Performance of Railway Freight Terminals: a Generalised Model
S Ricci, G Malavasi, University of Rome La Sapienza, IT
The railway freight terminals play a key role within the multimodal logistic chain. Therefore, the transit time through these terminals represents one of the most relevant terminal performances and at the same time a key component of the freight transport generalised cost, so that its quantitative analysis is a strategic activity, both in the terminal planning and in the logistic chain organisation. The transit time is composed by deterministic and stochastic components, which increase significantly the problem complexity.
The considered freight terminals are:
* land freight interchanges: interchange between trains and trucks;
* marshalling yards: modification of trains composition within the railway system;
* railway maritime terminals: interchange between ship and trains.
The transit time definition here adopted is: ?time period from the arrival of the single freight unit to the terminal gate from an external transport infrastructure to its exit from the terminal towards a different transport infrastructure?.
The model finalised to the determination of the transit time has been structured on the basis of its following general and, nevertheless, simple formalisation: TTR = TE (C, O) + TI (T, D, R) (1) where:
* TE depends upon external infrastructures and transport services formalised in two arrays including parameters and constraints:
* carrying capacity C (e.g. railway line bottlenecks, etc.),
* operation planning O (e.g. timetable structures of the transport services arriving to the terminal and departing from it, etc.);
* TI depends upon technologies, dimensions and operational rules in the terminal formalised in three arrays including parameters and constraints:
* terminal planning parameters T (e.g. check-in and transfer technology);
* trminal dimensions D (e.g. distances between gates and transfer area, number of tracks, etc.)
* operational constraints and rules R (e.g. speed limits, maximum loading weights, etc.).
Application results and research developments
The developed model is characterised by wide generality and applicability to different terminal typologies, lay-outs, dimensions and transfer technologies. The approach allows to highlight contributions and weights of the various activities and phases of the freight unit transit through the terminal by distinguishing operational and waiting periods, whose duration depends not only upon internal performances (technologies, dimensions and operational rules) but also upon external parameters and constraints (time distribution of vehicles arrivals and departures). Actually, the results of the application to some case studies show that the amount of time dedicated to the activities only depending upon internal parameters is generally very limited (about 5% in the land freight interchange case studies).
The present research is going to be developed in the following directions:
* consolidation and tuning of the methodological approach by means of a wider set of case studies application based on the comparison with experimental data;
* model explication finalised to the systematic identification of internal and external carrying capacity bottlenecks;
* integration of the proposed model within a more generalised procedure for the evaluation of the global transport time of the whole freight logistic chain.
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