Konstantinos G. Zografos

A heuristic algorithm for solving hazardous materials distribution problems

A type of decision of major importance that directly affects the performance of a distribution system is the routing and scheduling of delivery trucks. The determination of hazardous materials distribution routes can be defined as a bi-objective vehicle routing problem with time windows since risk minimization accompanies the cost minimization in the objective function. The objective of this paper is to present a new heuristic algorithm for solving the bi-objective vehicle routing and scheduling problem. The proposed algorithm has been applied to several benchmark problems. The results of these applications seem to be quite encouraging. Furthermore, the proposed algorithm has been integrated within a GIS based decision support system for hazardous materials logistics operations providing valid preliminary results on a set of case studies.

Algorithms for Itinerary Planning in Multimodal Transportation Networks

The itinerary planning problem in an urban public transport system constitutes a common routing and scheduling decision faced by travelers. The objective of this paper is to present a new formulation and an algorithm for solving the itinerary planning problem, i.e., determination of the itinerary that lexicographically optimizes a set of criteria (i.e., total travel time, number of transfers, and total walking and waiting time) while departing from the origin and arriving at the destination within specified time windows. Based on the proposed formulation, the itinerary planning problem is expressed as a shortest path problem in a multimodal time-schedule network with time windows and time-dependent travel times. A dynamic programming-based algorithm has been developed for the solution of the emerging problem. The special case of the problem involving a mandatory visit at an intermediate stop within a given time window is formulated as two nested itinerary planning problems which are solved by the aforementioned algorithm. The proposed algorithm has been integrated in a Web-based journey planning system, whereas its performance has been assessed by solving real-life itinerary planning problems defined on the Athens urban public transport network, providing fast and accurate solutions.

An optimization framework for the development of efficient one-way car-sharing systems

Electric vehicle-sharing systems have been introduced to a number of cities as a means of increasing mobility, reducing congestion, and pollution. Electric vehicle-sharing systems can offer one or two-way services. One-way systems provide more flexibility to users since they can be dropped-off at any station. However, their modeling involves a number of complexities arising from the need to relocate vehicles accumulated at certain stations. The planning of one-way electric vehicle-sharing systems involves a host of strongly interacting decisions regarding the number, size and location of stations, as well as the fleet size. In this paper we develop and solve a multi-objective MILP model for planning one-way vehicle-sharing systems taking into account vehicle relocation and electric vehicle charging requirements. For real world problems the size of the problem becomes intractable due to the extremely large number of relocation variables. In order to cope with this problem we introduce an aggregate model using the concept of the virtual hub. This transformation allows the solution of the problem with a branch-and-bound approach. The proposed approach generates the efficient frontier and allows decision makers to examine the trade-off between operator’s and users’ benefits. The capabilities of the proposed approach are demonstrated on a large scale real world problem with available data from Nice, France. Extensive sensitivity analysis was performed by varying demand, station accessibility distance and subsidy levels. The results provide useful insights regarding the efficient planning of one-way electric vehicle-sharing systems and allow decision makers to quantify the trade-off between operator’s and users’ benefits.

A Real Time Decision Support System for Roadway Network Incident Response Logistics

Incident-related congestion is a serious problem of great concern for most metropolitan traffic management authorities. The high economic and social impact associated with the incident-related congestion has prompted Traffic Management Agencies world-wide to develop incident management systems (IMS). Incident response logistics (IRL) encompass all actions needed for the effective deployment of incident response resources and constitute an essential component of any IMS. The incident management decision making environment suggests that decision support systems (DSSs) can be used in order to improve the quality of the decisions and expedite the decision making process of the IRL. The objective of this paper is to develop a DSS for supporting real-time decisions related to IRL. The development of the proposed DSS is based on an extensive user-requirements survey in six European countries and integrates mathematical models, rules and algorithms in a user friendly environment in order to minimise incident response time. The proposed DSS provides the following functionalities: (i) districting, (ii) dispatching of response units (RUs), (iii) routing of the RUs, and (iv) on-scene management and it has been demonstrated successfully under real life conditions and accepted as a useful decision making tool by its users.

