## 4 Discussion and Outlook  
The idea of an Intelligent Trackless Underground Mine has been proposed for a long time, but because of its high cost and difficulty to monitor and control, Trackless Underground transportation is not widely used, especially in the developing countries such as China. On the contrary, intelligent rail underground transportation is popular around the developing countries, not only because of its low cost but also because it is easy to monitor and control; however, there are still a large amount of problems to be solved in the intelligent rail underground transportation. With the precedent of the application of the CBTC system to the underground subway, this concept paper started the exploration in the possibility of application of the CBTC system to the underground transportation by reviewing the related literature. This concept paper briefly reports the progress in the present stage of the research to apply the CBTC system especially the three systems to the underground transportation in order to dedicate to solving the practical problems in the engineering of transportation in underground mines. The New Dynamic Fault Tree analysis method proposed by [PERSON] et al. [34] at the 2020 IEEE 23 rd International Conference on Intelligent Transportation Systems (ITSC) gave the inspiration to this \"concept paper\" to try to summarize and establish the analysis and the process of the fault event in order to solve the problem on the basis of the CBTC system. For the practical problem of the safety rear-end collision problem in the underground mine transportation, a series of analyses of the fault events have been established to estimate and control the hidden danger of the accident with the assistance of the ATP system. Meanwhile, in the practical problem of the transport efficiency problem, just a single analysis of the fault event has been established to make the underground mine transportation achieve the maximum efficiency with the work of the ATP system and the ATO system. The results suggest that the more complex the practical problems are, the more the analysis of the fault events needs to be established in the New Dynamic Fault Tree analysis method, and the more complicated the diagram of the process will be. For the practical problems of the underground mine transportation, safety and efficiency are relatively easier to solve with the assistance of the ATP system, the ATO system, and the New Dynamic Fault Tree analysis method compared to the real-time monitoring problem. As is known, the real-time monitoring of the transport units is the biggest problem in intelligent underground mines, and the ATS system of the CBTC system is the core to solve the biggest problem out of question. In 2018, [PERSON] et al. [64] combined the ATS system of the CBTC system with the Internet of Things technology, and they conducted a simulation in the simulation environment, achieving a good result. In fact, in 2017, that the combination of the CBTC system and Internet of Things technology would advance the CBTC system became an academic consensus [8]. Nowadays, most of the CBTC systems used in various countries are \"The Products\" combined with Internet of Things technology, but even such a complete CBTC system can not completely solve the problems in rail transportation of the underground mines. Thus, mainly four problems in the real-time monitoring of underground mines have been put forward by [PERSON] et al. [39] in 2015: (1) the real-time monitoring of the transport units, (2) the start-up time control of the transport units, (3) the route adjustment of the transport units, and (4) transport units tracking. For the real-time monitoring of the transport units, the identification of the transport units is the prerequisite for solving the problem; due to the number recognition sensors on the track and the ATS system, the identification and the monitoring of each transport unit can be realized, and the running of the whole process is fed back on the screen of the ATS system.