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Strengths and Limitations of Cellular-Automata Models and SOTL for the Realistic Representing of Traffic Flow

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Document pages: 14 pages

Abstract: Different computational methodologies and quantitative tools are used in the Transport and Traffic Research for modelling of Traffic Flow. One of most popular computational technique is Cellular-Automata Models (CAM), where the movement of vehicles is represented as a switch-jump from one cell to another. There is also a strong desire to embed Cellular-Automata Models and other popular traffic modelling technologies as a practical instrument for developing and improving intelligent traffic system strategies and road planning. It appears from many publications that some members of CAM community as well as roads and traffic specialists nowadays accepted that CAM results in its current state are already giving insights (as well as formal explanations sometimes) about the general tendencies of the dynamical properties of traffic flow. We demonstrate that, unfortunately, this belief has no foundation for it. For example, real phenomena for high density traffic (which is a most interesting and important case for the practitioners and drivers) is not well modelled by CAM despite the fact that impressive CAM plots for this situation are presented (and are misleading). It would be wrong and dangerous for traffic authorities to make serious changes in roads planning and current traffic control systems simply based on CAM publications and impressive plots presented there. As a highly abstract mathematical methodology CAM produces exquisite results that not directly related to the real traffic flow. We assume that many researchers working on CAM and their applications to real phenomena are already aware of their strengths and limitations. However, this understanding did not become a common knowledge between transport community and so this discussion is highly necessary. In the current paper We point out few essential properties-features of Cellular-Automata Modelling technique that are seriously limiting the practical use of this methodology for highly important as of real traffic modelling. We demonstrate that some impressive results obtained through the use of Cellular-Automata Models are, in fact, not well related to real traffic. In particular, when the high density traffic is modelled with the use of Cellular Automata technique, the relationship between velocity-in-model and velocity-real-traffic starts to be less trustworthy. Subsequently the Cellular-Automata Model results and plots for high density traffic should be vetoed and rigorously tested through other techniques. Hence CellularAutomata Modelling should not be considered as direct practical tool for the better design of traffic control system as its outcomes are not that promising as it was thought at the beginning. As We identify the strengths and limitations of CellularAutomata Models We suggest what could be done by us (i.e. transport researchers an traffic specialists) for the improvement of Cellular-Automata Models. Meanwhile, We propose the proper vetting of some common ways of misuse of Cellular-Automata results that can potentially lead to invalid real-world decisions and, hence, jeopardise the use of them in practical traffic control systems. These problems should be assessed if We want to avoid mathematical and logical flaws that lead to invalid or unreliable conclusions. The use of these computational constructions in transportation research and planning should fully exploit their strengths without exceeding their limitations.

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