Methodological framework for developing decision support systems (DSS) for hazardous materials emergency response operations

The production, storage, and transportation of hazardous materials are processes of vital economic importance for any advanced and technologically complex society. Although the production and distribution of hazardous materials is associated with economic development, there is a significant potential danger to the natural and social environment in the event of their accidental release, a fact that prompts for the development and implementation of methods and techniques that aim to improve hazardous materials risk management decisions. The objective of this paper is to present a unified framework for developing a Decision Support System (DSS) for supporting a vital function of risk management, namely the management of emergency response operations. The proposed framework recognizes the peculiarities of the hazardous materials decision-making environment which is characterized by: (i) multiple stakeholders, i.e., persons and organizations involved in and affected by hazardous materials risk management decisions; (ii) lack of a formal management structure for monitoring and controlling in a unified manner all Emergency Response Resources; (iii) lack of clear distinction and fragmentation of responsibilities of the actors involved in risk management operations; and (iv) dynamic/real-time decisions, i.e., risk determinants change over time. The proposed framework was used in order to develop a DSS for managing emergency response operations for large scale industrial accidents in Western Attica, Greece.

Solving the multi-criteria time-dependent routing and scheduling problem in a multimodal fixed scheduled network

Multi-criteria routing and scheduling in a multimodal fixed scheduled network with time-dependent travel times involves the determination of the non-dominated itineraries (i.e., paths enhanced with scheduled departures) under the following constraints: (i) visiting a given set of intermediate stops in a specified sequence, and (ii) strict time windows on the origin, the destination and the intermediate stops. The objective of this paper is to present the formulation and algorithmic solution for the multi-criteria itinerary planning problem that takes into account the aforementioned features. The algorithmic approach proposed is based on the decomposition of the problem to a sequence of elementary itinerary sub-problems, solved by a dynamic programming algorithm. The computational performance of the algorithms on a set of large scale test problems indicates non-prohibitive time requirements and encourages its integration into travel planning decision support systems.

Design and Assessment of an Online Passenger Information System for Integrated Multimodal Trip Planning

This paper presents the design and evaluation of an online passenger information system for delivering personalized multimodal trip planning services through the integration of wireless and Web-based communication technologies. The goal of the system is to provide real-time travel information throughout the entire life cycle of an interurban trip. Before the full-scale deployment of this type of system, it is essential to assess its impact on the involved stakeholders through a pilot application. The proposed system (ENOSIS) has been implemented and evaluated for supporting travel decisions in Greece. An evaluation framework for assessing the impacts of the ENOSIS system is proposed, and the evaluation results of the ENOSIS pilot application are also reported. The evaluation results provide significant evidence of the technical and operational efficiency of the ENOSIS services, while it is shown that the proposed system is cost effective.

Current Challenges for Intermodal Freight Transport and Logistics in Europe and the United States

The current issues and challenges related to the large-scale implementation of intermodal freight transportation systems in the United States and Europe are addressed, and open research issues and challenges are identified. As congestion and environmental impacts continue to worsen, intermodal transportation will continue to increase in importance. Therefore, it is necessary to establish a research agenda for an in-depth study of intermodal freight and logistics issues in the European Union and the United States.

Developing a conceptual model for examining the supply chain relationships between behavioural antecedents of collaboration, integration and performance

Purpose – The purpose of this paper is threefold: first, review the literature on the topic of behavioural antecedents of collaboration and their impact on supply chain integration and performance; second, lay the theoretical foundations and develop a conceptual model linking behavioural antecedents of collaboration, information integration, coordination of operational decisions and supply chain performance; and third, set out operationalisation considerations. Design/methodology/approach – A conceptual model with theoretical basis on Relational Exchange Theory (RET) and extant supply chain theory is developed as a causal model that can be operationalised using structural equations modelling (partial least squares) and a “single key informant” approach. Findings – Positive relationships between behavioural antecedents of collaboration (trust, commitment, mutuality/reciprocity), information integration, coordination of operational decisions and supply chain performance (efficiency, effectiveness) are hypot...

Integrated Passenger Information System for Multimodal Trip Planning

The integration of wireless and web-based communication technologies in advanced public transport information systems has led to the provision of passenger information services directly to the users. Most of the existing systems provide alternative travel plans either for urban or for single-mode interurban trips. The objective of this paper is to present an online passenger information system for delivering personalized trip-planning services for interurban multimodal trips, including plans for any constituent urban transfer. The proposed system accommodates the provision of critical real-time travel information (e.g., delay or cancelation of flights) to the user throughout the entire life cycle of an interurban trip. The major features of the system are the following: (a) determination of optimum itineraries in a multimodal public transportation network, (b) online updates of the departure times throughout the entire life cycle of the trip, and (c) dissemination of travel information through several communication channels. The proposed system supports two major trip-planning decisions: (a) itinerary planning for an urban trip through the local public transport network, and (b) combined urban and interurban trip planning. The focus of the paper is on the presentation of the design and implementation of the proposed system and its application for supporting trip-planning decisions in Greece. An evaluation of the system has indicated that it is user-friendly, is cost-effective, and meets travelers’ requirements.