Mathematics and Computers in Simulation 59(2002)57–71
A simulation tool for combined rail/road transport
in intermodal terminals
Andrea E.Rizzoli ∗,Nicoletta Fornara,Luca Maria Gambardella
IDSIA,Galleria 2,CH-6928,Manno,Lugano,Switzerland
Abstract
A simulation model of the flow of intermodal terminal units (ITUs)among and within inland intermodal terminals is prented.The intermodal terminals are interconnected by rail corridors.Each terminal rves a ur catchment area via a road network.The terminal is modelled as a t of platforms,which are rved by a number of gantry cranes and front lifters.The ur of the simulation model defines the structure of the terminal and the train and truck arrival scenarios.The train arrivals are defined in a train timetable,while the patterns of truck arrivals for ITU delivery and pick-up can be either statistically modelled or given as a deterministic input.The simulator can be ud to simulate both a single terminal and a rail network,that is,two or more interconnected terminals.During the simulation,various statistics are gathered to asss the performance of the terminal equipment,the IT
U residence time,and the terminal throughput.The simulation software has been implemented as a discrete-event simulation model,using MODSIM III as development tool.The simulator tool has been developed as part of the Platform project,funded by the Directorate General VII of the European Community.©2002IMACS.Published by Elvier Science B.V .All rights rerved.Keywords:Intermodal transport;Intermodal terminal simulation
1.Introduction
The “globalisation”of world economy has led to a constant decrea in the cost of transport (95%of world cargo moves by ship,transport costs account for 1%of the total cost [1]).Nowadays many intermodal terminals are still managed without a pervasive support of information technologies:the terminal management highly relies on well-assd policies,typical of each terminal,which have been defined by the managers on the basis of their experience.In most cas the policies are satisfactory since the terminals have sufficient resources in terms of tracks,equipment,human resources and they can support the current flows of freight.On the other hand,the growth of freight transport shows a rapidly increasing trend in the short and medium terms,which the current infrastructures and management tools cannot meet.笔记本电源适配器>企业年会致辞
∗
Corresponding author.Tel.:+41-91-6108664;fax:+41-91-6108661.
E-mail address:andrea@idsia.ch (A.E.Rizzoli).
0378-4754/02/$–e front matter ©2002IMACS.Published by Elvier Science B.V .All rights rerved.
PII:S0378-4754(01)00393-7
58 A.E.Rizzoli et al./Mathematics and Computers in Simulation59(2002)57–71
企业工会工作条例The European Intermodal Association established the working group“intermodal terminals”,which defined a t of minimum requirements for the intermodal terminals of the future(/ terminals.html).The standards define the minimum dimensions of a terminal able to guarantee sufficient traffic concentration and independent economic management using the currently available techniques. Irrespective,terminal operators prefer to explore whether new management methodologies can improve the terminal performance before investing in new equipment or enlarging the area of the terminals. Computer-bad simulation can provide the decision-makers with the help they need in creating the strategies for development.
突如其来的反义词2.Issues in the simulation of rail/road intermodal terminals
Rail/road intermodal terminals differentiate from maritime intermodal terminals since they are“inland”and they are nodes in a tightly interconnected network,compod of the rail and the road networks.They are usually smaller than their maritime counterparts and the residence time of ITUs in the terminal is usually much shorter(approximately24h).In such terminals,particular care must be devoted to the model of the arrival and departure process of trains and trucks at the terminal gate.While it is not the aim of this paper to enter into the details of what happens beyond the terminal gates,we remind the reader that a consistent number of rearchers have worked on the problem of the simulation and the optimisation of the rail network(for a review e[2],an application study is prented in[3])and a comparable, if not greater,effort has been put into the rearch on traffic simulation[4].The studies are of great importance since their results can be ud to model the“interfaces”of the terminal with the external world.The task of the modeller is therefore ead and s/he can concentrate on the modelling details of the terminal.
When integrating the rail,road and terminal components in a unique simulation framework,it is necessary to ensure the models to be congruent,that is to adopt the same“level of resolution”with respect to both time and description of ITUs.For instance,according to the required level of detail,the
intermodal transport can be modelled either as a continuous system,describing the ITUs as a continuous flow,or as a discrete system,where each single ITUs is reprented.If the ITU description in the road or rail networks is not congruent with the one adopted in the terminal,it is necessary to write“ad hoc”models to convert the different types of inputs and outputs.For instance,data on the traffic rate at the terminal gates,which could be obtained by the simulation model of the road network,can be ud to generate ITUs arrivals and departures in the terminal.In the Platform simulation model we also have adopted such an approach and it is described in Section4.2.
