روش شی گرا برای مدل شبیه سازی تقاطع تحت شرایط ترافیک ناهمگن

In developing countries like India, the traffic on roads is highly heterogeneous in nature, with vehicles of widely varying static and dynamic characteristics. In this type of traffic, vehicles do not follow lane discipline and they move freely over the entire width of roadway based on availability of space. To study this type of complex traffic flow and associated vehicular interactions, simulation is considered as an effective tool. An object-oriented methodology (OOM) for heterogeneous traffic simulation is proposed in this paper with focus on mid-block and intersection flow modeling. The paper presents the basics and advanced features of object-oriented programming (OOP) in detail in the context of traffic flow. The sample C++ code is discussed in detail to demonstrate the implementation of OOP features, such as encapsulation, inheritance and polymorphism. The contribution of this research work is the development of software objects for various components such as vehicle, traffic, link and node. This software can be adopted for heterogeneous traffic simulation programs, in general.

The difference between homogeneous and heterogeneous traffic at mid-block sections can be illustrated by comparing the photographs shown in Fig. 1. Homogeneous traffic (Fig. 1a) has traffic entity types, whose physical dimensions do not vary much. The vehicles also follow lane discipline in heterogeneous traffic (Fig. 1b and c). The vehicular composition include vehicles with widely different characteristics, such as motorized two-wheelers (MTW), cars (including jeeps and small vans), buses, auto-rickshaws (three-wheeled motorized vehicles), light commercial vehicles (LCV), trucks, and non-motorized vehicles such as bicycles and tricycles. Due to highly varying physical dimensions and speeds, it is difficult to impose lane discipline. Hence, the vehicles occupy any lateral position on the available road space. Small sized vehicles (MTW, bicycle) often utilize gaps between larger vehicles in the traffic stream. Due to complex driver behaviour, vehicular interactions and their manoeuvres, it is very difficult to model the traffic flow through analytical methods. So, modeling of road traffic flow through simulation technique is often resorted to.

In this paper, a flexible object-oriented model has been proposed for simulating heterogeneous traffic. The extendability of OOM has been exploited for obtaining the intersection simulation models from a mid-block simulation model. This enhances the code reusability, modularity, maintainability, and reduces the development time. Encapsulation, inheritance, polymorphism and other features of OOP were incorporated in the model. UML has been implemented in traffic simulation system, which creates a system that is much more efficient and it reduces the development time greatly. The validation of signalized intersection model, based on queue density and queue dissipation, indicates that the model is satisfactorily replicating the field conditions. The developed model for heterogeneous traffic flow conditions can be effectively used for mid-block and intersection studies under various roadway and traffic conditions as prevailing in developing countries like India. It is proposed to develop the model further to incorporate the effects of network, different geometries, traffic, and traffic control conditions to build a comprehensive software package for heterogeneous traffic.