Hanna Grzybowska

Vehicle Routing And Scheduling Models, Simulation And City Logistics

The distribution of goods based on road services in urban areas, usually known as City Logistics, contributes to traffic congestion and is affected by traffic congestion, generates environmental impacts and incurs in high logistics costs. Therefore a holistic approach to the design and evaluation of City Logistics applications requires an integrated framework in which all components could work together that is must be modelled not only in terms of the core models for vehicle routing and fleet management, but also in terms of models able of including the dynamic aspects of traffic on the underlying road network, namely if Information and Communication Technologies (ICT) applications are taken into account. This paper reports on the modelling framework developed in the national projects SADERYL-I and II, sponsored by the Spanish “Direccion General de Ciencia y Tecnologia” (DGCYT) and tested in the European Project MEROPE of the INTERREG IIIB Programme. The modelling framework consists of a Decision Support System whose core architecture is composed by a Data Base, to store all the data required by the implied models: location of logistic centres and customers, capacities of warehouses and depots, transportation costs, operational costs, fleet data, etc.; a Database Management System, for the updating of the information stored in the data base; a Model Base, containing the family of models and algorithms to solve the related problems, discrete location, network location, street vehicle routing and scheduling; a Model Base Management System, to update, modify, add or delete models from the Model Base; a GIS based Graphic User Interface supporting the dialogues to define and update data, select the model suitable to the intended problem, generate automatically from the digital map of the road network the input graph for the Network Location and Vehicle Routing models, apply the corresponding algorithm, visualize the problem and the results, etc. To account for the dynamics of urban traffic flows the system includes an underlying dynamic traffic simulation model (AIMSUN in this case) which is able to track individually the fleet vehicles, emulating in this way the monitoring of fleet vehicles in a real time fleet management system, gathering dynamic data (i.e. current position, previous position, current speed, previous speed, etc.) while following the vehicle, in a similar way as the data that in real life an equipped vehicle could provide. This is the information required by a “Dynamic Router and Scheduler” to determine which vehicle will be assigned to the new service and which will be the new route for the selected vehicle

Deployment and Calibration Considerations for Large-Scale Regional Dynamic Traffic Assignment: Case Study for Sydney, Australia

Dynamic traffic assignment (DTA) has received increasing attention in recent years, and there are numerous examples of practical implementations. This work adds to the literature by describing the ongoing experience of building the first large-scale simulation-based DTA model in Australia. The input data for the model are summarized, and an in-depth discussion and an analysis of model output and the calibration process are presented. Current results put 80% of the 322 calibration points spread across the network within an acceptable bound of error, but the project found that alternative metrics of network performance also must be considered so that other aspects of model realism are not neglected. The described DTA model could be used for evaluating important policy decisions and infrastructural development in the context of the macro- and mesoscale network operation. Additionally, this project is a proof of concept for the Australian region and may provide insight to practitioners interested in emerging areas of transport planning and traffic modeling.

Decision Support System for a Real-Time Field Service Engineer Scheduling Problem with Emergencies and Collaborations

Repeated replanning with a heuristic for solving a type of vehicle routing problem was used in a dynamic routing and scheduling problem. This problem occurs when field service engineers are assigned a sequence of jobs to attend. The jobs are geographically distributed, and not all jobs to be undertaken are known in advance of planning. This dynamic occurrence of job requests is stochastic. Jobs are assigned an emergency level, which is highest for repair jobs involving a person in danger. In addition, some jobs require two engineers; such jobs are referred to as collaborative. The presented approach reschedules the pending jobs in an event-driven manner (i.e., every time a new repair job is required). The event-driven scheduling process ensures that jobs of high importance, with a high emergency level, are completed promptly. This approach to event-driven replanning will allow companies to plan for real-world scenarios with significantly fewer resources than are used in practice.

Strategic dynamic traffic assignment incorporating travel demand uncertainty

ABSTRACT Dynamic traffic assignment (DTA) research has advanced greatly in terms of deployability, computational feasibility, and representing complex temporal phenomena. There have also been substantial contributions regarding various aspects of stochasticity within DTA. However, there are persisting limitations in terms of approaches which are both computationally tractable and provide more detailed representation of stochastic aspects. This paper explores the application of a novel Strategic User Equilibrium DTA (StrDTA) modelling framework, which captures the impact of users making a priori route choice decisions based on the knowledge of a range of possible travel demand scenarios (e.g. differing days or representative situations). The resulting stochastic DTA problem becomes complex due to the integration of multiple demand scenarios and the algorithmic adjustments necessary to find optimal paths. A new solution framework is proposed which still permits implementation, and a detailed case study is presented for the Sydney Central Business District network. Results demonstrate the importance of accounting for stochasticity in the routing algorithm rather than relying on assumptions of average values.

Decision Support System for Modular Construction Scheduling

The use of modular construction as opposed to traditional on-site construction presents an opportunity to improve a project’s economic and sustainable performance. At the same time, substantial savings in the overall project’s duration can be achieved. The potential for reducing the overall make-span period involved in manufacturing and assembling the modularised components, along with the constant need for aligning the work schedule with the in-house manufacturing schedule, leads to the need for a repetitive scheduling optimisation procedure for modular manufacturing operations. This paper presents a framework and a decision support system to schedule operations in modular building factories. The framework is divided into 3 layers; the first layer concerns the assignment of workers to workstations; the second layer solves the scheduling of jobs to workstations while the last layer governs the overall operations of production lines through formulating a parallel machine scheduling problem. For demonstration purposes, a computational test is conducted on the final optimisation stage using a practical case study to solve the parallel machine scheduling problem. To account for resource allocation and levelling, the model is presented as a resource constraint one. Results reveal the satisfactory performance of the proposed model.

Large-Scale Dynamic Traffic Assignment: Practical Lessons from an Application in Sydney, Australia

Traditional static traffic assignment models no longer meet the strategic planning needs of most major metropolitan areas, especially in regard to evaluating major infrastructure projects. One promising possibility is dynamic traffic assignment (DTA), which has been receiving greater attention in the research community for the last ten years. This work describes the ongoing experience of building the first large-scale DTA model in Australia. We divide our experiences into categories regarding data, implementation, and visualization, and we discuss the challenges faced as well as our methods for overcoming those challenges. Finally, we discuss initial model results and the calibration process. In the future, the DTA model described here could aid in evaluating important policy decisions and infrastructural development in the context of the macro/meso-scale network operation. This project serves as a proof of concept for the Australia region and may provide valuable insight to other practitioners interested in emerging areas of transport planning and traffic modeling.

Systemic Evaluation of the HERO-Based Ramp Metering Algorithm Using Microsimulation: Demonstration Analysis Using a Sydney Motorway

Ramp meters impact not only the performance of the motorway, but also the performance of the arterial road network. The available literature on the HERO ramp metering system is used to implement it as closely as possible using AIMSUN Application Programming Interface (API). The implemented algorithm is evaluated using a network wide approach. In addition, a set of novel measures are introduced that facilitate the evaluation of the impacts of a ramp metering system on the entire network.