A Systems Approach to Investigate the Rigidity of Intermodal Transport Systems

Disturbances within the European transport system have recently generated millions of pounds worth of damages and caused widespread passenger delays. The Eyjafjallajokull volcanic eruption demonstrated how a large scale disturbance within one transport sector can cause a series of knock on effects through other modes of transport, which were illequipped to deal with a significant fluctuation in demand. The cascading effects are a result of the rigid nature of the transport system caused by its complex structure and a lack of suitable preparation. Predicting the behaviour of complex systems is both costly and time consuming due to their data intensive nature. Additionally the transport system is dynamic and it is difficult to perform suitable quantitative analysis. A major challenge is to develop a system that can predict the changes in passenger demand between different modes of transports during a disturbance on one or more of these systems, which will enable the transport industry to implement suitable policies to cope with unexpected demand. This work suggests and analyzes a systems dynamics method incorporating impact analysis techniques which attempts to model and predict the rigid behaviour of an intermodal transport system. The intention of which is to design a predictive tool that can help forecast the direction and magnitude of passenger movement. This paper introduces the concept through the development and initial testing of a simplified dual-mode UK transport model created using system dynamics software. The model is tested with reference to data collected from the recent disturbances and thus suggests its potential predictive uses. As the model is still in the early stages of development further improvements are suggested and the benefits and drawbacks of the approach are discussed. I. Introduction SYSTEM of systems is a complex structure developed from numerous self contained systems, each capable of operating autonomously, that interact with each other through a series of relationships and linkages. These systems are notoriously difficult to analyze due to their emergent and evolutionary behaviour generating complex and often unpredictable interrelationships between each system. As such, systems of systems are often difficult to predict and large levels of uncertainty surround their performance characteristics 1 . Complex systems are found through many disciplines, developing from industry 2 into diverse fields such as biology 3 and climatology 4 . Consequentially, a number of negative traits associated with the behaviour can be seen within complex systems. Rigidity within the transport system arises due to the nature of the complex interrelationships between different transport modes. Due to the reliance of each transport mode on another, a large disturbance can cause widespread closures and delays, with large costs associated with system recovery. As each system was designed separately the interrelationships have developed over time meaning they tend to be dynamic, hence fluctuations in the relationships can depend on a number of factors largely based around human behaviour and trends. The complex behaviour of