Despite the above-mentioned differences between maritime and rail/road intermodal terminals,they display some common features that are invariant with respect to the modes of transport.For instance, all terminals must have a yard area where the ITUs are stored.In all terminals,cranes(gantry and front lifters)move ITUs to and from the various transport means.The ITUs enter and leave terminals through gates,where decisions are made regarding the destination of the ITUs within the terminal itlf. Besides structural similarities,terminals share common process such as the efficient storage of the ITUs on the yard,and the scheduling of loading and unloading operations.The benefit is that much rearch has been done on maritime terminals(e for instance[5–7]on terminal simulation,[7,8] on optimisation of container scheduling)and it can provide inspiration for application to the rail/road ctor.
A.E.Rizzoli et al./Mathematics and Computers in Simulation59(2002)57–7159 While the similarity of the intermodal structures facilitates the transfer of concepts developed for maritime intermodal transport to the rail ctor,many process have some distinctive features,especially regarding the handling of the ITUs.In the maritime transport ITUs are standardid ISO containers and they are stackable,while ITUs in the combined rail/road transport ctor can be containers,mi-trailer, swap bodies,each one with different characteristics and requiring a different way of swap bodies and mi-trailers are not stackable).Another obstacle to the technology transfer is reprented by the information technology systems currently installed in rail/road terminals:while maritime terminals have been investing in the IT ctor for a long time,rail/road terminals have not done the same.The conquence is that often data,such as the physical location of the ITU on the yard,which are necessary to implement efficient management strategies,are not available.
There are some signals that things are changing.The pressure of freight traffic on European roads is pushing the European Community to invest and promote intermodal transport as a viable alternative to long-haul road transport[9].The Platform project is one of the outcomes of this policy and we expect that this and other demonstrative projects will show the terminal operators ways to invest to improve the efficiency of their management procedures,thus enhancing their competitiveness with respect to road-only freight.
3.The Platform project
91视频怎么下载The Platform project wasfinanced by the IV Framework Programme of the Directorate General VII (transport)of the European Community.One of the aims of the project was the“implementation of a simulation environment for the asssment of impacts produced by the adoption of different technologies and management policies to enhance terminal performances”.To achieve this objective,the project needed to encompass all the phas of an intermodal transport of an ITU,a requirement for the comparison of the performance of intermodality against road-only-bad transport.
An intermodal transport along a rail corridor connecting two terminals T1and T2can be divided into three legs.The initial leg describes the trip from the origin of the ITU to thefirst terminal T1.This leg is usually managed by a forwarding company owning a truckfleet.Trucks pick-up and deliver ITUs in the company’s ur catchment area.The cond leg is the transport from T1to T2by train.The railway companies owning the rail network manage this leg.Often,different rail companies cooperate in transnational transports.The third andfinal leg is the transport from T2to the ITU destination that is again managed by a forwarding company.
野芒坡
To reprent the intermodal transport in all its parts the Platform integrated simulation environment will be compod of three modules:the road network planning and simulation module,which plans the management of the forwarders’orders and simulates the traffic of trucks on the road network;the terminal simulation module,which simulates the terminal nodes and the change of transport mode,from truck to train and back;the corridor simulation module,which simulates the rail network connecting the terminals. The three modules are designed to work in parallel in order to produce results on the performance of the integrated rail/road network.Typically,the road planning and simulation module accepts intermodal transport orders for transport of an ITU from city to city.It then books a place for the ITU on one of the train connecting two intermodal terminals and then schedules truck delivery and pick-up of the ITU. The scheduled truck delivers the ITU in the terminal,that is,this information is provided as input to the terminal simulation module.This module takes care of handling the ITU where it was booked on,then
60 A.E.Rizzoli et al./Mathematics and Computers in Simulation59(2002)57–71
英语四级怎么备考nds the train to the corresponding terminal.This action is handled by the corridor simulation module. At the receiving terminal similar actions are performed:the ITU is unloaded from train and loaded on the pick-up truck.The truck is pasd back to the road planning and simulation module,whi平安普惠利息
ch routes it to itsfinal destination.
In this paper,we prent the software component of the Platform project dedicated to terminal and corridor simulation.A thorough description of the road planning module can be found in[10]and its theoretical basis in[11].
An intermodal terminal can be regarded as a node in a network that models the connectivity of the origins and destinations in the supply chain.If we look at the performance of this network,we are interested in understanding if it is possible to increa the throughput of the nodes,that is,of the terminals.Since the rail network can sustain a marginal increa in traffic,an improvement in the terminal throughput might reduce the percentage of long-haul transports on the road.Becau of this obrvation,we model the internal process in the intermodal terminals in order to understand how an increa in the intermodal traffic affects the terminal performance.In the next ction,the modelling assumptions to simulate the terminal are described.
