Yannis Tyrinopoulos

Overview of nonlinear programming methods suitable for calibration of traffic flow models

The calibration of a macroscopic traffic flow model aims at enabling the model to reproduce, as accurately as possible, the real traffic conditions on a motorway network. Essentially, this procedure targets the best value for the parameter vector of the model and this can be achieved using appropriate optimization algorithms. The parameter calibration problem is formulated as a nonlinear, non-convex, least-squares optimization problem, which is known to attain multiple local minima; for this reason gradient-based solution algorithms are not considered to be an option. The methodologies that are more appropriate for application to this problem are mainly some meta-heuristic algorithms which use direct search approaches that allow them to avoid bad local minima. This paper presents an overview of the most suitable nonlinear programming methods for the calibration procedure of macroscopic traffic flow models. Furthermore, an application example, where two well-known macroscopic traffic flow models are evaluated through the calibration procedure, is presented.

Measuring the Effects of Economic Crisis on Users’ Perceptions of Public Transport Quality

Research was conducted to measure the effects of the economic crisis on public transport quality, user satisfaction, and transit demand. The survey used in this research extended a research effort that began in 2008; the survey aimed to analyze the variability of users’ satisfaction within different public transport systems. The survey was conducted in Athens, Greece, from November 2012 to January 2013, during the peak of the countrys economic recession. The content of the questionnaire that was used for the needs of the survey was similar to that of 2008 so that the results would be comparable. Passengers were asked to rate how important a series of metro and bus attributes were, their level of satisfaction with those attributes, their overall satisfaction with the main public transport operator they used, and the increase or decrease of their individual demand for public transport. A factor analysis was first performed to identify potential common patterns between the individual importance attributes. Ordered logit models were then estimated with the overall satisfaction as a response variable. Results of the analysis were then compared with the findings of the earlier (precrisis) research; this comparison revealed interesting adaptations in users’ perceptions of the public transport operators’ quality. Moreover, a hybrid choice and latent variable model was estimated to explore the overall satisfaction of the respondents. Finally, a demand model was developed; this model revealed the characteristics that led to the increase (or decrease) of public transit demand in the past 5 years.

Macroscopic traffic flow model calibration using different optimization algorithms

This study tests and compares different optimization algorithms employed for the calibration of a macroscopic traffic flow model. In particular, the deterministic Nelder–Mead algorithm, a stochastic genetic algorithm and the stochastic cross-entropy method are utilized to estimate the parameter values of the METANET model for a particular freeway site, using real traffic data. The resulting models are validated using various traffic data sets and the optimization algorithms are evaluated and compared with respect to the accuracy of the produced validated models as well as the convergence speed and the required computation time. The validation results showed that all utilized optimization algorithms were able to converge to robust model parameter sets, albeit achieving different performances considering the convergence speed and the required computation time.

Deployment of Intelligent Transportation Systems in South East Europe: Current Status and Future Prospects

Intelligent transportation systems (ITS) are a powerful technology, not only for gaining traffic and transport benefits, such as less congestion and shorter travel times, but also for economic growth. The European Union (EU) has already published a directive (2010/40/EU) to regulate the coordinated and coherent deployment of ITS in all EU-member states. However, ITS deployment in some EU member states has yet to be integrated. According to the European Commission, South East Europe (SEE) is an area in which ITS deployment is “fragmented and uncoordinated and cannot provide geographical continuity of ITS services throughout the region.” An overview is provided of the current deployment and implementation status of ITS in nine countries of the SEE area. The results highlight the strengths and weaknesses for further ITS deployment in these countries and the level of harmonization of their national laws with the European directive, a prerequisite that could alleviate the fragmentation of the ITS provision along different regions within the nations and also at cross-border areas. Afterward, the methodology for creating national roadmaps for ITS deployment is presented as well as the final roadmaps for each of the nine countries. The findings of these roadmaps are crucial for future ITS deployment in SEE countries; the level of maturity of ITS deployment in each country has been taken into account.

Intermodal Freight Transport Between Europe and Asia: A Structured Approach to Policy Making and Problem Solving

Strategic cooperation in all fields of economic activity between Europe and Asia is seen as beneficial for both sides and of outmost importance for the economic development and prosperity for both regions. Transport of goods between the two regions is by definition almost in its totality intermodal transport. Any actions or policies that facilitate such international intermodal transport are likely to contribute to better trade and better economic, political, social, and cultural exchanges. The purpose of this paper is to investigate the potential policies as well as areas of the European and Asian experience and practice in the field of inter-modal freight transport that could best be adopted for the improvement of intermodal freight and maritime transport between the two regions. It also provides the most important findings and conclusions from a series of events made by experts and industry on both sides and the recommendations made concerning the areas for the potential exchange of knowledge and best ...