The modelling of the transport system at a strategic level is a complex task, given the strict interrelation of transport with other systems such as society, the economy and the environment. When considering medium and long term horizons, dealing with both primary and secondary effects of transport policies is required to get a complete picture of the changes inducedin transport mobility and other sectors. In recent years there has been agrowing number of applications of System Dynamics Modelling in the transport sector. The System Dynamics approach dates back more than 40 years andallows the representation of complex linkages among various systems such as transport, environment and the economy. These links extend the focus. In conventional transport models, analysis is often restricted to the interaction of mobility demand and transport supply. The system dynamics approach has a huge potential to explore sustainable paths, paying attention to the development of the results through the years and the generated feed back effects. This paper presents the application of two different strategicSystem Dynamics models in the STEPs project, which is part of the 6th Framework Programme of Research of European Commission DG RTD. The STEPs (Scenarios for the Transport System and Energy Supply and their Potential Effects) project has the objective to develop, compare and assess possible scenarios for the transport system and energy supply of the future taking into account the effects on the environment and economic and social viability. The two strategic System Dynamics models applied in the STEPs project operate at different levels: the ASTRA model is a European one, while the scope of the MARS model is the metropolitan area of Edinburgh. Both models have been developed in the course of co-funded European research projects during the last few years. The ASTRA (Assessment of Transport Strategies) model is a System Dynamics model at the European scale, covering the 25 countries of the European Union and the neighbouring states, focussed on describing the linkages between the transport system, the economy and the environment. The relationships between the different systems in the model are manifold. For instance, the economic activity affects transport demand both because freight depends upon the amount of goods produced and traded andbecause higher employment rates correspond to higher personal mobility rates. On the reverse side, the level of consumption and investments in the transport sector spread over the whole economy by means of an input/outputmechanism. The effect on the environment (emissions) depends on the amount of traffic as well as on the technology development of the fleet. The strategic MARS (Metropolitan Activity Relocation Simulator) model of Edinburgh can deal with the transport and behavioural responses to several demandand supplyside instruments. The model assumes that land-use is not a constant but is rather part of a dynamic system that is influenced by transport infrastructure, this interaction process is modelled using time-lagged feedback loops between the transport and land-use sub-models over a period of 30 years. This paper is divided in two parts: the first part presents the methodology of the System Dynamics approach in the two different modelsand contexts (EU wide area and metropolitan area), presenting the sub-systems (from macroeconomic to transport use and to land use) and their linkages and feedbacks. The second part illustrates the results of the common STEPs scenarios based on diverse assumptions about the oil price development (pessimistic and business as usual) coupled with diverse policy strategies (demand management and improved technology development). The model outcomes of the transport and energy scenarios up to the year 2030 cover a wide range of fields and exemplify the time path development of the differentvalues. For the covering abstract see ITRD E135582.
Samenvatting