Using BDI agents to improve driver modelling in a commuter scenario

The use of multi-agent systems to model and to simulate real systems consisting of intelligent entities capable of autonomously co-operating with each other has emerged as an important field of research. This has been applied to a variety of areas, such as social sciences, engineering, and mathematical and physical theories. In this work, we address the complex task of modelling drivers’ behaviour through the use of agent-based techniques. Contemporary traffic systems have experienced considerable changes in the last few years, and the rapid growth of urban areas has challenged scientific and technical communities. Influencing drivers’ behaviour appears as an alternative to traditional approaches to cope with the potential problem of traffic congestion, such as the physical modification of road infrastructures and the improvement of control systems. It arises as one of the underlying ideas of intelligent transportation systems. In order to offer a good means to evaluate the impact that exogenous information may exert on drivers’ decision making, we propose an extension to an existing microscopic simulation model called Dynamic Route Assignment Combining User Learning and microsimulAtion (DRACULA). In this extension, the traffic domain is viewed as a multi-agent world and drivers are endowed with mental attitudes, which allow rational decisions about route choice and departure time. This work is divided into two main parts. The first part describes the original DRACULA framework and the extension proposed to support our agent-based traffic model. The second part is concerned with the reasoning mechanism of drivers modelled by means of a Beliefs, Desires, and Intentions (BDI) architecture. In this part, we use AgentSpeak(L) to specify commuter scenarios and special emphasis is given to departure time and route choices. This paper contributes in that respect by showing a practical way of representing and assessing drivers’ behaviour and the adequacy of using AgentSpeak(L) as a modelling language, as it provides clear and elegant specifications of BDI agents.     

A multioutput cost function for the services of Spanish ports' infrastructure

A long run multioutput cost function for the infrastructure services of Spanish ports is estimated using 286 observations on 26 ports during 11 years. Cargo specific marginal costs and the degree of economies of scale and scope are calculated up to a port level. Results show that liquid bulk and non-containerised general cargo present the lowest and largest marginal cost, respectively. Increasing returns to scale are present in general and for each and every port. A scope analysis indicates that port specialisation is not appropriate from the viewpoint of infrastructure.     

Workshop 5: Network and system planning

A renewed interest in public transport analysis and development has triggered a debate among policy makers, practitioners and stakeholders regarding technologies, design, pricing, subsidies and contract forms for optimal policy, including social well-being and the financing of public transport reform. Here we present contents and conclusions of workshop 5 of the Thredbo 12 Conference held in Durban, South Africa, where we analysed a series of recent theoretical developments on the links among demand, technology and the design of public transport systems, which we coupled with the examination of several case studies in order to feed the discussion regarding the relations among the strategic, tactical and operational elements that should be considered when designing a public transport policy.     

URANS simulations of catamaran interference in shallow water

This paper investigates the interference effects of wave systems on a multi-hull vessel in shallow water. A numerical analysis is made using the URANS code CFDSHIP-Iowa V.4 on the DELFT Catamaran model 372. The test matrix for numerical computations includes two separation distances (s = 0.17; 0.23) and the depth values of h/T = 8.2, 2.5 and 2, at several speeds ranging within Fr _H = 0.775–1.739. Numerical results are compared with the experimental data of the Bulgarian Ship Hydrodynamic Center, and verification and validation for resistance, sinkage and trim are also performed. Results show that, at critical speed (Fr _H ≈ 1), the presence of a finite depth significantly affects the catamaran total resistance, which, in shallower water, increases considerably with respect to deep water. At low h/T, small effects of the water depth on resistance occur at subcritical and supercritical speeds. The interference effects seem to be more relevant in shallow, rather than in deep water, with maximum IF values registered at critical speeds (Fr _H ≈ 1). Similarly to deep water, the lower the separation distance the greater the interference value. Moreover, in shallow water some negative interference is observed at Fr > 0.5. Wave patterns and wave profiles are analyzed and a comparison is made between several configurations of catamaran and a mono-hull vessel, in order to analyze how water depth and separation distance determine resistance and interference. Finally, a vortex instability study is also included.