# A Survey of Algorithms and Systems for Evacuating People in Confined Spaces
## 1 Introduction  
Research on evacuation wayfinding aims to develop methods and tools to direct evacuees out of hazardous areas in a timely and safe manner with the assistance of computer-aided systems. This multidisciplinary area that is based on the Internet of Things (IoT) proposes systems and algorithms that require advanced computing and sensing capabilities. It has to address the complexity of finding feasible or optimal solutions in highly-dynamic environments that are vulnerable to hazards, which can benefit from cutting-edge technologies, and has drawn considerable attention from both the industrial and academic communities.  
The research in this area may be highly technical when the use of sensors and robots is considered to aid evacuees in finding exits in a highly-disorganised emergency environment [1; 2; 3]. It also needs to dig deeply into human behaviour due to fear and panic. Because of its very nature, much of the related work regarding the evaluation of these technologies and solutions must rely on detailed simulations [4] because of the repeatability, low cost and time efficiency of such tools.  
Attempts at dealing with and managing disasters are deeply rooted in human history, and even folklore, owing to their impact on the social and economic aspects of societies. Many great disasters have been recorded in ancient literature such as the Deluge in the Bible. In ancient times, emergency management operations were often conducted in an unorganized, reactive manner. In the 20 th Century, laws or policies began to be promulgated worldwide to provide financial assistance and investmentafter a disaster, or as a means to carry out preventive measures [5], to provide emergency management in a more organised, proactive fashion. From the 1950s onwards, with the nuclear threat during the Cold War and the development of computer technology, many efforts have been dedicated to computer-aided civil defence programs [6; 7], which have motivated the development of systematic emergency management studies.  
The current research efforts in this area can be generally grouped into two directions: evacuation wayfinding and emergency search and rescue planning. Evacuation wayfinding, also known as emergency evacuation planning, is the process of directing evacuees out of hazardous areas with the aid of real-time routing algorithms or using pre-deployed static plans that are based on prediction and analysis from evacuee behaviour models. Emergency search and rescue planning, on the other hand, focuses on rescuing immobilised and incapatitated evacuees that are trapped in hazardous areas with the assistance of task assignment or resource allocation algorithms.  
This paper specifically reviews the developments and applications of the research field on evacuation wayfinding, from both the system design and algorithmic aspects. Owing to their open and inclusive nature, information and communication technologies (ICT) tend to influence, change, or even revolutionise research on emergency management, so that ICT now plays an important role in our survey, and a diagram explaining the structure of the paper is shown in Figure 1.  
Figure 1: A tree diagram explaining the structure of the paper. We summarise the classical research and ideas of evacuation wayfinding from both system structure and algorithm design perspectives.  
The remainder of the paper is organised as follows. We first summarize the research progress on the system design for evacuation wayfinding in Section 2. Then, we review the related research efforts in algorithm design in Section 3. Research trends and challenges are discussed in Section 4.1, and finally, we draw conclusions in Section 4.