4.The Platform simulation model
The analysis of the ur requirements,gathered from an in-depth literature review and from interviews to intermodal operators through Europe[12],identified the need to model three main proce
ss:the loading/unloading of ITUs onto/from the train;the storage of ITUs on the yard;the arrival and departure process of ITUs by truck.
Modelling the process requires a resolution of the model at the level of the single ITU move and this led to the lection of the discrete-event simulation paradigm.This approach is particularly apt to describe the inner workings of a terminal,for instance to evaluate the train loading and unloading process,but its computational cost can be excessive to simulate a real network of intermodal terminals.Nevertheless, the choice of a discrete model cannot be regarded as a dead-end for further investigations,since it can be employed to calibrate a continuous black-box model of the terminal,once the statistical distributions of its inputs and outputs are given[13].
The Platform terminal simulator has been developed in MODSIM III[14],a commercially avail-able object-oriented and process-oriented simulation language.The adoption of the object-oriented paradigm allowed software components to be defined that correspond to their real-world counterparts and with a similar behaviour.The terminal components modelled in the terminal simulator are as follows:
•The road gate,where trucks enter and leave the terminal.
•The rail gate,where trains enter and leave the terminal.The rail gate is connected to the shunting area, outside the terminal,where the rail network operator shunts trains before they enter the terminal.The rail gate is also connected to the rail tracks inside the terminal.
•The platforms,each compod by a t of rail tracks and by a buffer area.The buffer area is a temporary storage area for ITUs that are waiting to be loaded/unloaded to and from trains entering the platform. Each platform is rved by a t of gantry cranes,spanning the platform length and rving the t of rail tracks and the buffer area.
A.E.Rizzoli et al./Mathematics and Computers in Simulation59(2002)57–7161•The storage area,a longer term(usually24h)area to park ITUs.The front lifters,rve the storage area,they rve trucks directed to the storage area picking up the ITUs and storing them in the storage area.
The components are implemented in the simulation code as class,using the object-oriented pro-gramming language provided by MODSIM III.The modeller can easily asmble a rail/road terminal model creating instances of the class.Moreover,since the Platform simulation model reads from a databa the structure of the terminal model and creates the instances of the model components,the modeller does not need to write code to create different terminal instances.This allo
ws the Platform simulation module to be quite generic and to be able to model a variety of different terminal layouts and equipment.
The modeller creates model instances either specifying some characteristic he rvice time of a crane)or the subparts of a he number of rail tracks in a platform).In particular, she/he can define the yard layout:how many platforms are prent in the model,the capacity of the associated buffer areas,the number of gantry cranes working on the platform,and the number of rail tracks in the platform.Only one storage area can be defined and its capacity must be entered too.For each gantry crane,the modeller must specify the average number of moves per hour and the crane operating cost per hour.Then,the terminal storage must be defined:the size of the storage area and the number of front lifters rving it,with their performances(number of moves per hour and cost per hour).Finally,the modeller defines the terminal interface to the external world.The road gate is identified by the number of lanes and the average time needed to rvice a truck.This rvice time is an aggregate reprentation of the time required processing the papers when a truck shows up at the road gate.The rail gate is reprented by the number of shunting tracks,the number of link tracks between the shunting area and the terminal. The ur must also specify the average time required to move a train from the shunting area into the terminal.This average value is easy to compute since it mainly depends on the distance from the shunting area to the destination rail track.
In the next ctions we describe how the terminal model can be embedded in the simulation of an intermodal transport by rail corridor simulation(Section4.1),how truck arrivals and departures at the terminal gate can be modelled(Section4.2),and how the terminal components work together (Section4.3).
4.1.Rail corridor and rail network simulation
Intermodal transport involves transporting ITUs on a fully interconnected network,but intermodal corridors are commonplace.A corridor is a privileged point-to-point railway connection between two terminals.The creation of rail corridors made possible for intermodal transport to compete with road-only transport not only in terms of cost,but also in terms of time.Exploring the performance of intermodal transport over rail corridors was one of the objectives of Platform project and the characteristics of the corridors made its simulation a simple problem to be solved.The underlying hypothesis is that a corridor is an abstract reprentation of a path in a complex rail network.The simulation of a corridor link is driven by a timetable,which contains the departure and arrival times of trains.When a train travels from an origin terminal to a destination along a corridor,the simulator makes the train arrive in the destination terminal after a t time,given by the arrival time minus the departure time,plus a stochastically generated delay,to account for unexpected events.
