物件導向技術應用於捷運系統運轉模擬之模式構建

A Simulation Model for Metro Operations Using Object-Oriented Modeling Techniques

捷運系統行車調度極為重要，特別是當系統發生延滯事件時，須儘速調度處理，以免延滯現象快速擴散。本研究構建捷運網路運轉模擬模式，來模擬各種運轉整理策略的績效，模式中包含列車流模擬、旅客流模擬與行車調度模擬，三者間之關係必須界定清楚，並在模式中適當之連接。先前以傳統程序導向方式來構建模擬模式，程式相當複雜，而且不易擴充；本研究以物件導向技術來構建模式，以統一塑模語言（UML）作為物件分析（OOA）與設計（OOD）工具。首先，使用各種圖形描述系統內路網、車輛、時刻表、車站、旅客等元素之間的相互關係。其次，於設計階段充分運用封裝、繼承與多型等觀念，以利實作階段能有效重複使用程式碼，並提升系統開發效率。最後，以物件程式語言（OOP）C＋＋完成模式實作。實證研究針對臺北捷運淡水、新店、中和三條路線構成之「Y字型路網」進行模擬分析，評估延滯事件發生時，使用各種運轉整理策略之績效。模式中使用之行車調度策略包括：月台趕點、站間趕點、抓前車、抓後車、刪除列車與雙人乘務策略。

Rescheduling operations is very important for a rail transit system, especially under an abnormal condition, because a primary delay of one train may cause severe consequent delay for the following trains. This research develops a simulation model to evaluate the performance of various rescheduling strategies. Simulations of train flow, passenger flow, and traffic control operations are three main elements of the model. In order to solve the disadvantages of model building with traditional procedural programming techniques, we propose an object-oriented approach and construct a simulation model for metro operations. The unified modeling language (UML) is used as a tool for object-oriented analysis and design. Firstly, class diagram, activity diagram, and sequential diagrams are used to depict the relationship among the elements of a system, and some of them are listed as follows: network, vehicle, time schedule, station, and passenger. Further, in the stage of system design, this research uses the concepts of encapsulation, inheritance, and polymorphism in OOP (object-oriented programming) in order to enhance the reusability of software codes and improve the efficiency of the developed system. Thirdly, the system is implemented with OOP by C++ language. A case study for an Y-type MRT network, consisting of Tamshui line, Hsintien line and Chungho line, is conducted to demonstrate the functions of the model. The model is applied to evaluating, under primary delays, the effectiveness of rescheduling operations, such as changing speed or running time control, dwell time control, holding the preceding/following trains, cancellation of delayed trains, and double ending.