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Modelling dual-carriageway traffic behaviour as a complex system: A proposal for discussion.

Author - Timothy Hogan, Ian Clancy, Cathal Flynn


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1. Introduction

To reduce congestion, most road authorities are exploring new traffic-control strategies. Infrastructure improvements are very costly and each modification must be carefully evaluated for its impact on the traffic flow, computer traffic simulations form a cost-effective method for making those evaluations, a similar type of solution is also being used in other industries [4, 5].

The initial developmental stages of a microscopic traffic system model and the general definition of a microscopic traffic system model are outlined. In this traffic system model the behavior of vehicles and drivers are looked at in great detail, including interactions among vehicles, lane changing, response to incidents, and behavior at merging points. The microsystem model that has been designed is dual lane system with cars joining at the start of the system and at junctions spaced along the carriageway at distances similar to those of real world motorways.

This novel model with its assigned driver behaviours has a large amount of detail due to the nature of its interacting system, which became apparent when studying this system to achieve a satisfactory solution. Due to the intrinsically complex nature of this problem the question arose is the solution of this system in time a NP-hard  problem.

There is no shortcut or smart algorithm that would lead to a simple or rapid solution of this system involving many interacting and communicating cars on a multiple lane motorway. The consensus is that the only way to find a global optimal solution, which is the spread of driver distributions to achieve the shortest global transit times, over many runs of the system, is a computationally-intensive, exhaustive analysis.

2. Complex system

It is far from trivial to come up with an all-encompassing definition of complex systems, indeed an entire edition of one major publication was dedicated largely to this, studying area as diverse as geology, the economy and biology [6]. In the physics community the accepted definition is that a complex system comprises a large number of elements, building blocks or agents, capable of interacting with each other and with their environment [3,7].

There are multiple interactions between many different components; the components have a large degree of freedom. The interaction between elements typically occurs only with nearest neighbours but in some models the interaction is between distant elements. The common characteristic of many complex systems is that they display organisation without any externalorganising principle being applied [7]. The search for and study of complex systems are among some of the most elusive and fascinating systems investigated by scientists and engineers nowadays [8].

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