## 1 Introduction
Based on the existing train timetable of the railway section, the capacity utilization of the section was evaluated through two steps: compression and encryption. The UIC method (compressed method) is simple and effective, and many scholars have subsequently extended and expanded it based on the UIC406 method, forming a mainstream capacity assessment system in Europe. [PERSON] [20] extended the UIC406 method to assess the capacity of single-track railways. [PERSON] and [PERSON] [21] compared and combined the UIC406 method and a method independent of a timetable. [PERSON], [PERSON] and [PERSON] [22] proposed a compression optimization model and encryption method for train paths to evaluate the utilization rate and available capacity of the station. [PERSON] et al. [23] generated a compressed timetable based on the UIC406 method and applied it to Iranian railways. [PERSON], [PERSON] and [PERSON] [24] studied the application of the compression method in station capacity evaluation and realized the mathematical calculation of the compression method through maximum addition algebra. [PERSON], [PERSON] and [PERSON] [25] calculated the passing capacity of the railway section based on the buffer time of the compressed timetable and the encryption of trains in the idle time. Each section of the railway line, due to the differences in their status and function in the railway network, has a different internal structure and faces a different external environment. Therefore, the person responsible for timetable planning will adopt different strategies for different sections, which will have a great impact on the section carrying capacity. After a long period of operation and iterative optimization, high-speed railways in various countries have formed relatively stable train timetable characteristics, which will not be easily changed, and this information is contained in the train timetable structure [26]. The timetable-dependent method can use information on existing timetables to make the result more pertinent, which is more accurate than the analytical method based on the principle of statistical averaging in specific scenarios. Although the compression method can maintain the train timetable structure, the method changes the train arrival and departure time in the compression process without considering the relationship between the target section and the adjacent sections. In addition, the buffer time is deducted in this process, which will lead to larger capacity calculation results. Summarizing the above research in Table 1, it can be found that the core of the capacity assessment is the time occupied by trains of railway facilities and equipment. The purpose of this paper was to take the occupancy time of trains on timetables as the research focus directly to form a conceptual system and propose a derived method for the railway section carrying capacity assessment based on train timetables to make the capacity calculation process faster and the results more accurate. The contributions of this paper are: (1) a conceptual system centered on train occupancy time is formed, including standard trains, virtual trains, combined trains, and continuous train groups, to provide theoretical support for capacity assessment based on occupancy time; (2) a combined occupancy method of capacity assessment is formed, and the process and formulas are given. The remainder of this paper is structured as follows. Section 2 explains the concept of occupancy time and conducts a graphical analysis of the calculation of occupancy time of one train and two trains. A method combining two or more trains together is proposed to solve repeated occupancy problem in Section 3, and a derived capacity assessment is formed in Section 4. In Section 5, a case study is conducted for the Beijing-Shanghai high-speed railway. In the end, Section 6 summarizes the conclusions.