Abstract

"jats:p"The main purpose of the paper was the structural analysis of the connections network used by a railway carrier Koleje Dolnośląskie S.A. operating in southern Poland. The analysis used simulation methods. The analysis and simulation were based on graph theory, which is successfully used in analysing a wide variety of networks (social, biological, computer, virtual and transportation networks). The paper presents indicators which allow judging the analysed connections network according to an appropriate level of transport services. Simulation results allowed proposing some modifications for the improvement of the analysed connections network. The paper also demonstrates that graph theory and network simulations should be used as tools by transportation companies during the stage of planning a connections network. Document type: Article

Abstract

Background The efficiency of transport phases is a key factor in successful organ transplant operations. Reliability, safety, and punctuality must be in compliance with the European Union and national frameworks and be consistent with economic, quantitative, and level-of-service parameters. In this study we investigated the optimal numbers and locations of aircraft in the Italian territory by comparing performance indexes related to different time intervals and service design scenarios. Methods An integer linear programming model is described as an optimal service solution for covering the demand for extraregional organ transport by air between June 2015 and May 2016. Restrictions on aircraft utilization and actual length of the missions in cases of incompatible activities are the relevant input data of the model. Results Based on mission durations and their origin and destination, the model returns the optimal number and location of aircraft in various scenarios. The performance parameters required by law and the need to guarantee the service from/to the whole territory, together with the transplant figures performed and transplant center locations, have been taken into account to determine the most efficient spatial and numerical allocation. Conclusion The efficient design of an urgency-based service such as the transportation of organs for transplant purposes is not an easy task. Nevertheless, knowledge of the logistic chain and continuous monitoring and update of data and performance parameters can allow for collection of useful information to guarantee a high-performing service.