.Leader intervention is the behavior of trained leaders directly entering the site to provide evacuation information and guide people from dangerous areas24,27.Scope intervention refers to the act of providing people with security information such as routes and exits through broadcasting21and marking24.The scenarios for leader intervention are as follows: first, people cannot accurately access environmental information. Because the vision of the people is limited by the smoke or the lack of illumination, the leaders’ intervention becomes the main guiding behavior7. Secondly, the information acquired by personnel is uncertain. When a fire occurs in the tunnel, the warning information obtained by the personnel through the FM radio is uncertain, which leads to the invalidation of the scope intervention guidance4. The scope of intervention is as follows: first, the disabled escape. Disabled people with visual impairment are sensitive to LED signs in fires and can be effectively identified for escape3. Secondly, the route or exit is blocked. In the event of a fire or blockage at the exit, a dynamic identification system will display a warning message, which will be recognized by the evacuee, who will change the direction of movement and find a new evacuation route9. Thirdly, there are not enough leaders. In large public places, such as stadiums, due to the lack of leaders, people mainly by identifying signs to evacuate23. Although the effect of intervention behavior on evacuation in emergency has been studied, the effect of intervention behavior on evacuation in different dangerous emergency degree is not clear.
The degree of spatial knowledge integrity is an important factor affecting intervention behavior. For people with incomplete knowledge of space: first, the leader intervenes. Leaders directly into the site to conduct emotional evacuation and provide evacuation routes42, the experiment proved to be effective in guiding the evacuation of personnel5,10.But the number of leaders should not be too many, generally 10% of the total number of people for the best26,27. Second, scope intervention. The leader intervenes all the individuals in the space by means of information diffusion, such as broadcasting, and asks them to evacuate in order according to the signs42.For example, in large public places, the crowd for the environment is mostly unfamiliar, in case of emergency mainly follow the signs to evacuate23.For those with a complete knowledge of space: first, the intervention can enhance their familiarity with the route. Be familiar with route blocking and be able to navigate other routes27,46.Secondly, when the fire occurs, the smoke will affect people’s line of sight, in different visibility, light or sound can effectively guide the evacuation37.Finally, with the development of intelligence, the intelligent guiding evacuation system and signs developed for crowd evacuation also have good results2.However, the effect of the interaction of spatial knowledge integrity and intervention behavior on crowd evacuation is still unclear.
The degree of urgency of different risks is another important factor influencing intervention. The evacuation behavior is different in different dangerous emergency degree, such as: In Low Dangerous Emergency, people tend to scatter to escape44.In high-risk emergencies, people tend to congregate, often following others to escape, causing crowds, blocked exits and inefficient evacuations7.The intervention behavior is different for different emergency degree. For example, in low risk emergencies, fire information is provided to people through smoke detector and sound alarm systems to improve evacuation efficiency6,8.In high-risk emergencies, the ability to move people is significantly reduced, and leaders can more effectively provide evacuation guidance and reduce casualty rates6,8.However, in real life, the participants’ spatial knowledge integrity, intervention behavior and the degree of danger and urgency are integrated into one, for example, subway, shopping mall fire in the environment of people with different spatial knowledge integrity19,32, studying the intervention behavior of this emergency has realistic significance.
To test the behavior of crowd evacuation in fire emergency, there are four methods in the previous research: First, computer simulation. For example, by building a model to simulate the dynamic behavior of crowd evacuation, study the efficiency of crowd evacuation15,25,29.Or include influencing factors to the underlying model, such as the effect of leaders on population evacuation36,Effect of emotional contagion on crowd evacuation22.Second, the questionnaire survey. Investigate crowd behavior and characteristics, as well as crowd self-organization phenomena during evacuation, such as route and exit choice14, herd behavior30et al. Third, the simulation experiment2,15.Fourth, the virtual evacuation experimental study38,39.However, these methods have some limitations, such as lack of real population data or incomplete data, high cost, difficult to set up a controlled experimental environment, and so on. So virtual reality
(VR)-based immersive virtual environments (Ives) offer an alternative to crowd evacuation studies. Virtual reality is “A real or simulated environment in which the perceiver experiences telepathy”37.The evacuation behavior observed in virtual reality environments is qualitatively comparable to real-world behavior17.
IVE is an effective research tool with reasonable ecological validity, which can arouse human emergency behavior. It can control and manipulate key variables according to experimental design, and collect reliable qualitative and quantitative behavior data18,47.In this paper, the method based on IVE is used to solve three problems in this study. First, what is the effect of spatial knowledge integrity on evacuation behavior in virtual fire scenarios? Second, what effect does the degree of spatial knowledge integrity have on evacuation behavior under different emergency levels? Third, what effect does the interaction of spatial knowledge integrity and intervention behavior have on evacuation behavior under different emergency levels?