Copyright © 2010 John Wiley & Sons, Ltd

Introduction to the special issue: system dynamics and transportationSimon Shepherd and Guenter Emberger

The idea for this special issue on transportation was fi rst raised at an operational research conference in York, England, in 2008, where Simon Shepherd presented a simple model about toll competition. The following discussion with the executive editor then led to the idea that, while we were aware of a range of applications of system dynamics in the fi eld of transport, none of these had been written up in the system dynamics literature. The aim of the call for papers for this special issue was to try and bridge the gap between the two fi elds and at the same time to promote the use of system dynamics to those in the transport fi eld who seem wedded to the idea of equilibrium-based approaches and traditional four-stage transport models.

Transportation systems are complex, involving many different agents or stakeholders; there are many different feedbacks involved, with different time lags between responses of users, developers, operators and policy makers. System dynamics models not only offer a different perspective, with a whole system approach to transport planning, but also demonstrate to policy makers the importance of these feedbacks and lagged responses. The system dynamics platforms also offer specialised tools which aid in the understanding of the whole underlying system, calibration of models, optimisation of policies and ease of use through fl ight simulators. It was with these factors in mind that we selected our papers for this issue.

Our fi rst paper, by Enzo Bivona et al., provides an interesting case study of mainte-nance policies in a city bus company. The case describes the linkages between fl eet maintenance, human resources and training and other key policies such as fl eet renewal and their overall impact on service provision, customer satisfaction and profi tability of the company. Two scenarios are compared to try and combat the decline in fi nances. The fi rst is to cut all departmental budgets which, while effective in the short run, is shown to be unsustainable in the longer term; a classic use of system dynamics. The second policy is shown to be more sustainable. It includes some investment in new buses, reducing the average age of the bus fl eet and investment in training, which allows for increased service levels. This paper shows how the system dynamics approach can open the eyes of the decision makers to move away from simple cost-cutting policies to more sustainable ones which may have looked counter-intuitive at fi rst sight.

The second paper, by Konstantinos Triantis et al., continues the theme of maintenance but this time applied to road or pavement management. A dynamic micro-level simula-tion model of highway deterioration and renewal processes is presented. The model is calibrated with data from eight road sections in Virginia and is coupled with an opti-misation module which optimises maintenance operations. The analysis offers alterna-tive priority-setting schemes that improve current maintenance practices at the project and network levels. The approach suggests a move towards preventative maintenance over corrective maintenance to bring benefi ts to the system as a whole. Once again a

System Dynamics ReviewSystem Dynamics Review vol 26, No 3 (July–September 2010): 193–194Published online in Wiley Online Library(wileyonlinelibrary.com) DOI: 10.1002/sdr.454

194 System Dynamics Review

Copyright © 2010 John Wiley & Sons, Ltd. Syst. Dyn. Rev. 26, 193–194 (2010)DOI: 10.1002/sdr

move away from the traditional approach to the problem provides insight and results in alternative strategies.

The third paper, by Grit Walther et al., looks at the topical issue of take-up of electric and hybrid vehicles in California. In California, low-emission vehicle regulations mean that automobile manufacturers must reduce greenhouse gas (GHG) emissions of their vehicle fl eet and sell increasing shares of zero-emission vehicles (ZEV) or face high fi nancial penalties. Co-evolutionary development of powertrain technologies, associ-ated infrastructure coverage, vehicle types offered and customer behaviour during the adjustment to the regulations are modelled until 2021. The research shows that it is very diffi cult for manufacturers to avoid the ZEV penalties, even if alternative power-trains are offered to customers very early and in many segments. It also discusses the interaction between the GHG and ZEV regulations and concludes that manufacturers should consider these jointly rather than independently.

Our fourth paper, by Pauli Pfaffenbichler and ourselves, describes the development and application of the strategic land use and transport interaction (LUTI) model MARS. LUTI models have a long history dating back to the 1960s and since then they have moved from spatial interaction or statistical models, through econometric models to micro-simulation, cell-based automata and agent-based models. Alongside this, and perhaps enabled by more powerful computers, there has been a move towards more detail in representing space and individual behaviour. Our paper, however, presents an alternative approach which uses an intentionally developed strategic high-level model. Nevertheless this model still delivers comparable levels of statistical fi t in terms of validation but is easy to present to decision makers and planners. The paper introduces the concepts behind the MARS model, deals with validation and transferability between cities and provides example applications. The model has been applied in 18 cities around the world and has proved useful in both training planners and practitioners and in developing strategic policies at the regional/city level. The model is a departure from the norm in transport planning yet is seen as a useful tool at the design stage of strategic policy.

The fi fth paper, a research note by Davide Fiorello et al., gives an overview of the ASTRA model, which simulates the linkages between transport demand, the economy, the vehicle fl eet and environmental impacts at the European level. ASTRA is just one of the tools currently used to inform the European Commission about the impacts of European transport policy in the longer term. ASTRA is often used in conjunction with other tools such as the world energy model POLES and the fl eet development model TREMOVE, which are also run from a system dynamics platform. It is encouraging to note that, while traditional models such as the four-stage transport model still dominate the market in terms of research and application areas, clients such as the EU are taking note of other approaches such as these based on a system dynamics perspective.

In conclusion, we express the hope that through this special issue we will stimulate links between those in the transport fi eld and those in the system dynamics fi eld to improve and enhance the models and to further promote the use of system dynamics in transportation studies.